Effect of landscape pattern on river water quality under different regional delineation methods: A case study of Northwest Section of the Yellow River in China

Study region: A typical arid irrigation area of the Yellow River, Ningxia, Northwest China. Study focus: At present, few studies have evaluated the effects of nested watershed and runoff process on the relationships between landscape patterns and water quality. In this study, we aimed to quantify the relationships between landscape pattern and river water quality using two delineation methods. One method involved a water quality monitoring site only corresponding only to its own sub-watershed, while the other method involved a water quality monitoring site corresponding to all of its upstream sub-watersheds. New hydrological insights for the region: We collected water quality monitoring data, including DO, CODMn, NH3-N, TP, TN, pH for the irrigation period (May, 2021 - August, 2021) and the nonirrigation period (December, 2021 - March, 2022) for seven sub-watersheds. Our results revealed that when a water quality monitoring site corresponded to all the sub-basins involved in the runoff process, the correlations between landscape composition and water quality parameters were stronger. Additionally, the degree to which landscape configuration explained the overall water quality was greater in such cases. We also found that the buffer zone scale accounted for more than 97.3% of the overall water quality variation. These results highlight the importance of aligning water quality monitoring sites with the corresponding sub-watersheds and emphasize the significance of land-use management in the riparian scale near the Yellow River for water quality protection.