Table of Contents (Water Resources Engineering)

Sl # Name of Student Thesis Title
1 Moniz Ahmmod Mukto SHORT TERM RIVER WATER LEVEL FORECASTING USING ARTIFICIAL NEURAL NETWORK
2 Shamal Chandra Das PERFORMANCE EVALUATION OF IRRIGATION WATER DELIVERY SYSTEM OF GANGES―KABADAK (G-K) PROJECT
3 Fahmida Khatun EXPERIMENTAL STUDY ON LOCAL SCOUR AROUND BRIDGE PIERS AND ITS REDUCTION
4 Mashfiqus Salehin OPTIMAL EVALUATION OF AQUIFER PARAMETERS IN DHAKA CITY BY KRIGING
5 Asim Krishna Sajjan CHARACTERIZATION OF 1994-95 DROUGHT IN NORTH WESTERN REGION OF BANGLADESH AND ITS IMPACT ON AGRICULTURE
6 Nasreen Mohal SEDINENT DISTRIBUTION AT CHANNEL BIFURCATION USING TWO-DIMENTSIONAL CURVILINEAR MODEL
7 Abu Saleh Khan MORPHOLOGICAL CHANGES DUE TO CONSTRUCTION OF A BARRAGE ON THE TEESTA RIVER
8 Md. Manzurul Islam STUDY ON RAINWATER HARVESTING TECHNIQUES
9 Md. Abul Kalam Azad A STUDY ON THE PREDICTION OF SEDIMENT YIELD FROM THE HILLY CATCHMENT OF CHITTAGONG HILL TRACTS
10 Md. Shafiul Alam APPLICABLITY OF ALLUVIAL ROUGHNESS PREDICTORS FOR GANGES RIVER
11 Md. Monjur Kader EFFECTIVENESS OF PILOT DREDGING IN THE GORAI RIVER
12 Md. Siddiqur Rahman Sarker DEVELOPMENT OF A PHYSICAL MODEL FACILITY AND INVESTIGATION OF FLOW PATTERN DUE TO GROYNE ON THE RIGHT BANK OF JAMUNA RIVER NEAR KAZIRHAT-NATIBPUR AREA
13 A. K. M. Nazrul Islam Howlader A SCALE MODEL STUDY ON HEAD DISCHARGE RELATIONSHIP FOR REGULATOR WITH FLAP GATE
14 Mohammed Mamun A STUDY ON THE BRAIDING INDICES OF THE BRAHMAPUTRA-JAMUNA RIVER
15 Nepal Chandra Dey EVALUATION OF UNSATURATED HYDRAULIC CONDUCTIVITY OF SOIL BASED ON SOIL MOISTURE RETENTION DATA
16 Mohammad Kabirul Hasan A STUDY ON BAR CHARACTERISTIC OF THE JAMUNA RIVER
17 Sabina Sadek REGIONAL LOW-FLOW FREQUENCY RELATIONSHIPS FOR NORTH-WESTERN BANGLADESH
18 Kh. Md. Shafiul Islam A STOCHASTIC MODEL OF FLOW DURATION CURVES FOR SELECTED RIVERS IN NORTH-WESTERN BANGLADESH
19 Shikha Rahman SIMULATION OF SUBSURFACE WATER FLOW BY GALERKIN FINITE ELEMENT METHOD IN THE DHAKA CITY AQUIFER
20 Md. Abdur Raquib PERFORMANCE EVALUATION OF RUBBER DAM PROJECTS IN BANGLADESH
21 Khaled Al Mamun BASIN MODELLING BY UNIT HYDROGRAPH METHOD FOR SARI GOWAIN RIVER
22 Md. Ataur Rahman A HYDROLOGIC DETERMINATION OF INSTREAM FLOW REQUIREMENT OF THE GANGES RIVER
23 Md. Moinul Husain MODIFICATION OF DESIGN OF AN EXISTING REGULATOR TO MAKE IT FISH FRIENDLY
24 Syed Md. Anwaruzzaman EVALUATION OF SELECTED LOCAL SCOUR FORMULAE AROUND PIERS AND GROYNES
25 Md. Jalal Uddin APPLICABILITY OF ALLUVIAL ROUGHNESS PREDICTORS FOR GUMTI, KUSHIYARA AND MOHANANDA RIVERS
26 Md. Abul Bashar A REVIEW OF THE BANK PROTECTION WORKS AT SIRAJGANJ
27 Md. Shahidur Rahman Khan AN EVALUATION OF OPERATION AND MAINTENANCE PRACTICES OF FLOOD EMBANKMENTS
28 Syed Iqbal Khosru ASSESSMENT OF ENVIRONMENTAL IMPACTS OF WATER DEVELOPMENT PROJECTS USING OVERLAY TECHNIQUE
29 Md. Masud Hassan EFFECT OF URBANIZATION ON STORM RUNOFF CHARACTERISTICS OF DHAKA CITY
30 Mohir Uddin Ahmed AN EVALUATION OF DHAKA CITY FLOOD PROTECTION EMBANKMENT UNDER 1998 FLOOD CONDITION
31 Quazi Muhammad Ferdous AN EVALUATION OF THE IMPACTS OF POLDERS ON THE CHANGES IN LAND USE PATTERNS IN THE SOUTH-WESTERN REGION OF BANGLADESH
32 Mohammed Iqbal Hossain EVALUATION OF AQUIFER CHARACTERISTICS OF DHAKA CITY USING PUMPED WELL DATA
33 Ehsan Hafiz Chowdhury A STUDY ON GROUNDWATER RECHARGE AND DISCHARGE CHARACTERISTICS OVER A REACH OF GANGES RIVER
34 Md. Shahjahan Siraj THE EFFECT OF GATE WEIGHT ON HEAD DISCHARGE, RELATIONSHIP OF A REGULATOR WITH GRAVITY FLAP
35 A. K. M. Saiful Islam RAINFALL ESTIMATION OVER BANGLADESH USING SATELLITE DATA
36 Shyamal Kumar Datta DETERMINATION OF METEOROLOGICAL DROUGHT INDEX FOR NORTH-WEST BANGLADESH
37 Md. Asaduzzaman URBAN INFLUENCES ON SELECTED CLIMATIC PARAMETERS IN DHAKA METROPOLITAN AREA
38 Md. Matiur Rahman ANALYSIS OF THE BEACH MATERIALS AT THE KUAKATA COAST
39 Shyamal Kumar Bhattacharyya STOCHASTIC ANALYSIS OF DEFICIENCY OF CROP WATER REQUIREMENT UNDER RAINFED CONDITION IN BOGRA AND RANGPUR AREAS
40 Md. Abdur Rauf ANALYSIS OF RAINFALL CHARACTERISTICS OF NORTHEAST REGION OF BANGLADESH
41 Md. Hasan Ali COMPUTATION OF RUNOFF IN THE JAMUNESWARI RIVER BASIN OF NORTH-WEST BANGLADESH
42 Md. Mahbub Alam APPLICATION OF MACCORMACK SCHEME TO THE STUDY OF AGGRADATION-DEGRADATION IN ALLUVIAL CHANNELS
43 Md. Matiur Rahman LOW-FLOW CRITERIA FOR WATER QUALITY STANDARDS FOR SELECTED RIVERS
44 Sayed Ashraf Mahmud SUBSURFACE AERATION OF GROUND WATER FOR THE DEVELOPMENT OF LOW COST IRON REMOVAL DEVICE
45 K. M. Salzar Hossain EXPERIMENTAL STUDY OF LAUNCHING APRON AROUND ABUTMENT
46 Md. Ferdousur Rahman A STUDY OF FLOATING PUMP IRRIGATION IN BANGLADESH
47 Md. Asaduzzaman HYDRAULIC EVALUATION OF CONVENTIONAL AND MODIFIED TUBEWELLS IN BARIND PROJECT
48 A. K. M. Badrul Alam WATER BALANCE STUDY AND PERFORMANCE EVALUATION OF A LIFT IRRIGATION SYSTEM
49 Mohammad Shahjahan Mondal PERFORMANCE EVALUATION OF SOME SELECTED DEEP AND SHALLOW TUBEWELLS IN IRRIGATION DEVELOPMENT
50 Tarek Bin Hossain A STUDY OF AGGRADATION AND DEGRADATION OF THE KHOWAI RIVER
51 Md. Sabbir Mostafa Khan A STUDY OF FLOW CHARACTERISTICS IN A COMPOUND CHANNEL

 

Table of Details

Thesis Title

SHORT TERM RIVER WATER LEVEL FORECASTING USING ARTIFICIAL NEURAL NETWORK

 

Name of the Student

Moniz Ahmmod Mukto

 

Supervisor

Department

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 2001

Abstract

An artificial neural network (ANN) is a flexible mathematical structure, which is capable of modeling the complex, non-liner, and dynamic relationship between the input and output data sets. ANN models have been found useful and efficient, particularly in problems for which the characteristics of the processes are difficult to describe using physical equations. Moreover, artificial neural networks (ANNs) belong to a class of data-driven modeling, therefore, the quality and consistency of water level data is an important consideration for time series modeling using ANNs.

This study highlights the use of ANN in real-time forecasting of water level at a given site continuously throughout the year based on the water level time history data at the same site. An error back propagation algorithm with gradient descent optimization technique and adaptive learning rate for the construction as well as validation and verification of the neural network model has been used. Computer software named ‘WALF’ is also developed in MicrosoftTM Visual BasicTM based on the error back propagation methodology as the part of this study. The main objective of the study is to explore the sensitivity of the developed model to the calibration season and forecasting lead-time. The non-liner water level records of 18 years at Meghna Ferry Ghat of Meghna River have been used. In addition, the optimization procedure is further extended to the determination of the network control parameters for the supervised feed forwared network. Moreover, detail methodology for the selection of representative calibration, validation, and verification sets is also presented. This study also presents the important aspects of the validation and verification of ANN models including the selection of performance measures and analysis of residual errors for supervised learning networks. The generalization error of the ANN forecasting model have been estimated using the traditional (modified) train and test methodology. The performance measures, which are used in this study, are root mean squared error, mean squared error, mean absolute error, coefficient of efficiency, and correlation coefficient.

This study reveals that the ANN does provide a viable and effective approach for developing input-output simulation and forecasting models in situation that do not require modeling of the internal structure of the river basin. The consistency and quality checking of the selected stations and that of the water level records provides the quality input-output data for constructing the ANN model. Moreover, the ANNs are purely empirical models; therefore validation is critical to its operational success. While validation several neural networks using the traditional (modified) train and test methodology, the calibrated or trained model shows good generalization performance on verification sets. The analysis of residuals of the calibration and test sets can warn the user of the phenomena of overlearning or overfitting and provide and overall distribution of performance measures. To explore the choice of appropriate performance measures, it is found that correlation coefficient as a single correlation index between actual and predicted output shows spurious correlation with the increasing training tolerance due to clustering of forecasted and observed data. The coefficient of efficiency is a better choice in this respect, which can represent the true performance of the forecasting model.

The optimization technique used in this study for the optimization of ANN topology, parameters (weights), and network control parameters significantly reduces the operational cost of the water level forecasting model in terms of required amount of information and execution time. An optimized three-layered neural network topology is obtained which is designed as 2 input neurons in the input layer, and 4 and 12 hidden neurons in the first and second hidden layers respectively. To minimize the erroneous effect of the initial conditions in the process of model construction (i.e. initial random values of ANN parameters), several numbers of individual runs are considered with different initial conditions and the best learned network is considered for water level forecasting. Sensitivity analysis of the model to the calibration season demonstrates that the choice of content rather than length of the calibration and validation period does have a significant effect on the forecasting ability of the ANNs. It is revealed from the study that the ANN models should be calibrated and validated for a common season. In case of sparse data situation, wet period trained model can be used for the real time forecasting of any hydrologic year data but dry period calibration model should only be used for the prediction of dry period data. The forecasted values of water levels obtained show a very high degree of accuracy up to 7-lead-days within the ±0.5m error bound but as the lead-time increases, such as in case of 10 or 15-lead-days, the performance of ANN forecasting model also decreases rapidly. Moreover, plots of residual errors for the predicted and observed water level do not show any systematic distributions although there are noticeable large errors for the rising and falling limb between the predicted and observed water level hydrographs. This result signifies that the large error will be induced in case of the prediction of water levels at beginning and ending of the monsoon period in Bangladesh.

The foregoing studies shows that short term forecasting of river water levels in real-time sense is  possible through the use of neural networks. Moreover, it also significantly reduces the unnecessary data collection and operational time.

 


 

Thesis Title

PERFORMANCE EVALUATION OF IRRIGATION WATER DELIVERY SYSTEM OF GANGES―KABADAK (G-K) PROJECT

 

Name of the Student

Shamal Chandra Das

 

Supervisor

Department

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 200

Abstract

The study was conducted at Ganges―Kobadak Irrigation Project during the season Kharif-I and Kharif-II, 1999. The main objectives of the study were to critically review the different indicators developed and proposed by different authors for performance evaluation of irrigation project and to assess the performance of the system in terms of adequacy, efficiency, equity and dependability. Performance evaluation was carried out using indicators suggested by Bos et al. (1993). Eight tertiary units of three secondary canals were selected for this purpose. Data were collected through field measurement and from project officials.

A large number of performance indicators for irrigation project performance evaluation are discussed and many of the indicators are not applicable due to nonavailability of data.

Performance standards for the different indicators are required to compare the results and that the performance can be quantified accordingly.

The rotational Relative Water Supply (RWS) to the selected teriary units varied from 0.29 to 5.26 during Kharif-I season and 0.04 to 8.16 during Kharif-II season. This wide variation of RWS was mainly due to lack of control of flow. The secondary canal near the head of the system always received more water than the tail end canals.

The average seasonal irrigation efficiency of the selected tertiary units varied from 11% to 59% during Kharif-I season and 13% to 77% during Kharif-II season. The low irrigation efficiency was mainly due to misuse of irrigation water and poor water control. Lack of proper maintenance and interference of farmers in  water distribution in the upper reaches of the system were also responsible for low irrigation efficiency.

The coefficient of variation of relative water supply to different selected tertiary units varied from 0.01 to 0.68 during Kharif-I and 0.01 to 1.22 during Kharif-II season.

Ratio of actual to planned duration of water supply to the selected tertiary units varied from 0.79 to 1.43 during Kharif-I and 0.45 to 1.61 during Kharif-II. This reflects the fact that actual delivery did not follow the schedule and most of the selected tertiary units received water for greater number of days than programmed.

Overall, the system performed poorly in terms of efficiency and equity but it performed well in terms of adequacy and dependability of supply. Adequacy of the system was 2.31 and 1.7 for Kharif-I and Kharif-II seasons respectively but irrigation efficiency was poor (0.56 and 0.60 for Kharif-I and Kharif-II respectively). Equity in water delivery also found to be poor (0.63 and 0.76 for Kharif-I and Kharif-II respectively). Dependability of supply i.e. the ratio of actual to planned duration of water delivery was 1.20 and 1.06 for Kharif-I and Kharif-II seasons respectably.

Irrigated area performance (1.00) and production performance (0.89) were quite good during the Kharif-II season but these were not satisfactory (0.67 and 0.78) during the Kharif-I season. During the Kharif-I season the water delivery could not be made to a substantial portion of the targeted area due to inadequate head. Yield performance was satisfactory (0.89) during the Kharif-I season but it was not satisfactory (0.72) during Kharif-II. During the Kharif-II season supplementary irrigation could not be provided to the tail end of some secondary canal due to poor condition of canals. Cropping intensity performance was found to be satisfactory (0.995).

Economic performance such as total financial viability (0.55), financial self-sufficiency (0.002) and fee collection performance (0.008) was very poor. To keep the irrigation system functioning O & M allocation must be increased and at the same time emphasis must be given on increasing water tax collection. Without adequate recovery of operation cost, the future of the project will be uncertain.

 


 

Thesis Title

EXPERIMENTAL STUDY ON LOCAL SCOUR AROUND BRIDGE PIERS AND ITS REDUCTION

 

Name of the Student

Fahmida Khatun

 

Supervisor

Department

 

Dr. M. R. Kabir

Associate Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 2001

Abstract

There is a worldwide concern on damage of bridge caused by local scour around bridge pier. Structural failures of bridge induced by local scour usually occur in extreme cases of flood flows interacting with pier or when considerable sediment transport occurs and bed forms produced below the threshold condition due to very fine sediments. An additional complexity is the composition of the sediment, which is usually a mixture of alluvial sand and clay. Experience has shown all too often that scouring can progressively undermine the pier, as complete protection against scouring is usually prohibitively expensive. So, the designer must seek the ways to guide and control the process to minimize the risk of failure.

Regarding all the complexies mentioned above, the present experimentation is performed under mobile bed conditions with the aim of investigating the general characteristics of local scour, considering the riverbed materials and the pier shapes commonly employed in Bangladesh. Also experimental study is conducted to investigate the effect of cohesive sediment on local scour. An additional series of experiments is undertaken as the measures of reducing the potential local scouring around bridge piers. The total number of forty-five experimental runs are performed for this present case.

In evaluating the general behavior of local scour, non-cohesive ripple forming sediment is used. In this case a flat bed cannot be maintained even under the critical flow velocity. Although critical flow velocity is considered a demarcation point for distinguishing clear water and live bed condition by most of the earlier investigators, this consideration is not valid for this particular condition.

The scour map is constructed and analyzed to investigate the extent, slop and location of maximum scour hole. Also, parameters related to flow characteristics and pier geometry, which influence the maximum depth, are studied.

To investigate the effect of cohesive sediment content in riverbed, five sediment beds with different percentage of cohesive and non-cohesive materials are undertaken. The scour map as well as the sediment property is analyzed. A decreasing tendency of maximum scour depth with increasing degree of cohesiveness is found due to increase in inter-molecular bondage. Reduction of scour is further enhanced by increasing the non-uniformity of sediment sizes, which leads to armouring phenomena in the bed and scour hole. Dimensionless sediment number (D*), a more representative parameter, is introduced in this present study to express the characteristics of sediment mixture in terms of mean sediment diameter, sediment gradation, and percentage of both cohesive and non-cohesive sediment.

Scour around different pier shapes, pier with collar and pier with splitter are also experimentally investigated to observe their efficacy as reduction measures in non-cohesive sediment bed under live bed conditions. Circular and round-nose pier with different length-width ratio, keeping a constant effective width shows a considerable reduction in scouring due to stream aligning effect. Collar, an effective reduction measure in case of clear water condition, is also applicable for live bed condition as it reduce the down flow, but the effectiveness decreases at a certain amount in this case. Collar with round-nose pier is much more effective as both stream lining and reduction in down flow occurs simultaneously. Splitter, by stream lining the flow, also reduce scour in considerable amount if it is constructed at the upstream face of the pier.

Finally, a design guideline is proposed to estimate maximum scour in ripple-forming sediment bed where live bed condition typically prevails.

 

 


 

Thesis Title

OPTIMAL EVALUATION OF AQUIFER PARAMETERS IN DHAKA CITY BY KRIGING

 

Name of the Student

Mashfiqus Salehin

 

Supervisor /

Department

 

Co-Supervisor /

Department

 

Dr. Mahmmed A. Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

Dr. M. Rezaur Rahman

Associate Professor, IFCDR

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1998

Abstract

A geostatistical technique, kriging, has been applied in evaluating the groundwater flow parameter, transmissivity in Dhaka City. A second parameter, specific capacity, has also been used in the estimation procedure. Dhaka City has been chosen considering its importance from the view point of its ever increasing problem of groundwater shortage due to huge abstraction of groundwater by around 600 deep tubewells. A grid system of the metropolitan area of the city has been selected for generating transmissivity data at the node points. Groundwater parameter data are often scarce but have to be given at every node of a groundwater model grid. Kriging is the geostatistical interpolation method used most frequently for generating such data. Kriging considers the spatial structure of the variable in question and provides a best linear unbiased estimate with minimum variance of estimation error. The error is obtained in the form of standard deviation of the kriged values which are needed while assigning plausible  ranges of parameter values prior to model calibration.

Three kriging methods have been selected, viz., ordinary kriging, kriging combined with linear regression and cokriging. Ordinary kriging employs only the measurements of the main variable, i.e., transmissivity, while the other two methods use data of more than one variable where the variables are strongly correlated. A number of 50 transmissivity data and 200 specific capacity data have been used. A correlation coefficient of 0.84 was obtained between the two thus advocating the use of the latter two methods. A general computer program has been developed in FORTRAN77 to solve the kriging methods. The transmissivity data have been generated at the 457 node points of the selected grid system for each case. The three kriging methods have been compared and it has been inferred that the three methods provide data with almost identical ranges, but use of specific capacity data improves the estimates of the transmissivity and, in general, reduces the estimation error. Both kriging combined with linear regression and cokriging work almost equally well for Dhaka City. However, performance of cokriging seems to be slightly better.

With a view to clarifying the measurement network optimization procedure, two cases have been considered. In the first case, different densities of data measurement network have been studied which reveal that increase of measurement points reduces the standard deviation of estimation error or uncertainty. The need for judgement regarding the optimum number of measurement points has been highlighted. In the second case, the effect of an additional measurement point upon the variance of estimation erro has been tested and a procedure for locating new measurement site in the existing network has been elucidated. A sensitivity analysis has been performed, by following an indirect approach, to see the sensitivity of pumping water level to the measured transmissivity values. Lastly, two possible future scenarios of transmissivity field have been studied by considering reduced specific capacity data.

 


 

Thesis Title

CHARACTERIZATION OF 1994-95 DROUGHT IN NORTH WESTERN REGION OF BANGLADESH AND ITS IMPACT ON AGRICULTURE

 

Name of the Student

Asim Krishna Sajjan

 

Supervisor

Department

Dr. Muhammed Ali Bhuiyan

Associate Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 1998

Abstract

This study involves meteorological characterization of drought and water deficit in north western region. Estimation of crop yield and income losses for 1994-95, together with an assessment of shortage of drinking water and increase in disease incidence are also investigated through questionnaire survey.

The daily rainfall records of 35 sites in the north-western region of Bangladesh and three evaporation stations are used for this study. The analysis involves whether the selected rainfall series from a number of measuring sites of a region are discordant and determining the different sequential property with a view to apply simple analytical solutions to various problems related to stochastic behavior of wet and dry spells of rainfall sequences. The discordancy measure identifies no unusual sites. The daily rainfall record of monsoon period are persistenct in nature whereas in the premonsoon it is devoid of persistency. The persistent behavior of wet and dry spells are modeld by Markov (order 1) process using the theory of runs. As such , to build the model blocks, Poisson probability density function of the occurrence of spells is coupled with geometric distribution for the length of spells and the Weibull, normal, lognormal and gamma distributions for the total rain of wet spells. Random model appears to be a poor simulator and Markov model inferred as a promising one. Longest wet and dry periods are obtained by Markov model and largest rain-sum at different probability are drawn to identify the regional variation characterstics. The maximum longest dry spell is at lower part of Dinajpur and Rangpur districts which is 12-13 days at 50 percent probability and 19-20 days at 90 percent probability while the largest rain-sum (Sm) is at upper part consisting of Panchagarh, Nilphamari, Lalmonirhat and Kurigram which is about 350-450mm at percent probability while at 90 percent is 650-750mm. The maximum longest wet spell (Lwm) is at upper part of Rangpur, Kurigram, Lalmonirhat and Panchagarh.

Water availability and 10-day water deficit (i. E. demand) is calculated for the period of record 1976-96. 1994-95 has the higher deviation of 1132mm from the average rainfall. Exterme value type 1 (EV1) distribution is fitted to 10-day maxima for each station. Overall, EV1 distribution seems to fit the demand well.

To make an estimate of the agricultural damages, socio-economic and environmental impact, data related to these parameters are collected through questionnaire survey in Badarganj and Kishoreganj areas. Production and income losses are 30 and 60 percent respectively at Badarganj whereas at Kishoreganj it appears 15 and 25 percent. Badraganj is more severely affected area than Kishoreganj. In 1994-95 Boro and Aman crops were affected more than other crops. During the drought period there is no doubt about the increase of temperature and dust compared to normal years. Decline in water table below normal levels are also estimated. It has been observed that in 1994-95 groundwater level is about 2m below than the other years.

 

 


 

Thesis Title

SEDINENT DISTRIBUTION AT CHANNEL BIFURCATION USING TWO-DIMENTSIONAL CURVILINEAR MODEL

 

Name of the Student

Nasreen Mohal

 

Supervisor

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1997

Abstract

The morphological behaviour of bifurcation in rivers is a poorly understood problem with which many river engineers are confronted. Bifurcation can be found in deltas, in estuaries and in braided rivers. In one-dimensional mathematical simulation of a river reach that contains bifurcation, some nodal point relation is needed to obtain its sediment distribution in those branches. Determination of this nodal point relation is a problematic task. While the sediment distribution at channel bifurcation is a three-dimensional phenomenon, a two-dimensional mathematical model for morphological simulation with the inclusion of helical effect or secondary flow in the vicinity of bifurcation omits the need of nodal point relation to obtain its sediment distribution in the bifurcated channels.

The present study deal the two-dimensional mathematical modeling under the morphological module of the sediment distribution at channel bifurcation with the use of curvilinear grid along its main and bifurcated channel. For this study purpose, software called MIKE21-C developed at Danish Hydraulic Institute, Denmark has been used. In the model set up, an additional programme for the generation of grids has been modified and adapted to fit the intrinsic curvatures occurring in the bifurcation. A grid number of 75 in the x-direction and 25 in the y-direction give a resolution of 0.16m by 0.04m in the specified directions, respectively.

The model has been calibrated against the available physical model data conducted by Hannan (1995), Roosjen and Zwanenburg (1995) and Islam (1996). They conducted test runs in a bifurcation model constructed in the laboratory of Water Resources Engineering Department, Bangladesh University of Engineering and Technology. They used both symmetrical and asymmetrical noses for three discharge conditions, i.e., 201/s, 301/s and 401/s. the present mathematical model reproduced the physical model results for symmetrical nose satisfactorily. After the calibration, the model has been applied for different sensitivity runs. The scenarios of the sensitivity analysis include different Chezy’s number (25m1/2/s, 30m1/2/s,35m1/2/s), different sediment transport formulas as Engelund-Hansen and van Rijn, raised boundary water level in branch 2 by 5mm and different grain size diameters (d50) such as 0.19mm, 0.27mm and 0.35mm.

From the two-dimensional mathematical model simulations, a set of data of discharge ratio and sediment ratio have been calculated. This data have been set to the nodal point relation , where k is the coefficient and m is the exponent. It has been found that the value of exponent m increase with the increase of upstream discharges and is greater than 5/3 for all three upstream discharges which explain well with the findings of Hannan (1995) and Roosjen and Zwanenburg (1995). Sensitivity of the Chezy’s number gives higher sediment transport with increase in Chezy’s number of Engelund-Hansen formula. Sensitivity of different grain size has been tested using 0.19mm, 0.27mm and 0.35mm diameter and it has been found that the present setup is valid for grain size greater than 0.19mm. when testing sediment transport formula, with van Rijn sediment formula, a lower sediment transport volume has been found compared to Engelund-Hansen. Influence of boundary water of the sediment distribution at the bifurcation ahs been tested by raising the boundary water level at branch 2 by 5mm. Due to raised boundary condition, flow through branch 2 is reduced and also the sediment transport and in the branch 1 flow and sediment transport has been increase and thus increase the discharge and sediment transport ratios compared to the same boundary level in the two branches.

It is concluded from the study that sediment distribution at channel bifurcation is independent of upstream discharge for one type of nose and two-dimensional curvilinear modeling is a good tool for this type of study where several options and scenarios could be tested easily.

 


 

Thesis Title

MORPHOLOGICAL CHANGES DUE TO CONSTRUCTION OF A BARRAGE ON THE TEESTA RIVER

 

Name of the Student

Abu Saleh Khan

 

Supervisor

Department

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2001

Abstract

The Teesta Barrage having a length of 615.0 meters have started operation from August 1990. This study has been conducted to investigate the impact of the Teesta Barrage on the morphology of the Teesta River. Assessment of the long-term impact due to construction of the Barrage on the Teesta River along the total reach was also carried out. The reach under study is 121.0Km long starting from the Indian border to the outfall of the Jammuna River near Chilmari.

Cross-sectional properties at 20 locations of the Teesta River for the year 1988-89, 1991-92, 1994-95 and 1998-99 were analyzed. The results were used to update the work done by BUET in 1988 during the project “Review and Optimization of Planning and Design of Irrigation and Drainage System of Teesta Barrage Project”. It is observed that there is consistency in aggradation in front of the Barrage during the past 30 years. Overall there has been about 1 meter on the average aggradation during this period. But considering the period of the last 8 years the aggradation is only about 0.30 meters. Considering the change during the last 12 years and also along the total reach of the Teesta River it is seen that appreciable deposition is absent but there is quite a large amount of erosion downstream of the Barrage in between chainage 18 to 24 Km and also downstream of the Kaunia Railway Bridge between chainage 70 to 84 Km.

It was also observed from the analysis of the water level records between years 1990 and 2000 that the Teesta River bed level at Dalia and Kaunia stations both located at the downstream of the Barrage has degradated by about a meter.

The planform analysis with the images of 1984, 1994 and 1997 have revealed that during the past 14 years the river has shifted quite appreciably (2840 meters) towards the west in the middle part of the reach between the Indian border and about 15 Km upstream of the Kaunia Railway bridge. At 15 Km upstream of the Kaunia Railway Bridge the situation is just the opposite and the shifting is towards the northeast by about 3409 meters. The extent of erosion indicates that the river requires sediment from either the bed or banks of the river to maintain the equilibrium state after loosing sediment at the upstream of the Barrage due to sedimention.

Future prediction on the Teesta River sedimentation was made using the Mike 11 morphological module of DHI based on the channel geometry of 1997. The model results have shown that there would be 1 meter bed level rise in the 10 years period after the construction of the Barrage. This is similar to the findings of the average bed level change, which show that the extreme most upstream cross-section, the bed level change has been about 2.5 ft in the past 10 years. Also it may be seen that the degradation is more in the downstream part and the impact zone of the Barrage is the total reach upstream of the Barrage and also about 15-Km downstream of it.

 


 

Thesis Title

STUDY ON RAINWATER HARVESTING TECHNIQUES

 

Name of the Student

Md. Manzurul Islam

 

Supervisor

Department

 

Dr. M. R. Kabir

Associate Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2001

Abstract

Rural water supply in Bangladesh is based on groundwater, as it is free from pathogenic microorganisms and available in adequate quantity in shallow aquifers. In Bangladesh, except in coastal and hilly areas, a remarkable success has been achieved by providing 97% of rural population with tubewell water. In the coastal belt, high salinity in surface and groundwater and in the hilly areas, absence of good groundwater aquifers as well as difficulties in tubewell construction in stony layers and high construction cost due to deep depth groundwater table are the main constraints for the development of a dependable water supply system. At present, the success achieved in hand tubewell based rural water supply is on the verge of collapse due to presence of arsenic in groundwater at about 45 districts in Bangladesh in excess of acceptable levels in the shallow aquifers. Provision of arsenic contamination free water and saline free water is urgently needed. Some areas  lime Dhaka City, safe drinking water is also a great problem. Rainwater may be a good solution i.e., alternative source of the above mentioned problem. Bangladesh is a tropical country and receives heavy rainfall during the rainy season.

In this regard, this research explores the possibility of harvesting rainwater in rural communities of Bangladesh as well as densely populated city like Dhaka, using simple and low cost technology. In this connection, rainwater has been experimentally harvested at BUET in the monsoon using a small catchments area (15’ x 15’) made of water proof cloth and a Ferro-cement storage tank. A simple and low cost flushing technique has been developed to flush out the first few minutes of rain. It has been found that a single rainstorm was enough to fill the tank of 3200 liters capacity that can serve drinking cooking and dishwashing purposes for a family having five members for about 4(four) months. Therefore, with a carefully planned filling and usage of the tank, a family can have all of its drinking water from rain in most parts of Bangladesh. This research explored this issue in details for various arsenic affected regions of Bangladesh. Additionally, the research was also looked at the  quality aspect of the stored water. Initial test results indicated that the stored water has a slightly higher pH value (8.1 to 8.3) and presence of coliform bacteria (when water is stored for more than three months) was also detected. This latter problem was taken, care of through a simple indigenous filtering system traditionally used in rural Bangladesh. The traditional filtering system is made up of a number of pitchers placed vertically, where water is poured into the top pitcher and collected from the bottom most pitcher. In between, water seeps through a number of sand layer (from 12” to 24”) and gravel filtering layers. Contaminants were removed completely and coliforms were removed up to 60% of the total. This method has been used to purify water collected from ponds and rivers and likely to be very effective in removing minor levels of contamination found in rainwater. Depending upon the location, this combination of rainwater harvesting and indigenous filtering system is likely to be a better and cheaper alternative to extracting water from surface water sources such as rivers and ponds. This research also examined the relative costs of various materials such as ferro-cement, plastic, GI sheet and concrete used for the storage tank to determine the most economic option for water harvesting.

 


 

Thesis Title

A STUDY ON THE PREDICTION OF SEDIMENT YIELD FROM THE HILLY CATCHMENT OF CHITTAGONG HILL TRACTS

 

Name of the Student

Md. Abul Kalam Azad

 

Supervisor

Department

 

Dr. Md. Abdul Matin

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     February, 2001

Abstract

An evaluation has been made between predicted sediment yield using available prediction formula and field measurement. Prediction formula used in this study is “Revised Universal Soil Loss Equation (RUSLE) which is a universally accepted formula over the world. For the purpose of evaluation, six experimental plots are established at Bandeban of Chittagong Hill Tracts. This location has been selected in order to assess the soil erosivity of the hilly area for both conservation and non-conservation practice in ground. Among these plots three having conservation practice with hedge row and remaining three does not have any conservation practice. A hedge is a special type of plant having growth rate faster than normal plant, which is used to reduce the soil loss. In this study three-hedge row is used in each experimental plots. For the purpose of using prediction formula, various parameters such as the factor erosivity index (R), erodibility index (K), slope length factor (L), and slope steepness factor (S) are standardized utilizing the available measured data by fitting the results obtained from prediction formula. However the cover management factor C and the conservation practice factor P are calibrated by using the sediment yield obtained in the field measurement with that of the sediment yield obtained by prediction formula. In order to collect short duration rainfall data a modern aerodynamic raingauge recorder having a tip sensitivity of 0.2mm is used. Having been obtained all the parameters the prediction formula has been modified in this study for a particular type of soil and slope. This modified form of prediction formula can be used with reasonable accuracy for calculating sediment yield of a small plot for sheet and rill type erosion. Recently collected data for the year 1999 and 2000 has been utilized for calibration purpose. The sediment yield obtained by prediction formula and field measurements are shown in both tabular and graphical form. In the light of the comparison made between the sediment yield obtained by both the method, it is seen that the prediction formula can be applicable to the country like Bangladesh with reasonable accuracy. It is also seen that the percentage of discrepancy between measured and predicted sediment yield varies from – 28.62% to 26.486%. Again it is found that the use of conservation practice reduces the sediment yield by 33.73% for gentle slope, 48.05% for moderate slope and 51.02% for steep slope. From this study it is also seen that the value of erosivity index (R), maximum 30 minutes consecutive intensity (I30), event wise erosivity indes (EI30) and storm energy (Eg) can be determined without using the prediction formula and the places where auto raingauge recorder is not available. From the analysis it is also found that the maximum amount of sediment yield occurred in the steep slope without any conservation practice that is 61.424 mton/ha and minimum amount of sediment yield occurred in case of gentle slope, which is 14.25 mton/ha with conservation practice. However this prediction is limited to the size of the experimental plot and local rainfall pattern.

 


 

Thesis Title

APPLICABLITY OF ALLUVIAL ROUGHNESS PREDICTORS FOR GANGES RIVER

 

Name of the Student

Md. Shafiul Alam

 

Supervisor

Department

 

Dr. M. A. Halim

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg. April, 1998

Abstract

A  study has been conducted to investigate the applicability of some alluvial roughness predictors for the river Ganges utilizing data for the stations Hardinge Bridge and Baruria. Five methods based on overall roughness and eight methods based on division of roughnesses have been selected. The selected overall roughness predictors are: Simons and Richardson (1966), Garde and Ranga Raju (1970), Brownlie (1983), White et. Al. (1987) and Karim (1995). The selected predictors based on division of roughness are Einstein and Barbarossa (1952), Shen (1962), Engelund and Hansen (1967), Vanoni and Hwang (1967), Alam and Kennedy (1969), Haque and Mahmood (1983), Shen et. Al. (1990) and Van Rijn (1993). Some of the selected methods predict depth, some methods predict velocity and some methods predict both depth and velocity. However, there are some methods which predict roughness parameters directly, without predicting depth or velocity. The methods have been evaluated on the basis of depth and/or velocity, where possible, and all the methods have been evaluated on the basis of Manning’s n, Chezy’s C and Darcy-Weisbach friction factor f.

Assuming the flow of the river Ganges quasi-steady and quasi-uniform, the Manning, Chezy and Darcy-Weisbach formulas have been applied to compute the values of n, C and f. respectively. The roughness parameters n, C and f have also been predicted by using the roughness predictors. The roughness parameters predicted by the roughness predictors have then been compared with those computed by the Manning, Chezy and Darcy-Weisbach formulas. The grain roughness and the form roughness have also been separately predicted by using different roughness predictors. The predicted grain roughness has been compared with the grain roughness calculated by using the Strickler formula.

Almost all the roughness predictors seem to predict Manning’s satisfactorily in the moderate range of discharges. A few of them, however, predicts Manning’s n reasonably in the moderate as well as high discharges. But at low discharges only the Shen (1962) method seems to predict roughness parameters satisfactorily. In fact, only the Shen method shows a good agreement with the computed values of Manning’s n, Chezy’s C and friction factor f at low discharges when the roughness parameters change sharply. The predicted grain roughness by the Shen method also shows a very good agreement with the grain roughness compted by the Strickler formula. It seems that only the Shen method can be used for predicting the grain roughness, the form roughness and the total roughness for the river Ganges satisfactorily.

For the river Ganges, the bed form normally remain throughout the year except at very high discharges. During flood flow the bed form is due to erosion and during low flow the bed form is due to siltation or non-erosion of the existing bed form. At Hardinge Bridge the discharge ranges from 261 m3/s to 76000 m3/s, the Froude number ranges from 0.021 to 0.322 and the Reynolds number ranges from 0.66 x 106 to 45.74 x 106. At Baruria the discharge ranges from 28603/s to 1300003/s , the Froude number ranges from 0.029 to 0.315 and the Renolds number ranges from 0.83 x 106 to 33.33 x 106. Considering froude number as classification parameter, the bed form of the river Ganges is mostly in the lower flow regime i.e., ripple and dune as standing waves normally develops when Froude number is greater than or equal to 0.6 (Yalin, 1992) and anti-dunes develop when Froude number is more than 0.8 (Van Rijn, 1993).

At Hardinge Bridge the value of Manning’s ranges from 0.0109 to 0.1589 for discharge ranging from 12003/s to 7600003/s. The Darcy-Weisbach frietion factor f and Chezy’s C ranges from 0.0042 to 0.9960 and from 8.88 to 136.02, respectively. At Baruria the value of Manning’s n ranges from 0.0092 to 0.0907 for discharges ranging from 2860 to 130000m3/s. The Darcy-Weisbach friction factor f and Chezy’s C ranges from 0.0032 to 0.3794 and from 14.38 to 156.10, respectively. The Manning’s n for the river Ganges increases with decreasing discharge. At low discharges the n-value is maximum and decreases rapidly with increasing discharge. With further increase of discharge the decrease of the value of n becomes gradual and at high discharges, the Manning’s n becomes almost constant. The grain roughness is relatively less responsive to discharge than the form roughness. The variation of grain roughness with discharge is reverse to that of the total roughness. The variation of form roughness is similar to the total roughness, i.e. it increases with decreasing discharge.

The Manning’s n for the river Ganges attains its maximum value during March and attains its minimum value during the months of August and September. The Darcy-Weisbach friction factor f also shows a similar variation like Manning’s n over the year However, the variation of Chezy’s C is reverse to that of Manning’s n and Darcy-Weisbach friction factor f. The chezy’s C increases with increasing discharge and decreases with decreasing discharge.

 


 

Thesis Title

EFFECTIVENESS OF PILOT DREDGING IN THE GORAI RIVER

 

Name of the Student

Md. Monjur Kader

 

Supervisor

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     November, 2000

 

Abstract

The effectiveness of pilot dredging of Gorai has been studied on the basis of dredge and post dredge observed bathymetry. The dredge bathymetry stands for the bathymetry measured immediately after the dredge and the post dredge bathymetry stands for the bathymetry after the passage of first year flood flows over the dredged Gorai. It is found from the analyses of these bathymetry that the normalized bed levels of the dredge bathymetry has been lowered all along the dredge Gorai while the bottom bed levels is found to have been raised. This implies that the pilot dredging has increased the high level conveying capacity of the Goari while the low level conveying capacity has been decreased after the passage of first year flood flows over the dredged Gorai. Evidently this change in decreasing the low level conveying capacity of the dredged Gorai is due to the sedimentation in the deeper channel and therefore, the first year pilot dredge is not meaningfully effective in the sense of self-sustaining development for low flow augmentation. It is found that the bottom bed level of dredge channel has been raised close to the level of pre-dredge (Post monsoon 1997) state after the passage of first year flood event over the dredged channel.

They study considers a 30 km reach of Gorai which is studied to estimate changes in dredged bed levels and alignments at different discharge scenarios. The changes are computed using the MIKE21 hydro-morphological software which allows the study to estimate effective discharge responsible for low flow bed formation. In this study, dominant discharges of the Gorai river at Gorai Railway Bridge (GRB) is estimated at 4125 m3/s by Schafernak’s method (sediment concept) as it offers the most information about channel dynamics and the interaction of the channel to watershed hydrology. In addition, this effective discharge inherently allows for the optimization of channel size for specific sediment transport concern. The changes in dredged bed level of Gorai has been studied for three effective discharge scenarios, e.g.; 100%, 75% and 50% of dominant discharges.

The study finds that the effective discharge for low flow bed formation and transport capacity can be estimated at 50% of dominant discharge as it closely estimates the bottom bed levels of pre-dredge (post monsoon 1997) and post dredge (post monsoon 1999) state of bathymetry.

The bottom bed level of the regime state of bathymetry corresponding to 50% dominant discharge (which represents low flow bed formation) is found much higher than the dredged bed level, but closer to the bottom bed level of low flow pre-dredge bathymetry and the post dredge bathymetry as well. This indicates that the bottom bed level of the dredged Gorai will go back to its low flow pre-dredge state in course of time and therefore, dredging will not be effective for self sustaining low flow augmentation.

Regime state of bathymetry corresponding to the dominant discharge shows that the left bank entrance channel shifts toward west and the deeper channel at Kushtia becomes more close to the groynes. The Gorai mouth gets sedimented and the deeper entrance channel is silted up. This phenomenon was also observed during the monitoring of passage of 1999 flood over the dredged bathymetry. Regime bathymetry upstream of GRB shows that the deeper channel moves more towards eastern bank while this simulation pattern is supported by the second year dredge alignments.

On the basis of this study, it can be inferred that the first year dredge level will not be effectively maintained as the Gorai tends to go back to its low flow pre-dredge state. The study also gives an idea about the changes in alignment of deeper channel, for instance, shifting of deeper channel upstream of Kushtia more towards west and shifting of deeper channel upstream of GRB more towards the eastern bank.

 


 

Thesis Title

DEVELOPMENT OF A PHYSICAL MODEL FACILITY AND INVESTIGATION OF FLOW PATTERN DUE TO GROYNE ON THE RIGHT BANK OF JAMUNA RIVER NEAR KAZIRHAT-NATIBPUR AREA

 

Name of the Student

Md. Siddiqur Rahman Sarker

 

Supervisor

Department

 

Dr. Md. Khorshed Alam

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2001

 

Abstract

A physical model facility has been developed near building for the dept of Water Resources Engineering, BUET, Dhaka. This was along felt need of the department for hydraulic model studies. Previously this facility was available only at River Research Institute (RRI), Faridpur. The model studies at RRI concentrate on field problems and are not available for academic research. After developing the model, the aim was to prepare a physical bed model of Jamuna river for the reach length between Kazirhat and Ganges-Jamuna confluence to study the morphological response of the river due to groyne. The secondary purpose of the study was also to get an insight about the suitable location for the ferry ghat at Natibpur, which is under constant threat of erosion and deposition.

The sand bed in the physical model facility is 45.73m (150feet) long and 10.67m (35feet) wide. It is filled up with 0.81m (2feet 8 inch) depth of sand of D50 equal to 0.81mm. Two Rehbock weirs are incorporated as measuring devices in the system, one at the upstream end and the other at the re-circulating canal. Three gauge points on the western side to measure depth of water in the sand bed and one manually operated instrument carriage made of steel truss are also installed over the bed for data acquisition. The water supply in the system is developmed with a storage pool capacity of 210m3 with three centrifugal pumps (total capacity 1501/s) with control valves.

After the completion of physical model facility, the braided channel of Kazirhat – Ganges Jamuna confluence area, which is about 16 km long and 4 km wide, was represented on this model. The horizontal and vertical scale ratios are 1:400 and 1:60 respectively. For this purpose the river charts were collected from BIWTA.

Five representative discharges covering wide ranges of river flow were selected. By studying the flow lines and the morphological changes (mainly scour and siltation) the location of one groyne was identified around Natibpur. The model study showed that by providing a groyne at Natibpur the area d/s of the ferry ghat upto 1.5km could be protected at moderately high flow. The study also showed that the bank line from Natibpur upto the Ganges-Jamuna confluence near Aricha could be protected from scour by constructing four normal groynes in series with a gap of 800m c/c approximately.

 


 

Thesis Title

A SCALE MODEL STUDY ON HEAD DISCHARGE RELATIONSHIP FOR REGULATOR WITH FLAP GATE

 

Name of the Student

A. K. M. Nazrul Islam Howlader

 

Supervisor /

Department

 

Dr. M. R. Kabir

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1998

 

Abstract

There are about twenty drainage regulators having 2 to 21 vents exist in Khulna-Jessore Drainage Rehabilitation Project. These were constructed mainly using the developed head-discharge relation obtained from desk study. In this regard, drainage discharge may differ form the actual discharge because of using different values of contraction coefficient. For better operation and performance of these drainage regulators, accurate head-discharge relationship is necessary. Therefore an attemp was made to perform the physical model study for developing the exact head-discharge relation.

A scale model of ‘Sholmari regulator’ having 10-vents with gravity flap was developed using the selected length scale ratio of 1:10. A total of three twenty five experimental tests were conducted in a laboratory large tilting flume through the regulator for different opening angle of flap, different discharges, and different upstream and downstream waterlevels. All instruments were calibrated before their use.

Headloss-discharge relation for different opening angle of flap was developed. This model study result was significantly different from the result obtained from theoretical desk study. Based on model study necessary changes were introduced in determining different coefficients. But for without lap i.e., 90 degree flap angle, the plot fits well with the theory:q=f(∆h). In theis case computed discharge obtained from desk study is appeared to be higher (up to 20%) than the measured discharge. For submerged condition, drainage discharge depends on headlosses, upstream water level and the flap angles. The discharge coefficient did not remain constant because flap opening angle is directly related to the contraction coefficients. Thus model study identified 20 to 70% variation in discharge estimated by the equations based on desk study.

 


 

Thesis Title

A STUDY ON THE BRAIDING INDICES OF THE BRAHMAPUTRA-JAMUNA RIVER

 

Name of the Student

Mohammed Mamun

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1997

 

Abstract

A study has been conducted to determine the braiding indices of the lower Brahmaputra-Jamuna River lying within Bangladesh for the different years using different approaches. To carry out the study 13 satellite (LANDSAT TM and MSS) images covering the period 1973 to 1996 have been used. The images covering a reach length of about 270km were collected from the Environment and Geographic Information System Support Project for Water Sector Planning (EGIS). To calculate the time series of the braiding indices of the Brahmaputra-Jamuna river three different methods are used, they are braiding intensity ‘E1’ and total sinuosity ‘E2’ proposed by Howard et al. (1970) and braided channel ratio ‘E3’ proposed by Friend and Sinha (1993). For classification of the channel order, Bristow’s method for classification of branches and sub-channels was followed. Second and third order channels were used to calculate the braiding indices in the present investigation. For this study the whole river reaches within Bangladesh are sub-divided into several reaches based on different characteristics. For the reach type-I, the entire river reach is divided into eight sub-reaches according to various characteristics forms of the river e.g., relatively straight reaches, relatively stable island reaches etc. This reach was similar to the one used by Environment and Geographic Information System Support Project for Water Sector Planning (EGIS) of the Government of Bangladesh. In reach type-2 seven island sub-reaches was selected and those reaches were identified by the Consultant of Flood Action Plan-I i.e., for Brahmaputra river training studies (FPCO, FAP-I, 1991). Reach type-3 was selected on the basis of identification of nodal points on satellite images and six sub-reaches was identified and these sub-reaches were identified by EGIS (WARPO, 1997).

The study revealed that the Braiding Intensity ‘E1’ varies from 1.33 to 8.00 for the third order channel and from 1.00 to 4.33 for second order channel. Again Total Sinuosity ‘E2’ was found to vary from 1.46 to 7.90 for the third order channel and from 1.17 to 3.72 for second order channel. Braided Channel Ratio ‘E3’ on the same basis was found to vary from 1.77 to 7.17 for third order channel and from 1.00 to 3.33 for second order channel.

Close scrutiny on the results showed that the braiding indices for sub-reaches at upstream of Sirajganj appears to have been relatively steady during the 1970s, and then to have increased markebly during 1980s and 1990s. But braiding indices downstream of Sirajganj has a different trend. In the 1970s the degree of braiding downstream of Sirajganj decreased notably and by 1980, braiding indices reached its lowest values. These values are consistent with the predominantly Meandering course of the river that can be identified in the satellite image during this period. During the 1980s braiding intensity remained low, but total sinuosity and total braided channel ratio increased due to meandering growth in a very large second-order channel.

The study further indicated that the degree of brading was constant or declined slightly until the mid-1980s for Brahmaputra-Jamuna rive as a whole. But afterwards its started increasing and in 1996 became the highest during the period of record. Based on the current trends, it seems likely that the degree of braiding of the Brahmaputra-Jamuna deserve the highest technological considerations and remedial measures for arresting such trends. The Braiding indices calculated in this study are broadly consistent with those found in the pervious studies.

 


 

Thesis Title

EVALUATION OF UNSATURATED HYDRAULIC CONDUCTIVITY OF SOIL BASED ON SOIL MOISTURE RETENTION DATA

 

Name of the Student

Nepal Chandra Dey

 

Supervisor /

Department

 

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     November, 2000

 

Abstract

Hydraulic conductivity is one of the most important hydraulic properties that governs water flow in the soil. Groundwater recharge and contaminant transport mainly depend on the hydraulic properties of soil. The present study has been undertaken for the determination of unsaturated hydraulic conductivity and for the performance evaluation of different closed form equations. The experiments were conducted at three sites namely BUET  campus, BARI campus and CIP area, unsaturated hydraulic conductivity (K) was measured by using internal drainage method which follows Darcy’s law. At each side the unsaturated hydraulic conductivity was determined for two columns of unit cross sectional area and depth from 35-45 and 45-60 cm respectively. The unsaturated hydraulic conductivity was determined from the measured value of hydraulic gradient and rate of change of moisture content. The moisture content and soil moisture suction at different times were measured by using Time Domain Reflectrometry (TDR) technique and Tensiometer respectively. Textureal classifications of soil were done by Hydrometer method.

The unsaturated hydraulic conductivity of SiC soil of BARI campus varied from 0.2mm per day corresponding to moisture content of 36 percent to 24.0mm per day corresponding to moisture content of 49 percent. The value of this parameter of SiCL soil of BUET campus was found to verify from 0.07mm per day corresponding to moisture content of 35 percent to 25.0mm per day corresponding to moisture content of 48 percent. The HC varied from 40 to 0.8mm per day corresponding moisture content 51 percent to 34 percent for SL soil of CIP area respectively. The results are comparable to those of Joshua and Rahman (1983).

The ranges of soil moisture suctions (0 to 840cm of water) and soil moisture content were measured by Tensiometer and TDR in this experiment. Residual moisture contents corresponding to soil mosture suction of 15000cm were needed for the evaluation of empirical equations. So in this case, evaluation could not be performed based on this experimental data. On the other hand, empirical equations were developed based on a long range of soil moisture suction and soil moisture content. So, evaluation were done based on soil moisture retention data which were collected from field experiental by Joshua and Rahman (1983). The data were collected from three types of soils namely silty clay (SiC), silty clay loam (SiCL) and silty loam (SiL).

The field values of unsaturated hydraulic conductivity estimated by Joshua and Rahman (1983) were compared with the values estimated by four popular closed form models namely, Brooks-Corey (1966), Campbel (1974) and Bresler (1978) and Van Genuchten (1980). Parameters of each model were estimated based on soil-moisture characteristic curves.

Evaluation of unsaturated hydraulic conductivity models was done based on statistical analysis and graphical interpretation. Statistical analyses were done using four different measures namely, average percentage of measured value, Standard Error of Estimates (SEE), correlation coefficient and level of significance for goodness of fit. Model Predicted values of unsaturated hydraulic conductivity varied from 90 to 181 percent of the measured value. The VG model was found to give least deviation from the measured value (10%) among the four selected models. SEE of model value varied from 1.5 to 4.8. The least vlue (1.5) was given by VG. The correlation coefficient varied from 0.96 to 0.97. The highest value (0.97) was found for VG model and lowest value (0.96) for Campbel model. The level of significance for the goodness of fit varied from 40% to 70% in case of Chi-square test. VG model fitted to the measured values at about 50% and 42% level of significance respectively. The level of significance for Brooks-Corey model found to be only 40% which is not satisfactory.

On the basis of the above analyses, it can be concluded that VG model can be considered as most suitable among the four selected models and BC model was not found to give satisfactory results.

 


 

Thesis Title

A STUDY ON BAR CHARACTERISTIC OF THE JAMUNA RIVER

 

Name of the Student

Mohammad Kabirul Hasan

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 1999

 

Abstract

This study has been carried out to determine the bar characteristic of the River Jamuna for examining the morphology and dynamics of bar growth using overlay technique. The methoid has been applied in two segments for different years. To carry out the study 14 satellite (LANDSAT TM and MSS) images are used covering a period of 1973 to 1997. The images covering the reach length of about 240 km out of which 100km reach length has been taken for study purpose. First segment is licated at the upstream of the BANGABANDHU multipurpose Jamuna Bridge near Sirajganj extending from BTM Coordinate Northing 695000m to 74500m, Easting 460000m to 485000m and second segment near Bahdurabad extending from BTM coordinate Northing 750000m to 800000m, Easting 450000m to 480000m. The images are collected from Environmental and Geographic Information System Support Project for Water Sector Planning (EGIS). Related data of water level, discharge & cross-section are used and those are collected from Bangladesh Water Development Board (BWDB). To determine the bar characteristics, different parameters I,e average length, average width, area, age, distribution of land cover and flood depth map of selected bars have been analyzed.

Processing and analysis of the satellite images have been performed using the computer facilites of EGIS. The study segments are identified from the images(s) and then traced on the transparent sheet from the hard copy. Then the traced sheet(s) are digitized with proper geo-referencing procedure and digital maps for channels and bars/islands have been made using pc ARC/INFO. ArcView of GIS version has been applied for spatial  analysis and graphical presentation of the finding.

The bars/islands and channels of these digital maps are identified by different identification number(s). In this study for easy identification of bar/island and channel a general approach has been applied, for any image, such as bars/islands of which the length exceeds 12km starts from 100, identification number for bars less than 12km starts from 200 and for the whole channel identification number is 300. The alignment of bars/islands and channels of the identified digital map(s) have been checked by displaying on the respective image. Any missing and miss leveled were corrected, once the digital map is finalized then the topology has been build to get the arc attribute table (AAT) and polygon attribute table (PAT). These maps and attributed tables were used to examine the time series morphology and dynamics of bar growth.

The study reveals that the area, average width and average length of the selected bar in segment-I has a overall falling trend during the study period 1973-1977, but in segment-2 the bar has the rising trend. Based on the analysis, it seems that the area of the selected bar in segment-I from the year 1994 to 1997 in fact does not have any change, may be the morphological impact due to construction of Bangabandhu Multipurpose Jamuna Bridge at the down stream but on the other hand the bar area of the selected bar in segment-2 has the opposite trend.

From the analysis of bar age and common bar area in 1997 with respect to area of 1973 in both the study segments it has been found that in 24 years (1977-1973) the existing bar area in 1973 comes to about 2.5%, which indicates that if this trend continues the bar may disappear in about 30 years.

From the land cover analysis it has been found that during the study period 1973 to 1977, in segment-I and segment-2 areas of water and bar have increased 12% both combinedly and separately. In fact in terms of morphological point of view, the overall increasing trend of land cover in these segments in insignificant.

It is revealed from the Flood-Depth map analysis that in segment-I the selected bar has been inundated from 271ha to 418ha due to the change in water level from 7.33m to 9.05m. But due to the increase in water level ranged between 9.05m to 12.07m bar has been inundated from 418ha to 2218ha and at the water level 17.5 the whole bar has gone under water which is very much consistent with the 1988 and 1998 flood level. Similarly, in segment-2 the selected bar has also gone under water at water level 20.50m which is also consistent with the 1988 and 1998 flood level.

From the above analysis it is proved that overlay technique is a very good tool for studying the morphology and dynamics of bar growth for the braided reivers and might also be useful for Bar/Island development and settlement aspects.

 


 

Thesis Title

REGIONAL LOW-FLOW FREQUENCY RELATIONSHIPS FOR NORTH-WESTERN BANGLADESH

 

Name of the Student

Sabina Sadek

 

Supervisor

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     February, 1999

 

Abstract

This thesis briefly deals with regional low-flow frequency analysis. Low-flow quantiles are commonly used to describe stream characteristics and are used as parameters in various studies. Unfortunately, it can be difficult to estimate extreme low-flow quantiles, especially at sites with short record lengths. A great deal of research has been directed to the improvement of extreme quantile extimation procedure and regional frequency analysis has been found to be one of the best ways. The present study is undertaken with the objective of providing a method to obtain better estimates of low-flow of the streams in the north-west region of Bangladesh through regionalization.

Three steps are involved in this study. Selection of low-flow data series that satisfy such statistical criteria as randomness, stationarity, independence and homogeneity; choosing a theoretical distribution for modeling the data sample; and estimation of low-flow. Two different distribution selection methods were applied for the selection of appropriate probability distributions, namely the method of L-moment ratio diagram and the method of product moment ratio diagram. Weibull and the log Pearson type 3 (LP3) distributions were found to fit the low-flow data series of the selected rivers. However, the procedure based on moment ratio diagrams depends on subjective judgement. These two distributions are further subjected to a quantitative statistical test, namely Kolmogorov-Smirnov test for further screening. This test also suggested the Weibull and the LP3 as suitable probability distributions to fit the selected low-flow data.

The shape parameters of both the distributions have been regionally estimated over the north-west region yielding a regionally estimated skewness of 0.21 for Weibull distribution and –0.88 for LP3 distribution. These regional estimate were used to calculate low-flow quantiles for recurrence intervals of 10, 25, 50 and 100 year. These low-flow quantiles are compared to the low-flow quantiles obtained by at-site approach. It is found that, in case of Weibull distribution, for recurrence interval 10 year, the maximum relative differnce between regional and at-site quantile is about 40 percent whereas that for LP3 distribution is 13 percent. Generally regional estimates of low-flows showed better agreement with the corresponding values at sites with longer records. Moreover regionally estimated statistics have smaller sampling variations than those estimated only on the basis of at-site data. As such when low-flow estimates are not significantly affected in magnitude by process of regionalization, they are likely to exhibit smaller variances

 


 

Thesis Title

A STOCHASTIC MODEL OF FLOW DURATION CURVES FOR SELECTED RIVERS IN NORTH-WESTERN BANGLADESH

 

Name of the Student

Kh. Md. Shafiul Islam

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     May, 2000

 

Abstract

This study describes and demonstrates the use of probability model for representing stochastic flow duration curves for selected rivers in the north-west region of Bangladesh. Empirical flow duration curves are also generated, compared with the stochastic flow duration curves, and finally regional flow duration curves are generated.

The daily discharge records of 18 discharge gauging stations in the north-western region of Bangladesh are used in this study. The analysis involves estimation of mean daily discharge and their variance by rank, selection of homogeneous sites and a suitable probability distribution for obtaining the stochastic flow duration curve by combining the principle of order statistics. Based on homogeneity test using discordancy measures all of the above selected stations were found to be homogeneous. Four probability distributions: lognormal, gamma, generalized extreme value (GEV) and mixture lognormal, which possess the ability to match the combination of skewness and peakedness, were tested for modeling the stochastic flow duration curve. Based on c2 and K-S goodness-of-fit tests five parameter mixture lognormal distribution was found to be sutitable for modeling the stochastic flow duration curve.

The stochastic flow duration curves were derived applying five parameter mixture lognormal distribution for the selected gauging stations. Following this, such curves were separately obtained using observed flows and a comparison of the two showed that the mixture lognormal distribution is adequate for modeling the flow duration curve. Empirical flow duration curves for the selected stations were also generated and  compared with the stochastic flow duration curves. For a given station, discharge obtained from the stochastic flow duration curve for a given rank compared reasonable well with those obtained from the empirical flow duration curve at corresponding exceedence probability. Finally, regional flow duration curves are constructed using both stochastic and empirical approaches and their comparison showed that these two regional curves also follow the similar relationship.

 


 

Thesis Title

SIMULATION OF SUBSURFACE WATER FLOW BY GALERKIN FINITE ELEMENT METHOD IN THE DHAKA CITY AQUIFER

 

Name of the Student

Shikha Rahman

 

Supervisor /

Department

 

Dr. Muhammed Ali Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     August, 1998

 

Abstract

A two-dimensional mathematical model has been developed using Galerkin finite element method for simulation of transient saturated-unsaturated groundwater flow in multiaquifer system with window based, menu-driven, user friendly interface to provide on screen input data interpretation, to guide user through steps of data processing, and to generate reports and graphs from output results. The model is able to handle combined and system-dependent boundary conditions that can be used in practical situation of groundwater flow in the complex hydrogeological conditions of a country like Bangladesh in general and particularly for Dhaka City. Due to less complexity in 2-D simulation and the availability of GUI the model is easier to use and time efficient.

The program deals with a variety of boundary conditions encountered in real hydrogeological situation consisting of simple constant or time dependent prescribed head (surface water bodies) or prescribed flux boundaries (pumping well, recharging well etc.), complicated system-dependent and atmosphere-controlled boundary including the near-surface activities i.e., precipitation, evaporation, root water extraction and surface ponding caused by excess precipitation and also boundary along the riverside having variable seepage face conditions. With a view to make the model more user friendly and efficient in operation a Graphical User Interface (GUI) is designed to handle the user input, reporting the output and graph generation. This GUI is designed and implemented using Object Oriented Programming language Visual Basic that will make the Fortran program operable in the 32-bit faster windows environment.

To test the different features incorporated in the model, a number of published schematized problems have been simulated by the program. Five such problems are presented in detail in this thesis with simulated results. The program and the modification made were tested on the following examples:

1.          One-dimensional vertical soil column with the variable atmospheric boundary condition and with water extraction by plant roots,

2.          One-dimensional vertical soil column without the variable atmospheric boundary condition.

3.          Two-dimensional rectangular vertical flow domain with the variable seepage-face boundary condition, without influence of atmosphere.

4.          Two-dimensional vertical flow domain representing a simplified river bank situation with both variable atmospheric and variable seepage-face boundary conditions (Coarser Grid)

5.          Two-dimensional vertical flow domain representing a simplified river bank situation with both variable atmospheric and variable seepage-face boundary conditions (Finer Grid) The effect of grid fineness is tested in examples 4 and 5.

 

To verify the model responses in simulating a complex real hydrogeological situation Dhaka City aquifer is studied. The boundary conditions of the domain are derived from the river water level and piezometric level data. Model calibration of the parameters has been performed under this study. Simulated water balance components identify the river effect as the most dominating recharge mechanism of the area, which contributes around 60 percent of the total volume of abstraction. Urban recharge (taken 30% of the total abstraction) also contributes to the abstraction volume of the area. The results of simulation show that the approach is fruitful and can be used for detailed study of the groundwater status of the Dhaka City aqufer in future.

The program is proved to work well but have a disadvantage of being associated with the time step of the atmospheric input data, which is usually 1 day. Shorter and/or automatically set time step for the atmospheric input data, as well as for the boundary-condition subroutines, is therefore recommended.

A need has been also identified for yet more flexible treatment of combined and system-dependent boundary conditions (e.g. a combination of the variable atmospheric boundary condition with the variable seepage-face one) and for the coupling of the present model with a two-dimensional model of surface runoff in a flood plain.

 


 

Thesis Title

PERFORMANCE EVALUATION OF RUBBER DAM PROJECTS IN BANGLADESH

 

Name of the Student

Md. Abdur Raquib

 

Supervisor /

Department

 

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

M. Sc. Engg.     April, 1999

 

Abstract

This study is concerned with the performance evaluation of the rubber dam projects implemented in Bangladesh. Towards attaining this goal, the performance of the two completed pilot rubber dam projects named Idgaon and Bakkhali rubber dam projects in Cox’s Bazar district have been evaluated.

The aspects of evaluation were engineering, agricultural, environmental and organizational. Engineering evaluation involved identification of construction, operation and maintenance problems and mitigative measures. Agricultural evaluation involved assessment of impacts on irrigated area, cropping intensity and yield. Environmental evaluation involved evaluation of impacts on fisheries, drought, water logging, ground water table and boat communication. Organizational evaluation involved evaluation of organizational set-up including peoples’ participation and operation and maintenance cost recovery of the projects.

The evaluation was carried out through collection of data and information after proper discussion with the respondents using necessary checklists, making field visits and study of relevant documents. Data and information was gathered from the project beneficiaries, adversely affected local people and the service givers and the results were verified with the relevant experts at the thana level finalizing the same.

Major findings of this study are that the rubber dam projects have no major problem in construction, operation and maintenance. Moreover, implementation period is short due to simplicity in the construction work. Development cost is low compared to traditional water retention structures. Construction work of rubber dam has some limitation as implementation work requires special supervision and the rubber bags are not manufactured in Bangladesh. There is no major O & M problems. However, some minor problems such as leakage of rubber bags, disorder of pump machines, siltation over the rubber bags and clogging of foot valves were encountered which could be mitigated easily at the local level through the participation of the beneficiaries and the service givers. It has positive agricultural impact. An increasing trend in irrigated area and yield was observed. This is mainly due to improved water management in the project area and the people’s confidence in project operation. It has no adverse environmental impact except boat communication. Informal organizational set-up was there during the operation of the earthen dams. But the organizational set-up  was weak and the people’s participation and operation and maintenance cost recovery were not adequate. The existing organizational set-up were strengthened through institutional intervention. Present organizations are operating satisfactorily in respect of proper water management, resolution of conflicts, operation and maintenance and cost recovery of the rubber dams.

 


 

Thesis Title

BASIN MODELLING BY UNIT HYDROGRAPH METHOD FOR SARI GOWAIN RIVER

 

Name of the Student

Khaled Al Mamun

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1997

 

Abstract

The aim of this study is to develop a unit hydrograph of sari Gowain river basin. During the study, the rainfall-runoff characteristics of the basin were investigated. Also the physical and land use characteristics of the basin area and rainfall losses were studied.

In this study, the streamflow data were used for Sarighat station and the rainfall data was used for Kanairghat recording raingauge station. The Sarighat station is within the basin area and the Kanairghat station is near the basin area. Considering the data availability, 2 3-h UH for isolated storm and 22 3-h UH for complex storm were derived for the period 1990-1994 at Sarighat station. The time base of the isolated storm UH and the complex storm UH are 4 days and 5 days respectively.

To derive UH from complex storm, matrix method was used. A computer program in ‘C’ language was develop to solve the equations. Another ‘C’ program was developed for converting the 24-h streamflow data to 3-h data.

To judge the acceptability of UH, equvalent depths of runoff were computed for each derived UH of isolated and complex storms. The hydrograph derived for comples storm which occurred in July 4-11, 1994 showed the best agreement with the measured streamflows and may be used for estimation of streamflow.

 


 

Thesis Title

A HYDROLOGIC DETERMINATION OF INSTREAM FLOW REQUIREMENT OF THE GANGES RIVER

 

Name of the Student

Md. Ataur Rahman(2)

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     August, 1998

 

Abstract

This study concerns a hydrologic determination of instream flow requirements of the Ganges River. The instream flow requirements are defined as those flows which remain in the stream channel after diversions for off-stream uses such as urban and irrigation needs and, in some configurations, hydropower, are appropriately catered for (Maidment, 1992). These flows are essential within a stream to maintain its  natural resources at desired or specified levels. Knowledge of the instream flow requirements assists in planning for new projects and in evaluating existing projects and it is needed for proper understanding of the issue relating to the natural environment of stream. The main objective of the study is the determination of instream flow requirement of the Ganges on hydrologic analysis. The basic data need for this study consists of mean daily discharge for the period from 1934-35 to 1993-94 of the Ganges at Hardinge Bridge station. Other information collected include fish catch, navigation draft and discharge requirement for keeping salinity below harmful level. The daily mean discharge data was used to compute statistical characteristics of streamflow and it is seen that the maximum flow varied between 35,900m3/s in 1939 to 73,200 m3/s in 1961 and the minimum flow from 1,190 m3/s in 1953 to 2,360 m3/s in 1960 for the period 1934-35 to 1974-75 (pre-Farakka). On the other hand, for the period 1975-76 to 1993-94 (post-Farakka), the maximum flow ranged between 31,500 m3/s in 1989 to 75,800 m3/s in 1987 and the minimum flow from 261 m3/s in 1993 to 889 m3/s in 1977 with the exception of 1979 when 1,210 m3/s was available.

The methods used to determine the instream flow requirements of the Ganges, based on analysis of historic flow (Karim et al., 1995), were Flow-duration, Constant yield and Mean annual flow (MAF) method. The instream flow requirement for each months were estimated by using these methods.

The computed instream flow requirements based on analysis flow duration curve ranged from about 1,580 m3/s in dry season to 40,000 m3/s in thewet season. The corresponding values for the constant yield method ranged from 1,990 m3/s to 40,200 m3/s and those for the MAF method varied from 1,154 to 23,080 m3/s. A comparison of these values with the minimum discharges revealed that in the pre-Farakka period, the minimum observed discharge met the flow requirement for instream protection whereas that for the post-Farakka period falls much below the required flow. The bankfull discharge is found to agree with the higher value of the instream flow requirement during wet season.

The study shows that the minimum instream requirement is about 1,154 m3/s whereas the minimum flow of the Ganges ranged between 261 and 889 m3/s with the exception of one year when minimum flow was 1,210 m3/s. Since the recorded minimum flow is found to be less than the recommended flow for instream protection, the Ganges has suffered substantial morphological and environmental degradation as expected. On other hand, the minimum flow during pre-Farakka was 1,190 m3/s which is found to be very close to the calculated minimum instream requirement. Based on the results obtained the instream flow requirement in the dry months should range between 1,150 and 2,000 m3/s in order to restore and sustain the natural environmental of the Ganges. The methods applied for this analysis are easy to apply and can provide preliminary estimates of instream flow before undertaking any detailed, expensive and time-consuming analysis and study.

Combing the computed instream flow requirement estimates (1,150 – 2,000 m3/s) with the diversion requirements to meet agricultural needs (1,000 m3/s) and domestic water supply (150 - 200 m3/s) as estimated by FA4 (1993), total water demand is found to be in the range of 2,300 to 3,200 m3/s.

 


 

Thesis Title

MODIFICATION OF DESIGN OF AN EXISTING REGULATOR TO MAKE IT FISH FRIENDLY

Name of the Student

Md. Moinul Husain

 

Supervisor /

Department

 

Dr. A. Nishat

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 1998

 

Abstract

Bangladesh is a flood prone country and thus there is a necessity of flood management. Presently, most of the flood management project are aimed to support agriculture sector. The traditional way of flood protection has been in the form of construction of embankments, regulators, sluices and pumps. These projects interfere with the environment and ecosystem of the floodplain and the connected rivers and inevitably affects the open water fisheries sector as migratory routes and nursing grounds of many species of fish are hampered and disturbed. In recent years, majority of fresh water fish have declined both in abundance and bio-diversity.

Barriers to migration of fish has been identified as a major contributing factor in these declines. As a mitigation measure, fish pass and fish friendly regulators are to be constructed to support the natural migration pattern of fishes as far as possible. During the last several decades hundreds of sluices and regulators have been constructed without any provision for meeting the requirements of fish movement. Study are needed to see if the existing structures can be modified to make them fish friendly

This study was taken up to develop an understanding of the migrational behavior of various species of fish available in Bangladesh and set up desing criteria of fish passes. The study also aimed at determination of the cost of modification of an existing regulator as a case study.

The concept of a fish passes is of recent origin in our country. So far three fish passes have been constructed in the country. They are: Fish Pass in Kawadighi Haor of Manu River Project in Moulvi Bazar, Jugini Inlet of Compartmentalization Project, Tangail and Marichar Danra Regulator of Marichar Danra Sub-Project in Nawabgonj district. Based on performance evaluation of these structures and review of available literature on fish passes, a set of design criteria have been developed.

The existing regulator of the Udghal Bell Project at Gilutia in Sunamganj was hosen for modification to make it fish friendly and to assess the probable cost of modification.

The study recommends a maximum exit velocity of 1.5m/sec to be allowed by the regulator. To facilitate migration of fish fry, the gate should be operated in pre-monsoon season i.e. during April to June period. Presently gates are kept closed during this period. The design of the regulator should ensure overshot regulation with sufficient back water depth. Vertical gate may be placed below the floor of passage to regulate depth of water of 15cm ove it by raising the top of the gate maximum head difference between inside and outside the embankment may be limited to 3.00m and minimum depth of water in the outflow channel in the country side must be maintained at 1.00 meter. The sit level  may be fixed on the basis of lowest water level available during April-May months.

The design of the existing regulator of the Udghal Bell has been modified to meet the above mentioned criteria. The cost of modification of the existing regulator is approximately 25% of the original cost.

 


 

Thesis Title

EVALUATION OF SELECTED LOCAL SCOUR FORMULAE AROUND PIERS AND GROYNES

 

Name of the Student

Syed Md. Anwaruzzaman

 

Supervisor /

Department

 

Dr. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1998

 

Abstract

Scour around any obstruction is the lowering of a portion of the riverbed below its natural level. This is caused due to the large scale eddy structures or a system of vortices, which are developed near the obstructions. Though the mechanism of scour is difficult to quantify but its study gives considerable guidance in predicting the magnitude of scour around any hydraulic structure. The determination of scour depth is required for the design of any foundation of hydraulic structures for its safety.

This study was under taken with a view to testing the predicting performance of selected scour depth formulae against the data of scour depth of different piers of East-West interconnector, Hardinge Bridge, laboratory and model tests. For this purpose empirical formulae of Inglis (1949), Blench (1962), Ahmed (9162) and Shen et al (1969) were chosen to test the efficacy against the data of piers of East-West Interconnector and Hardinge Bridge. The study revealed that scour depth prediction by blench formula indicated better correlation compared to other formulae.

Empirical formulae of Inglis (1949), Ahmed (1962), Blench (1962), Larra (1963), and Shen et. Al (1969) were considered for prediction of scour depth using the laboratory test data of different piers. In this case performance of Blench formula appeared to be better compared to other formulae for a particular pier size as well as for different pier size. The study revealed that scour depth increases with the increase in angle of attack and the highest value was found for 300 angle of attack. The study further indicated that scour depth increase with the increase in pier size.

Empirical formulae of Ahmed (1953), Liu et. Al (1961) and Breuser (1991) were tested against the laboratory data of groynes. Prediction by Breuser formula was found to be closer compared to other formulae in this case. Thus the study reveals that depending on the situation, the prediction capability of a particular formula could different.

 


 

Thesis Title

APPLICABILITY OF ALLUVIAL ROUGHNESS PREDICTORS FOR GUMTI, KUSHIYARA AND MOHANANDA RIVERS

 

Name of the Student

Md. Jalal Uddin

 

Supervisor /

Department

 

Dr. M. A. Halim

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1999

 

Abstract

This study has been performed to determine the applicability of alluvial roughness predictors for Gumti, Kushiyara aand Mohananda rivers. Eleven roughness predictors are evaluated- six are based on division of roughness and five are based on overall roughness. The selected methods are evaluated on the basis of Manning’s n, Chezy’s C and Darcy-Weisbach friction factor f and, where possible, on the basis of depth and/or velocity. To predict the roughness characteristics of a alluvial rivers, hydrological data, e.g. discharge, cross-sectional area, mean velocity, river width, water surface slope and grain size data of bed materials are needed. The discharge stations Jibanpur, Sherpur and Chapai Nawabganj are selected for the rivers Gumti, Mushiyara and Mohananda, respectively. The required hydrological and grain size data of the selected rivers have been obtained from BWDB and SWMC, respectively.

Th manning, Chezy and Darcy-Weisbach formulae are applied to clculate the roughness coefficients n, C and f, respectively. The roughness coefficients are also predicted by using the selected roughness predictors and then these values were compared with the values obtained by Manning, Chezy and Darcy-Weisbach formulae. Accuracy of different predictors has been determined on the basis of MNE and the standard deviation of the MNE.

Out of the eleven selected roughness predictors, the Einstein and Barbarossa (1952) is the only method, which can satisfactorily predict roughness coefficients for full  range of discharges for all the rivers. Some of the roughness predictors seem to predict Manning’s n satisfactorily for the full range of discharge of a particular river, e.g. the Shen (1962) method for Gumti river. Shen (1962) method for the Kushiyara river predicts Manning’s n about 100% higher than the calculated values for all discharges. Simons and Richardson (1966) method predicts Manning’s about 48% higher for the Gumti river and 87% higher for the Kushiyara river than the calculated values for all discharges. Some methods predict Manning’s n satisfactorily only for moderate to high range of discharge of a particular river, e.g. Haque and Mahmood (1983) and Shen et al (1990) methods for the Kushiyara river.

Some of the methods, e.g. Engelund and Hansen (1967), Van Rijn (1993), Garde and Ranga Raju (1977), Brownlie (1983), White et al (1987) and Karim (1995) methods predict roughness coefficients of poor quality for any discharges and all the rivers.

The Einstein and Barbarossa (1952), Shen (1962) and Brownline (1983) methods for the river Gumti and Brownlie (1983) and Karim (1995) methods for the river Kushiyara predict depth satisfactorily.

During analyses of the hydrological data collected from BWDB for the river Mohananda, the data did not seem reliable, because the calculated Manning’s n from observed data vary form 2.316 to 0.081 which are about 30 to 3 times higher than form its normal ranges. So no conclusion could be drawn for the predictors in case of the Mohananda river. But Einstein and Barbarossa (1952) and Shen (1962) methods seem to predict reasonable roughness coefficients for the full range of discharges and Haque and Mahmood (1983) method seems to predict reasonable results for moderate to high discharges of the Mohananda river.

The Manning’s n for the Gumti and the Kushiyara rivers is maximum when the discharge is low and decreases with increasing discharge. For the river Gumti detail analyses indicate the presence of bed forms in all discharges, i.e. throughout the year. For the river Kushiyara; bed forms are only present in the range of low to medium discharges but at high discharges the river bed becomes plane. The response of grain roughness to the change in discharge is relatively less than that for from roughness. The variation of grain roughness is responsive to that of the total roughness but the variation of form roughness is similar to the total roughness.

The Manning’s n for the river Gumti is maximum during the month of March when discharge is low; and attains minimum value during the months of May to October when high flow takes place. The Manning’s n for the river Kushiyara is maximum during the month of February when the discharge is low and minimum during the month of July to September when the discharge is high. The Mohananda river attains the maximum discharge in the month of September and the minimum discharges in the months of December to May.

 


 

Thesis Title

A REVIEW OF THE BANK PROTECTION WORKS AT SIRAJGANJ

 

Name of the Student

Md. Abul Bashar

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1999

 

Abstract

Bangladesh is a flat land formed mainly by the sediments deposited by the three mighty rivers, the Padma, the Meghna and the Jamuna. Rivers flow in alluvial deposits are generally active and associated with the process of erosion and deposition. A study has been conducted to review the bank protection work and associated morphological changes near and around Sirajganj town. The major feature is to assess the bank protection works undertaken so far around Sirajganj. In addition, the nature and causes of erosion and to study the morphological changes brought about by the river in the vicinity of the town have also been studied.

Study of cross-sections of the Jamuna at Sirajganj indicates that the deep channel of the main flow is moving adjacent to the right bank. The sharp bend on the left bank located at just upstream of Sirajganj is mainly responsible for server erosion at Sirajganj. From the analysis of bankline movement of the Jamuna near Sirajganj it is observed that the Channel is migrating towards west at the rate of 29.19 meter per year. Revetment alone as bank protection measures proved ineffective for a braided and heavy silt carrying river like the Jamuna. The groyne at Sailabari constructed in 1977 was found to be effective upto 1984. The groyne helped formation of shoals and siltation at downstream. During the flood of 1987 & 1988, this groyne again proved to be effective and still working well. The groyne at Ranigram constructed in 1986 and the revetment works constructed as per design and specifications at this location were found to function satisfactorily. Earlier the revetment was used in isolation and was proved to be unsatisfactory. In the 70’s and 80’s groynes were used as bank protection structure. It worked well but not upto the mark, as damage was found to occur every year. In 1998 Ranigram groyne was modified to build the Sirajganj hardpoint. This structure is effective for diverting the flood flows. Thus it appears from the study that two or more types of bank protective measures is more suitable than a single type in protecting the erosion.

The cross-sections XJ6 (6km downstream of Sirajganj town) shown the deep channel shifted to the left bank and there was deposition of silt at the right bank. This was possible due to protective works down at Sirajganj.

But the deep channel in the upstream of Sirajganj town flows near the right bank. At section located 1555 meter upstream from Sirajganj town, it is observed that the bed had been silted up about 6 meter during the period in between 1988 and 1998. It is also observed that the river bank shifted from west to east during the above period. This happened due to shifting of deep channel towards the left bank. Thus due to protective works at the right bank Sirajganj town is saved from further erosion.

 


 

Thesis Title

AN EVALUATION OF OPERATION AND MAINTENANCE PRACTICES OF FLOOD EMBANKMENTS

 

Name of the Student

Md. Shahidur Rahman Khan

 

Supervisor /

Department

 

Dr. A. Nishat

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 1998

 

Abstract

Embankment, one of the earliest civil engineering structures, is still the most favoured option for flood control due to it’s simple construction method and use of local labour and material. The recorded history of construction of embankments in Bangladesh dates back to thirteenth century. Effectiveness of the embankment is very important in delivering benefits and for this purpose effective operation and maintenance (O&M) of embankment needs utmost care. Failure of embankment is a common phenomenon in Bangladesh. This study was taken up to evaluate the present day O & M position of flood control embankments.

The main causes of failure of embankments have been identified as: erosion, overtopping, public cut and improper maintenance. Embankments normally do not fail due to design deficiency. Failures due to river erosion, breaches etc., in turn can be linked to poor O&M. Many of the O&M related problems are linked to poor planning and construction. Incomplete evaluation of hydro-morphological impact inside/out side the poldered area often forces people to make public cut to remove drainage congestion.

For evaluation of effectiveness of then maintenance procedure, the performance of the polder and the O&M approach as prevailed in the Meghna-Dhonagoda Irrigation Project (MDIP) was taken up. RRA of the project revealed that either operational requirements and operational problems were not considered during planning/construction stage; or committees proposed for O&M were not functioning & water control structures were under the domination of vested interest groups; or officials were not trained nor did attend to their duties properly. The study found the absence of systematic accounting of O&M expenditure on project basis. The average O&M expenditure has been found to be more than the standard rate; and yet the maintenance were of poor quality. Identification of arrangement for O&M financing was neglected as usual.

The constraints to the achievement of an acceptable level of project operation and maintenance are lack of motivation, organizational & institutional difficulties. O&M resource constraint is part of a more complex problem involving lack of public consultation, construction time and cost over-run, non-availability of proper & suitable O&M manual in the field level; tasks, responsibility & accountability of concerned officials not being defined/poorly defined etc. The major issues with respect to proper operation and maintenance are: non availability of sufficient fund which affects the physical work programme, failure to recover cost, non involvement of beneficiaries, incomprehensive planning, poor construction, compaction not being done upto required degree and overlapping of construction and operation. Deficiencies in BWDB’s organizational arrangements, procedures and lack of training of field staff negates O&M activities whatever is possible within the practical circumstances.

Maintenance of embankments is grouped as preventive maintenance, periodic maintenance and emergency maintenance. The O&M stage should directly involve the local population. The routine preventive maintenance has to be done by Embankment Maintenance Groups (EMGS) and periodic maintenance has to be done by Landless Contracting Societies (LLCs). The group formation may be done through Bangladesh Rural Development Board (BRDB) or NGOs. However technical supervision will have to be the responsibility of ‘Bangladesh Water Development Board (BWDB)’ Emergency maintenance has to be got done by engaging contractors.

The study revealed that the difference of flood heights of 25 years and 100 years returen periods is less than 1 meter. The embankment with 25 years return period if properly constructed with 1m freeboard should be able to withstand flood of 100 years return period. However in extreme cases, some extra measures like flood wall of gunny bag etc., may be required to prevent overtopping. The study also revealed that there was not much difference in achievement of degree of compaction between the uncompacted and  conventionally compacted embankments. The increase in cost of construction, if the conventional 4.2m wide compacted embankment is changed to the 6.5m wide road cum flood control embankment is about 2% more only. Design of embankments with dual purposes of flood control and road communication can partially mitigate the adverse impact on navigation. Construction of embankment-cum-public road; will  ensure constant use, more attention of local people and better maintenance of the embankment itself. This type of wide embankment can be used for afforestation without any risk of damage to the hydraulically/structurally minimum required section.

 


 

Thesis Title

ASSESSMENT OF ENVIRONMENTAL IMPACTS OF WATER DEVELOPMENT PROJECTS USING OVERLAY TECHNIQUE

 

Name of the Student

Syed Iqbal Khosru

 

Supervisor /

Department

 

Dr. Ainun Nishat

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     June, 1998

 

Abstract

Environmental Impact Assessment (EIA) has been made mandatory for all water development projects in Bangladesh, to be carried out at project planning stage. The main objective of EIA is to identify the probable effects, both beneficial and adverse, resulting from the project. Then through EIA, suggestions are given to the planners so as to minimize and mitigate the negative or adverse impacts and enhance the positive or beneficial impacts. EIA then prepares an Environmental Management Plan (EMP) for future monitoring of the project, both during and after its implementation so that sustainability is ensured.

There are number of techniques for carrying out EIA namely: Checklist, Matrices, Networks, Environmental Evaluation System, Overlay Technique, Environmetal Impact Indices and Cost-benefit Analysis. Besides, many institutions have developed their own guidelines for EIA. Bangladesh has adopted the Weighted Matrix method and a guidelines for carrying out EIA of water development projects has already been developed and adopted. Every method has some advantages and disadvantages in their application. As for example, Network method has been found suitable for identifying secondary and as well as tertiary impacts. Overlay technique is considered suitable for presentation of spatial variation in impacts.

This study was taken up to carryout a comparative study of the various methods of EIA and evaluated whether some elements of Overlay technique can be adopted while presenting findings through Weighted Matrix method in accordance with the approved guidelines. To carry out these objectives, data available from post evaluation of the System Rehabilitation Project (SRP) were used. SRP, during 1990-95, rehabilitated 35 water development projects of the Bangladesh Water Development Board (BWDB). A multidisciplinary Evaluation Team assessed seven SRP projects, using EIA methodology.

In this study, data of two projects were used. GIS based mapping technique was used to produce the Overlays. For comparison with conventional method, some important environmental components (IECs) were chosen, namely: Flood Control, Drainage, Irrigation, Crop Damage and Capture Fisheries. Other IECs, relevant to water resources development and management projects have been identified on the basis of various studies available on evaluation of completed projects. Preliminary assessment of suitability of overlay techniques and availability of data led to selection of the aforesaid five parameters. For this type of projects, modification in flooding characteristics and changes in cropping are most significant parameters.

It has been found that EIA results can be better presented through Overlays for the selected IECs. Impact of probable floods, corresponding to various return periods, and matching with any river water level, on the project area, can be clearly represented by Overlays for the selected IECs. Impact of probable floods, corresponding to various return periods, and matching with any river water level, on the project area, can be clearly represented by overlay. Similarly improvement in drainage in post-monsoon condition can be better represented with spatial variation shown on the maps. Impact of the project on potentials as well as actual performance of irrigation were clearly visible in Overlay maps. Impacts on capture fisheries, studied with overlays, clearly demarked the areas of potential conflict between agriculture and fisheries. It was observed that in the projects studied, such conflict was prevalent over small areas. On the other hand flooding pattern has significantly adverse impact on agriculture. These analysis would be of great value in future water management practices.

Finally it can be said that, overlay mapping can bave very important role in the EIA process. The conventional method can not assess the impact and quantify the spatial variation. The method is also very flexible and the importance of the time function can be well addressed.

 


 

Thesis Title

EFFECT OF URBANIZATION ON STORM RUNOFF CHARACTERISTICS OF DHAKA CITY

 

Name of the Student

Md. Masud Hassan

 

Supervisor /

Department

 

Dr. M. F. Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     July, 1997

 

Abstract

An urban or urbanizing watershed can be defined as an area in which all or part of the watershed will be covered by impervious structures, such as roads, sidewalks, parking lots and houses. In Bangladesh, the urban centers are expanding rapidly. During the  last 25 years or so rapid urbanization has taken place in Dhaka city. Substantial increase in build-up areas has taken place due to development of residential and commercial areas mostly through private land developers and real estate business. This trend is likely to continue in future. These activities resulted in substantial increase in impervious area, created obstruction to natural drainage pattern, and reduced detention basins, which in turn lead to an increase of the flood peak and shortening of the runoff concentration time. The main objective of this study was to investigate the impact of land use changes due to urbanization on storm runoff characteristics of Dhaka city.

To assess the impact of urbanization on runoff characteristics, rational method and rainfall runoff model have been used. Due to nonavailability of land use data, only four years of land use data could be gathered. The past and present status of impervious area as well as the trend of impervious area in future was estimated through the analysis of land use data. Runoff coefficient C was also estimated with this land use information. A correlation was developed between runoff coefficient and percent impervious area.

The modeling study focuses on the impact of urbanization which causes increase of volume and peak rate of runoff. Urbanization of a watershed changes its response to precipitation. The most common effects are reduced infiltration and decreased travel time, which result in significantly higher peak rates of runoff. The volume of runoff is determined primarily by the amount of precipitation and aby infiltration characteristics related to soil type, antecedent rainfall, type of vegetal cover, impervious surfaces, and surface retention. A rainfall runoff model was used for the assessment of impact of urbanization. NAM modeling system developed by the Danish Hydraulic Institute (DHI) and available with the Surface Water Modelling Centre (SWMC) was applied for theis study. In this study, 1986 to 1995  rainfall and evaporation data were used. The model results indicate that there would be significant impact on runoff due to urbanization. Future Scenarios with future land use pattern for the year 2010 as estimated by JICA (1992) were considered and the volume and peak rate of runoff under future scenario was computed.

 


 

Thesis Title

AN EVALUATION OF DHAKA CITY FLOOD PROTECTION EMBANKMENT UNDER 1998 FLOOD CONDITION

 

Name of the Student

Mohir Uddin Ahmed

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     April, 1999

 

Abstract

Embankment is the most favoured option for flood control due to its simple construction method and use of local labour and manpower. In 1987 and 1988 Bangladesh experienced two of the most severe floods on records. Vast areas of the country including the capital city Dhaka were flooded to an unprecedented degree with flood level 1.50 m higher han normal for periods up to four weeks. In the wake of these floods, in October 1988 the government of Bangladesh (GOB) established a committee for flood control and drainage of greater Dhaka with the primary objectives of preparing a flood control plan for Dhaka metropolitan area, based primarily on the 1987 JICA study on storm drainage system improvement for Dhaka city and the 1988 “Jansen Report” on cause of  1988 flood and recommended solutions. In January 1989 the committee submitted a detailed scheme for phased investment in flood protection.

In view of the high priority, the government immediately initiated pahse I of the recommended works on a crash programme basis using their own resources. These works included construction of about 30km of embankment and 7km of protection wall along the westerly periphery of the city to provide protection to about 136.50 sq.km. in the highly urbanized westerly part of the city.

The recent flood in 1988 is one of the catastrophic flood in the history of Bangladesh. The 1998 flood is specially characterized by its prolonged duration in 1954 the water level above danger level continued for 19 days and that in 1988 flood continued for 25 days while in 1998 the water level above danger level exceeded even more then 6 weeks at many places.

1998 flood is the first severe flood that Bangladesh experienced after the construction of Dhaka city flood protection embankment. The objective of the study is to evaluate the effectiveness of the existing flood protection embankment for Dhaka city with respect to the 1998 flood conditions. The evaluation is done based on field visit and collection of data from the flood forecasting and Warning center of BWDB. The field visit started from Tongi Railway Bridge and covered the whole peripheral embankment along Turag river up to Kellar mohr and the DND project area. During field visit few locations were identified where the embankment suffered failures. The evaluation is carried out with respect to various causes leading to failure of earthen embankment. The present physical condition as observed are also mentioned in this report.

From the analysis it is concluded that the existing embankment section in most of the locations are adequate against hydraulic failure with respect to over toping but the free board is inadequate at few locations. The existing embankment section is mostly inadequate against seepage through embankment body. The seepage line cut the down stream face of the embankment section but remains well within the down stream face with respect to design section. In this respect the embankment needs to be re-sectioned at several locations as per design. However the embankment section is adequate against sliding of foundation against horizontal pressure of water under 1998 flood condition. The sections of the existing drainage channels of the city are mostly inadequate to discharge storm water to the rivers. In this respect the storm drainage system needs to be maintained in proper sections needed for the individual catchments.

Seepage occurs through the embankment body at many locations of DND embankment. The existing flood wall has no sufficient free board and in many locations there is no free board with respect to 1998 flood conditions.

 


 

Thesis Title

AN EVALUATION OF THE IMPACTS OF POLDERS ON THE CHANGES IN LAND USE PATTERNS IN THE SOUTH-WESTERN REGION OF BANGLADESH

 

Name of the Student

Quazi Muhammad Ferdous

 

Supervisor /

Department

 

Dr. A. Nishat

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     July, 1997

 

Abstract

The objective of the study was to understand the changes in agricultural land use pattern (and people’s perception of the projects) as a result of construction of polders in the South-Western coastal belt of Bangladesh. Three polder were selected for in depth study. Rapid Rural Appraisal technique was used to collect information. A checklist/questionnaire covering socio-economic conditions, occupational patterns, change in overall environment, area and internsity of land use pattern, changes in crops and cropping pattern was prepared during the planning stage of the survey works. Farmers were selected for interviews randomly with attention being paid to their experience in farming and age.

The poldersation in the coastal belt was initiated a primarily with the aim of tidal flood protection and create environment for improving the agricultural production and thereby improve the socio-economic condition of farmers of the area. People felt secured against periodic inundation by high tides. Prior to poldersation, local people used to construct embankments on temporary basis, every year. Therefore, they were familiar with the technical solution adopted for flood protection.

No remarkable change in agricultural land use pattern was observed immediately after the project was completed. Gradually the fallow lands were brought under cultivation and improved varieties of rice were introduced. Before the polderisation less than 30% of the coastal area are under cultivation and the land was single cropped. The crop area and crop yield increased and double cropping and triple cropping have been possible in certain areas because of the flood protection facility in existence. Changes in land use pattern may summarized as from fallow to agricultural land; then from low yield variety of High Yield Variety paddy; andvery recently from paddy cultivation to shrimp farming. In fact, in many polders shrimp (either freshwater or saline water variety) are prominent land use category.

It has been observed that immediately after completion of polders, they functioned properly. But soon conditions deteriorated, in some areas, mainly due to siltation in the out fall channels of drainage regulators. This resulted into water logging and forced into further changes in land use. Fisheries replaced paddy production in such case.

 


 

Thesis Title

EVALUATION OF AQUIFER CHARACTERISTICS OF DHAKA CITY USING PUMPED WELL DATA

 

Name of the Student

Mohammed Iqbal Hossain

 

Supervisor /

Department

 

Dr. Muhammed A. Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1997

 

Abstract

Dhaka WASA has divided the whole city into six zones to administer its operations of potable water supply and safe sewerage disposal. The construction and the development test data of 44 selected tubewells from these six zones have been analyzed to evaluate its aqufer and well specific properties. Parameters, such as, transmissivity and storativity are evaluated to characterize the aquifer properties while well efficiency and skin factor are evaluated to demonstrate its well specific parameters. Another important parameter called specific capacity is also determined to represent the productivity of both the aqufer and the well itself.

The development tests on the deep tubewells of DWASA are performed without installing piezometers. Thus, the pumping tests conducted by DWASA can be treated as a single well test. Determination of transmissivity and storativity are therefore constrained with the utilization of the well tests under the confined and/or leaky aquifer system, there are 5 suitable methods selected from literature to overcome the lack of piezometer readings. The selected 5 methods are Jacob’s straight line method, Theis’s recovery method, Papadopulos-Cooper’s method (curve fitting), Hurr-Worthington’s method and the Logan approximate method. Among these 5 methods, Jacob straight line method gives consistently higher transmissivity values than the other 4 methods. Jacob method is very sensitive to the non-linear well losses which have been found in appreciable magnitude for the most of the wells tested in Dhaka city. Papadopulos-Cooper method is valid for fully penetrated confined aquifer, mostly not the case existing for the configuration and aquifer system analysed here. Hurr-Worthington and recoverymethods have been judged the most suitable methods for the aquifer system in Dhaka city. Out of these two, Hurr-Worthington method is selected to draw the iso-transmissivity lines to represent its variations instantaneously in Dhaka city. It is seen from the map (Fig. 5.1) that the south-western part and north-eastern corner of Dhaka city have higher transmissivity (700-1000m2/d) values than the rest of the city. The majority of the city area representing transmissivity values ranging from 400 to 500m2/d. The Hurr-Worthington method evaluates the transmissivity by using the corrections due to well losses on its observed drawdowns. While the aquifer loss is dependent on the aquifer characteristics only, the well loss arises from the combined effect of screen entrance loss and frictional loss inside the pumped wells. The aquifer losses in Dhaka city are found to vary from 8.2m to 20.9m and the total well losses from 2.1m to 14.7m. As the well losses are found appreciable in Dhaka city compared to its overall drawdowns, it dictate the use of an appropriate  method which takes care of these losses in its transmissivity determination. In this respect, Hurr-Worthington method may be a better option to be used for Dhaka city aquifer system. The Logan method, known as an approximation method uses the specific drawdown data for transmissivity determination is liable to produce some error under vertical leakage and transient aquifer responses.

For the selected single well methods, the storativity values can only be provided by the Papadopulos-Cooper method and its values vary from 1.5x10-6 to 9.5x10-5. It is seen from the iso-storativity map (Fig. 5.2) that the south-western part of Dhaka city have the highest storativity values than the rest of the city. The majority of the city area representing storativity values of about 2x10-5. Both the specific capacity and the well efficiency are important to measure the performance of a well. In Dhaka city, the specific capacity of the wells varies from 219m2/day to 550m2/day and well efficiency varies from 45 to 86 percent. Low efficiency as low as 70 percent is the indication of inadequate and poor well development: Again, skin effect is to account for the head losses in the vicinity of a well. Skin factor in Dhaka city is found to vary 0.32 to 8.06

 


 

Thesis Title

A STUDY ON GROUNDWATER RECHARGE AND DISCHARGE CHARACTERISTICS OVER A REACH OF GANGES RIVER

 

Name of the Student

Ehsan Hafiz Chowdhury

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     September, 1998

 

Abstract

In this study groundwater recharge and discharge characteristics are investigated over a selected rech of the Ganges river from Hardinge Bridge to Rampur Boalia of Rajshahi district. Four transacts were selected on the Ganges river such that maximum number of wells fall along these transact lines. For each transact line the groundwater levels were compared with the river stage. The range of influence of groundwater movement was obtained by observing the relative levels of the groundwater wells with the river stage. Then the river was terned as effluent or influent depending on whether the groundwater levels are higher or lower than the river stage.

Ganges river shows a high seasonal variability of flows and levels. Annual maximum, minimum and average flows of the Ganges were estimated as 75,800m3/sec, 261 m3/sec and 10,700 m3/sec at Hardinge Bridge. Annual maximum, minimum and average water levels were calculated as 19.35 m(PWD), 7.81 m(PWD) and 12-.06 m(PWD) at transact 4-4 in Rampur Boalia and 14.97 m(PWD), 4.48 m(PWD) and 9.00 m(PWD) at transact 1-1 near Hardinge Bridge. Groundwater levels show a variation of around 10 meters between the maximum and minimum values in a given year.

Correlation of river stage and groundwater level hydrographs were investigated for the period 1974-1994 for all the four selected transacts. This study reveals that the groundwater levels respond with the seasonal variation of river stages. In the dry months of a year, the groundwater levels were found to be higher than the river stage and the flow direction is from aquifer to the river. As monsoon approaches, the river stages rise at a faster rate than the groundwater levels and the flow direction changes from river to the aquifer. The computed hydraulic gradient of groundwater movement towards or away from the river varied from values as low as 0.005 m/km to as high as 13 m/km. Transmissivity of aquifer ranges from 875 m2/day to 6000 m2/day in the selected reach. The estimated transmissivity compared well with the values that were available from previous reports.

For the purpose of studying the groundwater level fluctuation and trends, piezometric surfaces were generated for the years 1974, 1980, 1985, 1990 and 1994 for the month fo February-March and July-August, considering all the groundwater observation wells and the river stages for corresponding weeks. During the dry periods, higher potential lines are seen to be away from the river and lower potential lines are near the river, meaning that flow is from aquifer to the river. In monsoon, this trend reverses with the higher potential lines being closer to the river and lower potential lines lying further from the river. This means that flow is from river to the aquifer. Groundwater flow is generally from north-west to suth-east direction. Higher values of groundwater flow occur towards the river in the lower part that the upper part of the study reach. The quantity of groundwater flow was estimated, and found to have a maximum value of 57 m3/day/m at transact 1-1 and 3.0 m3/day/m at transact 4-4 respectively. The effluent and influent effect extends upto about 300m to 20km in a direction perpendicular to Ganges flow, depending on the relative levels.

Net annual maximum groundwater recharge from the river was estimated as 640 m3/day/m and a minimum of 11 m3/day/m in the 70km study reach. Net discharge from the groundwater aquifer towards river was estimated as 1519 m3/day/m to 117 m3/day/m. Trend of groundwater movement towards the river decreases annually at a rate of 13.80 m3/sec during the period of 21 years.

 


 

Thesis Title

THE EFFECT OF GATE WEIGHT ON HEAD DISCHARGE, RELATIONSHIP OF A REGULATOR WITH GRAVITY FLAP

 

Name of the Student

Md. Shahjahan Siraj

 

Supervisor /

Department

 

Dr. M. R. Kabir

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2001

 

Abstract

Regulator may defined as a hydraulic structure cosists of piers at regular intervals are generally constructed across the channel to control the flow. These structures are capable of both draining out water from the catchment and entering water from riverside.

In Bangladesh, Bangladesh Water Development Board is the Government Organization mostly responsible to build these kind of hydraulic structure for irrigation, flood control and rainage. Khulan-Jessore Drainage Rehabilitation Project is one of the large project of BWDB having 20 drainage regulators consist of 2-21 vents. These regulators were constructed mainly on the basis of the head discharge relationship obtained from the theoretical equations. Proper operation and performance of these regulators can be ensured with accurate head-discharge relationship. As the co-efficient of contraction plays a sensitive role in computation of discharge, drainage may vary significantly from the actual discharge in case of poorly judged contraction values. In this regard head-discharge relation was developed through a scale model of Sholmari regulator which is to constructed. Also the effect of gate weight in head-discharge has been investigated.

With the model of Sholmari regulator a total of sixty-four test runs were constructed for different gate weights and discharges in the Hydraulics and River Engineering laboratory, WRE, BUET. The flume was calibrated with respect to a rehbock weir placed at the tail end of the flume before the experiment was started.

Head-loss discharge relationship for different weight of flap has been developed. From the analysis it has been found the experimental result significantly differ from the theoretical results. To have good matching of the computed results with the theoretical results some modifications have been proposed. These modifications are proposed in contraction of co-efficient as well as in area computation. The proposed values of co-efficient of contractions are m2=0.70 and m4=1-0.20 cosj instead of m2=0.50-0.70 and m4=1-0.35 cosj respectively. In area computation A5=1.5 Avent is proposed instead of A5=2 Avent. The measured discharges were found to vary within the range of 12% to 23% than the theoretical discharges. But with the proposed modified equation discharge were found to vary within the range of 0.16% to 6.3%

 


 

Thesis Title

RAINFALL ESTIMATION OVER BANGLADESH USING SATELLITE DATA

 

Name of the Student

A. K. M. Saiful Islam

 

Supervisor /

Department

 

Dr. Md. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     December, 1999

 

Abstract

An attempt has been made to estimate rainfall in Bangladesh from GMS-5 data using Convective Stratiform Technique (CST) and these estimated rainfall was calibrated with the raingauge rainfall for all the Bangladesh Meteorological Department (BDM) raingauge stations located at different parts of the country. At first, rainfall and cloud characteristics were studied. It was found that the average lifetime of a single call cloud was about 12 hours while multi-cell cloud lasted about 18 hours. The speeds of the movement of clouds were found to be higher during developing stages than the mature stages and the movement of cloud usually followed the direction from south or southwest to northeast or east. The average correlation coefficient between raingauge rainfall and cloud top temperature was found –0.46.

Due to the lack of the suitable image processing software for GMS-WEFAX data, a number of computer programs have been developed for image processing and for CST analysis. All these programs were written in ‘C’ language, compatible in all MS-DOS / Windows based operating system and can run independently with little execution time and effort.

To adapt CST algorithm in Bangladesh region, some modifications were made on the calculating slope parameter, determining startiform threshold temperature and assignment of both convective and startiform rain rates. Due to the different data resolution for Bangladesh region,, the slope parameter of each convective core, k should be 0.167 and it should be calculated from six surrounding pixels. The value of x to determine stratiform threshold temperature varies between the range 5K to 7K for all the raingauge stations of the country. Convective rain rate 20 mm/h and stratiform rain rate 3.5mm/h were found best fit in this study. CST rainfall was calculated for the whole country and calibrated it with rainfall from all the BMD raingauge stations. It was found that CST rainfall had better agreement with raingauge rainfall than the previously calculated GMS-5 Precipitation Index (GPI) rainfall for Bangladesh. By CST method the deviation from raingauge was varied from 1.2mm to 15.2mm per day while by GPI method the deviation from raingauge was varied from 1.2mm to 15.2mm per day while by GPI method it was varied from 1.0mm to 22.5mm per which was over estimated.

Though, results obtained from this study looks satisfactory and encouraging, rainfall estimation always need long term database for verification, it may be recommended to continue research put into that direction. In future efforts, it is suggested to use radar data if possible to verify the assigned convective and stratiform rain rates.

 


 

Thesis Title

DETERMINATION OF METEOROLOGICAL DROUGHT INDEX FOR NORTH-WEST BANGLADESH

 

Name of the Student

Shyamal Kumar Datta

 

Supervisor /

Department

 

Dr. Muhammed Ali Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     September, 1997

 

Abstract

A drought represents shortage of water during a certain period which may cause adverse impacts to the affected area. This study deals with meteorological drought for the north-west region of Bangladesh. Meterological drought is defined as  the period in which rainfall is below the normal rainfall. The method applied provides a measure of rainfall deficit severeness relative to mean rainfall deficit for a given time series of a point rainfall station.

Rainfall is the only input to this study. Six rainfall stations have been selected on an arbitrary basis from the north-western region of Bangladesh. Rainfall record for the period of 1962-95 for these six stations is available without any missing. For this study rainfall data have been arranged on the fortnightly basis. The reason for choosing fortnightly basis is that irrigation requirement is usually calculated and applied on a 10-day basis but it has been assumed that paddy can sustain on the residual soil moisture for another 4 to 6 days without serious loss of  production. Merely by inspecting a rainfall record, it is always not possible to decide in which data a drought begins. Consequently a method have to be applied for deciding whether or not a fortnight of deficient rainfall constituted the onset of a drought. There are several methods of drought analysis exist in the literature. For this study, the analysis developed by Herbst et al. (1966) has been followed for the evaluation of drought. Based on this method, the date of onset and termination as well as duration of drought have been determined for the concerned rainfall stations. Index of drought severity and the weighted drought severity index have also been calculated for the given time series of each station.

It is apparent from the analysis that, there is neither distinct similarity in the date of onset and termination of drought among the stations in the region nor there is a similarity in the drought duration. From the analysis it is also observed for the six stations that the drought duration varies between 11.03 and 28.32 percent time to the time series (1962-95) at different number of spells of occurrences. The severe most drought index value is 2.13 that is obtained for the station Rangpur (R206) during the period 1978-79. the range of values for drought index vary between 0.56 and 2.13 and the weighted drought index between 4.92 and 126.65 for the stations concerned. Here the drought indices calculated enable the intensity of droughts to be compared irrespective of their seasonal occurrence, while the weighted drought indices obtained represent the extent of duration with intensity in the area.

 


 

Thesis Title

URBAN INFLUENCES ON SELECTED CLIMATIC PARAMETERS IN DHAKA METROPOLITAN AREA

 

Name of the Student

Md. Asaduzzaman

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     February, 1998

 

Abstract

In this study, efforts have been made to study the effect of urbanization on selected climatic parameters such as rainfall, surface temperature and atmospheric pressure for Dhaka metropolitan area. The development of Dhaka metropolis was very rapid between the 70’s and 90’s of this century. Dhaka city is often criticized as the city of unplanned growth, which if continued would have adverse effects on the environment and economy. An understanding of the changes in the magnitude of rainfall, surface temperature and atmospheric pressure due to increased urbanization is essential for proper land use planning and checking unplanned growth of metropolitan area. Mymensing and Tangail have been chosen together with Dhaka city to compare the changes of climatic parameters between less urban area and a highly urban area. The annual and seasonal data were studied for the period from 1953 to 1995 for Dhaka, 1951 to 1995 for Mymensing and 1962 to 1995 for Tangail. The data required for theis study are daily values of rainfall, maximum temperature, minimum temperature and atmospheric pressure.

Changing trends of summer, monsoon and annual data series of rainfall for Dhaka show different patterns from that of less urban area i.e. Mymenshingh and Tangail. Annual rainfall and monsoon rainfall of Dhaka does not show any significantly increasing or decreasing trend; only the pre-monsoon rainfall shows a linearly increasing trend. One day annual maximum rainfall and the number of monsoon rainy days for Dhaka exhibit a significantly decreasing trend. Whereas, these data series of rainfall for Mymensingh and Tangail show a significantly increasing trend. Coeficient of variation of mean monthly rainfall is less in Dhaka than the other two less urban stations. Significantly decreasing trend of coefficient of variation of annual rainfall for Dhaka and Tangail provides the evidence that the increase in the rainfall variability is occurring at a slower rate, and this rate of decreasing tendency is more in Dhaka than Tangail. The decreasing trend of coefficient of variation of annual rainfall for Mymensingh is not significant.

Surface temperature in Dhaka, a rapidly growing urban area, exhibits an increasing trend during the last two to three decades compared to less urban area. Significant urban heating effects have apparently taken place in Dhaka, as urban-affected temperature increase of 0.75°C to 1.15°C over 43-year period have been found in this study. In contrast, temperature for less urban area, showed decreasing trend over this period. The urban warning appears to be predominant in minimum temperature displaying considerately more increase than maximum temperature. Increasing annual mean temperature in Dhaka indicates that the greatest contribution to the warming of the mean temperature is due to the increase in minimum temperature. One day annual maximum and minimum temperatures of Dhaka increase by about 1.15°C and 2.4°C, respectively over the 43 year period; while Mymensingh showing a small downward trend exhibits the characteristics of a non-urban area. It appears from this study that change in temperature i.e. urban warming is taking place in Dhaka.

Average annual atmospheric pressure of Dhaka and Mymensingh are 1007.7 mb and 1008.5 mb respectively. Annual atmospheric pressure of above stations exhibit year to year variation. A significantly increasing change in annual average atmospheric pressure has been found in Dhaka, but not in Mymensingh.

 


 

Thesis Title

ANALYSIS OF THE BEACH MATERIALS AT THE KUAKATA COAST

 

Name of the Student

Md. Matiur Rahman

 

Supervisor /

Department

 

Dr. M. K. Alam

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1999

 

Abstract

The Kuakata beach is about 19.5 km long and lies between the latitudes 21°45¢N and 21°55¢N and longitudes 90°15¢E and 90°15¢E. The beach extends between the Nilgonj river confluence at the extreme west and the dead portion of Gangamati khal confluence at the east. The coast is covered mostly by dense plantation to the northward whereas to the south it is directly exposed to the Bay of Bengal.

A reconnaissance survey was made and eleven nos. of stations at an interval of 2.0km along the length were selected for collecting beach material samples from the surface, at 0.6m and 1.0m depth. The location of the stations were fixed by a Nav 1000 Pro Global Position Survey (GPS). Bed and bank samples from Nilgonj river and Gangamati khal were also collected. Total one hundred five samples, each 2 kg in weight were collected by hand scrapping and were preserved in the plastic bags and carried to Hydraulics and River Engineering Laboratory in BUET for necessary analysis.

The 1st field trip for survey works of this study started on 8th June 1999 and continued till 13th June 1999. A team consisting of four members equipped with GPS receiver, leveling instrument etc. worked to do the necessary leveling works across the beach at different stations. Preliminary analysis of the data collection were then done and it was felt necessary to collect few more field data to close the gap in the earlier data collection programme. A 2nd field trip was therefore made between 25th and 29th September 1999.

Tke Kuakata beach has no definite trend of shape. The beach surface elevation increases @ 1:10,900 from Nilgonj confluence (ch. 0.00km) at the west upto 8.00 km at the east. The beach elevation then decreases @ 1:3,400 upto chainage 10.00 km at station 6. The part between ch. 12.00 km and ch. 16.00 km is more and less the same and the profile takes the form of a trough shaped between ch. 16.00km and ch. 1950 (Dead portion of Gangamati khal confluence at the east).

The Kuakata Coast is wider and the beach slope lies between 1:19 and 1:66 (vertical to horizontal). The beach slope within the fore3shore zone has minimum value (1:66) at station 11(ch.19.50km) where the beach is flattest and maximum value (1:19) at station 4 (ch. 6.00km). The beach slopes at stations 1 and 2 (ch. 0.00km and ch. 2.00km) are the same and also at stations 3 and 6 (ch. 4.00 km and ch. 10.00) are more and less the same.

The grain size distribution curves were plotted and the sorting characteristics of the sand were studied both along and across the beach. The beach sands are dominated by fine sand with a trace of medium sand and fine-grained materials (slit and clay). Coarse sand is absent from the whole beach. There is no trend of variation of surface particle sizes across the beach profile and the mean diameter (d50) can be considered around 0.20mm all throughout the beach. The trend is same both at 0.6m and 1.0m depth from the surface. However, a trend of decrease of particle size, it is noticeable that the particle size in the western side is slightly coarser than the eastern side.

A comparison of the result has been made with the earlier studies of the Cox’s Bazar-Teknaf Coast. It has been found that the mean diameter (d50) of the beach materials of Kuakata Coast has the similarity with those of 10km coastline portion at the extreme south at Teknaf along the Cox’s bazaar-Teknnaf Coast. But Cox’s Bazar-Teknaf beach sand is finer than the Kuakata beach sand. An interesting similarity was also found in the wave breaking phenomena for both the coasts, which is of spilling type.

Finally recommendations have been made for further studies.

 


 

Thesis Title

STOCHASTIC ANALYSIS OF DEFICIENCY OF CROP WATER REQUIREMENT UNDER RAINFED CONDITION IN BOGRA AND RANGPUR AREAS

 

Name of the Student

Shyamal Kumar Bhattacharyya

 

Supervisor /

Department

 

Dr. Muhammed A. Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc.  Engg.    February, 1999

 

Abstract

The study involves with finding out crop water requirement (CWR) and characterization of stochastic behavior of surplus and deficiency of crop water requirements. Crop water requirement is calculated by CROPWAT, a computer software released in 1991 by agriculture division of FAO. Availability of crop water requirement (ACWR) is obtained by subtracting CWR from rainfall. Deficit or negative values are termed as deficiency of crop water requirement (DCWR) and positive values are simple termed as surplus. Deficiency of crop water requirement is related to drought, the main concern of this study. Study has also been logically focused on surplus of crop water requirement. On the basis of theory of runs and direct enumeration technique a general method is presented herein to interpret the surplus and deficiency of crop water requirements characteristics in periodic stochastic process. The methodology developed has been applied to some hypothetical and observed (actual) ACWR sequences at north-western zone of Bangladesh.

Monthly climatic data (temperature, wind speed, humidity, bright sunshine hour) and rainfall record of two stations (Rangpur and Bogra) in the north west region of Bangladesh are used here. The analysis has been performed for 32 years. A number of functional truncation levels (normal, median, 40th and 60th  percentile of five-day availability of crop water requirement) have been assumed here to form positive and negative deviations. The periodic stochastic process with enumeration technique has shown good relationship between observed and simulated expected deficit durations for truncation level at median values, while no good relation for any of truncation levels has been found for surplus duration. Assuming ACWR speels are persistent or independent in nature, Markov (order 1) and random process respectively, under the theory of runs are modeled by using Poisson probability density function of the occurrence of spells, coupled with geometric distribution for the length of speels, and the Weibul, normal, lognormal, Gumble and exponential distributions for the deficit and surplus sums of respective ACWR spells. It is found that, longest period of deficit is better predicted by Markov model while longest surplus period with random model gives better performance. Random model appears comparatively good for surplus-sum and surplus spell because of its less persistence nature than deficit. For truncation level at normal values, deficit-sum and surplus-sum can best be obtained by Markov-Weibul model and random-Weibul model respectively. No good relationship has been found between observed and simulated ACWR spells and their respective spell-sums for truncation level at median values. Under the above application of the periodic stochastic models, it has been found that the two stations from northwest Bangladesh have very similar surplus and deficit (drought) spells characteristics.

 

 


 

Thesis Title

ANALYSIS OF RAINFALL CHARACTERISTICS OF NORTHEAST REGION OF BANGLADESH

 

Name of the Student

Md. Abdur Rauf

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1997

 

Abstract

The aim of this study is to summarise the changing behaviour of rainfall in space and time over the northeast region of Bangladesh. During the study various rainfall parameters were investigated and mathematical relationships were established.

Updated  isohyetal maps of mean monthly, monsoon (June-September) and annual rainfall were constructed for the study region. Spatial distribution of mean monthly, monsoon and annual number of rainy days were investigated. Normal monsoon rainfall of selected 32 stations within the region have been estimated and normal annual rainfall chart has been updated. Temporal variability of rainfall and unmber of rainy days over the region has been investigated. Moving average and percent departure of rainfall for every year with reference to the normal rainfall were worked out for this purpose.

Attempts were made to establish mathematical relationships between number of rainy days and monsoon rainfall total and between mean daily rainfall intensity and monsoon rainfall total. Various forms of equations were examined. Analytical  probability distributions were fitted to 1-, 2-, 3-, 5-, 7- and 10-day maximum rainfall values. Normal, lognormal and Gumbel (EV1) distributions were examined and all of them were found good for maximum rainfall values. Gumbel distribution was found to be better. Pattern of Gumbel parameters over the region for 1-,3-,5-, and 7-day maximum rainfall were presented on the base maps. Binomial and Poisson discrete probability models were tested to monsoon and annual number of rainy days. Normal approximation to Poisson distribution was found suitable to describe monsoon and annual number of rainy days.

HYMOS (HYdrological Modeling System), developed at Delft Hydraulics, the Netherlands, has been extensively used for probability distribution and other analysis in performing the study.

 


 

Thesis Title

COMPUTATION OF RUNOFF IN THE JAMUNESWARI RIVER BASIN OF NORTH-WEST BANGLADESH

 

Name of the Student

Md. Hasan Ali

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     March, 2001

 

Abstract

A study has been conducted for computation of runoff in the Jamuneswari basin located in the North West Region of Bangladesh. The basin is a moderate size of approx. 1055.77km2 drainage are. The main river systems of the basin are the Jamuneswary channel of about 123 km length and its two tributaries, the Burikhora Chikly in the west of about 41 km length and the Bullai in the east of about 41 km channel length.

In conducting the study data on landuse, soil, climate, digital elevation model, infrastructures, river systems, hydro-climatic gage locations, long term flow, water level river cross sections and other model results were collected from relevant organizations within the country.

To fulfill the objectives of the study hydrologic modeling tools was used like HEC-HMS (version 2.0) that have functionality of simulation hydrographs at any components of a hydrologic basin. The Geographic Information System (GIS) tools e.g Arc/Info 7.2. and Spatial Analyst of ArcView 3.1 having grid based hydrologic analysis functionality of any watershed was also used in analyzing spatial data and to provide inputs to the HEC-HMS model.

The hydrologic processes and complexity was investigated, analyzing flow data, climatic data, soils permeability, landuse and land cover data. The spatial variability of runoff potentials of the area was also studied and thus hydrological behavior of the basin was clearly understood. It shows that the basin has moderate to high runoff potentials with very quick runoff peaks and therefore the basin is highly responsive to the heavy shower.

In the study GIS techniques for stream delineation, sub-catchments/watershed delineation and computation of hydrologic modeling parameters (e.g. SCS curve number-CN, Muskingum K and X etc.) were used. A best method among the options in ArcView (spatial analyst) to create an accurate DEM (digital elevation model) surface from the raw point observed data was also investigated. The computed hydrologic modeling parameters were written to HEC-HMS compatible file format. The hydrologic model developed under HEC-HMS to compute runoff uses a basin model for SCS unit hydrograph transformation, SCS Loss method, Muskingum channel routing method and theissen polygon weight method to account rainfall distribution. The minimum slope method of baseflow separation was implemented in the modeling. Model results were compared with the observed runoff and also with the NAM (a part of MIKE 11 software) result. Some of the model parameters were further investigated and re-build the model.

The study proved the usefulness of DEM data to delineate streams, ephemerals rivers, channels, creeks etc. for hydrological modeling. The DEM should be accurate and at representable scale for the area.

The study showed the usefulness of LANDSAT TM image to obtain landuse classification for SCS-CN value calculation for hydrologic modeling specially for the SCS loss rate method.

An interface between GIS and HEC-HMs developed and implemented in the study to create a comprehensive HEC-HMS model for the study basin. The interface was quite successful with the SCS-unit hydrograph, SCS-Transformation, thiessen polygon meteorological model and Muskingum River routing options. The model result shows reasonable fit with the observed data in the early monsoon period and a relatively poor fit in the monsoon period. This reflects re-investigation of some of the model parameters that were assumed due to non-availability of data e.g. overland flow velocity, velocity in the streams, evaporation loss and antecedent moisture condition to compute CN value.

Finally recommendations were put forward for further study.

 


 

Thesis Title

APPLICATION OF MACCORMACK SCHEME TO THE STUDY OF AGGRADATION-DEGRADATION IN ALLUVIAL CHANNELS

 

Name of the Student

Md. Mahbub Alam

 

Supervisor /

Department

 

Co-Supervisor/

Department

 

Dr. Md. Ali Bhuiyan

Professor

Department of Water Resources Engineering, BUET, Dhaka

Dr. M. R. Kabir

Associate Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     July, 1998

 

Abstract

Aggradation and degradation are ubiquitous phenomena that occur in most alluvial channels. The complete Saint Venant equations describe the unsteady onen channel flow conditions. The continuity equation for the conservation of sediment mass needs to be solve along with the hydrodynamic equations to determine aggradation and/or degradation of channel bottom. In these viewpoints, a one-dimensional mathematical model has been developed that computes the aggradation-degradation of channel bed. The MacCormack explicit finite difference scheme has been used in the model. This scheme is second-order accurate, handles shocks and discontinuities in the solution without any special tratment, and allows simultaneous solution of the water and sediment equations, thereby obviating the need for iterations.

The developed model has been applied to two different case studies. The first case is a laboratory investigation where experimental results were obtained due to imposing extra sediment load. The sediment overloading produces aggradation in the channel. It has been found that the model simulates most of the test runs with a reasonable accuracy.

In order to verify the ability of the model to real field situation, it has been applied to simulate Jamuna river reach from Bahadurabad to Sirajgang. A test run for three years has been done using field data for that period. The agreement between the computed results and measured data is quite satisfactory.

The successful application of the model strongly demonstrates that the model is valid in solving unsteady open channel flow problems in conjunction with sediment transport. The different problems just require incorporating the appropriate initial and boundary conditions.

 


 

Thesis Title

LOW-FLOW CRITERIA FOR WATER QUALITY STANDARDS FOR SELECTED RIVERS

 

Name of the Student

Md. Matiur Rahman

 

Supervisor /

Department

 

Dr. M. Fazlul Bari

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 2000

 

Abstract

Low flow quantiles are commonly used to describe stream characteristics and are used for establishing water quality standards. The objective of this study is to investigate the surface water quality in terms of parameter concentrations and specified standards as wellas to develop low flow criteria for water quality standards. Water quality and stream flow data for Brahmaputra at Bahdurabad, Surma at Sylhet and Karotoa at Panchagahr were collected and analyzed. The Department of Environment collects surfacw water quality samples without any information and reference to the water discharge values at the time of sampling.

Analyses performed in this study began with obtaining concurrent discharge values form BWDB database for the dates on which water quality data were available. To gain an insight of the discharge-water quality relationships, first the variation of water quality parameter concentrations with discharge was investigated by visual inspection of plots and linear regression. For comparison, water quality standards for irrigation use, fish culture and drinking water were superimposed on these plots. In case of Brahmaputra river measured BOD concentrations exceeded both the drinking water and fish culture standard, whereas for Surma river about a half of the measured values exceeded the standard, and for Karotoa river concentrations were found to be below the standards for all uses. Plots for DO and pH showed that their amounts were well above the standard values for all of the three rivers. All measured concentrations of coliform in Brahmaputra exceeded the drinking water standard, several values exceeded irrigation standard, and fish standard was generally met. It is seen that the discharge water-quality plots showed substantial scatter although a decreasing trend in parameter is expected with increasing discharge. It may be due to the fact that all the available water might not serve to dilute the polluting substances. In rivers it is not uncommon for waste effluents to remain segregated along a shore line for many miles below the outfall. Regression equations relating water quality with discharge were not found to be useful in predicting parameter concentration as a function of discharge in term of such criteria as correlation coefficients and other test statistics.

One of the critical elements of any water quality standard is the low-flow criterion to be applied. Usually low flows corresponding to 7-day, 10-year return period or 10-day, 25-year return is used. These flow values were computed using best-fit probability distributions. Then to assess the exceedence probabilities of 7Q10 and 10Q25 flow values, flow duration curves were obtained for each of 7-day and 10-day annual low flow series. Computed 7Q10 and 10Q25 flows were found to exceed 99.99 percent of the time. Estimates of such exceedence probabilities provide guidance in setting level of effluent treatment required for protection of water quality. For example if the 7-day, 10yr flow is equaled or exceeded 99% of the time of a given river, it would be required to provide effluent treatment which should be adequate 99% of the time.

 


 

Thesis Title

SUBSURFACE AERATION OF GROUND WATER FOR THE DEVELOPMENT OF LOW COST IRON REMOVAL DEVICE

 

Name of the Student

Sayed Ashraf Mahmud

 

Supervisor /

Department

 

Dr. Abdul Hannan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     October, 1999

 

Abstract

The relative purity and abundance of ground water increase it’s usage. In some places the iron content in ground water is so high that this metal must be removed before water can be used for drinking or industrial purposes. Iron occurs in two states of oxidation in nature the ferrous (divalent) and ferric (trivalent) forms.

The subsurface aeration technology developed oxidizes the ferrous ion, which is soluble in water, to the ferric ion, which is insoluble before it comes to the treatment unit for further action and separation. This method achieves a high degree of oxidation in the ground water during it’s lifting. An airlift pump is employed in the tube well instead of turbine or submersible pumps. Air is forced down into the well under water and an air-water mixture is build up which has a lower density and thus come out of the well. The mixture obviously becomes enriched with oxygen.

The air compressor used in an air lift pump serves at least four pruposes-lifting of water, aeration of water; regeneration of encrusted tube well and frequent cleaning of iron sludge from the interstices of the course media flocculator in the flocculation chamber. The encrustation of tube well strainer develop higher draw down, causes failure of shallow tube well and hand pump tube well. The regeneration is necessary for the encrusted tube wells for ensuring required discharge resulting energy saving- thus the operating cost. On the other hand regeneration of flocculators increases the efficiency of the coarse media bed.

The unit cost of production of treated water in the subsurface aeration technology has been found to be Tk. 1.20/m3 while those of DPHE urban water supply is Tk. 1.81/m3, calculated assuming 15% discount factor, in areas where ground water had higher Iron content (Fe>5ppm).

The dose of sodium Hexa-metaphosphare for the regeneration iron encrusted tube well has been calculated and has been found to be suitable for the use in regeneration work supported by air surging from the air compressor.

The process of precipitation of iron in the aquifer has only a slight affect on aquifer permeability. The clogging of aquifer surrounding the well will not occur for a period many times longer than the life span of a typical well.

 

 


 

Thesis Title

EXPERIMENTAL STUDY OF LAUNCHING APRON AROUND ABUTMENT

 

Name of the Student

K. M. Salzar Hossain

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2001

 

Abstract

An investigation was undertaken to study the behaviour of launching apron in a straight rectangular laboratory channel. Since launching apron is a counter measure adopted to limit scour in sand bed around some structure, initially the investigation was incorporated on local scour study. The scouring information obtained during the scour study was used for designing launching apron. Then the behaviour of launching apron was studied. The study was made under clear-water condition and channel bed formed ripples during test runs. The hydralic parameters were set so that the flow is close to the critical condition of sediment transport that is clear water condition.

For scour study, three vertical-wall and three sloping –wall abutments were used. Vertical-wall abutments were made of half-inch thick particleboards and sloping-wall abutments were made of metal. Around these structures, the scour depth, scour contour and scour pattern were observed. Each test was run for 7 hours and 30 minutes. This test running time was selected based on the limitation of laboratory pump and in an attempt to reach equilibrium stage. Results were compared with some existing prediction-methods and data. It was found that in the case of vertical-wall structures results were comparable with existing prediction methods and data of ther investigators. However, in case of sloping-wall structures, the existing prediction methods consider the sloping face of structures to be extended beyond the maximum scour level. Where as, structures that were used during present study, had their sloping face extended up to initial bed level only. From the initial bed level, the structures had vertical faces. Thus, the existing formulae might not be able to predict the scour depth around those structures. Therefore, for this type of structures probably new shape factors or slope factors need to be found out.

After the scour study, one vertical-wall abutment was selected for apron study. Apron was laid around that abutment in six different settings. During the apron study also each test was run for 7 hours and 30 minutes to maintain uniformity among the tests. It was found that, when apron material was laid around a structure, the apron behaved like a submerged extension of the original structure. The effect of the submerged extension was found to be quite significant in scour formation and in vertical velocity distribution within the scour hole formed.

It was also found from vertical velocity distribution within the scour hole at maximum scour depth location that, the laid apron material around the structure also deflected water flow in addition to the structure itself in a significant way in a laboratory channel. Therefore, it seemed that launching apron was protecting the structure in two ways―one was by forming a protective layer on the sloping face of the developed scour hole and the other was by forcing the scour hole to be formed away from the structure.

Finally, recommendations were put forward for further extension of this study.

 


 

Thesis Title

A STUDY OF FLOATING PUMP IRRIGATION IN BANGLADESH

 

Name of the Student

Md. Ferdousur Rahman

 

Supervisor /

Department

 

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     June, 1997

 

Abstract

Irrigation by floating pumps has been practiced in Bangladesh since 1961-62. A pilot project comprising twenty-six floating pump was taken up in 1988-89. Until 1990-91 the responsibilities of commissioning, operation and maintenance of pumping unit including construction of channel upto secondary level lied with Bangladesh Agricultural Development Corporation (BADC). Farmers was charged a specific water rate per unit area. Subsequently, the beneficiaries participation were encouraged and the responsibilities of operation and maintenance of pumping unit and construction of field channels were transferred to farmers group. BADC looks after seasonal maintenance and provided necessary mechanic and operator services. It also monitors the performances of schemes. Farmers group pay service charges for floating pumps.

This study has been undertaken to conduct a time series analysis of the performance parameters and assess the impact of change in management. A case study was also carried out on six selected schemes to get an insight into the operation and maintenance issues at the field level. Four parameters namely area irrigated, irrigation cost, number of farmers benefited, and yield have been chosen to assess the impact.

The time series analysis indicated that the area irrigated per unit of discharge increased by 92% and the irrigation cost per hectare decreased by 12% due to change in management. Under the changed management floating pumps were operated by the scheme managers who tried to maximize the use of facilities. The total number of direct beneficiaries were found to be increase but the number of farmers benefited per hectare was decreased by 9%. This is because the same farmers increased this irrigated area under changed management. The yield was found to be increased by 9% which may be attributed to improved water management. The results of case study indicated that the two tier i.e. Central Level and Block Level management systems exists in each of the six schemes. So, the overall management of scheme was shared by two levels. It improved the services to the farmers. However, the farmers have been reported to be deprived because they had to pay 2 to 4 times higher irrigation charges to scheme managers. Profit is shared among the members of Central Management Committee resulting in the emergence of local level waterloards.

 


 

Thesis Title

HYDRAULIC EVALUATION OF CONVENTIONAL AND MODIFIED TUBEWELLS IN BARIND PROJECT

 

Name of the Student

Md. Asaduzzaman

 

Supervisor /

Department

 

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     August, 1999

 

Abstract

Barind in north-west Bangladesh is the land where surface water is very limited. So groundwater exploitation for irrigation is being practiced for the last 24 years through deep tubewells (DTW). At present more than 6300 DTWs are operating in the Barind area. But in some locations, it was observed that DTW discharge was below the acceptable limit 91.20 cusec). In order to overcome this difficulty an innovative well design involving four screens projecting upward was developed an implemented. This study was taken up to compare the performance of conventional wells with that of the modified wells.

For this study 10 conventional and 10 modified wells were selected considering lithological condition, well construction and range of discharges. Analysis of the step drawdown test data was done to compare the performance of modified wells with that of the conventional wells. Five parameters namely specific capacity, screen entrance velocity, well loss, well efficiency and well deterioration index were chosen to assess the performance of the wells. The performance of wells in respect of specific capacity could be significantly improved (24%) through design modification. In modified design, use of longer screen and increased well radius made the entrance velocity lower than the conventional wells but this modification seem not to be cost-effective as the entrance velocity was found to be lower than the recommended value of 3cm/sec. The values obtained for well loss could be reduced and also the well efficiency could be improved through modification of design. Also the values of well deterioration index was calculated and it was found that the well have been moderately deteriorated irrespective of its design.

Also the hydraulics of the modified wells was considered and it was found that the main reason for the improved performance was that the wells had their screens at shallow depth, which reduced the vertical component of flow thereby reduced the drawdown.

 A numerical model was used to gain an understanding of the effect of design modification on well performance. Results of numerical model simulations indicate that the drawdown at both the abstraction as well as observation wells were considerably less for modified design. This supports the idea that the drawdowns are reduced due to reduction in vertical component of flow.

 


 

Thesis Title

WATER BALANCE STUDY AND PERFORMANCE EVALUATION OF A LIFT IRRIGATION SYSTEM

 

Name of the Student

A. K. M. Badrul Alam

 

Supervisor /

Department

 

Dr. M. Mirjahan

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc. Engg.     January, 2000

 

Abstract

Chandpur Irrigation Project (CIP) is one of the successful irrigation projects of Bangladesh Water Development Board. Although the project has abundant sources of irrigation water, the desired benefit of irrigation has not been achieved, possibly due to absence of improved management and technology, lack of farmer’s awareness and inadequate infrastructure facilities. This study has been performed to estimate demand and compare it with the irrigation water supply and to evaluate the system performance in terms of water balance parameters. Water balance study and performance evaluation was performed for irrigation seasons of 1996 and 1998. The inputs (Irrigation water supply and rainfall), outputs (Crop water use and percolation losses) and storage change were calculated for each 10-day period.

Irrigation water supply was calculated from the combined discharge and the operating hours as recorded in the logbook. Seepage and percolation from rice field and canal network was considered for this study. The former was taken as 2.5 mm/day and later one was calculated by an assumed value based on global average value of conveyance loss. Crop water requirement was computed using CROPWAT software developed by FAP. Required crop data and climatic data were collected from Department of Agriculture Extension and Bangladesh Meteorological Department respectively Effective rainfall was calculated by USDA soil conservation service method.

The results show that water deficiency occurred in 3 decades out of 10 in 1996 and in 2 decades ot of 11. Irrigation water supply situation was more adequate in the irrigation season of 1998 compared to 1996. Seasonal average value of Relative Water Supply was found to be 1.21 in 1996 and 1.08 in 1998. Seasonal Project Efficiency was computed as 62.0% in 1996 and 64% in 1998. On the other hand Water Delivery Performance was computed as 60.9% in 1996 and 48.0% in 1998.

In the irrigation season of 1998 substantial improvement of project performance in terms of water adequacy and efficiency was observed which might be due to the rehabilitation works carried out by the project authority of CIP in 1997.

 


 

Thesis Title

PERFORMANCE EVALUATION OF SOME SELECTED DEEP AND SHALLOW TUBEWELLS IN IRRIGATION DEVELOPMENT

 

Name of the Student

Mohammad Shahjahan Mondal

 

Supervisor /

Department

 

Co-Supervisor /

Department

Dr. Abul Fazal M. Saleh

Professor

Department of Water Resources Engineering, BUET, Dhaka

Dr. M. Mirjahan

Professor

Department of Water Resources Engineeing

 

Degree and Year of Published

 

M. Sc. Engg.     March, 2000

 

Abstract

Performance evaluation of five Deep Tubewells (DTWs) and ten Shallow Tubewells (STWs) of Rajbari district has been carried out in the present study. The broad objective of the study was to evaluate the performance of these schemes using some selected standard indicators. The performance indicators used in this evaluation have been broadly classified into three groups: hydraulic indicators, agricultural indicators and socio-economic indicators. For the quantitative assessment of the hydraulic indicators, field measurements were taken during 1998-99 Boro season. Questionnaire survey of farmers and pump owners was carried out for the quantitative as well as qualitative assessments of agricultural and socio-economic indicators.

Results of the analyses show that delivery performance ratio of DTWs is 0.93 and that of STWs is 1.21. The average discharges of both DTWs and STWs (53 1/s and 17 1/s, respectively) were greater than the respective national averages (46 1/s and 12 /1s). the average STW discharge was even greater than the target discharge (14 1/s) as most of the STW owners used strainers of larger diameter (greater than 10 cm) and motors/segines of higher capacity (greater than 6.0 bhp). DTWs and STWs have water delivery performance of 0.85 and 0.98, respectively. Though the seasonal operating hours of both DTWs and STWs (1127 hours and 1054 hours, respectively) were below their respective national average (1223 hours and 1216 hours, respectively), yet the actual command areas (23.7 ha and 6.04 ha, respectively) were above the respective national average command areas (23.1 ha and 4.3 ha, respectively). This has happened because the actual volumes of abstraction, 213838 m3 for DTWs and 60360 m3 for STWs, were more than the national average by 5.6% and 13%, respectively.

No relationship was found between pump discharge and command area. But, a good correlation was found to exist between the volume of water lifted and the command area (r2 is 0.96 for DTW and 0.90 for STW). The slope of the regression line (command area versus volume) for DTWs was found to be 1.5 times of STWs. This indicates that’s increase in command area per unit increase in volume of water withdrawl was more for DTWs compared to STWs.

In the unlined portion of the DTW canal, the average conveyance loss was 6.5 m/day and it was 1.4 m/day for the lined portion. In STWs which are unlined, the average conveyance loss was 4.1 m/day. In the present study area, irrigation canal density (45.23 m/ha and 55.13 m/ha in DTW and STW schemes, respectively) was very low compared to past studies. The average land preparation requirement was found to be 108mm in the present study compared to around 200  mm of past studies. The seepage and percolation losses in the farmers’ fileds of the study area were found to be 5.3 mm/day.

Dependability of water deliveries of STW and DTW schemes (0.85 and 0.79, respectively) was satisfactory during 1998-99 Boro season. For STWs, significant improvement has occurred in the utilization of irrigation water per Boro season in the present study are (999mm) over national average 1222mm). But for DTWs, this has remained near the national average (902 mm in the present study versus 877 mm, the national average). Equity in water delivery, was not ensured in both DTW and STW schemes. Inadequacy in lengths, maintenance and sections of irrigation canals, frequent power disruptions and presence of non-irrigated and non-rice fields, enen fallow lands, around project periphery were mainly responsible for this lower equity.

Agricultural performance, evaluated in terms of irrigated area performance (0.79 and 0.76 for DTWs and STWs, respectively), yield performance (1.16 for both DTWs and STWs) and production performance (0.92 and 0.87 for DTWs and STWs, respectively), was almost the same for both DTW and STW schemes and was greater than the national averages. The average yields during Boro season. Total financial viability of DTW and STW schemes (3.23 and 3.61, respectively) was quite high during 1998-99 Boro season, But, the profitability of farmers was 1.06 and 1.05 for DTWs and STWs, respectively during the same period. Fee collection performance was exactly 100%.

Further improvement of irrigation performance of the STWs and DTWs of the study area is possible by increasing pump operating hours and irrigation canal density, adequate sectioning of irrigation canals, timely cleaning of vegetation, closing of rat holes, cracks, etc. Performance of STWs can be further improved by reducing the present level of water utilization (999 mm) to that of DTWs (902mm). Supply of irrigation water for land preparation should be matched with farmers’ demand to ensure higher yield, higher price, early and risk free harvesting, etc. Average irrigation water charge, which is much higher in the study area compared to other irrigation projects, is to be decreased to distribute benefit of irrigation equally between scheme farmers and pump owners.

 


 

Thesis Title

A STUDY OF AGGRADATION AND DEGRADATION OF THE KHOWAI RIVER

 

Name of the Student

Tarek Bin Hossain

 

Supervisor /

Department

 

Dr. M. Monowar Hossain

Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Degree and Year of Published

 

M. Sc.  Engg.    August, 1997

 

Abstract

The study was conducted to investigate the aggradation and degradation of the Khowai River bed. Assessment of future sedimentation along the Khowai river was also carried out. The reach extends from Ballah to the confluence of Khowai-Dhaleswari River and has an overall length of 87km. To carry out the investigations 39 sections of the Khowai River from Ballah to the Khowai-Dhaleswari confluence for the year 1988, 17 cross sections from Shaistagang to  Khowai-Dhaleswari confluence for the year 1988, 17 cross sections form Shaistaganj to Khowai-Dhaleswari confluence for the year 1994 and a thalweg profile for the year 1965 were collected in the digitized form from FAP-6. Data on suspended sediment concentrations at the Shaistaganj station between years 1964 and 1993 were also collected from River Research Institute (RRI), Faridpur. Mean daily water levels for the gauge stations at Ballah, Chunarughat, Shaistaganj and Habiganj form 1964 to 1994 and mean daily discharges at Shaistaganj station for the same years were collected from Surface Water Modelling Centre (SWMC). Bed material gradation curves for the year 1992 at Chunarughat gauge, Shaistaganj gauge, Habiganj gauge and downstream of Habiganj gauge were collected from FAP-6. Suspended sediment particle size distribution curves for the year 1991 and 1992 at Shaistaganj were collected from SWMC.

Cross-sectional properties at 17 locations between Shaistaganj and the Khowai-Dhaleswari confluence between years 1988 and 1994 were analyzed and it was observed that the river between the reach is becaming narrower and the average thalweg level has degraded by 1.29m between Shaistaganj and 6.6 km downstream of Habiganj. The total reach of this degreded thalweg is about 21km in length. After that up to the confluence of Khowai and Dhaleswari river the average thalweg level has again suffered degradation by 2.03 m on an average during the study period. The cross sectional area at bankfull stage is beign increased at the rate of 10.1 m2 per year since 1988. It was also observed that in most of the occasions the cross sectional area above banjfull stage has reduced indicating deposition of sediment on the berms and flood plain on both sides of the river. The overall cross section of the 23.44 km reach below Shaistaganj is being reduced at the rate of 14.48 m2 per year since 1988.

It was also observed from the analysis of the water level records between years 1964 and 1994 that Khowai river bed level is being aggraded at the gauge stations at Ballah, Chunarughat, Shaistaganj and Habiganj by 0.96m, 0.2m, over 1 m, and 1.5 m respectively since 1964.

Study on the thalweg profiles between years 1965 and 1988 suggested that the Khowai River has aggraded by 1 m between Ballah and Chaunarughat and degraded by 1 m between Chunarughat and Shaistaganj. Mean bed level profiles of 1988 and 1994 suggested average aggradation by 0.4 m between Shaistaganj and 6.6 km downstream of Habiganj. After that up to the end of the river i.e. the confluence of Khowai and Dhaleswari River it suffered degradation by 0.5m. the mean bed level profile of 1994 showed a scour hole due to the loop cut made by BWDB in the year 1992 at 9 km downstream of Habiganj.

Analysis of bed material curves and suspended sediment particle sixe distribution curves based on Einstein’s theory suggested that the inflowing sediment load at Shaistaganj stations consisted of 30% coarser fraction of the suspended load and 70% wash load.

Future prediction on the Khowai River sedimentation was made using HEC-6 based on channel geometry of 1988. The study revealed that there would be continued deposition of sediment indicating continued aggradation of the bed level along the study reach of the river.

 


 

Thesis Title

A STUDY OF FLOW CHARACTERISTICS IN A COMPOUND CHANNEL

 

Name of the Student

Md. Sabbir Mostafa Khan

 

Degree and Year of Published

 

M. Sc.  August, 1999

Supervisor

Department

Dr. M. R. Kabir

Associate Professor

Department of Water Resources Engineering, BUET, Dhaka

 

Abstract

The flow characteristics in a compound channel, with the faster flowing main river and slower moving flood plain, is very complex and inadequately understood. The present thesis consists of two parts―development of a 1-D steady uniform flow numerical model and experimental verification.

The governing equation of the 1-D steady uniform flow model is obtained from the general continuity and momentum equation. The the governing equation is converted into finite difference equations. The solution technique considers total symmetry for the compound section. Because of the difficulty in obtaining sufficiently accurate and comprehensive field measurements of velocity and shear stress in compound channels under unsteady and non-uniform flow conditions, considerable reliance must still be placed on well focused laboratory experiments under steady and uniform flow conditions. The experimental set-up cosists of a symmetrical compound section with fixed bed slope. The width of the flood plain is varied. Then for the widest flood plain, the roughness in the flood plain is varied by introducing artificial roughness strips.

The total discharge increases with the increase in depth and width of the compound section. The model discharge overestimates the experimental discharge for higher depths of flow and underestimates for lower depths of flow. The discharge decreases with the increase of flood plain roughness for the same depth ratio. Discharge in both the flood plain and main channel decreases with the increase in flood plain roughness. Due to the lateral transfer of longitudinal momentum, the point velocities, in a vertical at the main channel, increase form the bed upto some level and then decrease continuously until the water surface is reached. The channel bed shear stress decreases from a maximum value at the mid section towards a minimum value at the wall of the flood plain. Further studies will help in better understanding of the phenomena with 2-D or 3-D unsteady numerical models.