Contrasting quantity and quality flows in China's intercity virtual water trade reshape water scarcity and inequality

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.

Trade of commodities can lead to virtual water flows between trading partners. When commodities flow from regions of high water productivity to regions of low water productivity, the trade has the potential to generate water saving. However, this accounting of water saving does not account for the water scarcity status in different regions. It could be that the water saving generated from this trade occurs at the expense of the intensified water scarcity in the exporting region, and exerts limited effect on water stress alleviation in importing regions. In this paper, we propose an approach to measure the scarce water saving associated with virtual water trade (measuring in water withdrawal/use). The scarce water is quantified by multiplying the water use in production with the water stress index (WSI). We assessed the scarce water saving/loss through interprovincial trade within China using a multi-region input-output table from 2010. The results show that interprovincial trade resulted in 14.2 km3 of water loss without considering water stress, but only 0.4 km3 scarce water loss using the scarce water concept. Among the 435 total connections of virtual water flows, 254 connections contributed to 20.2 km3 of scarce water saving. Most of these connections are virtual water flows from provinces with lower WSI to that with higher WSI. Conversely, 175 connections contributed to 20.6 km3 of scarce water loss. The virtual water flow connections between Xinjiang and other provinces stood out as the biggest contributors, accounting for 66% of total scarce water loss. The results show the importance of assessing water savings generated from trade with consideration of both water scarcity status and water productivity across regions. Identifying key connections of scarce water saving is useful in guiding interregional economic restructuring towards water stress alleviation, a major goal of China’s sustainable development strategy.

Water footprint (WF) is a measure of the actual appropriation of water resources. WF accounting can provide a scientific basis for the managements of water resources. In this study, a multi-regional input-output model is employed to measure the quantity of blue WF (WF) and inter-provincial virtual water (VW) flows in China for the years of 2007 and 2010. The results show that: (1) China’s total WF increased from 205.42 billion m3 in 2007 to 229.34 billion m3 in 2010. Approximately 42% of the WF was attributed to VW embodied in inter-provincial trade. Xinjiang is the largest province of VW export, whereas Shanghai had the largest net VW inflows. (2) From 2007 to 2010, the share of the agricultural sector in the entire VW trade declined, but was still as high as 82.78%, followed by the industrial sector. (3) The north-to-south and south-to-south patterns were witnessed in the domestic VW flows. The provincial WF variations are found to be affected by the per capital GDP, total water resources, per capita water resources, and urban population. (4) By linking VW with an integrated WAVE+ (water accounting and vulnerability evaluation) factor, it was found that virtual scarce water (VSW) was mainly exported by the provinces in northern China. At the national level, the amounts of VSW inflows were consistently greater than those of VSW outflows for both years, 2007 and 2010, implying an increased pressure on the provinces with water deprivation issues. Overall, these results can provide a basis for refining the spatiotemporal allocation of water resources and mitigating the conflict between water supply and demand in China.

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