Growing WATER Scarcity and Its Implications For WATER-For- FOOD In China.

Water is the first and foremost constraint threatening China’s food security. Hence, ‘who will feed China’ could be to large extent translated into ‘who will water China’. The paper attempts to find out a win-win solution for water-for-food by reviewing and assessing water and food situations in the recent decade, through using an integrated analytical framework based on green and blue water approach From 1998 to 2010, the annual precipitation in China slightly declined. The relative share of blue water (i.e. Internally Renewable Water Resource or IRWR) and green water (i.e. water falling on and being directly used by terrestrial ecosystems) changed greatly, with the green water increasing from 49.7% to 55.8%, and blue water falling from 50.3% to 44.2%. Moreover, the declining rate of IRWR is faster than that of precipitation. This may prophecy a growing role of green water played in sustaining water for food, and water for life (ecosystem) as well in years to come. Besides the declining blue water resources, food security in China may be complicated by increasing variations in precipitation and IRWR, especially in 13 breadbasket provinces (BPs) where the grain output accounts for some 70% of the national total. A positively linear relationship can be observed between c.v. of precipitation and IRWR., suggesting a variability exists for blue water for food production in BPs over 1998-2010. Another concern is the high dependence ratio of food production on groundwater and the consequential over-tapping of groundwater and the spreading drawdown cones in most of BPs. For instance, groundwater is responsible for 80% of blue water supply in Hebei Province. Such high share of fossilized groundwater in crop production is unsustainable and the bubble arising out of it will eventually burst out. Given the shrinking blue water, the growth trend of China’s grain outputs persisted to present time since 2004. The gains in crop water productivity (CWP) may partly account for the increased crop outputs with modest increase in water consumption. The result of Broadly-defined Agricultural Water Resource (BAWR), in which both green and blue water components are incorporated, shows that soil-held green water plays a major role in crop production, and consequently the soil-water-derived actual evapotranspiration represents in most part the total crop water consumption. Despite already high blue and green water depletion rates at most river basins in China, ample room for improvement still exists for southern basins (i.e. Yangtze, Southeast, Pearl). The paper also concludes that water productivity of major grain crops of China is already high. The further improvement on it requires the synergic effort through reinforcing field management, enhancing crop yield, and optimizing cropping patterns and systems to achieve real water savings at multiple spatial scales (i.e. plant stand, farm fields, watershed, basin).