Increase in economic efficiency of water use caused by crop structure adjustment in arid areas.

The Heihe River is located in the arid zone of northwestern China. In its middle-reach region, irrigation agriculture is well developed. With rapid population growth and expansion of the cultivated land in this region, effective water resource use is vital for the sustainable development of the river basin and the increase of incomes from farming practices. In this study, based on farmer survey data, the input parameters of the CROPWAT model were modified, the water use amount was simulated after deducting the influences of climate, seeds, and irrigation systems, and the variation of economic efficiency of water use (EEWU) induced by crop structure adjustment from 2001 to 2012 was analyzed. The results show that simulations for evapotranspiration of maize based on the CROPWAT model are in accord with the observed data. From 2001 to 2012, due to changes in the regional crop structure, EEWU in the study area increased by about 40%. In the arid areas in northwest China, crop structure adjustment has a huge potential for improving EEWU and increasing incomes from farming practices.