ANALYSIS OF UNSTEADY FLOW TO A FINITE RADIUS WELL CONSIDERING WELL STORAGE

Abstract

Hydrogeologists occasionally have a need for a method of analysing the effects of pumping from non flowing well of large radius, especially in Asian countries like Indonesia where most of the existing wells are dug wells. Existing solutions are not suitable for this purpose, because they do not take into account the relatively large storage capacity of the well itself. For example, the Theis (1935) equation is based on the assumption that the well can be idealised as a mathematical line sink that has no storage capacity. The solution given by Hantush (1964) for a well of a finite diameter assumes that the rate at which water is pumped from the well is equal to that entering the well, so that the storage capacity of, the well is neglected. Papadopulos and Cooper (1967) solved the drawdown in and around a well of large diameter in a confined aquifer for constant pumping rate taking into consideration the effect of the water stored within it. Their solution is based on the solution given by Carslaw and Jaeger (1959) for an analogous problem in heat flow. In case of a centrifugal pump, the_ pumping rate is not constant and depends on the drawdown and is not known as the drawdown is not known. Solution for unsteady flow to well with finite radius for varying pumping rate is not available so far....