ASSESSMENT OF LONG-TERM WITHDRAWAL RATE FOR A COASTAL AQUIFER

The long-term safe withdrawal rate for a coastal aquifer in Mannar Island of Sri Lanka was assessed through the simulation of interface movement. A range of estimates of natural recharge sequence was first obtained from a water balance study considering the variations of factors affecting the soil moisture balance. The representative recharge sequence was then determined through the simulation of a field observed interface profile along a selected section. Following this, the sustainability of continuous water withdrawal in the future was assessed by limiting the extent of salt-water upconing. An increase in the withdrawal rate in the future would be possible through proper monitoring of the system response.