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Watershed Health


Examine the health of over 150 subwatersheds in the County using the Interactive Map below by zooming in or searching by address.


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Clean and healthy streams provide us many services. By protecting our watersheds and preventing pollution, we secure our quality of life and reduce the costs of government cleanup programs. Also, keeping our water clean helps protect the water supply for people and animals that live downstream, allowing them to experience the same benefits. We can measure the health of our streams using the Stream Conditions Index.

The Stream Conditions Index measures the aquatic biological community and ranks the stream according to four categories (like a report card). Stream Conditions are determined by sampling of stream fish and bugs. Fish and bugs live in streams year round and are subject to any the changes in water quality or habitat that might occur. If conditions are poor, sensitive fish and bugs can’t survive and won’t be found in that stream the following year. 

After sampling fish and bugs, the resulting data, including the number and types or organisms, are input into an Index of Biotic Integrity (IBI).  IBIs are multi-metric (Utilizing several measurements) equations that rate a waterbody with a unitless score.  These scores can then be used to determine if the stream is in Poor, Fair, Good, or Excellent condition.

  • Poor stream condition is a combined IBI score (fish and bugs) of 0-41.  Poor conditions most often occur in places where changes made by humans to the natural environment have substantially altered the structure of the biological community.  These areas are often highly developed or urban and don’t have good stormwater management.

  • Fair stream conditions have combined IBI scores of 42-63.  These conditions occur most often in places anthropogenic stressors have impacted an area, but the area still supports viable biological communities.  This  condition describes many streams in suburban areas with some stormwater management, as well as areas that have had major agricultural impacts.  The biological communities in fair streams are dominated by species that are tough and can survive in most conditions, but may have a few organisms that are sensitive to stressors left.

  • Good conditions are described by combined IBI scores of 64-88.  These conditions are often found in the less developed areas of the county, suburban areas with the latest stormwater management techniques, and areas with lots of protected land in their watershed.  Many of the County’s sensitive species can survive in these streams.  Stream bugs like dragonflies and caddisflies are common.  Fish like sculpins, darters, and longnose dace are common in these streams as well.

  • Only Montgomery County’s best streams are rated excellent and must have a combined IBI score of 89-100.  Most often, only highly forested watersheds with minimal development are in excellent condition.  Here our most sensitive fish and stream bugs live.  Fish like trout, shield darters, and comely shiners are found.  Highly sensitive stream bugs like stoneflies and mayflies are common in these watersheds.

Image of a eastern box turtle
Excellent streams with a diversity of fish and aquatic bugs are also great habitat for other wildlife including amphibians and reptiles. 


Montgomery County searched for and recorded information from the healthiest streams or those “most recovered” from historic land disturbances remaining in the County to establish the stream conditions index. All County streams are measured against this ‘yardstick’ to better understand the overall health of the stream. County watersheds are sampled on a rotating schedule and are visited at least once every 5 years. 


Our Healthiest Streams

Image of Patuxent River State Park

All County streams are ranked as ‘Excellent’, ‘Good’, ‘Fair’, or ‘Poor’ through the Stream Conditions Index. Streams ranked in an ‘Excellent’ condition are the healthiest streams.

These healthiest streams are located in the far northern and western portions of the County, where some are protected through public ownership of large portions of their watersheds. You can visit many of these ‘excellent’ streams and learn for yourself what a healthy stream looks like and see and hear the many animals and plants that depend on clean and healthy streams.  

Some portions of the healthiest streams rely on private landowner stewardship to keep them healthy. Portions of the Little MonocacyBennett Creek and Ten Mile Creek are in excellent condition and are privately owned. In addition, there are County-designated Special Protection Areas that contain high quality waters. 


Patuxent River State Park

Image of a sycamore tree over the Patuxent River Located on the border of Montgomery and Howard Counties between Route 27 and Georgia Avenue, Patuxent River State Park represents one of the largest tracts of forest in Montgomery County.  Comprised of over 5,000 acres with more than 1,500 acres in the Maryland Wildlands program this area is remote and lacks many developed trails. The Patuxent River and its tributaries are among some of the most recovered streams in Montgomery County.

Patuxent State Park is managed for passive recreation including hiking, hunting, fishing, birding, and horseback riding.  The park features over 10 miles of catch and release trout stream (Patuxent River) and is a popular spring time fishery.  In the fall, hunting is a popular activity with hunting seasons lasting from September through the end of January.  The park also offers year round access for hikers and horseback riders with a few maintained trails.  It is recommended users in the fall and winter months wear hunter orange and avoid using the trails at dusk and dawn when hunters are most active.

To visit Patuxent River State Park and one of Montgomery County’s best streams, park where Hipsley Mill Road crosses the Patuxent River.  From there, travel downstream along a fisherman and equestrian trail.  Notice the massive Sycamores and maples looming over the water.  These trees are important for providing fish habitat and preventing erosion.  They also shade the stream keeping cool and healthy. 

As you continue downstream, you’ll notice how the stream transitions from deep pools that glide into shallow riffles that run back into deep pools.  The riffles are crucial habitat for stream bugs, and are also help add oxygen back into the streams.  The pools serve as important fish habitat, and help keep the stream cool.  

Don’t be alarmed by the trees that have fallen across the stream.  This natural process provides important habitat for fish and bugs.  

Keep a sharp eye out for Belted Kingfishers perched above the river looking for their next meal or majestic Wood Ducks relaxing on the cool waters. 

After walking a little over a half a mile downstream from Hipsley Mill Road, you will come to the confluence of the Patuxent River and the Cabin Branch tributary.  If you continue downstream, be careful, the trails are not maintained by park staff and can be hazardous.  Before you visit the park we suggest you check out the Patuxent River State Park page  on the Maryland Department of Natural Resources website for additional information.  When you visit we suggest you wear a sturdy pair of boots that can get muddy and dirty and take water to drink.  Keep in mind much of this area is a Maryland Wildland and can be remote.  As always when you are enjoying our beautiful parks remember to Leave No Trace.


Little Bennett Creek

Image of Little Bennett Creek The publicly owned portions of the Little Bennett Creek watershed are within Little Bennett Regional Park. At a little over 3,700 acres, the interior of the park is reached by hiking over more than 20 miles of trails. This watershed area is recovering from many years of farming, logging and use of the streams for mill races and dams. Today, you will have to look very hard to see remnants of this older use of the land and waters. Much of the watershed is now forested, with clear headwater streams flowing into the Little Bennett Creek. 

Little Bennett Regional Park is an easily accessible, family-friendly park with many trails.  The Montgomery County Parks Department manages this resource.  You can visit their website for information to plan your visit. Be sure and print out the park map before you go. 

A great place to go for a first visit is the Kingsley Parking Area. From Clarksburg, go north on Clarksburg Road for several miles until you descend into the Little Bennett Creek stream valley. Once you cross over Little Bennett Creek, look for the parking lot ahead on your right. This is a popular destination so if it is full, continue on Clarksburg Road for about a mile until you see the Browning Run Parking Area on your right. 

From the Kingsley Parking Area, you can walk upstream towards the one room Kingsley School house, about all that remains of the community of Kingsley. Little Bennett Creek will soon be next to the trail. Natural surface trails offer an opportunity to continue in a loop back to the parking lot or you can retrace your steps.         


Ten Mile Creek

Image of Ten Mile CreekTen Mile Creek is located in the Clarksburg area and flows into Little Seneca Lake, a reservoir, which flows into the Potomac River. Ten Mile Creek is considered a reference stream in Montgomery County, with its mainstem dominated by forested area with gently rolling hills. Its tributaries are generally spring fed by cool high quality groundwater and consist of many wetland areas.

The main public portion of Ten Mile Creek is owned by Montgomery County Parks Department and is connected to Black Hill Regional Park, where Ten Mile flows into Little Seneca Lake.

To access Ten Mile Creek, drive west on West Old Baltimore Road from the entrance of Black Hill Regional Park (on Lake Ridge Drive). Take your first left on to Ten Mile Creek Road after crossing Clarksburg Road and park in the pull off area. There are paved trails walking downstream towards Little Seneca Lake. If you want to explore the more natural scenery, there are dirt trails walking upstream until the land becomes privately owned (north of West Old Baltimore Road).


Tier II (High-quality) Watersheds

The State of Maryland established Tier II regulations 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, 2.3MB)



Streams on the Way to Recovery

Streams and rivers that function well bring benefits to the local neighborhood and the entire County. Healthy streams have abundant aquatic life such as fish and stream insects, stable streambanks and very little erosion.

Image of a restored Booze Creek.

Healthy streams are the ones that show the least impact from more than 300 years of land use change as Montgomery County evolved, grew in population size and developed.  In the more urban areas of the County, streams are victims of decades of increased development pressure and little or no stormwater control.  


Changes in the County that Impacted the Health of Streams:

  • Removal of native forests and other natural features

  • Soil erosion that devastated the stream environment.

  • Use of streams to power over 50 mills, mill dams and races.

  • Rapid and spreading imperviousness through post WWII development.

  • Channelization and loss of headwater streams.

  • Little stormwater management controls in the early development of the County.

  • Population growth to more than 1 million people.

The Department of Environmental Protection is attempting to reverse these impacts by adding stormwater management and physically restoring the streams. With funds collected through the Water Quality Protection Charge and substantial State and Federal grants, DEP has been able to protect several miles of streams. The results are healthier streams with more fish and other aquatic life.

Years of careful planning, permitting, designing and public involvement go into every project. Project goals differ depending on the stream, and can include water quality improvement, streambank stability, habitat improvement or assistance in flood control.

Once construction is complete, DEP documents improvements from restoration projects through monitoring.

View photos of some of the County’s best success stories:


Image of the Turkey Branch. Image of Turkey Branch after restoration

Turkey Branch Before Restoration    

Turkey Branch After Restoration      



How Does the County Help?

The natural environment is important to all of us and the County has many programs focused on protecting our natural resources, especially streams.  

DEP is responsible for a number of key programs to assess and reduce pollution in streams, improve stream habitat and water quality, maintain our infrastructure, and engage residents in protecting local streams.


County Biologists sampling a local stream

History of DEP's Stream Protection Programs

Montgomery County has long been a leader in natural resources protection. Beginning in the 1970's, the County was among the first in the nation to require stormwater management for new development.  

Back then, regional concerns about water quality in the Potomac River and its tributaries led to the monitoring of water chemistry in County streams. Very few problems were found based on parameters such as pH, dissolved oxygen, and water temperature, although many streams showed signs of obvious physical damage and degradation.  

In 1994, the County changed its monitoring focus to the organisms that live in the streams: fish and aquatic insects.  The type of aquatic life in a stream directly reflects the extent of human impacts on stream. Degraded streams have lesser quality food and unstable habitat for aquatic wildlife.  The County established its biological monitoring program with the goal to systematically evaluate the 1,500 miles of streams and use the data to set priorities for protection and restoration.


County biologist checking USGS stream gauge.

DEP Partner Agencies

Below are links to other partner agencies that help fight pollution in our streams and protect water quality.  While these agencies all have programs needed to reduce impacts to our streams, ultimate success depends on our residents.   Find out how you, your family and neighbors can help protect the streams in your community.