Impact of land use and urbanization on river water quality and ecology in a dam dominated basin

Improving water quality and ecological status is an important foundation for sustainability development. Increasing human activity and the corresponding land use change lead to the deterioration of river water quality (WQ) and water ecology (WE), but the pathway is complex, especially in dam dominated basins with the altered streamflow by the joint regulation of multiple dams and sluices that leads to changes in WQ seasonally. However, the research on this issue is inadequate and it is urgently needed since a large number of dams and sluices have been built worldwide for socioeconomic benefits, putting the basin's WQ and WE under pressure. Based on water ecological experiment, a framework was proposed to assess the impact of land use (LU) and urbanization on WQ and WE in different scenarios derived from human activities (low, and intense) and seasonality (winter, and summer) in a dam dominated basin. The framework was applied to the Shaying River Basin located in the Central China as a case study. The remote sensing of Landsat 8 OLI_TIRS images and Geographic Information System (GIS) were combined by using the support vector machine classification method to extract the land use patterns and to map the spatial distribution diagrams of WQ and WE indicators based on in-situ experimental data. A canonical correlation analysis method and Pearson correlation testing were adopted to evaluate the impact of LU and urbanization on WQ and WE in the basin. Results showed that LU and urbanization had a great impact on WE compared to WQ due to the slow reaction of ecosystem in the basin. Because the former was resulted by long-term regulation of dams and sluices, and the latter was related to the short-term changes of river environment. Moreover, the former was attributed to the latter largely. LU and urbanization impact on WQ had a significant seasonality with higher impact in winter than in summer, and the seasonality of the impact was weakened as the disturbance of LU and urbanization increased. The seasonal variation of WE indicators was almost not significant in our study due to their adaptability to surrounding environment. Our results provide insights to water resources management and ecological restoration in the Shaying River Basin and other similar basins with intensive dams and sluices.