Simplified Hydrogeology of Bangladesh
Bangladesh is characterized by one of the world’s most productive aquifer composed of Holocene alluvial sediments of the Ganges-Brahmaputra-Meghna (GBM) delta system. Groundwater development in Bangladesh was initiated by BADC in the 1960s for dry season irrigation purpose. Hydrogeological investigation was initiated by BWDB in collaboration with UNDP in the 1970s. It is when fresh water bearing shallow aquifer has been identified and millions of shallow hand tube wells were installed as recommended by UNICEF. However detailed hydrogeological study of the Quaternary alluvial aquifers was carried out in the 1980s.
Bangladesh is characterized by tropical monsoon climate with mean annual rainfall ranging from 1250mm in the western and central part to more than 5000mm in the northeastern part. About 85% of the total rainfall occurs during the monsoon. Mean temperature ranges from a minimum of 11⁰C to a maximum of 29⁰C in the winter (November-February) and from a minimum of 21⁰C to a maximum of 34⁰C in the summer (April-September). Evaporation rate ranges from 70-90mm in the winter to 180mm in the dry period.
The higher percentage of rainfall in monsoon together with peak inflow of the major rivers sometimes causes flooding. Increased river flows and higher stage affect the water table in the adjacent floodplains. High monsoon rainfall together with infiltration from the major river channels causes the groundwater table to rise above the ground surface.
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