The objective is to provide an estimate of the use value of the U.S. High Plains aquifer in agriculture. A regional production function for the crop sector, based on countylevel observations, was estimated. Two main estimation procedures were used. The first used a system of equations and instrumental variables, the second accounted for spatial effects. Using the estimated production responses to irrigation, we estimate the average gross value of groundwater for agriculture to be $165/acre at 2007 prices. Using spatial statistical analysis, we found significant spatial relationships that increased this estimate to $174