Dynamic change in the water-level fluctuation zone of the Danjiangkou Reservoir and its influence on water quality

Abstract

The water-level fluctuation zone (WLFZ) of the Danjiangkou Reservoir is the last barrier to ensure the water quality of the middle route of the South-North Water Diversion (SNWD) Project and has therefore received widespread attention. Based on the 17-year serial dynamics of the Danjiangkou Reservoir WLFZ extracted from satellite images from 2000 to 2016, this study analyzed the annual and inter-monthly changes in inundation area as well as the non-flooded area within the WLFZ. The first comprehensive map of the temporal and spatial nitrogen (N) and phosphorus (P) release characteristics of the Danjiangkou Reservoir WLFZ is presented. The results showed that the inundation area underwent a significant increasing trend during this period, and the WLFZ was more frequently affected by off-season alternative drying-wetting than before the water diversion. The total amounts of N and P released into the water from the WLFZ soil layer are considerable (7.6 tons of P and 301.2 tons of N per year) and increasing. Optimizing land use in the WLFZ is an important means to ensure water quality in the Danjiangkou Reservoir and the sustainability of the SNWD Project.