Dissertations/Theses - Department of Water Resources Engineering
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Item Optimal water application decisions with deficit irrigation(Department of Water Resources Engineering, BUET, 2004-12) Shirazul Islam, Md.; Fazlul Bari, Dr. M.A linear programming based optimization model was developed for tubewell irrigation system in the high Barind tract area of Bangladesh to maximize profit for wheat and Boro rice from the available land and water supply. The study area comprises four thanas, viz. Tanore of Rajshahi district, Nachole and Gomstapur thanas of Chapai Nawabgonj district and Niamatpur thana ofNaogaon district. The area is within a deep tubewell irrigation project and the available land area for irrigation is about 90660 ha. There are 1463 deep tubewells in the study area and the design capacity of each tubewell is about 56 litre per second. Available water for irrigation from 1463 tubewells in the area ranges from 13355 to 14786 ha.m at design discharge during the irrigation season from November to May assuming 16 operating hours a day. At 80% and 60% of design discharge, the water availability varies from 10684 to 11829 ha.m and 8013 to 8871 ha.m, respectively over the irrigation season. Irrigation equalling full crop water requirement and 10, 20, 30, and 40 percent deficit crop water requirement along with 20, 50 and 80 percent dependable rainfall were considered in the model. Deficit irrigation was applied at vegetative and yield formation stages of Boro rice and wheat. For estimating yields of Boro rice and wheat under different crop water requirements, yield response factors at vegetative and yield formation stages of the crops were determined by field experiments. The values for Boro rice were 1.53 and 0.60 at vegetative stage and 0.29 and 0.28 at yield formation stage, respectively in the first and second years offield experiments. The corresponding values for wheat were 0.21 and 0.18 at vegetative stage and 0.47 and 0.46 at yield formation stage. The model was first solved without any constraint on land area under Boro rice and wheat using both experimental yields and current farmer's yields. In the solution obtained with experimental yields, all area was covered with wheat whereas with farmer's yields about 98% ofthe area was covered by wheat, only 2% area being under xvi i • Boro rice at full discharge level of tubewells. At 80% and 60% of design discharge of .tubewells, all area was found to be under wheat. In this situation, the seasonal profit using experimental yields were found to be 140 to 155% higher than that obtained with farmer's yields. Next the model was solved with constraints on the maximum and minimum areas under each crop using both experimental and farmer's yields. For Boro rice, the specified maximum and minimum areas were 50000 and 31449 ha, respectively and those for wheat were 60000 and 3613 ha, respectively. At full discharge level, after satisfying the requirement of minimum area under Boro rice, the remaining area was found to be under wheat. At 80% design discharge, the minimum area specified under Boro rice was found to split under 20% and 30% deficit irrigation, the remaining area being under wheat .mostly at 40% deficit irrigation. In this case, the seasonal profit using experimental yields were found to be 27 to 71% higher than that obtained with farmer's yields. Comparing the incremental profit with and without any constraint on area under crops, the profit under unrestricted condition was found to be higher. However, all area under wheat, as found in the case of unrestricted situation, may not be acceptable to the farmers who are mostly rice growers. It seems judicious to consider 80% of the design discharge of tubewells in irrigation planning as the pump efficiency gradually decreases with time thereby reducing the amount of pumping water. Under restricted condition, deficit irrigation appears in solution and keeping Boro area close to the present practice, remaining land area is left for wheat thus encouraging crop diversification. Practicing deficit irrigation, not only the existing farmers of the project will be benefited but also additional farmers will be benefited from BMDA deep tubewells.Item Study on groundwater depletion and land subsidence in Dhaka city(Department of Water Resources Engineering, 2006-08) Zakir Ahmad; Bhuiyan, Dr. Muhammed AliGroundwater is the primary source of safe water to meet the essential demands of people in Bangladesh. Dhaka the capital city, with its enOlmous population takes a huge toll on its groundwater resources. In order to meet this growing demand various organizations mainly DWASA and private users have already installed nearly 2000 high capacity DTWs. Continuous pumping with so many wells from an area less than 450 km2 has rendered the groundwater resources in stressed condition. This is likely to cause some adverse environmental impact like land subsidence. Many countries of the world have already experienced land subsidence of severe magnitude due to excessive groundwater pumping. Formation beneath the city of Dhaka is also susceptible to such phenomenon. This gives an early indication for an urgent need to alleviate pressure on the upper aquifers being exploited and explore for more suitable and sustainable sources to supplement the present water supply. DWASA is entrusted with supply of piped water to Dhaka Metropolitan City and its adjacent area. At present 75% city area is under DWASA water supply coverage, out of which 82% is from groundwater sources. In an attempt to find alternate sources DWASA has started exploiting the deep aquifer at a depth of around 300 m. But the source and recharge mechanism of this aquifer is yet unknown and can not support the development of .J a long tenn strategy for water supply of Dhaka City. From the previous studies, the development of Ground Water and Land Subsidence Model by EPC and MMP (1991) and its updating by BUET (2000) have been the most important and relevant to the present study. In the wake of recent development the previous model has become an inadequate tool to simulate the deep aquifer. So the current A, study was undertaken to setup a groundwater and land subsidence model that is flexible enough to simulate deep aquifer system and any other new changes. A versatile groundwater modeling tool called 'MODFLOW-2000 with Argus ONE' has been used for the current study. MODFLOW-2000 uses the coupling of law of conservation of mass and Darcy's equation to simulate groundwater flow. The subsidence module is integrated into MODFLOW -2000 to compute the land subsidence using the groundwater model. The subsidence is computed basing on the Terzaghi's theory of one dimensional consolidation. The groundwater model under the current study covers an area of 8,778 km2 and includes the districts of Dhaka, Manikganj, Gazipur, Narshindi, Narayanganj and Munshiganj. The model area is discretized to 500 m grid inside Dhaka City. In the vertical direction the model is defined by 6 geologic layers. The model was calibrated by matching the hydro graphs within and outside the Dhaka Region. The calibrated model was then used to estimate the land subsidence in and around Dhaka City. The simulated hydrographs at important places of Dhaka City confirms the declining trend of groundwater level. The piezometric levels at Motijheel and Gulshan are found to be -52 and -43 m PWD respectively in December 2004. The corresponding subsidence as estimated by the model is maximum 4.9 cm. Results of model scenario runs indicate that the groundwater in the upper Dupi Tila aquifer would stabilize by April 2006 if no increase of abstraction is allowed after December 2004. Subsidence results for the same scenario shows that subsidence almost ceases with the stabilization of groundwater. Results of another scenario shows abstraction from deep aquifer with 94 wells in operation would deplete the groundwater by 20 m in 2020. But the situation in deep aquifer can only be confirmed after collecting observed data for a complete hydrological cycle. If the current situation prevails the condition in the upper aquifers will worsen and many existing wells will go inoperative. Recharge from rainfall has become negligible due to lowering of water level and increased urbanization. The reduced storage capacity of the aquifers may cause land subsidence of such magnitude that may affect life and property. All these facts suggest that a comprehensive policy must be undertaken to counter/prevent the possible adverse effects on groundwater resource of Dhaka City.Item Performance evaluation of selected small scale water resources development sector sub projects of lged in Sylhet(Department of Water Resources Engineering, 2009-09) Purkaystha, Taposh Kanti; Khan, Dr. Md. Sabbir MostafaThe Small Scale Water Resources Development SecUr Project (SSWRDSP) aims to ensure sustainable agricultural production in about 190,000 hectares of cultivated land and to alleviate poverty through income generation in the western half area of Bangladesh under Phase-I. Because of improving performances of Phase-I sub projects Phase-II of the SSWRDSP is being implemented in the eastern districts of Bangladesh. The project is under implementation by Local Government Engineering Department (LGED) and is jointly funded by the Asian Development Bank (AD B), International Fund for Agricultural Development (IF AD) and the Government of Netherlands (GON). These schemes are demand driven and are identified by the people based on local water related problem. The scheme planning, design and construction are done in consultation with stakeholders towards achieving sustainable agricultural growth. Beneficiary contribution amounting to 3% of earthworks (dykes and channel re-excavation) and 1.5% for water control structures of the investment costs has been made mandatory. This arrangement has developed sense of ownership among the beneficiary farmers and they are taking responsibility in maintenance for longer-term sustainability of the completed system. This study evaluates five selected SSWRDSP-II sub projects of LGED in the North-Eastern District of Sylhet. Two types o[ sub project were selected namely, Water Conservation type & Flood Management type. Agricultural, Participatory, Socioeconomic and Environmental performance indicators were used in this study. Irrigation area performance indicator showed 80%, 50% & 60% of target achievement in Boromchara, ChirChirChara & ShialiChara water conservation type sub projects respectively. While flood management performance indicator showed 55% & 46% of the targeted area protected from flash flood in BaghaBeel & DuliaSatbila flood management type sub projects respectively. Production performance indicator reveals considerable increase in production in post project condition(2008) compare to pre project condition(2005) and they are 45%, 193%, 147%, 140% & 40% increase in production for BaghaBeel, BoromChara, ChirChirChara, DuliaSatbila & ShialiChara sub projects respectively. On the other hand, participatory management performance showed poor performance regarding regularity in attendance [or the members' of the WMCA. Even though Guideline for Participatory Water Management was followed regarding committee formation but activities of WMCA were not found satisfactory. There was no change found in land holding pattern for the farmers in the selected sub project areas but moderate change in wage rate & crop land value was found in post project condition (2008). Environmental performance indicators did not showed adverse effect but it will be too early to comment regarding this. 0 & M responsibility of the sub project was not being handed over to the respective WMCA even though stipulated time has already been over and therefore the main objective of the SSWRDSP was not addressed so far. Eventually micro credit activities run by the WMCA become the main interest of the beneficiaries rather than sustainable 0 & M. So, long-term sustainability is sti II unproven, because not much time has elapsed for the O&M arrangement to be properly tested. Majority of the people of Sylhet region are expatriate and that is why they are not dependent on the agricultural production for their livelihood rather remittance plays important role in the local economy. Therefore the overall performance of the selected sub projects in this region is not impressive.Item Study on spatial and temporal variation of evaporation and related climatic parameters(Department of Water Resources Engineering, 2009-03) Tanvir Ahmed; Khan, Dr. Md. Sabbir MostafaFactors affecting the rate of evaporation from soil or water bodies can be broadly divided into two groups, meteorological factors and surface factors. The variation of evaporation and other climatic parameters related to it such as temperature, solar radiation, bright sunshine hour, wind speed, air pressure, relative humidity and rainfall of Bangladesh is the main objective of this study. Data of twenty five meteorological stations of Bangladesh have been collected to achieve the objectives. The source of these climatic data is the Bangladesh Meteorological Department (BMD).lt is identified from analysis that in Bangladesh higher rate of evaporation occurs from the month of March to May and in April it is maximum. Minimum evaporation rate occurs in the months of December and January. In Bangladesh temperature is maximum in April or May. The variation of temperature is little from April to September. Temperature begins to decrease from the month of October and falls at lowest in January. It is also observed from the analysis that in most of the locations of Bangladesh the solar radiation is high in the month of April and May and low in the month of December and January. From the analysis it is found that air pressure is minimum in the month of June and in some locations in July. On the other hand the air pressure is maximum in December and in few locations it is in the month of January. The variation of air pressure is not that much significant. In Bangladesh the average annual humidity is 79%. In most of the locations maximum amount of humidity occurs in the month of July and minimum amount of humidity occurs in March. Average maximum length of bright sunshine hour occurs in the months between January and April as these months are almost cloud free. Minimum length of sunshine hours in all the locations was observed in July. From the analysis, it is found that maximum rate of rainfall occurs in the months of June and July at the time of full monsoon. Average annual maximum rainfall occurs in Sylhet (4100 mm) and minimum rainfall occurs in Rajshahi (1527 mm). The average annual total rainfall of the country is 2354 mm. It is also obtained from the study that in most of the locations wind speed is maximum in the month of April and minimum in the month of November. The correlation coefficient between evaporation rate and the other climatic parameters are determined in the study. The correlation coefficient (r) between evaporation rate with solar radiation, temperature and wind speed is large and positive. It means evaporation rate is increased with the increasing value of radiation, temperature and wind speed. On the other hand the value of r between evaporation rate and bright sunshine hour, relative humidity and pressure is small but in case of bright sunshine hour and rainfall it is positive and in case of relative humidity it is negative. Again the value of r between evaporation rate and bright sunshine hour is positive and medium. Four approaches i) Energy Balance Method ii) Aerodynamic Method iii) Combined Aerodynamic and Energy Balance Method and iv) Priestly-Taylor Method have been used in this study for the computation of evaporation rate and their performance were evaluated. The best result was obtained from the Energy Balance method. Then Priestly- Taylor Method, Combined Method and the Aerodynamic Method respectively performed well. None of the above mentioned methods gives reasonable results in Bangladesh.Item Runoff computation of Halda river basin using soil moisture accounting method(Department of Water Resources Engineering, 2002-10) Roushan Ara, Syeda; Bari, Dr. M FazlulIn this study basin runoff was simulated using the computer model of the Hydrologic Engineering Centre-Hydrologic Modeling System, called HEC-HMS for the upper part of the Halda river basin given rainfall and catchment parameters. The graphical user interface of the HEC-HMS was used to edit, execute and view model data. Data needed for this study included soil, land use, digital elevation model, point elevation, contour line, stream network, rainfall, evaporation, and river discharge. Detailed stream network was created using topographic maps of 1:50000 scale. Required maps and data were collected from Water Resources Planning Organisation (WARPO), Institute of Water Modeling, and Soil Resources Development Institute. The HEC Data Storage System (DSS) was used for storage and retrieval of time series data. Geographic Information System (GIS) tools e.g. Arc/Info 8.02 and Spatial Analyst of ArcView 3.2 were used for delineating watershed and stream network from Digital Elevation Model (DEM). The chosen basin area was divided into sub-basins and the loss rate parameters such as interception, infiltration and base flow were estimated. Most of the parameters i.e. canopy interception and surface storage, soil profile and tension zone depth of Soil Moisture Accounting (SMA) model were calibrated during simulation. No groundwater zone was considered in this study region because percolation rate became zero as model suggested. Flow directions, flow accumulation points, flow path lengths, sub-basin areas were determined from DEM. Hydrologic modeling parameters (i.e. length of longest flow path, SCS curve number, lag time, stream velocity, Muskingum X, Muskingum K etc.) and appropriate rainfall station weightage were estimated using ArcView GIS as input parameter of the model. The rainfall excess was transformed into direct runoff using Soil Conservation Service (SCS) unit hydro graph method. Runoffs from subbasins were combined at the confluences and hydro graphs routed through a channel network using Muskingum channel routing. The simulated daily runoff for the entire year was compared with the observed runoff and that computed using another lumped conceptual model called NAM model of the Danish Hydraulic Institute. The peak flow of simulated runoff was 426.08 m3/s on 24th June and observed runoff was 202 m3/s on 24th June. NAM computed peak flow was 405.61 m3/s on 25th June. Thus HEC-HMS overestimated the peak runoff by 52.3% as compared to observed peak runoff and by 4.8% as compared to peak runoff by NAM model. HEC-HMS and NAM results agreed reasonably well.Item Impact evaluation of command area development in Meghna Dhonagoda irrigation project(Department of Water Resources Engineering, 2005-10) Mahfuzur Rahman, Md.; Miah, Dr. M. MirjahanImproved water management is of utmost importance for flood control, drainage and irrigation schemes in Bangladesh, as nearly 80 million people live and farm on the floodplains. Water management abounds on these floodplains aI1d people have taken measures to cope with water since time immemorial. The crucial importance 0 f F CDI systems for the livelihood of many millions of people makes it necessary to understand water management practice in FCDI systems and to develop appropriate institutions and management strategies for them. Many studies on water sector in Bangladesh concluded that the intended benefits from -f' FCDI systems have not materialized. This is attributed in part to institutional weaknesses. One of the key approaches for tackling these institutional weaknesses is increasing people's participation in water management. At present the Government of Bangladesh is committed to the participatory development and management of FCDI systems. Earlier, many of the irrigation, drainage and flood control schemes in Bangladesh were jointly managed by the Government and the beneficiaries. Further, it is widely experienced, even in the older schemes, that the beneficiaries are not performing their role well in these jointly managed schemes, and that they fail to become active partners in the day to day management. At present, Bangladesh Water Development Board (BWDB) has been giving emphasis to ensure people's participation for their water systems management following Guidelines for Participatory Water Management (GPWM). Command Area Development Program (CADP) incorporating Participatory Approach of water management following GPWM has been applied in some BWDB projects like Meghna Dhonagoda Irrigation Project (MDIP), Teesta Irrigation Project (TIP) and Pabna Irrigation and Rural Development Project (PIRDP) to some extent. In the present study, field investigation was performed to evaluate the impact of Command Area Development Program (CADP) in Meghna Dhonagoda Irrigation Project (MDIP)implemented from 1996-97 to 2002-2003 taking into consideration the hydraulic, agricultural, socioeconomic, environmental and institutional aspects. For the hydraulic, agricultural, socio-economic, environmental and institutional aspects, the impacts of CADP on the performance of MDIP were assessed comparing the values r of se.lected indicators for the pre and post CADP situations. The hydraulic indicators were used to compare the relative water supply (RWS) and water level for some selected canals with pre (1999) and post (2003) CADP situation. The agricultural indicators directly reflect irrigated agricultural systems. Performance in terms of year wise irrigated area, cropping intensity, yield and production has been used as agricultural indicators. The socio-economic indicators used in this study include fee collection performance and financial self-sufficiency and this relates to long -ternl impacts of agricultural strategies. Water quality, natural vegetation and fish have been considered as parameters for assessing the environmental impact. { In total 388 Water Management Groups (WMGs) were formed in MDIP during 1998 to 2003 under Command Area Development Program following the GPWM. Forty-one WMGs were selected to assess their performance during the irrigation season of 2003. Sets of indicators were also identified to evaluate the impact of CADP on the performance of the project. Questionnaires were prepared and used for systematic collection of data during the field study. The results of the evaluation study revealed that RWS to the field and water level in irrigation canals in post CADP situation was higher than pre CADP situation and the actual water levels were very close to Full Supply Level (FSL). This means that overall reliability of the canal system has been improved after CADP in MDIP. RWS values with an average of 0.93 were achieved during post CADP for Boro rice. Moreover this was not satisfactory because RWS value at or close to 1 .0 represents scarcity 0 f water. Actual irrigated area has been increased by three times as compared to the benchmark year, 1996-97 and irrigated area coverage increased by a bout 6 a % . Cropping i ntensi ty was increased from 200 % to 250 %. Yield for HYV Boro rice was increased from 4 ton/ha to 4.75 tonlha. Production of HYV Boro rice was increased by about 3 times compared to benchmark year. After the CADP in MDIP, irrigation fee collection was started from 2001-02. And still now it quite insignificant and only from the fee collection, it is not possible to make the project 0 & M financially self-sustaining. There was no remarkable environmental change for water quality and natural vegetation after CADP in MDIP. But fish production has increased by two times as compared to the benchmark year. From the institutional aspects, the result of the evaluation study revealed that though all selected WMGs were registered, their activities in all cases were not satisfactory. Still now all farmers are not members ofWMGs, only 61 % of selected WMGs were involved in maintaining their field channels and 76 % of WMGs received technical support from BWDB, but all selected WMG members have received training from NGO and BWDB during 1998 to 2003, and there is lack of linkage between WMGs and BWDB project level authority and amount of fee collection is very poor. Considering all these aspects, the CADP in MDIP produced significant positive results in terms of crop productivity; agricultural returns, supply and distribution of irrigation water. However, efforts should be made to further improve the interaction between the WMG and BWDB and collection of irrigation fee to make 0 & M of the project sustainable.Item Study on the effect of char movement on river morphology around upper Meghna - Dakatia confluence(Department of Water Resources Engineering, 2008-12) Shume Akhter; Hossain, Dr. M. MonowarThe present study has been conducted to investigate the planform characteristics and change of river morphology due to Char movement around Upper Meghna-Dakatia confluence lying in Bangladesh. To carry out the study satellite images (LANDSAT MSS, TM and IRS, L1SS) From MIKE 21 C modelling based study it was found that no change in lell bank ncar Chandpur occurred due to bank protection works. At right bank opposite to Chand pur from point 1 (E 548714, N 577998) to point 2 (E 562675, N 567553), few meters of bank line shifting occurred. At the samc time at some location sedimentation occurred, IiIle shi IiiIlg became zero and sand bar formed. From the satellite image of the year 2004, the bank line shifting has been found to be 135 m/year. The model predicted 144,180 and 252 m/year bank line shifting for average (1 in 2-year return period), intermediate (1 in 10-year return period) and extreme (1 in 1OO-yearreturn period) flood events respectively. The study revealed that the actual velocity exceeded the design velocity. As a result the scour depth (-63 m) was found to be higher than that of the design scour depth of the protective works. But when Char-l is extended in northeast direction then the velocity is decreased than the design velocity. Sediment transport of the Lower Meghna at 1.5 km downstream of Chand pur was estimated using half day tid,al cycle measurement data. The value of sediment transport for the month of September was found as 0.93 million tons and corresponds to approximctely 272 million tons/year. Sediment transport was also estimated using MIKE 21C, it was found as 233 million tons/year by Engelund Hansen and 109 million tons/year by Van Rijn formula. Total sediment transpOli load was also calculated by Engelund Hansen and Hossain equation and was found as 423 million tons/year and 893 million tons/year respectively. covering the period ti'om 1973 to 2004, bathymetric data, water level and discharge data has been used. All of the data have been collected from CEG1S and IWM. Several field visits were conducted with a view to obtaining better idea on the complex morphological behavior around Meghna-Dakatia confluence. The length of the study area is considered approximately 82 km from Mawa to Salempur. From the analysis of satillite image of various years, it was appaernt that the river system is not only characterized by a wide river bed of several kilometers in which the various channels developed in combination with large propagating sand bars, but also gradually shifting of the whole lower Meghna both in westward and eastward direction. From analysis it has been found that over 31 years, left bank maximum erosion rate was 323m/year and right bank maximum erosion was 113 m/year. Analysis of time series of satellite imagery shows that from 1973 to 1993 two Chars, named Char-l (between the confluence of Padma and Upper Meghna river) and ChariI' Char was present at upstream of Chandpur. ChariI' Char was almost diminished in 1993. Another Char was formed named Char-2, at downstream of Char -1 during the period of 1993. Area of ChItem Physical model study on bank protection by revetment in a reach of the old Brahmaputra(Department of Water Resources Engineering, 2002-09) Shoma Tanzeeba; Hossain, Dr. M. MonowarBangladesh is one of the largest deltas in the world, which has been fOl1ned mainly with sediment deposited by the three mighty rivers namely the Ganges, the Jamuna and the Meglma. These alluvial rivers are continuously shifting their positions and changing shapes as a consequence of hydraulic and geomorphic forces acting on its bed and banks. The nature of this bank erosion and channel shifting problems demands intensive and careful 10ng-tel1n study both by physical (scale model) and mathematical models. For long term and short term hydraulic research activities including morphological studies on alluvial channels, a physical model facility has been developed the Department Water Resources Engineering, Bangladesh University of Engineering and Technology. This setup covers approximately 61 m length and 11.5 m width. It is equipped with 45.73m long and 10.67m wide sand bed, storage pools for water supply, upstream and downstream reservoirs, sedimentation tank, pumps, recirculating canal, measuring devices like weirs, water level recorders, point gauges, side rails and carriages etc. This physical model has been used for the study on bank protection by revetment. In general, revetment structures are popular as bank protection work in Bangladesh. The different types of revetment, which are mainly used here, are cubical concrete blocks and loose stones. In the present study the perf011l1anCeof hexagonal block for bank protection work was evaluated and was compared with cubical blocks. Previous application of hexagonal block in case of wave attack has shown that it is very effective and less costly as a protection work. In this research work, applicability of the hexagonal block in case of current attack and its performance has been evaluated. With this view, a scale model of an erosion prone reach of the Old Brahmaputra river has been developed. Then the perfol1nance of these two types of blocks i.e. hexagonal blocks and cubical blocks have been evaluated by placing them in the eroded bank keeping same condition for both of the blocks in different scenarios. The variables that are considered for the perfol1nance evaluation are different bank slopes (2H: 1V and 3H: 1V) and different values of velocity ranges. It has been revealed from the study that hexagonal blocks required 50% less amount of material as compared to cubical blocks of equivalent weight for the selected bank protection area. Inspection of the bed profile showed that hexagonal shaped revetment structure suffered less damage than the cubical shapes for both the bank slope conditions. From side slope stability coefficient it can be concluded that flatter side slopes gives more stability for both the cases compared to higher side slope which is close to the angle of repose of the material. On the other hand, comparison between cubical and hexagonal type of revetments on same side slope gives better stability for hexagonal type revetment blocks. Other factors such as, time required for placement of these two kinds of blocks show that cubical blocks require 40% more time than as compared to hexagonal block due to their smaller shape and size.Item Performance evaluation of irrigation water delivery system of Ganges - Kobadak (G-K) project(Department of Water Resources Engineering, 2001-04) Das, Shamal Chandra; Miah, Dr. M. MirjahanThe 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 tertiary 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.Item Selection of statistical distributions for extremes of precipitation in south east region of Bangladesh(Department of Water Resources Engineering, 2002-12) Shaheenur Akhter, MS.; Bari, Dr. M FazlulFor abstract please see full text