This paper is the result of ecological geological survey engineering.

Objective Shaanxi section of Han River Basin is located within the Qinling−Daba Mountains biodiversity and water conservation functional area, serving as the critical water source for the middle route of the South−to−North Water Diversion Project. Exploring the water conservation function of this area, especially quantifying the water conservation in dry year, is of great significance for guaranteeing the water transfer safety of the project, protecting ecological environment, and managing regional water resources.

Methods This study utilized the InVEST model to calculate the water yield and water conservation of the study area in wet year (2018) and dry year (2001), delineated water function zones and analyzed the primary drivers influencing water conservation function.

Results The water conservation in the study area was 244.1×10⁸ m³ and 147.94×10⁸ m³ in wet and dry years, respectively. Despite minimal changes in the areas of grassland, forestland, and farmland between the two periods, increased precipitation led to a significant improvement in average water conservation depth. Strong water conservation function areas were mainly distributed in the west of the study area and the southern Daba Mountains, while low function areas were concentrated in intermontane basins and densely urbanized region.

Conclusions The water conservation of Shaanxi section of Han River Basin in dry year exhibited the potential to support the water transfer demand of the middle route of the South−to−North Water Diversion Project. Precipitation and potential evapotranspiration were the primary driving factors influencing changes in water conservation function in the study area. Variations in geomorphological characteristics and elevation gradients served as important endogenous controlling factors for spatial differences in water conservation function. In contrast, land use types acted as a key regulatory factor leading to spatial heterogeneity in water conservation function, particularly in intermountain valley basin areas where significant human activities resulted in relatively weaker water conservation function. These findings provides valuable insights for water resource management and sustainable development in the Qinling−Daba mountainous region, offering critical guidance for advancing high-quality ecological civilization development in the study area.