Characteristics of Spatial and Temporal Variations of Water Production Functions in the Semi-arid Watershed of the Loess Plateau

Under the background of climate and land use change, it is of great significance to study the spatial-temporal characteristics and response of water production and analyze the spatial-temporal differentiation and variation trend of water production function in the Malian River Basin. Based on InVEST model, the temporal and spatial characteristics of water yield and the effects of land use type, elevation, precipitation, and actual evapotranspiration on water yield in Malian River Basin from 1990 to 2020 were quantitatively analyzed. The results show that: (1) The total water yield of the basin in 1990, 2000, 2010 and 2020 was 4.563×10⁸, 2.640×10⁸, 3.853×10⁸ and 3.264×10⁸ m³, respectively. The spatial pattern of water yield in different periods was basically the same, showing the spatial difference characteristics of high in downstream and low in upstream; The depth of water produced in the whole basin is mainly reduced, the significant reduction area is concentrated in the middle and upper reaches, and the extremely significant reduction area is mainly in the middle and lower reaches. (2) The water production capacity of urban land, construction land and high coverage grassland was the strongest, while that of water area was the weakest. The higher the precipitation, the lower the altitude, the smaller the actual evapotranspiration and the lower the vegetation coverage, the stronger the water production capacity. (3) There was a significant positive correlation between water production and precipitation, and a negative correlation between altitude and actual evapotranspiration. The order of influence degree of each influencing factor on water production was precipitation > altitude > actual evapotranspiration > land use. (4) The southwest of the basin as a key functional area of water production should be planned for protection, while the northeast of the basin is a low-value area of water production, and human activities should be reduced to focus on protecting ecosystem stability and biodiversity. The spatial-temporal pattern of water production in the Malian River Basin changed significantly from 1990 to 2020, and the precipitation factor is the main driving factor.