Modeling for Equitable Groundwater Management

Freshwater lens on small islands may easily be overexploited or due to overdrafts of fresh water by pumping which causes of the water table a rise or up-coning of the saltwater. Present study is concerned with using a three-dimensional-difference numerical model to simulate the groundwater flow and model to predict the behavior of groundwater system in Island. The simulations were done using variable density-2000 for three selected pumping schemes. Hydraulic heads(groundwater level) is the highest at the center of the island and in radial shape towards the coast in all the pumping schemes(PS1-PS3). The chloride concentration in the studied aquifer increased 98.7% in the pumping well if the pumping rate is doubled by the (PS2 to PS3). The 1.4% seawater-freshwater mixing moves further to inland about 1.6m when the current pumping rate was doubled moves backward to sea about 1.7m if the current pumping rate is by 50%. This preliminary model of Manukan island aquifer shows an overexploitation of groundwater in Manukan Island contributes the seawater intrusion. Adjusting the future groundwater pumping and improv-ing groundwater management strategies are necessary protect the freshwater aquifers. The current numeri-cal model is a representation of the aquifer in Small Island which can be in similar small islands with similar hydrogeological conditions elsewhere.