Finite element modelling of a heavily exploited coastal aquifer for assessing the response of groundwater level to the changes in pumping and rainfall variation due to climate change

Coastal aquifers are always under threat of seawater intrusion due to over-extraction of groundwater. The objective here is to assess aquifer response to variation in pumping and rainfall recharge due to projected climate change by groundwater modelling in a heavily exploited aquifer. Finite element groundwater flow modelling was carried out from March 1988 to December 2030 using FEFLOW software. Steady state calibration was done to match observed and simulated groundwater head by varying aquifer parameters within the allowable range. Transient state calibration was carried out during the period March 1988 to December 2002. The calibrated model was validated by comparing the simulated and observed groundwater head from January 2003 to December 2012. Groundwater head was predicted for a period until 2030 under eight different scenarios of changes in pumping and rainfall recharge. This prediction indicated that 10% increase of recharge and 10% decrease of pumping causes 3 m and 6 m increase in groundwater head in upper and lower aquifers, respectively, by the end of 2030. Groundwater recharge can be increased by rejuvenation of existing surface water bodies, check dams and construction of proposed check dams. Thus, increase of groundwater recharge and decrease in well field pumping is achievable to restore this heavily exploited coastal aquifer in another 20 years.