Assessing agricultural water use effect of China based on water footprint framework

Abstract: Efficient utilization of agricultural water resources contributes to regional food, water and ecological security. The aim of this paper is to evaluate agricultural water use efficiency taking into account both efficiency improvement and total input control in agricultural production. In view of the study of irrigation water efficiency and total input control, the agricultural water use effect (AWE) index was established based on water footprint and irrigation development framework. For a selected region, the smaller AWE means the better agricultural water use effect. The temporal and spatial pattern of AWE in China during 2000-2014 and its relationship with traditional irrigation water efficiency indices were analyzed based on the calculation of regional agricultural water footprint (AWF), irrigation efficiency (IE) and irrigated land proportion of arable land (IPA) in 31 provinces, municipalities and autonomous regions of China. The results showed that the average annual AWF in China was estimated to be 1.097 2×1012 m3 in the observed period, and the proportions of blue and green water footprints were 13.1% and 86.7% respectively. Both the blue and green water footprint increased over time due to the expansion of agricultural production scale. The spatial difference of AWF and its composition were large, and both the water footprint per unit cultivated area and green water proportion decreased from the southeast to the northwest in China. All of the national IE, irrigation water use and blue water proportion in AWF as a whole improved over time in the latest 15 years. Meanwhile, national AWE value increased from 0.113 in 2003 to 0.137 in 2014, indicating that the agricultural water use situation of China was deteriorating. The space difference of AWE was large and maintained stable in each year of the study period. High AWE values were found in the Huang-Huai-Hai Plain and the Western China, and the low values existed in the southeastern coastal areas of the country. The AWE in the economically developed areas was improved obviously, and the maximum growth rate of AWE occurred in Heilongjiang, which was about 7.81% per year. We also found that there was no spatial consistency between AWE and traditional irrigation water use efficiency evaluation indicators, such as IE and irrigation water productivity. The northern agricultural main producing areas with high irrigation efficiency and irrigation water productivity should pay attention to the assessment of irrigation water utilization and enhance the agricultural water use effect. Only the index AWE can be used for the agricultural water use efficiency considering both efficiency improvement and total input control assessment in current study. The evaluation of AWE can be used as a basis for scientific research and decision-making on efficiency improvement and total quantity control of regional irrigation water resources.