Water ecological footprint size, depth and its spatial pattern correlation in the “Four-city Area in Middle China”

Three-dimensional ecological footprint method is used to distinguish the capital flows and capital stocks of water resources, and measure water ecological footprint size (WEFsize) and water ecological footprint depth (WEFdepth) of 38 regional cities “Four-city Area in Middle China” from 2010 to 2019, and analyze its spatial correlation. The research results are as follows: Firstly, WEFsize per capita of 38 regional cities in the “Four-city Area in Middle China” from 2010 to 2019 had obvious differences, and with large inter-annual fluctuations. The high value area of water resource capital flows occupancy rate (ORFLOW) was distributed in the 13 regional cities, its average capital flows occupancy rate was more than 80%. The low value area of ORFLOW was distributed in the 18 regional cities. Secondly, the annual average value of WEFdepth in the 23 cities of the “Four-city Area in Middle China” was all greater than 1. The high value area of use ratio of stocks to flows (URSTOCKFLOW) for water resource was distributed in the 8 regional cities, its average value was as high as 6.97. The low value area of water resource URSTOCKFLOW was distributed in the 15 regional cities, its average value was as low as 0.02. Thirdly, the relationship between WEFsize and WEFdepth has significant regional differences on an intercity scale. The utilization level of capital stocks and capital flows presents complementary situation on the whole. Fourthly, during the study period, WEFsize and WEFdepth across regional cities in the “Four-city Area in Middle China” had a positive spatial autocorrelation. WEFsize had H-H cluster mainly in CS of 2010 and 2019, CS, PX and XY of 2014, CS and LD of 2016. WEFdepth was in H-H cluster in BB of 2010, BB and XT of 2014, BB and HN of 2016 and 2019. These findings not only provided a new research method for water ecological footprint analysis by measuring the size and depth of water ecological footprint in “Four-city Area in Middle China”, but also provided a theoretical basis for sustainable utilization of water resources in other urban agglomerations.