Optimum design of a recharge filter for recharging the dug wells: a field application

Abstract

Artificial recharging of the abandoned and/or functional dug wells through a recharge filter is an efficient and economical method for mitigating and maintaining depleting water tables. An optimum sizing of the recharge filter is necessary to avoid its over-design or under-design and has a minimum cost. Optimum sizing of the recharge filter for the dug well recharging has received very little attention, especially in India. In this paper, analytical expressions for designing the recharge filter were derived based on the concept of maximization of the hydrological water balance equation. Optimum sizing of the recharge filter based on the minimum cost was formulated using the optimization model. The optimization model was solved using the Snopt non-linear programming optimization model of the AMPL software. The results of the optimization model were also compared with the analytical framework. Sensitivity analyses using an analytical framework indicated that size, time of filling and empty time for the recharge filter were more sensitive to the changes in watershed area and watershed condition as compared to the diameter of the discharge pipe, the porosity of the filter material and depth of the recharge filter. It could be concluded that the derived optimization model incorporating the derived analytical expressions can successfully be used for optimum sizing and evaluation of the effectiveness of the recharge filter of any shape and locations in different hydro-climatic regions.