This page provides links to online maps and GIS downloads to assist in implementing TMDLs. The resources below include maps of every approved TMDL (categorized by pollutant) as well as shapefiles relating to the implementation process. Two separate TMDL maps are provided for nitrogen, phosphorus and sediment; one map for those TMDLs that were developed by the state, and one map for those TMDLs which are part of the 2010 Chesapeake Bay TMDLs. All downloads are

TMDL Maps by Pollutant

  Nutrients    Bacteria
    Nitrogen: State TMDLs​
(view | download)     E. coli (view | download)
    Phosphorus: State TMDLs
(view | download)     Enterococci (view | download)
    Nitrogen & Phosphorus: 2010 Bay TMDLs (view | download)     Fecal Coliform (view | download)
  BOD: Biochemical Oxygen Demand   Trash
    BOD / CBOD / NBOD (view | download)     Trash (view | download)
  Low pH   Sediment
    Calcium Carbonate Equivalents
(view | download)     Sediment: State TMDLs (view | download)
    pH Surrogates (view | download)     Sediment: 2010 Bay TMDLs (view | download)
  Metals   Organochlorides
    Aluminum (view | download)     Chlordane (view | download)
    Iron (view | download)     PCBs: Polychlorinated Biphenyls (view | download)
    Mercury (view | download)    

TMDL Data Center Updates

Additional geographic resources for TMDL implementation

Watershed Delineations

County Boundaries

Stormwater Delineations

  • Phase 6 - NPDES-Regulated Stormwater Systems (download​)
  • Phase 5 - NPDES-Regulated Stormwater Systems (info | download)

Land Cover

Other Mapping Resources