ABSTRACT
The continual replenishment of groundwater storage and its sustainable utilization is indispensable to meet the ever-increasing water needs of the Killinochi district of northern Sri Lanka. To ascertain the sustainable exploitation of this resource, a modeling study was conducted there. A widely accepted 3D modular groundwater flow model was employed to simulate the hydrodynamics and stresses of the Killinochi basin for an initial stabilization period of 1 year, followed by a 3-year period simulation. Spatially distributed recharge was considered using the recharge package and the multiplier function to incorporate the effects of variable infiltration rates in the recharge estimation. A literature review on the availability of data and prior groundwater investigations in the area shows a huge gap in soil and aquifer hydraulic parameters, water-level information, and related aquifer and confining bed geometry data. Therefore, it was not possible to calibrate the model following the standard calibration techniques. However, in the conceptualization process, all efforts were made to make sure that the model domain fairly followed the actual field conditions of the Killinochi basin by incorporating all available data. In addition, a comparison of the simulated zonal water budgets with the zonal budgets calculated based on observed data from International Water Management Institute (IWMI) and water resources board (WRB) reports 192were used to validate the results of the model. The recharge pattern from the model results follows a close resemblance to the rainfall pattern, which can be explained by the more or less flat topography of the basin. We believe the flat topography has limited any significant contribution of the lateral inflows to the groundwater dynamics. Hence, the simulated heads and the recharge and flow patterns obtained at the end of the simulations were to the most part influenced by the interaction between percolated rainwater and the groundwater aquifer as a function of land use and soil physical properties.
