Effects of human activities and climate change on water quality and health risks of typical urban rivers in arid/semi-arid areas: a ten-year historical analysis

Water resources are scarce in arid and semi-arid regions. Urban rivers, vital water sources, are susceptible to the influences of climate change and human activities. However, there have been few studies analyzing the responses of water quality and health risks to these factors over long-term scales. This study focused on the Diannong River (Shizuishan section) in the upper reaches of the Yellow River from 2011 to 2020. The results reveal significant declines (P < 0.05) in water quality index (WQI), non-carcinogenic risk (HI), and carcinogenic risk (R) during the study period. Regression models based on corrected Akaike information criterion and partial least squares path models demonstrated that human activities contributed significantly to WQI, HI, and R (78.2-85.9%), exerting positive effects on water quality improvement and health risk reduction. Changes in population, land use, and GDP were identified as core reasons. Economic restructuring played a crucial role in ameliorating water pollution. It is noteworthy that continuous environmental protection funds over the decade did not yield significant beneficial effects. The contribution of climate change ranged from 14.1% to 21.8%. Extreme climate indices, especially the maximum length of wet spell, maximum length of dry spell, and growing season length, exerted negative effects on WQI, HI, and R. Temperature and evaporation only inhibited the decrease in WQI, but not HI and R. Under sustained pressure from urbanization and climate change, similar rivers in arid and semi-arid areas can enhance the security and availability of water resources by controlling GDP, urban and farmland area, and population.