Analysis of spatial and temporal evolution and drivers of water production in the upper reaches of the Black River

The upper reaches of the Heihe River Basin are the main flow-producing area of the whole basin, which is of great significance for maintaining the ecological balance of the basin, and the spatial and temporal characteristics of its water yield and its response to changes are of great significance for the development, utilisation and management of the basin's water resources. Based on the water yield module of the InVEST model, the water yield of the upper Heihe River Basin in 2000, 2005, 2010, 2015 and 2020 was evaluated by using Geodetectors and scenario analyses, and the temporal evolution of water yield and its response to climate change and land use change in the past 20 years were analysed. The results showed that: (1) from the point of view of spatial distribution, the northwestern and central parts of the study area in the upper Heihe River Basin during the period of 2000-2005 were the areas with low values of water yield, while the depth of water yield was higher in other areas; the spatial distribution of water yield during the period of 2010-2020 was distinctly characterised by a pattern of high south-east, high north-west and low north-west; (2) the water yield during the period of 2000 , 2005, 2010, 2015 and 2020, the water yield of the Upper Heihe River was 37.78×10⁸ m³, 35.74×10⁸ m³, 44.28×10⁸ m³, 49.80×10⁸ m³, 45.80×10⁸ m³, respectively, and the water yield was generally on a rising trend first, with a larger increase; (3) the results of the Geodetector showed that the annual evapotranspiration ( 0.5162), mean annual temperature (0.4522), and annual precipitation (0.3383) factors have an explanatory power of more than 30%, and the interaction between climate factors has the strongest explanatory abilityindicating that climatic factors are the dominant factors affecting the spatial differentiation of water yield, and to a certain extent dominate the changes in the spatial differentiation of the water yield in the upper part of the Heihe River Basin. from 2000 to 2020, the changes in precipitation in the upper part of the Heihe River Basin have a large influence on the water yield, and the land area has a large influence on the water yield. water yield is large, and land use changes have a smaller impact on water yield.