Publications

The Chesapeake Bay Total Maximum Daily Load, or Bay TMDL, divides the Chesapeake Bay watershed into 92 subwatersheds or segmentsheds. Each segmentshed is a discrete land area that has its own waste load and load allocations. To view and interact with this map through ArcGIS Online, visit ChesapeakeData.

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This map depicts interpolated mean salinity throughout the Chesapeake Bay and its tidal tributaries from 1985 through 2018. The salinity of the Chesapeake Bay and its tidal tributaries varies from season to season and year to year, and depends largely on the amount of freshwater flowing into the Bay. Salinity can affect such things as the distribution of underwater grass species, the habitat fish use to spawn, the distribution of oysters and the likely distribution of the oyster-killing parasites Dermo and MSX. To view and interact with this map through ArcGIS Online, visit ChesapeakeData.

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This map illustrates the counties, and sometimes municipalities, that are entirely or partially within the Chesapeake Bay watershed. To view and interact with this map through ArcGIS Online, visit ChesapeakeData.

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The Chesapeake Bay and its tidal tributaries include a range of habitats that differ by salinity and depth. These habitat differences are reflected in the Bay's designated uses, each of which has corresponding water quality criteria. These designated uses include: Migratory Fish Spawning and Nursery, which protects tidal freshwater and low-salinity habitats used by migratory fish during the later winter and spring spawning and nursery season; Shallow-Water Submerged Aquatic Vegetation, which protects underwater grass beds in shallow waters near the shoreline; Open-Water Fish and Shellfish, which protects tidal creeks, rivers, embayments and the mainstem Bay year-round; Deep-Water Seasonal Fish and Shellfish, which protects deep water and bottom habitats during the summer months; and Deep-Channel Seasonal Refuge, which protects the deepest portions of the Bay during the summer months.

The attainment of water quality standards for the tidal Chesapeake Bay's designated uses can be viewed on the Watershed Data Dashboard.

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The Chesapeake Bay and its tidal tributaries include a range of habitats that differ by salinity and depth. These habitat differences are reflected in the Bay's designated uses, each of which has corresponding water quality criteria. These designated uses include: Migratory Fish Spawning and Nursery, which protects tidal freshwater and low-salinity habitats used by migratory fish during the later winter and spring spawning and nursery season; Shallow-Water Submerged Aquatic Vegetation, which protects underwater grass beds in shallow waters near the shoreline; Open-Water Fish and Shellfish, which protects tidal creeks, rivers, embayments and the mainstem Bay year-round; Deep-Water Seasonal Fish and Shellfish, which protects deep water and bottom habitats during the summer months; and Deep-Channel Seasonal Refuge, which protects the deepest portions of the Bay during the summer months.

The attainment of water quality standards for the tidal Chesapeake Bay's designated uses can be viewed on the Watershed Data Dashboard.

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The Chesapeake Bay and its tidal tributaries include a range of habitats that differ by salinity and depth. These habitat differences are reflected in the Bay's designated uses, each of which has corresponding water quality criteria. These designated uses include: Migratory Fish Spawning and Nursery, which protects tidal freshwater and low-salinity habitats used by migratory fish during the later winter and spring spawning and nursery season; Shallow-Water Submerged Aquatic Vegetation, which protects underwater grass beds in shallow waters near the shoreline; Open-Water Fish and Shellfish, which protects tidal creeks, rivers, embayments and the mainstem Bay year-round; Deep-Water Seasonal Fish and Shellfish, which protects deep water and bottom habitats during the summer months; and Deep-Channel Seasonal Refuge, which protects the deepest portions of the Bay during the summer months.

The attainment of water quality standards for the tidal Chesapeake Bay's designated uses can be viewed on the Watershed Data Dashboard.

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Underwater grasses, also known as submerged aquatic vegetation or SAV, grow in four different salinity zones: tidal fresh, which represents freshwater areas; oligohaline, which represents salinities of 0.5-5 ppt; mesohaline, which represents salinities of 5-18 ppt; and polyhaline, which represents salinities of 18-30 ppt. Because different species of SAV are generally found in waters of a specific salinity range, tracking changes in SAV abundance by salinity zone can help track changes in the abundance of different SAV species. To view and interact with this map through ArcGIS Online, visit ChesapeakeData.

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This map depicts the co-occurrence of habitats for multiple water column and bottom-dwelling fish and shellfish species, as documented in Habitat Requirements for Chesapeake Bay Living Resources, Second Edition (1991). These species' habitat requirements can be affected by nutrient over-enrichment (which can impact dissolved oxygen) and sediment (which can impact light penetration).

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The ecoregions shown in this map were derived from Omernik (1987) and from subsequent refinements of Omernik's framework. Designed to serve as a spatial framework for environmental resource management, ecoregions denote areas within which ecosystems (and the type, quality and quantity of environmental resources) are generally similar. The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of the patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and integrity (Wiken 1986; Omernik 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife and hydrology.

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This map depicts the 11 hydrogeomorphic regions within the Chesapeake Bay watershed, as determined by generalized lithology (rock type) and physiography (based on geologic formations). These hydrogeomorphic regions, or HGMRs, have been used to assess the significance of groundwater discharge as a source of nitrate load to non-tidal streams in the Chesapeake Bay watershed (Bachman and others, 1998). This work is part of the U.S. Geological Survey's (USGS) efforts to develop an understanding and provide scientific information for the restoration of the Chesapeake Bay and its watershed.

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