had been operating erratically during 2004, which made it impossible to deliver the surface water volumes pledged to Irrigation District 038 in Río Mayo, Sonora, at the start of each agricultural cycle, and caused an overexploitation of groundwater. In order to solve this problem, the State Water Commission of Sonora asked IMTA to determine optimal policies of joint dam-aquifer operation. To do so, methodologies based on dynamic programming and genetic algorithms were used. As a result, an operation policy was recommended that considers an extraction volume from the dam dependent of the storage level at the beginning of the agricultural cycle. Specifically, a minimum extraction volume of 400 hm3 and a maximum extraction volume of 1,100 hm3 were determined. This policy allows to eliminate the deficit in the surface water volumes pledged to the irrigation district and reduce extractions from the Valle del Mayo aquifer. References Dams completed in 1955 Dams in Mexico Buildings and structures in Sonora 1955 establishments in Mexico