ABSTRACT
In deriving efficient management policies to control groundwater nitrate pollution, it is important to conduct integrated modeling which takes into consideration soil, unsaturated and saturated zones. In groundwater management regional studies the influence of the unsaturated zone is often neglected. The unsaturated zone can have an important influence on the time delay of nitrate transport and therefore on accomplishing the good groundwater chemical status required by the EU Water Framework Directive. In this paper a simple unsaturated zone model is coupled with a hydro-economic framework that obtains the spatial and temporal fertilizer application rate that maximizes the net benefits in agriculture constrained by the quality requirements in groundwater at various control sites. The integrated model was applied to El Salobral-Los Llanos aquifer in Spain. The fertilizer allocation that accomplishes with the nitrate concentration in groundwater was obtained. The results show that a delay of about 7 years can be expected on accomplishing the quality requirements when considering the unsaturated zone, while the total benefits do not have a considerable change.
