Water Availability in China's Oases Decreased Between 1987 and 2017

The significant expansion of China's oases during recent decades has inevitably increased water demand, profoundly affecting the regional water budget. While streamflow and precipitation have increased in China's oases under climate change, it remains uncertain whether this augmented water supply will suffice to meet the increasing water demand of oases, presenting a great challenge to guarantee regional water security. Here we used a process-based crop water model, oasis land use datasets, vegetation maps, and observational data on streamflow and grain production to estimate the impacts of China's oasis dynamics on regional water resources from 1987 to 2017. We found that the water demand in oases significantly increased during 1987-2017, and oasis areas that have existed since 1987 accounted for a greater proportion of the increased water demand than newly expanded oasis areas. Although increases in precipitation and streamflow largely offset the additional water demand, 60.3% of counties in oasis regions experienced a decrease in water availability after 1987 because of a spatiotemporal mismatch between water supply and demand, and some counties suffered water deficits. Our findings provide a quantified basis for identifying and optimizing water use structures for water security in oases.