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Watersheds of Montgomery County, Maryland.
View an enlarged version of the map  (PDF, 1 pg, 1.2Mb)
Countywide Watershed Conditions
The map above displays stream conditions from the 2000-2008 watershed monitoring cycle. The blue areas are in "Excellent" condition, green areas are "Good," yellow areas are "Fair," and red areas are in "Poor" or impaired condition.
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Tier II (High-quality) Watersheds
Tier II regulations were established to provide additional, mandatory protection for waters of better quality than the minimum federal and state water quality standards. These high-quality waters are known as "outstanding waters" and are so designated through biological monitoring and data assessment (such as the Maryland Biological Stream Survey). Anti-degradation provisions of the Clean Water Act require that any discharge permits, water/sewer plan amendments, development activities, and other activities in the watershed must not impact the existing level of water quality. If impacts are unavoidable, special exemptions must be established through legal process with the Maryland Department of the Environment.
View a map of Tier II watersheds in Montgomery County (PDF, 2 pp, 2.3Mb)
Total Maximum Daily Load (TMDL) Watersheds
EPA-approved quantitative assessment studies (TMDLs) have established pollutant loading limits for waterbodies in several County watersheds. These loading limits represent a maximum amount of a pollutant that a waterbody can receive in order to meet water quality standards. The pollutant loading is distributed among various sources of that pollutant (e.g., point sources or nonpoint sources).
Pollutant loading from point and nonpoint sources is reduced by implementing a variety of measures known as best management practices or BMPs. Meeting TMDL loading reductions is a requirement of the County's NPDES MS4 Stormwater Permit.
View a map of the County’s water quality impairments with EPA-approved TMDLs.
View Maryland Department of the Environment’s TMDL site.
Maps of TMDL Watersheds by Pollutant Type
- Bacteria impairment (PDF, 2 pp, 678K)
- Biological impairment (PDF, 2 pp, 682K)
- Nutrient impairment (PDF, 2 pp, 682K)
- Sediment impairment (PDF, 2 pp, 679K)
- Toxics impairment (PDF, 2 pp, 672K)
- Trash impairment (PDF, 2 pp, 666K)
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