Spatiotemporal heterogeneity of urban and rural water scarcity and its influencing factors across the world

Abstract

Water scarcity is essentially caused by the spatiotemporal mismatch of water availability and water withdrawal. However, existing studies are still insufficient in revealing the spatiotemporal heterogeneity and rural–urban differences of global water scarcity and its influencing factors. Therefore, this study aims to fill this gap. From 1960 to 2014, both of the water-scarce population and its proportion in the total population showed a growth trend. The annual growth rate of water-scarce urban population was higher than that of water-scarce rural population, but the standard deviation of monthly water-scarce rural population was higher than that of water-scarce urban population. The proportion of water-scarce population was high and also variable across months in the middle- and low-latitude countries of the Northern Hemisphere, such as Pakistan, Mexico and Iran. Expansion of water-scarce areas had contributed to 60% of the global water-scarce population growth, while the relative contribution of population increases in the initial water-scarce catchments was about 40%. As for the expansion of water-scarce areas, the relative contributions of irrigation, domestic, and industrial water withdrawal were 35.28%, 24.28%, and 17.02%, respectively. In most high-latitude countries of the Northern Hemisphere, industrial water withdrawal was the main influencing factor. In several Southern Hemisphere countries, domestic water withdrawal was the most influential factor. In most Asian countries, the impact of irrigation water withdrawal was considerable. In addition, the impacts of water availability and irrigation water withdrawal were greatest in July, while the impacts of domestic and industrial water withdrawal were greatest in December. The relative contributions of water availability and irrigation water withdrawal were highly variable in Iran, Pakistan and India. The monthly variability in industrial water withdrawal was high in European countries. There was high variability in all influencing factors in China and some Central Asian countries. According to the variability of water scarcity and influencing factors, water-scarce countries should implement effective water resources management, based on the potential solutions such as the construction of water conservancy facilities, virtual water trade, and improving the efficiency of water use and recycling.