Future water security in the major basins of China under the 1.5 °C and 2.0 °C global warming scenarios.

Freshwater is an essential resource for human lives, agriculture, industry, and ecology. Future water supply, water withdrawal, and water security under the impacts of climate change and human interventions have been of key concern. Numerous studies have projected future changes in river runoff and surface water resources under climate change. However, the changes in the major water withdrawal components including agricultural irrigation water, industrial, domestic and ecological water withdrawal, as well as the balance between water supply and withdrawal, under the joint impacts of climate change and socio-economic development have been seldom investigated, especially at the basin and national scales. In this study, changes in surface water resources, agricultural irrigation water, industrial, domestic and ecological water withdrawal, as well as the balances between water supply and withdrawal, under the baseline climate (2006-2015), 1.5 °C and 2.0 °C warming scenarios (2106-2115) in the 10 major basins across China, were investigated by combining modelling and local census data. The results showed that water withdrawal exceeded water supply in the basins of Liao River, Northwest River, Hai River, Yellow River and Huai River in the baseline period. Under the 1.5 °C and 2.0 °C warming scenarios, the shortage of water resources would aggravate in the above-mentioned basins and the Songhua River basin. And the surplus of water resources would reduce substantially in the basins of Yangtze River, Southeast River and Pearl River. Overall, the difference between water supply and water withdrawal was 435.88 billion m during the baseline period, and would be 261.84 and 218.39 billion m, respectively, under the 1.5 °C and 2.0 °C warming scenarios. This study provides a comprehensive perspective on future water security in the 10 major basins across China, has important implications for water resources management and climate change adaptation.