Past, current and future water footprints, water scarcity and virtual water flows in China

Abstract

The increasing water consumption as a result of population growth and economic development, especially in fast growing developing countries, puts an increasing strain on the sustainable use of the globe’s finite freshwater resources and poses a key challenge for the future. The objective of the thesis is to evaluate past, current and future water footprints (WFs), water scarcity and virtual water (VW) flows at both river basin and national level in China, focusing on the agricultural sector, high spatial resolution modelling, uncertainties, inter- and intra-annual variation and benchmarks. A case study for the Yellow River Basin (YRB) for 1996-2005 show that uncertainties in key input variables together generate an uncertainty of ± 30% (at 95% confidence interval) in the estimated WFs of crops. The inter- and intra- annual variation of WF of crops and blue water scarcity in the Yellow River Basin over 1961-2009, as well as the inter-annual variability of crop-related green and blue WFs and inter-regional virtual water (VW) trade in China over 1978-2008 were simulated. The green-blue WF per tonne of crop reduced significantly due to improved crop yields over past five decades, while the grey WF increased dramatically because of the growing application of fertilizers. On average, the YRB faced moderate to severe blue water scarcity during seven months (January-July) per year. Historically, the net VW flow within China was from the water-rich South to the water-scarce North, but intensifying North-to-South crop trade reversed the net VW flow since 2000. On average, 35% of the crop-related WF of a Chinese consumer was outside its own province. The thesis further investigated the green and blue WFs and VW trade in China under alternative scenarios for 2050 focusing on the agricultural sector. The results show that Changing to a less-meat diet can generate a reduction in the WF of food consumption of 44% by 2050 as compared to 2005. Finally, based on a case study for winter wheat in China (1961-2008), it is found that when determining benchmark levels for the consumptive WF of a crop, it is most useful to distinguish between different climate zones.