近四十年密云水库消落带演变轨迹及水淹频率分析OACHSSCD

The Water-Level Fluctuation Zone(WLFZ)serves as a critical ecohydrological interface in reservoir littoral areas,profoundly influencing ecosystem structure and function.As a dynamic transitional buffer,it plays an irreplaceable role in regulating nutrient cycling,supporting biodiversity,and maintaining shoreline stability.As the primary drinking-water source for Beijing,Miyun Reservoir has experienced pronounced water level fluctuations over the past 40 years,driving substantial landscape evolution of its WLFZ.Consequently,accurately characterizing these spatiotemporal dynamics is not only of great scientific significance but also essential for the precise ecological monitoring and adaptive management of large-scale reservoirs.Focusing on Miyun Reservoir,this study developed an automatic method combining a multi-index water extraction scheme with binary time-series range analysis based on long-term Landsat satellite images(1984-2024).To ensure the reliability of the results,high-resolution Sentinel-2 data were utilized for accuracy assessment.This framework effectively quantifies the spatiotemporal distribution and inundation frequency structure of the WLFZ,revealing its evolution under the combined effects of climate variability,shoreline topography,and human regulation.The results show that:(1)Over the past 40 years,the WLFZ averaged 17.54 km2 and followed a four-stage trajectory:an initial period of"natural expansion,"followed by"drought-driven contraction,"subsequent"recovery via water transfer,"and finally a phase of"high-level compression."Spatially,the WLFZ is predominantly concentrated on the gentle northern shore and the Chaohe inflow delta,with limited development along steep southern banks and around islands.Notably,the significant water level rise induced by the South-to-North Water Diversion Project was identified as the dominant anthropogenic factor driving recent WLFZ reconfiguration.This has resulted in a"narrowing"effect on ecological space,which has compressed the habitat available for vegetation.(2)The inundation frequency exhibits a tri-centric structure of"high-frequency core-medium-frequency belt-low-frequency margin."The area proportions of these zones have shifted dramatically over time:evolving from a balanced pattern under natural conditions to a dominance of low-frequency zones during drought periods,followed by structural recovery,and finally transitioning to a regime dominated by permanent inundation.Accordingly,we propose a restoration framework based on inundation frequency zoning coupled with ecological flow regulation.Specifically,we recommend a three-zone restoration model:prioritizing natural recovery supplemented by artificial management in the high-frequency inundation zone to mitigate eutrophication risks;establishing flood-tolerant and drought-resistant herbaceous corridors in the medium-frequency inundation zone;and constructing"tree-shrub-herb"composite ecological buffer belts in the low-frequency inundation zone to intercept terrestrial pollution.These findings provide technical support and practical reference for refined monitoring and ecological restoration of reservoir WLFZs.