Transboundary water conflicts between urban and rural populations often center on water use in the agricultural sector. Public officials may select a water conservation policy as the primary tool for reducing agricultural water use with the goal to improve water availability to urban areas and future generations. The Groundwater Management Act of 1980 (GMA) in Arizona was designed, in part, to induce water conservation in irrigated agriculture to sustain economic growth in an arid climate. Our mixed-method evaluation design merges qualitative, interview-based information with an estimated water demand function using panel data. We find that the GMA began with a flawed design and evolved through political circumstances into a ineffective water conservation tool. We explain nearly all water use in Arizona's agricultural sector from 1984-2002 using prices and weather data. We found no statistical evidence that the management plans of the GMA directly contributed to reduced water demand in Arizona's agricultural sector over the study period.