Diffuse groundwater pollution is a growing concern everywhere in the world and one of the most problematic and widespread of the vast number of potential groundwater contaminants are nitrates, which often primarily comes from the intense use of fertilizer in agriculture.Groundwater pollution has provoked a normative and a recommendation development. In Europe the Nitrate Directive was established in 1991, and the Water Framework Directive (WFD) in 2000. The WFD states that all water bodies have to reach a good quality status by 2015. The WFD explicitly recognizes the role of economics in reaching environmental and ecological objectives. One of the elements that the WFD mentions is the cost-effectiveness analysis (CEA) as a method to obtain the most costeffective program of measures to reach good water status.A hydro-economic modeling framework is developed for determining optimal management of ground water nitrate pollution from agriculture. A holistic optimization model determines 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. Since emissions (nitrogen loading rates) are what can be controlled, but the concentrations are the policy targets, we need to relate both. Agronomic simulation models are used to obtain crop yield and nitrate leaching functions in terms of water and fertilizer use, while numerical groundwater flow and solute transport simulation models were used to develop unit source solutions that were assembled into a pollutant concentration response matrix. The integration of the response matrix in the constraints of the management model allows simulating by superposition the evolution of groundwater nitrate concentration over time at different points of interest throughout the aquifer resulting from multiple pollutant sources distributed over time and space. In this way, the modeling framework relates the fertilizer loads with the nitrate concentration at the control sites. The benefits in agriculture were determined through crop prices and crop production functions. In this way, this framework provides a practical tool for analyzing the opportunity cost of measures for reducing nitrogen loadings and assessing their effectiveness for maintaining groundwater nitrate concentration within the target levels.The management model was applied to a hypothetical groundwater system. Optimal solutions of fertilizer use to problems with different initial conditions, planning horizons, and recovery times were determined. The illustrative example shows the importance of the location of the pollution sources in relation to the control sites, and how both the selected planning horizon and the target recovery time can strongly influence the limitation of fertilizer use and the economic opportunity cost for meeting the environmental standards. There is clearly a trade-off between the time horizon to reach the standards (recovery time) and the economic losses from nitrogen use r...