Loss of water quality in streams is an increasing problem in Uruguay, and dairy production stands out as one of most influential activities in diffuse nutrient losses (Failde et al., 2015). Santa Lucía river basin with a 13,681 km2 surface, has a high relevance to Uruguayan society because it is the main source of drinking water for metropolitan area of Montevideo, where 60% of country population lives. The objective of this work was to develop a spatially explicit optimization model that allows reaching certain levels of dairy production, minimizing the export of phosphorus to the surface waters.