The problems of saline water upconing and intrusion are of major concern in the Indus Basin of Pakistan. The withdrawals of fresh water overlying saline groundwater have resulted in inferior quality of pumped water and degradation of the aquifer. The continuous use of such qualitatively inferior water for irrigation has severely affected fertile lands causing agro-economic declination. Nearly 197 billion cubic meters (bm3) of fresh water has accumulated in the form of a thin layer over saline water, and over 20 bm3 of fresh water is being recharged annually in saline zones of the basin. In these situations skimming wells can play an important role in augmenting irrigation supplies and watertable control, as well as alleviating degradation of the aquifer. However, the working efficiency of skimming wells is not fully known. To investigate the effectiveness of various skimming wells, a density dependent finite element numerical model was modified and applied. In the present study an analytical equation was developed by gauging the effects of temperature and viscosity on the hydraulic conductivity of the porous media subjected to the saline water. The new equation was incorporated into the model. Simulations of flow and solute transport towards single, two-strainer, radial, compound and recirculation wells were performed. Physical modelling of such skimming well configurations was undertaken to calibrate the numerical model. The double-strainer well method performed better than the other skimming configurations tested in this study.
