Water resources efficiency assessment in crop production from the perspective of water footprint

Reducing water use and relieving negative environmental consequences contribute to regional water and ecological sustainability. This work examined water resource efficiency (WRE) and the effects of effective crop water use from the perspective of the water footprint. WRE was defined as the ratio of consumptive field water use (CWU) to the total crop water footprint (CWF), including the blue water footprint applied (BWFA), green water footprint (GWF), and grey water footprint (GYWF). WRE for the cultivation of the main crops (rice, wheat, maize, beans, and tubers) produced in China during the period of 1996-2015 was determined from estimates of provincial CWFs and CWUs. The results show that national CWF was estimated as 678.5 Gm3, of which GWF comprised 55.1%; the national crop CWU was approximately 455.6 Gm3 in the period considered, and this included 82.1% green and 17.9% blue water. The spatial patterns of CWF and CWU densities differed greatly but were stable over time, with increasing trends exhibited from 1996 to 2015. The national WRE for crops was 0.672, and that for beans was 0.869, an efficiency larger than that of any other crop. The indices for rice and wheat were approximately 0.630. WRE cannot be replaced by the global efficiency (GEF) or generalized efficiency (GE) indices, either for scientific evaluations or for considerations of spatial distributions. This study aids in the evaluation of effective water resource consumption by considering the process of agricultural water use, and also the impact of crop production on water quality and quantity. Hence, WRE is an advanced indicator linking measurements of water footprint with assessments of crop management and the sustainability of regional water resources.