GENERATION OF AN APPROXIMATE SOLUTION FOR LARGE UPCONING BELOW A PUMPING WELL

Abstract

When water is pumped from well tapping an aquifer that comprises fresh water underlain by salt water, the interface between the two rises or "Upcones". The extent of upconing affects the quality of the pumped water. Therefore, it is important, that the upconing of interface does not exceed a prescribed threshold. The upconing can be estimated employing available analytical solutions. However, these analytical solutions are valid only for small upconings. In the present study, an approximate solution for large upconing below a pumping well is developed. This is accomplished by computing the upconings (small as well as large) by invoking an existing numerical model and also by an analytical solution, under various hydro geological and geometric conditions. The difference between the two estimates of the upconing is deemed tobe the error in the analytical estimate. An approximate form of the error function is arrived at by subjecting the array of computed errors, to a regression analysis. The function so derived is added to the analytical solution, to get an approximate solution which holds for large upconings as well.