Spatiotemporal variations of water conservation in the Ganjiang river headwater region under climate and land use change

Abstract With water resource shortages becoming a global concern, water conservation (WC) is a key factor for the sustainable development of watershed ecosystems. WC in the headwater region is sensitive to both climate and land use changes, and once damaged, it is difficult to restore. However, few studies have analyzed the spatiotemporal variations of WC in the Ganjiang River headwater region (GJHR). Therefore, this study applies the Water and energy transfer processes in large river basin (WEP-L) model and the water balance equation to assess the spatiotemporal variations of WC in the GJHR during 1957–2018. Results show that: (1) the annual mean WC was 552.3 mm during 1957–2018, and with an increasing trend of 0.85 mm/a. (2) WC ranged from 44.2 to 1178.6 mm, with higher values in the north and south, while lower values in the west. The highly and extremely important area are mainly in the north central and southern parts of the GJHR, they provide water resources security for the GJHR, which needs to be protected on a priority basis. (3) From 1980 to 2014, the dominant land use change was the conversion of forest to farmland, leading to a reduction in forest and an increase in farmland. (4) The decrease in forest and increase in farmland reduced WC. Precipitation was the main factor influencing the spatiotemporal variations of WC. There is obvious spatial heterogeneity in the WC in the GJHR. Future ecological restoration planning should prioritise a scientifically optimised spatial layout that enhance WC capacity and mitigating regional disparities. These findings provide a scientific basis for water resources management and ecological restoration in the source region.