Abstract：
Reservoir nearshore areas are influenced by both terrestrial and aquatic ecosystems, making them sensitive regions to water quality changes. The analysis of basin landscape hydrological features provides limited insight into the spatial heterogeneity of eutrophication in these areas. The complex characteristics of shoreline morphology and their impact on eutrophication are often overlooked. To comprehensively analyze the complex relationships between shoreline morphology and landscape hydrological features, with eutrophication, this study uses Danjiangkou Reservoir as a case study. Utilizing Landsat 8 OLI remote sensing data from 2013 to 2022, combined with a semi-analytical approach, the spatial distribution of the Trophic State Index (TSI) during flood discharge periods (FDPs) and water storage periods (WSPs) was obtained. Using Extreme Gradient Boosting (XGBoost) and SHapley Additive exPlanations (SHAP), explained the relationships between landscape composition, landscape configuration, hydrological topography, shoreline morphology, and TSI, identified key factors at different spatial scales and validated their reliability. The results showed that: (1) There is significant spatial heterogeneity in the TSI distribution of Danjiangkou Reservoir. The eutrophication levels are significant in the shoreline and bay areas, with a tendency to extend inward only during the WSPs. (2) The importance of landscape composition, landscape configuration, hydrological topography, and shoreline morphology to TSI variations during the FDPs are 25.12 %, 29.6 %, 23.09 %, and 22.19 % respectively. Besides shoreline distance, the Landscape Shape Index (LSI) and Hypsometric Integral (HI) are the two most significant environmental variables overall during the FDPs. Forest and grassland areas become the most influential factors during the WSPs. The influence of landscape patterns and hydrological topography on TSI varies at different spatial scales. At the 200 m riparian buffer zone, the increase in cropland and impervious areas significantly elevates eutrophication levels. (3) Morphology complexity, shows a noticeable threshold effect on TSI, with complex shoreline morphology increasing the risk of eutrophication.
摘要：
水库近岸地区受陆地和水生生态系统的影响，使它们对水质变化敏感。对流域景观水文特征的分析对这些地区富营养化的空间异质性提供了有限的见解。海岸线形态的复杂特征及其对富营养化的影响往往被忽视。为了全面分析海岸线形态与景观水文特征之间的复杂关系，富营养化，本研究以丹江口水库为例。利用2013年至2022年的Landsat8OLI遥感数据，结合半分析方法，获得了洪水排放期（FDP）和蓄水期（WSP）期间营养状态指数（TSI）的空间分布。使用极端梯度提升（XGBoost）和Shapley添加剂扩张（SHAP），解释了景观构成之间的关系，景观配置，水文地形,海岸线形态，和TSI,确定了不同空间尺度下的关键因素，并验证了其可靠性。结果表明:(1)丹江口水库TSI分布存在显著的空间异质性。海岸线和海湾地区的富营养化水平很高，具有仅在WSP期间向内延伸的趋势。(2)景观构成的重要性,景观配置，水文地形,在FDP期间，海岸线形态对TSI的变化为25.12%，29.6%,23.09%,和分别为22.19%。除了海岸线距离，景观形状指数（LSI）和超测量积分（HI）是FDP中两个最重要的环境变量。森林和草地面积成为WSP期间影响最大的因素。景观格局和水文地形对TSI的影响在不同的空间尺度上有所不同。在200米河岸缓冲区，农田和不透水区的增加显着提高了富营养化水平。(3)形态学复杂性，对TSI有明显的阈值效应，复杂的海岸线形态增加了富营养化的风险。
