Map Tools & Spatial Data

Map Tools

USGS Nontidal Monitoring Station

  • The USGS website provides information on the water quality loads and trends at the nontidal monitoring stations in the Chesapeake Bay Watershed. Methods, data, results, and interpretations are available for nutrient and sediment loads and yields (per-acre loads), and trends in nutrient and sediment loads.
  • This USGS Data Release summarizes the loads and trends measured at the Chesapeake Bay River Input Monitoring stations for the water years 1985-2020. Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in major rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay River Input Monitoring (RIM) Network stations.
  • The Chesapeake Bay Nontidal Monitoring Loads and Trends page shares the short-term water year nutrient and suspended-sediment load and trend results and background information for the Chesapeake Bay Program's nontidal network (NTN). It provides primary findings for nitrogen, phosphorus, and sediment trends and examines results for river basins and individual sites. 

Chesapeake Bay Watershed Data

The Chesapeake Bay has an Open Data Portal with spatial information about BMPs, habitat and much, much more. This is also where you can go to download the CAST delivery factors already mapped. Also see some datasets for direct download at the bottom of this page.

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. Much of these data came from CAST and are presented in a way that helps people understand the need for watershed improvement.

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.

The Chesapeake Progress website has a page on Water Quality Standards Attainment and Monitoring, which provides text and visuals to share the results of nutrient and sediment monitoring progress toward the Bay TMDL. Here you will find interactive graphs and maps representing the watershed data over the years, as well as downloadable excel files and PDFs. 

CAST Phase 6 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 for Download

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.
    • If you are working at a scale of Maryland 8-digit watershed, use these images and spreadsheet to map to a CAST modeling segment.
  • Hydrologic Unit Codes (HUCs)
    • HUCs spatial data are available for download through this USGS website.
  • Hydrogeomorphic Regions GIS
    • This dataset includes the boundaries of the 11 hydrogeomorhpic regions in the Chesapeake Bay watershed.
  • 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
  • Stream Layer GIS KMZ
    • This dataset includes the stream layer that is used by the Chesapeake Bay Program. This layer is for visual purposes only. Please note that the stream layer is not used in any CAST calculations (i.e., loads).