Maps

This map shows population estimates within the Chesapeake Bay watershed on a county-by-county basis for the year 2010. These are actual Census Bureau population figures provided after the last decennial census (2010). However, for counties not completely within the Chesapeake Bay watershed, the population numbers were derived as a proportion of the total county based on land area.

This map displays the segmentsheds used by the Chesapeake Bay Program. A segmentshed is the discrete land area that drains into each of the 92 Bay Program segments (see map of Chesapeake Bay Segmentation Scheme) that have TMDLs associated with them.

This map displays the segmentsheds used by the Chesapeake Bay Program. A segmentshed is the discrete land area that drains into each of the 92 Bay Program segments (see map of Chesapeake Bay Segmentation Scheme) that have TMDLs associated with them.

This map displays the segmentsheds used by the Chesapeake Bay Program. A segmentshed is the discrete land area that drains into each of the 92 Bay Program segments (see map of Chesapeake Bay Segmentation Scheme) that have TMDLs associated with them.

This map shows the location of point sources of nutrient pollution and priority agricultural watersheds as identified by the Chesapeake Bay Program with input from the Natural Resources Conservation Service (NRCS). Point sources include both monitored and estimated data submitted from or approved by each jurisdiction. Priority agricultural watersheds include SPARROW catchments ranking in the top quartile for delivered loads of nitrogen or phosphorus from agricultural sources normalized by the total amount of agricultural areas within the catchment. The priority areas were further refined to emphasize high loading areas which also contained potential agriculture-related water quality impairments based on individual state 303d (impaired waters) lists.

This map shows the location of point sources of nutrient pollution and priority agricultural watersheds as identified by the Chesapeake Bay Program with input from the Natural Resources Conservation Service (NRCS). Point sources include both monitored and estimated data submitted from or approved by each jurisdiction. Priority agricultural watersheds include SPARROW catchments ranking in the top quartile for delivered loads of nitrogen or phosphorus from agricultural sources normalized by the total amount of agricultural areas within the catchment. The priority areas were further refined to emphasize high loading areas which also contained potential agriculture-related water quality impairments based on individual state 303d (impaired waters) lists.

This map shows a quartile ranking within Maryland of the delivered yield (load per area) of Total Nitrogen from urban sources. Delivered yield is the amount of nutrient that is generated locally for each stream reach and weighted by the amount of in-stream loss that would occur with transport from the reach to Chesapeake Bay. The cumulative loss of nutrients from generation to delivery to the Bay is dependent on the travel time and instream-loss rate of each individual reach. This map shows estimates of Total Nitrogen based on mean conditions for the late 1990's time period using the SPARROW model from USGS. SPARROW, or SPAtially Referenced Regressions On Watershed (SPARROW) attributes, uses a nonlinear regression approach to spatially relate nutrient sources and watershed characteristics to nutrient loads of streams throughout the Chesapeake Bay watershed.

Fish passage is a key component to the restoration of anadromous fish (shad and river herring) in the Chesapeake Bay watershed. These fish are blocked from much of their historic spawning areas, which included waters over 200 miles from the Bay. Maryland, Virginia, Pennsylvania and the District of Columbia have set goals to provide fish passage to make much of those historic spawning areas once again accessible to migratory fish. Other species that benefit from the unblocking of streams include eels, native species such as brook trout and other resident species.

The map shows the average Index of Biological Integrity Score for phytoplankton by monitoring station.

American shad were once the most abundant and economically important species in the Chesapeake Bay. Shad are anadromous fish and spend most of their lives in the ocean, returning to freshwater rivers to spawn after they reach maturity. Data for the York and Potomac Rivers were provided by the Virginia Institute of Marine Science via an ongoing Catch per Unit Effort (CPUE) study involving American Shad gill-netting. Data for the Susquehanna and James Rivers represent published fishway passage values for Conowingo and Boshers Dams, respectively.