Indicator: Submerged Aquatic Vegetation (SAV) Abundance (1984-2024)

Access the Indicator Materials: - Analysis & Methods - Data File - Map Service Acreage distribution and percent cover of submerged aquatic vegetation (SAV) in the Chesapeake Bay and its tributaries are measured from photo-interpreted aerial imagery collected during growing-season surveys. Satellite imagery is used when necessary to supplement aerial imagery and complete the dataset. The Chesapeake Bay Program Segmentation scheme divides the Bay into 93 segments grouped into four salinity zones: Tidal Fresh, Oligohaline, Mesohaline, and Polyhaline. The Bay is also divided into three geographic zones: the Upper Bay, which includes the Susquehanna River and extends to the Chesapeake Bay Bridge; the Middle Bay; and the Lower Bay, which extends to the mouth of Chesapeake Bay and includes the James River. SAV bed density is categorized into four classes based on a subjective comparison with the density scale, ranging from very sparse to dense. Note: This Indicator supported progress tracking toward the Submerged Aquatic Vegetation (SAV) Outcome in the original Chesapeake Bay Watershed Agreement, adopted in 2014. The Watershed Agreement and SAV Outcome were revised in 2025.获取本指标相关材料：- 分析方法 - 数据文件 - 地图服务 切萨皮克湾（Chesapeake Bay）及其支流的沉水水生植被（Submerged Aquatic Vegetation, SAV）的面积分布与覆盖百分比，通过对生长季调查期间采集的航空影像进行目视解译完成测算。必要时将采用卫星影像补充航空影像，以完善本数据集。 切萨皮克湾项目分区方案将海湾划分为93个片区，并归入4个盐度分区：潮汐淡水区（Tidal Fresh）、低盐区（Oligohaline）、中盐区（Mesohaline）与高盐区（Polyhaline）。该海湾同时被划分为3个地理分区：涵盖萨斯奎哈纳河（Susquehanna River）并延伸至切萨皮克湾大桥的上湾；中湾；以及延伸至切萨皮克湾河口并包含詹姆斯河（James River）的下湾。 沉水水生植被（SAV）群落密度依据密度等级通过主观比对划分为4个等级，覆盖范围从极稀疏至茂密。 备注：本指标用于追踪2014年通过的原版《切萨皮克湾流域协议》中沉水水生植被（SAV）目标的落实进展。该流域协议与SAV目标已于2025年完成修订。