Assessing grain crop water productivity of China using a hydro-model-coupled-statistics approach. Part II: Application in breadbasket basins of China

We assessed the basin-scale crop water productivity (CWP) on staple grain crops, i.e. rice, wheat, maize, soybean, at major breadbasket basins of China over time periods of 1997-2004. The multiple-year average CWP was 1,06 kg m(-3) for the selected basins (equivalents of 946 m(3) water consumption in producing 1 metric ton of crop economic yield), varying from 0.97 kg m(-3) to 1.18 kg m(-3.) Of all the water consumed in crop production, irrigation water contributes 28-41%, while soil-stored precipitation contributes 59-72%, confirming the crucial yet hitherto under-estimated role played by green water in total crop yield formation. The blue water depletion rate ranges from 0.48 to 0.87, with most of the basins exceeding 0.50, while the green water depletion rate from 0.39 to 0.85, with the majority of basins being beyond 0.60. We conclude that both blue and green water shortage will contribute to water scarcity in grain crop production. The mission of ensuring China's food security will entail multiple trade-offs among water security, ecosystem conservation, environment protection, and human development with increasing challenges in the years to come. However, increasing water productivity through research innovation and technological upgrades at river basin scale is a key to mitigating water stress that may be caused by increasing food production in the coming decades. (C) 2010 Elsevier B.V. All rights reserved.