In this paper, we assess the output-oriented technical efficiency of agricultural production functions in order to compare, over time, economic and environmental production processes in the different regions of the Spanish Ebro basin, in a climate change context. The measurement of technical efficiency in agriculture can provide useful information about the competitiveness of farms and their potential to increase its productivity moreover can help in the crops adaptation to water pressure by improving the management of scarce resources. Here, we generate an agricultural water efficiency index to evaluate the adaptation of some Mediterranean crops to the water pressures in this area. We estimate frontier production functions and technical efficiency measures, using panel data models. This will allow us to observe changes in production due to individual specific effects and those that are time specific. To characterize our model, we use historical data, about crop yields, water requirements and climate as well as socio-economic and geographical aspects of the most representative crops in the provinces of the Ebro basin during 1976-2007. Then we generate a ranking of the most efficient crops across geographical areas, given their water use and other inputs, to evaluate policy scenarios with adjustments in water supply.