At a Glance


  • Watershed Recreation Areas: March 15-November 30: conditions permitting, open 1/2 hour before sunrise to sunset. Closed from December 1 through March 15.
  • Azalea Garden at Brighton Dam: open 7 am –sunset.


  • Brighton Dam is free.
  • A day or seasonal permit (fee) is required at the other Triadelphia Reservoir sites described here. Cost is $6 per person for a day-use pass or $72 per person for a seasonal pass.
  • Permits can be purchased at Brighton Dam, at WSSC Headquarters near Laurel, or online.
  • Annual senior passes are free but must be obtained in person.

Tips: Bring a scope.

Best Seasons: Spring, summer and fall. No access in winter except at Brighton Dam itself.

Breeding Bird Atlas Blocks (includes entire WSSC Triadelphia watershed property in Howard and Montgomery Counties): Sandy Spring NE, Sandy Spring CE, Clarksville NW, Clarksville CW

Local MOS Chapter: Howard County Bird Club

Triadelphia Reservoir (Brighton Dam)

Brighton Dam Visitor Center – 2 Brighton Dam Rd, Brookville, MD 20833
Greenbridge – 310 Greenbridge Rd, Brookeville, MD 20833
Pigtail – 5525 Green Bridge Rd, Dayton, MD 21036
Big Branch – 14810 Triadelphia Mill Rd, Dayton, MD 21036
(301) 206-7485

Note: As of July 14, 2022, WSSC has posted a public health advisory with respect to contact with the water at Triadelphia Reservoir. Toxic bluc-green algae have been detected in the water, and may cause illness upon contact or ingestion. See the WSSC website for more information.

Triadelphia Reservoir is an 800-acre reservoir behind Brighton Dam on the Patuxent River in Howard and Montgomery Counties. With a total of over 240 bird species reported at its various access points – just on the Howard County side – Triadelphia is the #1 eBird Hotspot within Howard County.

The dam, reservoir, and surrounding lands are owned by WSSC (Washington Suburban Sanitary Commission), which manages drinking and wastewater in the Washington, DC metropolitan area. In Howard County, WSSC owns 2,384 acres at Triadelphia, including the lake itself. There are four sites on the reservoir – the dam and three boat launches – that provide birders with opportunities to view the water and bird the mostly wooded edges of the reservoir.

Brighton Dam: Brighton Dam Road runs across the top of the dam. There is a sidewalk along the north side only. (Snow is not cleared, so in the winter it may not be usable.) From this vantage point, one looks out on an expanse of water at the southern end of the reservoir. In the distance, a small section of the main reservoir can be seen.

Pigtail: At Pigtail, located northwest of the dam, a long gravel road ends in a parking lot with a boat ramp at the north end of a cove. When water levels are high, there is water adjacent to the parking lot. During late summer, under normal conditions, mudflats will begin to emerge just south of the parking lot. The path along the east side of the cove allows birders to walk parallel to the flats and the water.

Big Branch: Big Branch is also located northwest of the dam, but farther upstream than Pigtail. Much of the productive area can be seen from the parking lot and boat ramp located at the head of the cove. (A telescope is valuable.) When water levels begin to drop, mudflats emerge close to this location. In the course of weeks or months, the flats may expand south a considerable distance so that walking from the ramp along the left (east) edge may allow closer looks at shorebirds.

Greenbridge: This site is actually on the Montgomery County side of the reservoir, a little north of the dam. From the boat ramp on Greenbridge Road, one can view the dam area as well as upstream.  Also, look for the stairs leading from the parking area down to the inlet, and go left around the inlet to a wide dirt road. If you proceed along that road you will come to another vantage  point at a pipeline crossing the reservoir. In late summer into fall, dropping water levels expose mud, providing shorebird habitat.


An aggregate total of 241+ species have been reported on the Howard County eBird hotspots for Triadelphia Reservoir. There are multiple eBird hotspots covering specific sites around the reservoir:

There are additional eBird hotspots for other areas of Triadelphia Reservoir that are not mentioned here.

The predominant birds at Triadelphia are waterfowl, eagles, shorebirds, gulls, terns, and woodland birds. Unusual shorebirds such as American Avocet, Ruddy Turnstone, and Sanderling have been seen at Greenbridge Road. Red-throated Loon and Western Grebe have also been seen at Greenbridge Road.  Bald Eagles are abundant in winter at Brighton Dam, with two dozen or more present. A few Bonaparte’s Gulls can be present in winter.  Large numbers of Common Mergansers winter on the reservoir, often with a few Red-breasted Mergansers among them.  Sometimes the mergansers are mugged by gulls, with every once in a rare while, an unusual one such as Lesser Black-backed or Glaucous among them.

Cliff Swallows nest on Brighton Dam, starting in May.  As water levels drop in late summer into fall, shorebird habitat increases at all sites except Brighton Dam.

Wheelchair Access: 

The parking area at the Big Branch boat launch offers good views of the water and shoreline, allowing birding from or near the car for those who are mobility impaired. Water views are more distant from Pigtail and are challenging from Brighton Dam because of the 4-foot high concrete barrier as well as the need to cross the road to reach the paved walkway on the north side of the roadway across the dam.

Pet Policy:

Service animals are the only pets allowed at the Azalea Garden and Brighton Dam Recreation Area.

Special Features:

Established in 1959, the Azalea Garden at Brighton Dam is home to over 20,000 azaleas planted as understory in a 5-acre hardwood forest. Kousa dogwood trees were added in the 1990’s and the garden is also home to Montgomery County’s champion fringe tree. The garden is a nationally-known treasure, as visitors from around the country come to Maryland specifically to see the beautiful azaleas. Most of the azaleas are hybrids from non-native stock, but they do attract some pollinators. The peak bloom period varies from year to year, but is usually between mid-April to early May.  For more information about the garden, see ◾ Other recreational opportunities at Triadelphia Reservoir include boating and fishing. There is no swimming. There are picnic tables at the Visitor Center and at Big Branch. See the WSSC website at the link below for details and regulations. ◾ A seasonal list of birds, butterflies, dragonflies, mammals, and herps is available at, courtesy of the Howard County Bird Club. ◾ The Howard County Bird Club, a chapter of the Maryland Ornithological Society, holds bird walks at Triadelphia Reservoir and at other sites in the county; such walks are free and open to the public. See the Howard County Bird Club’s calendar for more information. ◾ The Howard County Bird Club has a detailed online guide, “Birding Howard County,” on their website at Edited by Joanne Solem, the online guide replaces an older printed guide, now out-of-print. The website is up-to-date and extremely detailed. Check it out! ◾ For additional information on Montgomery County sites at Triadelphia Reservoir, consult the printed Birder’s Guide to Montgomery County, Maryland published by the Montgomery Bird Club; to order, see


WSSC has posted a short video on YouTube that captures the Azalea Gardens at Brighton Dam during peak bloom.


Paved lots; see area map at link at left.


1A) To reach the Brighton Dam Visitor Center from Baltimore or from points south: Take I-95 or I-295 to MD Route 32 and go north on Route 32 toward (and past) Columbia. From Route 32, take Exit 20 onto MD Route 108/Clarksville Pike and go south for just a few hundred feet, passing to the south side of the over Route 32. After the overpass, take the first right to go west on Ten Oaks Road. In 0.7 miles, there will be a roundabout; take the second exit to go onto Brighton Dam Road. The Visitor Center will be on your left (south side of the road) in 3.1 miles. Note that the Visitor Center is actually in Montgomery County. At the Visitor Center, you may pick up a map which shows access points to both reservoirs in both counties, or download a map from the trail map link below and you may buy an access pass if you do not already have one.

1B) To reach the Brighton Dam Visitor Center from points west: Take I-70 east to Exit 76 to go south on MD Route 97/Roxbury Mill Road toward Olney. Go 7.8 miles and turn left (southeast) onto MD Route 650/New Hampshire Avenue. in 3.0 miles, turn left to go east on Brighton Dam Road. The Visitor Center will be on your right in 1.1 miles. From the Visitor Center, follow directions in #2, 3, and 4 above to reach other birding spots on the reservoir.

2) To reach Greenbridge (in Montgomery County) from the Visitor Center: Exit the parking lot and turn left (west) onto Brighton Dam Road. In 1.1 miles, turn right (north) onto MD Route 650/New Hampshire Avenue. In 0.4 miles, turn right again to go east on Greenbridge Road and follow to its end at the boat launch parking area.

3) To reach Pigtail Branch from Greenbridge: return to MD Route 650/New Hampshire Avenue and turn left to go south. In 0.4 miles, turn left (east) onto Brighton Dam Road and go 2.8 miles, crossing the dam. Then make a sharp left to go north on Highland Road. Go 1.2 miles and at the roundabout, take the third exit to go west on Triadelphia Mill Road. Go 1.6 mile and turn left onto Greenbridge Road and follow to the parking lot near the boat launch at the end of the road.

4) To reach Big Branch from Pigtail: Return to Triadelphia Mill Road and turn left to go west. The parking area and boat launch will be ahead on your left (west side of the road, which is angling toward north at this point) in 1.5 miles.

There are additional access points around the reservoir; see the trail map at the link at left for locations.

Nearby Sites:

Middle Patuxent Environmental Area; Patuxent River State Park – Annapolis Rock Road Area; Patuxent River State Park – Hipsley Mill Road Area; Western Regional Park.


Bottomland Deciduous Garden or Arboretum Freshwater Marsh or FloodplainFreshwater Pond, Lake, or ReservoirMud Flats (Tidal or Non-Tidal)


BeginnersBoat or Canoe/Kayak LaunchEntry Fee (for Some Areas, Other Areas Free)FishingHiking/Walking TrailsHuntingParkingPets AllowedPicnic AreaRestroomsVisitor Center, Interpretive Displays, ExhibitsWater ViewWheelchair Accessible FeaturesYoung People / Families


#1 Hotspot in County or CityPonds, Lakes, and ReservoirsThe Rivers of the Western Shore