Optimal positioning of groundwater supply wells in residential areas with uncertain information

Abstract

A simulation-optimisation based methodology has been proposed for identifying economically and ecologically optimal locations for new groundwater supply wells. The purpose of optimisation was to find cost effective extraction locations with a minimum possibility of getting contaminated or drying out within a reasonable time period. A simulation model developed with MODFLOW (modular three dimensional finite-difference groundwater flow model) and MT3DMS (modular three dimensional multispecies transport model) was used to determine the spatiotemporal effects of potential pollution sources and water withdrawals. Monte Carlo method was used with the simulation models to incorporate the uncertainty in the behaviour of potential pollution sources and water extractions. This integrated methodology was illustrated using a small hypothetical case study. The results indicate that readily invisible hydro-geological factors such as heterogeneous characteristics of subsurface strata, irregular gradients, and varying aquifer thickness have a significant influence on the sustainability of a water supply well. The well positioning decisions recommended by the proposed model can be explained and justified based on scientific data. It finds potentially feasible and sustainable locations for new water supply wells, given uncertain information on future events. Since the uncertainty of available information is taken into account, this methodology is suitable for locating wells in poorly understood aquifers utilised for residential supply. The same methodology can be used to determine landfill locations, minimising negative environmental impacts.