The Measure of Scarcity of Blue and Green Water and Its Driving Factors via the SWAT Model: An Application to the Upper Qingjiang River, China

Blue and green water is vital for the economy and life. Water scarcity occurs when the water resource supply is insufficient to support human, ecological and economic activities within a certain time and space. The water scarcity index quantifies regional blue-green water shortages providing a new perspective for evaluating water usage. Moreover, analysing the driving factors of blue-green water changes can offer a reliable reference for exploring their causes. Taking the Qingjiang River as an example, this study first used the SWAT model to simulate the upper Qingjiang River's monthly streamflow. Then, management levels were mapped to township scale via GIS to calculate blue-green water scarcities. Finally, a geo-detector detected the impacts of natural and socio-economic factors on blue-green water. The results show that (1) the SWAT model has good simulation results and accurately describes the water cycle process in the upper Qingjiang River. (2) From 2010 to 2022, the blue water scarcity indices were stable, whereas the green water scarcity indices first increased but then decreased. (3) The driving force of interaction is stronger than the single-factor effect on blue-green water. This study examines water resource conditions in the basin, offering insights for township-scale water resource management.