Bangladesh Water Development Board Research Articles

Spatial relationship of groundwater arsenic distribution with regional topography and water-table fluctuations in the shallow aquifers in Bangladesh

The present study has examined the relationship of groundwater arsenic (As) levels in alluvial aquifers with topographic elevation, slope, and groundwater level on a large basinal-scale using high-resolution (90 m × 90 m) Shuttle Radar Topography Mission (SRTM) digital elevation model and water-table data in Bangladesh. Results show that high As (>50 μg/l) tubewells are located in low-lying areas, where mean surface elevation is approximately 10 m. Similarly, high As concentrations are found within extremely low slopes (<0.7°) in the country. Groundwater elevation (weekly measured by Bangladesh Water Development Board) was mapped using water-table data from 950 shallow (depth <100 m) piezometers distributed over the entire country. The minimum, maximum and mean groundwater elevation maps for 2003 were generated using Universal Kriging interpolation method. High As tubewells are located mainly in the Ganges–Brahmaputra–Meghna delta, Sylhet Trough, and recent floodplains, where groundwater elevation in shallow aquifers is low with a mean value of 4.5 m above the Public Works Datum (PWD) level. Extremely low groundwater gradients (0.01–0.001 m/km) within the GBM delta complex hinder groundwater flow and cause slow flushing of aquifers. Low elevation and gentle slope favor accumulation of finer sediments, As-carrying iron-oxyhydroxide minerals, and abundant organic matter within floodplains and alluvial deposits. At low horizontal hydraulic gradients and under reducing conditions, As is released in groundwater by microbial activity, causing widespread contamination in the low-lying deltaic and floodplain areas, where As is being recycled with time due to complex biogeochemical processes.

An Assessment of Flood Forecasting in Bangladesh: The Experience of the 1998 Flood

Floods are among the most costly natural disasters interms of human sufferings and economic losses inBangladesh. Approximately 20% of the countryexperiences normal annual flooding while all thehistorical catastrophic floods inundated more thanfifty percent of the country's total area. The recentflood in 1998 has been found to be more severe thanall previous floods. During the flooding season of1998, the Flood Forecasting and Warning Center (FFWC)of the Bangladesh Water Development Board (BWDB)prepared daily flood bulletin and incorporatedinformation about rainfall, rise/fall of riverwater, flood forecasting for 24 and 48 hr inadvance and warning messages (if any). The FFWCattempted to provide adequate services to the localand national level decision-making process. Theforecasting procedure adapted by the FFWC was based onhydrological information, forecaster's experience, andmodel simulation. This paper primarily examines therole and activities of the FFWC, especially in floodforecasting and warning. Identification of the causesand consequences of 1998 flood is the other pertinentarea of discussion of the paper. Findings of this research revealed that the flood of1998 was caused by heavy downpour in the upstream thatwas drained out through the major rivers inBangladesh. Three major rivers' peak was synchronizedand characterized it as the most prolonged flood inthe history of Bangladesh. It also revealed that,despite various limitations, the flood forecasts ofthe FFWC were reasonably adequate to meet nationaldemand during the crises of 1998.

The Bangladesh Meghna–Dhonagoda irrigation project

AbstractThe Meghna‐‐Dhonagoda Irrigation Project (MDIP) began in 1977 as an effort to reduce the constant threat of floods in the Chandpur district of Bangladesh, to expand agricultural production and employment opportunities, and to improve power supply, communication, social services, and health conditions. With a US $24 million loan from the Asian Development Bank (ADB), the project was to have been completed in 1983. Unfortunately, it remains incomplete and defective, despite long delays and an expenditure many times more than originally estimated. The project's failures primarily stem from inability or unwillingness of the Bangladesh Water Development Board (BWDB) to supervise the consultants and contractors and then to correct their mistakes. However, the ADB could also have played a more useful role in facilitating technical and managerial improvements.

Mineralogical study of Sediment samples of Kachua, Chandpur district for investigation of arsenic bearing minerals

Sixteen sediment samples of different depth (up to 122 m) were studied by X-ray diffraction (XRD) method. The samples were collected from a test borehole, which was drilled by Bangladesh Water Development Board (BWDB) at Kachua, Chandpur district. All the samples were characterized and different minerals have been identified in the samples. Quartz is the major mineral and was found to be in the range of 54.97 - 97.88 %. Two arsenic bearing minerals namely, iron arsenate, Fe2As(AsO4)3 and arsenic selenide telluride, AsSe0.5Te2 were found in the samples of depth 55.20 m and 100.60 m, respectively. Bangladesh Atomic Energy Commission (BAEC) in collaboration with the United States Geological Survey (USGS) conducted the groundwater sampling campaign for shallow and deep tubewells in Kachua upazila. From the hydro-chemical results, the concentrations of arsenic in shallow tubewells were found above the maximum permissible limit (50 ppb). Concomitantly, the mineralogical study of sediment samples in the same area reflects that the shallow aquifers of Kachua upazila are contaminated by arsenic due to the presence of arsenic bearing minerals. doi: 10.3329/jbas.v32i1.2436 Journal of Bangladesh Academy of Sciences, Vol. 32, No. 1, 1-12, 2008