Spatiotemporal variations in land use impacts on river water quality in a mountain-to-plain transitional basin in arid region of northern China

Abstract

Land use, as an integrated representation of natural conditions and human activities, significantly impacts river water quality. Understanding the spatial and temporal variability of these influences offers valuable insights for improving water quality through the implementation of best management practices. This study examined the impact of land use on river water quality in the Dahei River Basin, a typical mountain-to-plain basin located in the arid region of northern China, which is also the last first-order tributary of Upper Yellow River. Hierarchical clustering analysis was employed to analyze the spatial distribution characteristics of river water quality and redundancy analysis was used to explore the impacts of land use on water quality in upstream buffer zones with radii from 500 m to 14,000 m. The results indicate that river water quality conditions in the mountainous region are much better than in the plain region. In both the dry and wet seasons, land use significantly affects water quality variation, particularly at the 8000 m buffer zone, although the mechanisms differ. In the wet season, the non-point source pollution from storm runoff erosion dominates the positive correlations between water pollution levels and the areas of cropland and urban regions, while for the dry season such positive correlations may come from elevated soil electrolyte levels due to groundwater irrigation and point source pollution from urban activities. For land use types that show a negative correlation with water pollutant levels, the stronger correlation observed in grasslands compared to forests region may be attributed to grasslands' better adaptation to arid conditions. The findings from this study enhance our understanding of the spatiotemporal variations in land use impacts on river water quality and can provide guidance for land use planning at the basin scale in arid regions.