Identification of pollution sources in transient groundwater systems

Abstract

A methodology using a nonlinear optimization model is presented for estimating unknown magnitude, location and duration of groundwater pollution sources under transient flow and transport conditions. The proposed optimization model incorporates the governing equations of flow and solute transport as binding equality constraints, and thus essentially simulates the physical processes of transient flow and transient transport in the groundwater systems.The proposed inverse model identifies unknown sources of pollution by using measured values of pollutant concentration at selected locations. Performance of the proposed model for the identification of unknown groundwater pollution sources is evaluated for an illustrative study area in a hypothetical confined aquifer under different cases of data availability. The effect of observation well location vis-a-vis pollution source location on identification accuracy is also investigated. Performance of the developed identification model is also evaluated for a condition when concentration measurements are missing during few initial time periods after the pollution sources become active. The effect of specified initial guesses of the variable values on the optimal solutions are also investigated. These performance evaluation results demonstrate the limitations and potential applicability of the proposed optimization model for identifying the sources of pollution in transient groundwater systems.