Water Quality Assessment and Pollution Control of Urban Road Stormwater Runoff in Arid Regions: A Case Study of Yinchuan, China

To further investigate stormwater runoff patterns, pathogenic risks of pollutants on urban roads, and mitigation of urban non-point source pollution, road runoff monitoring and sampling were conducted in selected sections of central Yinchuan, a city in the arid region of northwestern China. Processed data—including rainfall, flow rate, and water quality parameters (conventional five indicators and heavy metals)—were obtained from ten rainfall events in 2024. Through analyses of water quality characteristics, influencing factors, runoff flushing patterns, and stormwater control measures, the current status of road runoff pollution was clarified. The Nemerow pollution index method was applied to evaluate pollutant levels and assess human health risks. Results indicate that pollution levels in Yinchuan are relatively mild, with most pollutant concentrations below the Class IV surface water quality standard. Basic rainfall parameters—peak rainfall intensity (PRI), average rainfall intensity (ARI), and previous sunny days (PSD)—together with urban functional zones, significantly influence pollutants in rainfall runoff, with the antecedent dry period showing the most pronounced effect. Analysis of the runoff scouring effect reveals that scouring of the conventional five water quality indicators (SS, COD, TN, NH 3 -N, and TP) is substantially more evident than that of heavy metals. The runoff control depth for roads in central Yinchuan ranges from 0.9 mm to 40 mm, sufficient to manage runoff pollution from small to medium-sized rainfall events. The Nemerow pollution index remains below 8.36, with no severely polluted areas identified, indicating relatively low pollution in Yinchuan’s urban core. Quantitative human health risk assessment suggests that health risks associated with heavy metals on roads are low, with no significant exposure risk, implying that stormwater runoff in Yinchuan poses no substantial threat to human health. This study provides a valuable reference for non-point source pollution control via stormwater runoff management in arid-region cities.