Vulnerability Analysis of the Coastal Sandy Aquifers in the East Coast of Sri Lanka with Recharge Change Consideration

Abstract

Groundwater is the only source of water for domestic as well as agricultural purposes in the sand aquifer in be- tween sea and lagoon configuration typically found in the eastern Sri Lanka. This study was carried out to estimate the safe yield and assess the vulnerability of the sandy aquifer on the eastern coastal belt of Sri Lanka by rapid urbanization, agriculture and as well as climate change. A typical aquifer system was modeled as a part of a synthetic study to under- stand the sustainability of these coastal aquifers based on the observations made through a pilot field site in the eastern coastal sand stretch in Sri Lanka. Two dimensional model simulations were carried out representing 2000 m length, 22 m deep and 2 m wide model domain respectively. The safe yield of the aquifer is estimated to be 0.37 m 3 /m 2 for an average hydrological year and 0.18 m 3 /m 2 for a dry hydrological year. Water balance in the aquifer system is in equilibrium with the present recharge. However, it is important that the wells to be placed at least 750 m inland from the sea and lagoon re- spectively to avoid salt and brackish water intrusion. According to the modeling results, currently the aquifer system shows no signs of depletion or sea water intrusion. However, increase of population, increase of pumping, and reduction of recharge due to climate change can increase the aquifer vulnerability for contamination by salt and brackish water.