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.
Highlights
The reservoir water-level fluctuation zone (WLFZ) refers to the periodically submerged and exposed ecozone created by artificial hydrological regulation and the seasonal and spatial variability of natural rainfall [1,2,3]
Though the total amounts of N and P released from WLFZ soil to overlying water were estimated to contribute approximately 13% and 7% of the water quality monitoring content, respectively, which absented the consideration of flow disturbance and surface runoff, their values are more likely to be enriched in local inactive water bodies such as bays
This work provides a novel perspective from which tracking the characteristics of the WLFZ and provides a new approach to estimating the effects of N and P released from WLFZ soil to water in space
Summary
The reservoir water-level fluctuation zone (WLFZ) refers to the periodically submerged and exposed ecozone created by artificial hydrological regulation and the seasonal and spatial variability of natural rainfall [1,2,3]. The WLFZ is customarily depicted as the area between the highest and the lowest water levels historically attained in reservoir management [4]. It is a main channel for the interchange of material, energy, and information and maintains the dynamic equilibrium, biodiversity, and ecological health of the aquatic-terrestrial ecosystems [5]. Constant changes caused by natural events and human activities create the need for monitoring the condition of WLFZ over time. Hydrological process can help to link these macro- and micro-scale studies closely [8,9]
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