Spatiotemporal evolution of water conservation from 1991 to 2020 in Tibet Autonomous Region, China

Tibet is an essential part of the "Asian water tower". Exploring the spatiotemporal patterns of water conservation in the context of global change is of great importance. In this study, the InVEST model was used to estimate water conservation in Tibet from 1991 to 2020, and the main influencing factors were investigated. The results are: 1) The mean water conservation depth is 84.32 mm, and a spatial pattern with lower values in the northwest and higher values in the southeast of Tibet is observed; 2) There is a significant increase in water conservation from 1991 to 2020 at a rate of about 0.72 mm/year (P < 0.05). Meanwhile, there is an upward trend in water conservation over 81.98% of the area in Tibet; 3) Except for the eastern part of Tibet, the climate is changing toward warm and humid, and the increase in precipitation is greater than the evapotranspiration demand. Therefore, the water conservation is changing positively; 4) The degradation of grasslands has resulted in a 21.14% reduction in water conservation in Tibet. Notably, the water retention capacity of grassland soils in Tibet exceeds that of forested land in drylands. Strategic measures are needed to protect the ecological integrity of Tibet. These include establishing protected areas such as the Nu Chiang Source, implementing measures to conserve native grasslands, and regulating the cultivation of plantations in water-scarce regions.