Geologic, Hydrologic, and Geochemical Characterization of the Deep Ground Water Aquifer System In the Bengal Delta of Bangladesh
Geology: John Whitney, firstname.lastname@example.org
Hydrology: David W. Clark, email@example.com
Headquarters management is provided by: Verne R. Schneider, firstname.lastname@example.org
|Overview:||Tens of thousands of people, located primarily
on the Bengal Delta of southern and eastern Bangladesh, have been stricken
with arsenical dermatitis, hyperkeratosis, and chronic and acute cases of
arsenicosis, and other related diseases and maladies as a result of drinking
arsenic-laden ground water extracted from over 10 million tube wells that
have been installed in the shallow, unconfined aquifer system that exists
throughout Bangladesh. The World Health Organization estimates that 40-60
million people are at risk from drinking arsenic-contaminated water in Bangladesh,
and that this health risk also extends into West Bengal, India and into
Most of the highly arsenic-contaminated wells in the delta are completed in the "shallow aquifer", which commonly lies at a depth of 50-150 feet below the surface. Due to the complex sedimentologic nature of the delta, it is difficult to predict whether or not the zone of high arsenic is hydrologically separate from the deeper aquifer system. The deeper aquifer systems within the delta have been shown to contain nearly arsenic-free water, and thus they are a largely untapped source of potential drinking water for people in Bangladesh. The deeper aquifer systems are probably the most valuable unused natural resource in the country, yet a detailed understanding of the groundwater quality and quantity in these systems does not yet exist. Before this valuable resource can be exploited, it is essential to understand whether or not the deeper aquifer systems will remain arsenic free if developed over time.
During January 2002, the Government of Bangladesh (GOB) sponsored an International Workshop, which resulted in recommendations for providing alternative sources of safe water. Possible sources of safe water include rainwater, surface water, and deep ground water in addition to new or revamped water-treatment and water-distribution systems. The current project addresses the recommendations for using additional water wells, completed in both shallow and deep aquifers, as sources of safe water. The United States Geological Survey has been asked by USAID and US State Department, Dhaka to assist the government in Bangladesh in developing a strategy to better understand the ground-water arsenic situation and in particular to study possible alternative sources of clean water.
The USGS is currently conducting research on the deeper aquifer system in Bangladesh in areas associated with high levels of arsenic in the shallow ground water. The work uses an integrated geologic, hydrologic, microbiologic, and geochemical approach to characterize the deep aquifer system and to develop mappable criteria that will identify sources of safe ground water. This work is an integral step in the characterization of the hydrogeological framework needed to define the potential for developing safe and sustainable ground water sources. The important questions to address are, "To what extent can the deep aquifer system of the delta be reliably used to provide an alternative drinking-water source for the Nation?"; "How much good-quality water can be produced from this resource?"; and, "How long will it last?".
The answers to these questions are scientifically challenging, yet these answers are needed to justify the costs of developing this resource and to ensure that this resource is not knowingly, or unknowingly, contaminated. There are three general components to the current project, namely: (1) evaluation of the hydrology, geochemistry, microbiology, and geology of the deep aquifer at selected sites; (2) coordination of ongoing and planned work among several GOB agencies; and (3) capacity building. The USGS is working with many GOB agencies, other Donor Nations, International agencies and other interested parties to help better define the problem of developing an integrated system of ground water utilization and to develop methodologies to better understand the complexity of the natural hydrogeologic system.
Click any image below to view a larger version
Arsenic distribution in the shallow aquifer in
Bangladesh Map prepared by J. W. Rosenbloom
|The USGS has been asked by US State Department
and the USAID in Dhaka to assist the government in Bangladesh in developing
a strategy to better understand the ground-water arsenic situation and,
in particular, to study possible alternative sources of clean water. This
work directly contributes to USGS efforts to understand the occurrence and
mobilization of arsenic in water and sediments.
Interactive map site: http://idims.wr.usgs.gov/
Survey of Bangladesh
Bangladesh Water Development Board
Bangladesh Atomic Energy Commission
Dhaka University Geology Department
Bangladesh Arsenic Mitigation and Water Supply Program
U.S. Department of State
U.S. Agency for International Development