Trends in China’s agricultural water use during recent decade using the green and blue water approach

China agricultural water use and management are facing enormous challenges in the 21st century.The core concepts of the paradigm shift in the global scientific research and public policy are regarding the agricultural water use and management in the last decade,i.e.,green water(GW),blue water(BW),the crop water productivity (CWP),and the broadly-defined agricultural water resources(BAWR),as well as matching between the cropland and the BAWR.Using these concepts,we propose an integrated framework for assessing China's agricultural water use of 1998-2007.The results reveal that among all the water that is potentially available for the cropland use,the GW contribution accounts for 57%and the remaining 43% are coming from BW.The CWP of major grain crops have already been at or approaching to the higher levels as measured by the international standards.Further improvement on the subject is thus limited.Based upon our estimated value of BAWR,the bottom line of water resources for the China's food security should then be set at 7 800×10⁸m³.