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More grain in the North China Plain with less water consumed: a response to Chris Perry

In his letter defending Frederiksen and Allen (2011) against the critique by Gleick et al. (2011) in the area of water accounting, Chris Perry (2012) pointed to our article “Less Water, More Grain in Dry Hebei Province, China” (Jia et al. 2011) as an example of failing to do “traditional” water accounting properly. He was particularly worried that our conclusion that “there is little need for concern about a grain production crisis induced by water shortage” would divert the authorities in North China from the proper path of reducing water consumption through controlling evapotranspiration. To make his case, he cited a study involving Professor Liu Changming, a distinguished member of my institute, using twentieth-century data from Luancheng County in Hebei (Kendy et al. 2003). First of all, I would like to thank Dr Perry for the opportunity to elaborate on this critical issue, and to reassure him that I am well aware of the difference between total water use in agriculture and the consumed fraction, and of the consequences of focusing only on reducing the former. In fact, 15 years ago I argued, in a paper about the estimation of real water savings due to canal lining (Jia 1997), that more attention should be paid to water consumption in assessing the net effects of water saving technology. So, why did we use water use and not water consumption to calculate water productivity in our article, as well as the preceding Jia et al. (2010)? The main reason is that water consumption data are not as comprehensive or available, and when they are at hand (as they tend to be for the North China Plain), they are based on samples. Figures for consumption on a wider scale are derived by calculating the consumption/use ratio at those locations and applying that ratio to water use data. Fortunately, based on the information available to us, our conclusion of “more crop per drop” also holds when we consider water consumption, even if the latter is something of a guess. As indicated in Figure 1 for Hebei Province (which is representative of the North China Plain), water use has declined by about 10%, especially since 2002, while grain output has increased by about one-third. Even in the unlikely case that water consumption actually did not fall, there was significantly more crop per drop, however you measure it. The same phenomenon has occurred elsewhere in China. So it is very easy to come to the conclusion that indeed less water has produced more grain in all of China, in the Hai River basin, and even in Hebei Province. Perhaps in some places, such as suburban Luancheng