Monitoring the Coastal Groundwater of Bangladesh

Abstract

The low-lying topography and geographic position makes Bangladesh very vulnerable regarding the anticipated impacts of climate change that likely affects nearly all sectors of socio-economic life, where water sector is the most vulnerable and sensitive among them and country's coastal areas are at the greatest risk. The primary source of fresh water in the coastal belt is groundwater. But very few studies have been conducted to assess the influence of climate change on this resource. There is also high vulnerability to contamination with salinity due to mixing of pre-existing fresh and saline groundwater accelerated by irrigation pumping and vertical infiltration of salt water from periodic storm surge flooding. Changing climate and population stress might affect various components like recharge, discharge, storage, and water quality. The volume of water which is retained in the top soil is required for agriculture and has a role on the process of evaporation, recharge of groundwater, and innovation of runoff. Tidal saltwater wedge because of rising sea levels would cause to encroach further upstream in rivers, resulting salinity intrusion in aquifers. To know the evidence of changes in the events of hydrologic cycle including groundwater quality and storage is very important in order to adapt with the climate change impacts. The principal source of the irrigation water in Bangladesh is groundwater since decades and is one of the major factors making the nation almost self-dependent in crop production. Bangladesh being a very low-elevated country, where main part of the landform in the coast is up to 2--3 m above mean sea level, sea-level rise can cause increased intrusion of saline water both in surface water and in groundwater system. Inadequate safe water for irrigation and water supply will create more stress on fresh water. Therefore, it is important to map fresh water---saline water distribution in coastal aquifers with other important physico-chemical parameters and predict future changes in this environment due to both climate change and anthropogenic stresses. Considering this, a monitoring network has been established by Bangladesh Water Development Board in 19 coastal districts with monitoring wells at variable aquifer depths down to 350 m. The objective of the project, under the support of Bangladesh Climate Change Trust, is to establish a long-term monitoring network to assess and monitor coastal water resources both on quantitative and on qualitative aspects. This paper focuses on to determine the potential of available fresh water resources and distribution of salinity in aquifers both spatially and vertically, mainly based on the monitoring data, for sustainable long-term use of very scarce fresh water in the region.