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Patuxent River Watershed

The Patuxent River watershed in Montgomery County drains to two reservoir systems maintained by Washington Suburban Sanitary Commission (WSSC). These are the Triadelphia and Rocky Gorge Reservoirs. The Patuxent River begins in Frederick and then flows through seven counties: Howard, Montgomery, Prince George's, Anne Arundel, Charles, Calvert, and St. Mary's Counties. It is a major tributary to the Chesapeake Bay and has been the focus of inter-jurisdictional watershed protection since the early 1980's. 


Image of the Hawlings River, a subwatershed of the Patuxent River.


Patuxent River Primary Management Area (PMA)

One of the outcomes of the early interjurisdictional focus was the establishment of the Primary Management Area (PMA).  The PMA is a stream buffer and transition zone within which land uses are closely managed to reduce nonpoint source runoff and nutrient loads, and to improve and protect stream conditions. The ultimate goal for the primary management areas along the Patuxent River and its tributaries is to maintain low-density, low-intensity land uses within 1/4 mile of the mainstem and within 1/8 mile of tributaries, and to actively establish a minimum 50-foot forested buffer strip along all streams.

The PMA guidelines are applied to development projects that are submitted to the Maryland-National Capital Park and Planning Commission (M-NCPPC) for subdivision and/or site plan review and are otherwise voluntarily implemented and strongly encouraged on remaining parcels throughout the watershed.


In Montgomery County, the Patuxent River has three subwatersheds:

The total drainage area of these watersheds is approximately 61 square miles, about 7% of the total Patuxent River basin. Principle land use in the Patuxent Reservoirs watershed consists of agricultural cropland, pasture, and large lot residential, with many large areas of forested parkland. Since 1996, there has been a local, inter-jurisdictional agreement to protect the resources of the reservoirs, tributaries, and contributing drainage. More about the Patuxent Reservoirs Watershed Protection Agreement is found on the WSSC website.


► Patuxent Watershed Implementation Plan (PDF, 4.68MB)


How Can I Help Protect the Patuxent River Watershed?

Individuals interested in the health of the Patuxent River can contact the Patuxent Riverkeeper or the Patuxent River Commission to learn how they can help protect this resource.

Map of the County with the Patuxent River watershed highlighted.