Map Tools

USGS Nontidal Monitoring Station

This website provides information on the water quality loads and trends at the nontidal monitoring stations in the Chesapeake Bay Watershed.

Map Viewer

The Chesapeake Bay Watershed Model Phase 6 Map Viewer provides basic mapping functionality for a subset of Public Reports for Load Scenarios available from CAST. It also contains map layers for several commonly requested data layers associated with the Chesapeake Bay suite of models.

Chesapeake Bay Watershed Data Dashboard

The Watershed Data Dashboard is a visualization tool to consolidate and provide accessibility to Chesapeake Bay watershed monitoring, modeling, trends, projections and explanations for use in watershed management planning and implementation.

CAST Public Reports - Compare Map

Use the Compare Map tool available in Public Reports (logged off of CAST account) and Results (logged into CAST account) on the navigation bar to compare nitrogen, phosphorus, and sediment loads at either the edge-of-stream (EOS) or edge-of-tide (EOT) between the publicly-shared scenarios available in CAST. The publicly-shared scenarios include annual progress, no action, Everything by Everyone, Everywhere (E3) and the Phase 2 Watershed Implementation Plans (WIP2).

Spatial Data

Shapefiles are available for download as GIS layers and KMZ files. The GIS layers were simplified to produce the KMZ files. The KMZ layers are suitable for web mapping, but not for area or boundary calculations. Boundaries could be shifted by up to 10 meters with the simplification to remove polygon vertices. For most accurate layers, download the shapefiles.

  • Segmentation GIS  KMZ
    • This dataset includes Phase 6 Land-River Segments. Phase 6 Land-River Segments represent the union of land segments, which are primarily based on county boundaries, and river segments, which are based on small watershed boundaries.  The segmentation is designed so that each land-river segment drains to only one of the 92 tidal water segments.
  • Combined Sewer Overflow GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program. The CBP collected these data in 2017 directly from state regulatory agencies, counties, and municipal organizations.
  • Municipal Separate Storm Sewer System (MS4) GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program. The CBP collected these data in 2017 directly from state regulatory agencies, counties, and municipal organizations.
  • Federal Lands GIS  KMZ
    • This dataset is maintained and created by the Chesapeake Bay Program for use by the Federal Facilities Workgroup.  The dataset used information and resources related to the water quality improvement efforts of federal facilities within the Chesapeake Bay Watershed. Data is compiled from various authoritative data sources including the Protected Areas Database V. 1.4, Federal Agencies, and in some cases States and other jurisdictions.
  • Maryland Regulated Area GIS  KMZ
    • This dataset includes MS4 areas provided by the Maryland Department of the Environment. MD_SHA is under the jurisdiction of the Maryland State Highways Administration. MD_STATE is under the jurisdiction of other state agencies.
  • Direct Loads GIS  KMZ 
    • Direct Loads Include Wastewater, Rapid Infiltration Basins, Large Monitored Septic Systems, and Developed Land Spray Irrigation



Each BMP is developed following a Protocol that was approved by the Chesapeake Bay Program Partnership. The Protocol and detailed reports for each BMP are available at the links below. A Quick Reference Guide provides general information about a BMP and how it functions within the Chesapeake Bay Program reporting and modeling structure. This Guide provides a single place to learn key information about most BMPs. 


A crosswalk of commonly-used BMP names to the CAST BMP name may be helpful in selecting the CAST BMP that best represents your management action. The NRCS practice codes and names are also available in the NRCS-CAST file.


BMP costs included in CAST are developed by contractors to the EPA and are in 2010 dollars. The original costs were reviewed with the states who provided input. Additional BMPs were approved by the Chesapeake Bay Program Partnership since the original TMDL costs were determined. The costs are available by going to the Public Reports drop down in the top menu bar and selecting Cost Profiles. You can also log in to CAST and edit the costs by creating your own Cost Profile. CAST provides costs associated with each scenario using the cost profile you select. The data available in the Cost Profiles is summarized to include only the capital, operations and maintenance and opportunity costs, without the research notes that are included in the files below.


The 2010 Chesapeake Bay TMDL for Nitrogen, Phosphorus and Sediment set allocations for the Bay. Major jurisdictions create Watershed Implementation Plans for how to achieve the allocations. The Phase III Watershed Implementation Plans are under development and Interim Expectations have been established. BMPs are expected to be verified. Information on verification is below.