Assessing the Impact of Water Diversion on Hydrodynamics and Water Quality in the Upper Taihu Basin, China

Abstract

Owing to the substantial spatiotemporal variability and intricacy in the hydrodynamic and water quality responses to water diversion, the determination of impact on the aquatic environment has been predominantly qualitative. The quantitative assessment of the impact of anthropogenic activities (water diversion) on the aquatic environment has the potential to enhance the accuracy of a comprehensive benefit evaluation. The present study utilised hydrological data, encompassing flow rate (Q) and water quality index (WQI) in the lakes Taohu and Gehu basin (TGHs), from two typical water resource allocations in the Taihu basin. The study revealed how hydrodynamics and water quality in response to water diversion. Furthermore, it introduced the concept of “water diversion impact value” to quantify the impacts of water diversion on the aquatic environment. The results indicated when the overall water diversion effect showed enhancement in water quality, the WQI impact value was positive alongside a negative Q impact value ($E^{\mathrm{WQI}}=1.417,E^Q=-14.2m^3/s$); Conversely, when water diversion improved hydrodynamic conditions, the WQI impact value was negative accompanied by a larger positive Q impact value ($E^{\mathrm{WQI}}=-3.17,E^Q=7.215m^3/s$). Principal component analysis (PCA) further validated these results, demonstrating that prolonged and stable diversion was positively correlated with WQI, while short and fluctuating diversion was positively correlated with Q, thereby supporting the method of evaluating the effects of water diversion using impact values. In addition, the TGHs was divided into three distinct components: namely mainstream areas, tributary areas, and lake areas, in accordance with the respective hydrological compartment. The present study set out to explore the response mechanisms of three distinct hydrological compartments to water diversion. The findings revealed that the impact extremes predominantly occurred in the mainstream areas, exhibited minimal occurrence in lake areas, and manifested within the range between the two in tributary areas. The diversion impact value has been shown to be a reliable metric for evaluating the effects of water diversion, thereby providing substantial theoretical underpinnings for the enhancement of aquatic environments.