In a study of water management in t

In a study of water management in the San Juan River Basin of New Mexico reported in 1981, Gilliland and Fenner (3) found that improving irrigation efficiencies did not significantly change water depletion. The hydrology and chemistry of the river basin system were such that there was only a slight effect on the salinity of the river. For the conditions of the study area, they found that efforts to improve irrigation efficiency were not cost effective and were not feasible for agriculture. Changes in irrigation efficiency did not significantly change the basin evapotranspiration and therefore did not effectively change the basin leaching fraction. It is also possible that increased consumptive uses due to better water distribution, i.e., higher irrigation efficiencies, was offset by lower volumes of saline return flows so that there was no net change in downstream water quality. Their findings emphasize the need for a complete water management evaluation on a basin scale to determine the water quality effects of increasing irrigation efficiencies.