Mitigating negative water quality and quality externalities by joint mangement of adjacent aquifers

Abstract

Groundwater basins are usually separated into aquifers that are hydrologically interrelated. This interrelation may take the form of water movement from one aquifer to another. When differentials in water quality exist, pumping from one of the aquifers can cause water movement that may be associated with degradation of its quality. A management policy that considers this interrelation may be preferable to an independent management of each aquifer. This paper develops a dynamic optimal control model to evaluate joint versus independent management. The optimal joint pumping management, in which two adjacent aquifers of different water qualities are interrelated, is analyzed and compared to independent aquifer pumping, and the situations where joint management is not required are identified. Policy implications are then derived and discussed. Finally, the theoretical model is applied to a case of interrelated aquifers in southern Israel. The empirical model identifies conditions (interest rate, agricultural fresh water supply rainfall recharge, price of surface water, drinking water quality standards) under which a joint policy is preferable. The empirical results confirm the theoretical ones.