AQUIFER RESPONSE CONSIDERING WELL STORAGE

Abstract

Response of an aquifer means information about overall aquifer behavior including yield and drawdown at different field conditions due to a system of wells. Pumping well may be a borewell (negligible well storage) or a dugwell (adequate well storage). Study of aquifer response enables us to derive information about yield and drawdown, for known values of aquifer parameters,at the pumping well,thus specific capacity or discharge-drawdown ratio for selecting type of pump and for estimating cost of pumping. With the knowledge of ground water cost based on the quantity of water pumped and lift, one can develop most efficient and beneficial pumping system for agricultural, industrial or domestic water supply.The other aspect of the study is to investigate aquifer parameters through pumping test data.Pumping test may be performed either at a bore-well or a dugwell. Furthermore,the pumping well may be surrounded by a number of pumping,non-pumping or observation wells which may or may not posses enough well storage. -Thus,the observed data may result in wrong estimate of aquifer parameters unless these are matched with suitable type curves.(Which have been evolved after giving due consideration to the storage of pumping wells and other nearby wells which are not pumping),In the present study,a general formulation of the problem, involving a large number of pumping,non-pumping wells, is proposed by using discrete kernel approach. Various possible situations of wells are analysed and discussed. Storage and interference effect of pumping/non-pumping wells are found quite significant to avoid the possible use of conventional available type curves. To have correct estimate of the aquifer parameterrit is suggested that type curves should be developed in accordance with the proposed formulation and subsequently be used.