At a Glance


  • Watershed Recreation Areas: March 15-November 30: conditions permitting, open sunrise to sunset. Closed from December 1 through March 14.
  • Azalea Garden at Brighton Dam: open 7 am –sunset.
  • Brighton Dam Visitor Center: March 15-November 30: 7 am – 8 pm; December 1 – March 14: 7 am – 4:30 pm; closed Thanksgiving Day, Christmas Day, and New Year’s Day.


  • Brighton Dam is free.
  • A day or seasonal permit (fee) is required at the other Triadelphia Reservoir sites described here. Cost is $5 per person for a day-use pass or $70 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. ■ There is an extensive set of Watershed Regulations, too much to summarize here. Please read the Regulations before visiting. ■ Restrooms are at the parking areas in season and at the Visitor Center year-round.

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

Howard County Side:
Pigtail – 5600 Green Bridge Rd, Dayton, MD 21036
Big Branch – 14801 Triadelphia Mill Rd, Dayton, MD 21036

Montgomery County Side:
Green Bridge – 2800 Greenbridge Rd, Brookeville, MD 20833
Triadelphia Recreation Area – 2600 Triadelphia Lake Road, Brookeville, MD, 20833

(301) 206-7485

Access Notes: Effective January 5, 2023, due to playground renovations at the Triadelphia picnic and playground areas, a section of the parking lot will be closed until further notice. The rest of Triadelphia recreational area will remain open (fishing pier and shoreline fishing areas).

A sediment removal project on Triadelphia Reservoir is anticipated to begin in Spring/Summer 2023. During that time, all boat ramps will be closed and no boating will be allowed. Additionally, the Greenbridge and Pigtail recreational areas will be closed to ensure public safety due to the construction activity.

For further information or to check the status, see


Triadelphia Reservoir is an 800-acre reservoir behind Brighton Dam on the Patuxent River, spanning the county line between Howard and Montgomery Counties. Montgomery County lies on the south side of the reservoir and Howard County is on the north side. With a total of over 240 bird species reported at its various access points, Triadelphia is one of the top birding hotspots in both counties.

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. At Triadelphia, WSSC owns 2,384 acres of land in Howard County and 1,132 acres in Montgomery County. WSSC provides a number of public recreation facilities at Triadelphia. There are five sites on the reservoir – the dam and four recreation areas – 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. The dam is the only part of Triadelphia that is open in the winter, but snow is not cleared, so  it may not be usable. From the vantage point of the dam, 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 on the Howard County side, 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. Additional details and suggestions for birding at Pigtail are available in the Howard County Bird Club’s online Birding Howard County Site Guide.

Big Branch: Big Branch is also located northwest of the dam in Howard County, 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. Additional details and suggestions for birding Big Branch are available in the Howard County Bird Club’s online Birding Howard County Site Guide.

Greenbridge (aka Green Bridge: WSSC is inconsistent in the spelling of the name of this site, sometimes using one word and sometimes two words): This site is 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. More details can be found in the entry for “Four Gems along the Patuxent,” authored by Rick Sussman in the Birder’s Guide to Montgomery County, Maryland, published by the Montgomery Bird Club. The book is now out of print, but a scanned version is available as a free downloadable PDF on the Montgomery Bird Club’s website. Consult the entry for “Four Little Gems along the Patuxent” beginning on page 160 for more details.

Triadelphia Lake Road: The Triadelphia Lake Road area is located on the Montgomery County side, much farther upstream than Greenbridge. The boat launch area at the end of Triadelphia Lake Road provides a good view of the water area. In addition, this area gives you the opportunity bird the fields along the road as well as a couple of trails through the woods. Rick Sussman, who authored the Triadelphia Recreation Area entry in the downloadable Birder’s Guide to Montgomery County, Maryland, suggests four walking routes: at a field at a a locked gate on the right side of the road as you approach the reservoir; along two trails that start at the gravel overflow parking lot on the right as you approach the reservoir; and along a trail from the main parking area at the boat launch along the edge of the reservoir.  Consult the entry for Triadelphia Lake Road beginning on page 84 in the Birder’s Guide to Montgomery County, Maryland for more details.


An aggregate total of 250+ species have been reported on the ten eBird hotspots for Triadelphia Reservoir. There are multiple eBird hotspots covering specific sites in both counties:

Howard County

Montgomery County

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 may 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 and are a speciality of this site.  As water levels drop in late summer into fall, shorebird habitat increases at all sites except Brighton Dam.

Wheelchair Access: 

The parking areas at the Big Branch, Pigtail, Greenbridge, and Triadelphia Recreation Areas generally offer 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 opposite side of the roadway from the parking area.

Pet Policy:

Service animals are the only pets allowed. No other pets.

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 and Triadelphia Lake Road. See the WSSC website at the link below for details and regulations.
  • A st of seasonal lists of birds, butterflies, dragonflies, mammals, and herps is available at, courtesy of the Howard County Bird Club.

Local MOS Chapters:

The Howard County Bird Club and the Montgomery Bird Club, both chapters of the Maryland Ornithological Society, hold bird walks at Triadelphia Reservoir and at other sites in their respective counties; such walks are free and open to the public. See the Howard County Bird Club’s calendar and the Montgomery Bird Club 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!

The Birder’s Guide to Montgomery County, Maryland, published by the Montgomery Bird Club, is now out of print, but a scanned version is available as a free downloadable PDF on the Montgomery Bird Club’s website. Check this one out, too!


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


Paved lots at the dam and at the four recreation areas; see reservoir map at link at left.

Brighton Dam Visitor Center

  • 2 Brighton Dam Rd, Brookville, MD 20833; note that the Visitor Center parking lot is located across the road from the dam walkway and is on the south end of the dam, on the Montgomery County side.
  • GPS Coordinates: 39.191422, -77.006772
  • Google Map Link: 2 Brighton Dam Road

Howard County Side:

  • 5600 Green Bridge Rd, Dayton, MD 21036
  • GPS Coordinates: 39.218401, -77.006154
  • Google Map Link: Pig Tail Recreation Area

Big Branch

Montgomery County Side:

Triadelphia Lake Road Recreation Area


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 the Triadelphia Road Recreation Area (in Montgomery County) from Greenbridge: Exit the parking area and follow Greenbridge Road westbound to MD Route 650/New Hampshire Avenue and turn right to go north on Route 650. In 2.5 miles, turn right to go north on MD Route 97/Georgia Avenue. Go north on Route 97 for just a half-mile, then turn right to go east on Triadelphia Lake Road, which will end at the Recreation Area in just under a mile.

4) To reach Pigtail Branch in Howard County from the Visitor Center:  Exit the parking lot and turn right (east) onto Brighton Dam Road, and go 1.6 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.

5) 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.

Nearby Sites:

Howard County: Centennial Lake & Park ■ David Force Natural Resource Area ■ Howard County Conservancy – Mount Pleasant Farm ■ Lake ElkhornMiddle Patuxent Environmental Area ■ Patapsco Valley State Park – Daniels Area ■ Patapsco Valley State Park – Henryton ■ Patuxent River State Park – Annapolis Rock Road Area ■ Patuxent River State Park – Hipsley Mill Road Area ■ Rockburn Branch Park ■ Schooley Mill Park ■  Western Regional Park ■ Wilde Lake

Montgomery County: Black Hill Regional Park ■ Blue Mash Nature Trail ■ C&O Canal – Pennyfield, Violette’s & Riley’s Locks ■ Little Bennett Regional Park ■ Lois Y. Green Conservation Park ■ McKee-Beshers Wildlife Management Area (Hughes Hollow)Rock Creek Regional Park – Lake Needwood ■ Rock Creek Regional Park – Meadowside Nature Center & Lake Frank ■ Seneca Creek State Park ■ Wheaton Regional Park – Brookside Gardens, Brookside Nature Center, Pine Lake Area


Bottomland DeciduousConifersHedgerowsUpland Deciduous Garden or Arboretum Old Fields, Shrubby Meadows Freshwater Marsh or FloodplainFreshwater Pond, Lake, or ReservoirMud Flats (Tidal or Non-Tidal)Rivers & Streams


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


Ponds, Lakes, and ReservoirsPrivate Sanctuaries and PreservesThe Rivers of the Western Shore