Clarifying Regional Water Scarcity in Agriculture based on the Theory of Blue, Green and Grey Water Footprints

Water scarcity mitigation in regional agricultural systems contributes to water use efficiency improvement. Blue (WSIblue), green (WSIgreen) and grey (WSIgrey) water scarcity indices were proposed to describe various water stresses in detail and further determine the type of regional water scarcity. WSIblue and WSIgreen reveal resource-based water scarcities, and WSIgrey characterizes environment-based water shortages. Provincial water scarcity indices of China from 2000–2014 were calculated and analyzed in the current paper. The results indicated that the national WSI, WSIgrey, WSIblue and WSIgreen values are 0.84, 0.16, 0.39 and 0.89, respectively. China is facing a high water stress, manifested as a resource-based water shortage. Northwest and Northeast China experience a severe water quantity scarcity with high WSIblue and WSIgreen values, and the central and eastern regions exhibit a high WSIgrey value. Eastern China faces both serious resource-based and environmental water shortages. The constructed blue, green and grey water scarcity indices compensate for the inability of the existing index to determine the type of water shortage and indicate the reason for water scarcity. They also provide a targeted guiding significance for the formulation of effective measures to improve agricultural water resource management and alleviate regional water scarcity.