Spatio-temporal variation of gray-green-blue storage capacity in nine major basins of China

Most of China's territory is influenced by the East Asia monsoon, and thus, the spatio-temporal distribution of surface water resources in China is extremely uneven, causing many water-related issues, e.g.. water scarcity and flooding. As the basis and essential condition of economic and social development, water-related infrastructures provide the material basis and guarantee for regulating and storing surface water resources and solving multi-dimensional water problems. The infrastructures that play an important role in surface water resource regulation and storage mainly include three types: Gray (such as dams), green (such as forests), and blue infrastructures (such as lakes). Gray infrastructures can reduce the flood peak and increase water supply during dry seasons by regulating and storing water so that the seasonal and inter-annual fluctuation of runoff is reduced, which plays an important role in water storage, water supply, flood control, and disaster mitigation. However, excessive gray infrastructures would have adverse effects on the social economy and environmental ecology. Unlike gray infrastructures, green and blue infrastructures can not only benefit water resource management but also have ecological functions, such as improving water quality and enhancing ecosystem services. Thus. it is significant to couple gray, green, and blue infrastructures to regulate the spatio-temporal distribution of water resources. However, research on the spatial distribution and temporal variation of water storage capacity is still lacking, which hinders the coordinated regulation and comprehensive management of surface water resources. Therefore, in the present study, the spatio-temporal distribution of the three aforementioned infrastructures was compared and analyzed on basin scale, based on the latest data of darns, root zone storage capacity, natural lakes, and so on. Results indicated the following: (1) Gray water storage capacity has exceeded that of the natural terrestrial surface ecosystem in the Yangtze River Basin and the Southeast Basins, where human activities are intense. (2) Gray water storage capacity has increased significantly in nine major basins from 1955 to 2020, but the timing of construction varies in different basins. (3) Green water storage capacity did not change much, the Songhua-Liaohe River Basin and the Huaihe River Basin increased slightly. (4) Blue water storage capacity shows a constantly increasing trend on the whole, in which the water storage capacity in the inland river basin (including the endorheic basin on the Tibetan Plateau) significantly increased. Our study revealed the basic information and spatio-temporal variation of gray-green-blue water storage capacities in nine major basins of China, which could lead to better coordination between natural and artificial water infrastructures and provide support for multidimensional optimization of water resource allocation.