Influence of Land Use Change on Green and Blue Water Resources in Xixi Basin of Southeast China during 1970s–2018

As one of the factors affecting water resources, land use is influenced by humans and is of great significance to water resources management. This paper used SWAT model parameter calibration and verification to study the impacts of land use change on green and blue water in Xixi Basin of China from the 1970s to 2000 and 2018, and the inter-annual, monthly and spatial variations of green and blue water were analyzed using multiple averages from 1974 to 1979. The results showed that (1) under rainfall conditions from 1974 to 1979, land use change caused the annual average quantity of green water to decrease from 625.35 mm in 1970s to 619.88 mm in 2018, a decline of 5.47 mm; the annual average quantity of blue water increased from 1019.44 to 1029.59 mm, a change of 10.15 mm. Because of land use change, green water coefficient generally decreased slightly. (2) During the 12 months of a year, green water decreases, and blue water increases were mainly concentrated in May and June. In June with the greatest changes, green water decreased by 5.12 mm, at a rate of 6.28%; blue water increased by 4.33 mm, at a rate of 2.65%. (3) Because of land use change, the green water decreases and blue water increases were mainly concentrated in the upper sub-basins of the basin, and changes were mainly caused by green water decreases and blue water increases from 1970s to 2000. (4) In Taozhou Township, the possible impact of the reduction in green water on rain-fed agriculture should be paid attention to; during the flood season, especially in June, the possible influence of increased blue water on floods in areas such as Hutou Town and Bailai Township should be considered. This study can provide a scientific basis for the rational and efficient use of water resources in a region.