Hydro-environmental response to the inter-basin water resource development in the middle and lower Han River, China

As one of the most important influencing factors, inter-basin water resource development has been exerting an increasingly evident impact on the hydro-environment of river basins. The Han River was selected as a case study to reveal the hydro-environmental response to China's inter-basin water resource development. The hydrological changes and water-quality variations resulted from the middle route of the South-to-North Water Transfer Project (SNWTP) and the Three Gorges Reservoir (TGR) operation were examined based on a hydro-environmental model. The results indicated that the runoff reduction is obvious after the SNWTP operation, and the low-flow duration significantly increased by 4–5 months. Consequently, the flow decrease significantly contributed to the water quality deterioration in the middle and lower Han River, while the Yangtze-Han Water Diversion Project (YHWDP) can not alleviate the situation completely. Moreover, the nutrient assimilative capacity decreased after water diversion, which agrees with the hydrological changes along the middle and lower Han River. The quantitative analysis performed in this study distinguishes the spatiotemporal variation in water quality variables using the integrated model. It provides insights into water quality management under the influences of inter-basin water resource development.