The Patapsco is a river in central Maryland which flows into the Chesapeake Bay in Baltimore, Maryland. With its South Branch, it forms the northern border of Howard County, Maryland.
The Patapsco proper begins at the confluence of the North and South Branches, near Marriottsville, approximately 50 miles (80 km) inland. The South Branch rises further west at Parrs Spring, where Howard, Carroll, Frederick, and Montgomery counties meet. The North Branch flows southward from its origins in Carroll County. Through most of its length, the Patapsco is a minor river, flowing for the most part through a narrow valley. The last 10 miles (16 km) form a large tidal estuary inlet of Chesapeake Bay. The inner part of this estuary provides the harbor of Baltimore, composed of the Northwest Harbor and the Middle Branch.
It is south of the Back River (although that river is sometimes considered part of the same watershed), and north of the Magothy River.
The Patapsco has a watershed area (including the water surface) of 680 square miles (1,760 km²), or 632 square miles (1,637 km²) of land. Thus, its total watershed area is 7% water.
Patapsco Valley State Park is adjacent to 32 miles (51 km) of the Patapsco, encompassing a total of 14,000 acres (57 km²) in five different areas. Liberty Dam and its reservoir, located on the north fork, is a major component of the Baltimore city water system. Besides Baltimore, the river also flows through Ellicott City (the county seat of Howard County) and Elkridge.
Nearly 35 miles of the Patapsco River, from Woodbine in the west to Elkridge in the east, flows through the Patapsco Valley State Park. Only a one-mile stretch through Ellicott City lacks public access to the river from the Patapsco Valley State Park.
The Patapsco River is managed as a put-and-take trout fishery (5 trout/day) through nearly 10 miles of the Patapsco Valley State Park. The upper trout fishery is in the South Branch of the Patapsco River and was first stocked in 1990. The stocked area begins at Main Street in Sykesville (Carroll County) or West Friendship Road (Howard County) and extends downstream 6.45 miles to the confluence with the North Branch Patapsco River within the McKeldin Area of Patapsco State Park. The lower section of put-and-take trout water, located northwest of US Route 1 in Elkridge within the Avalon Area of the State Park, was first stocked in 1989. Trout are stocked from Bloede Dam downstream 3.52 miles to the B&O Viaduct. Another popular trout fishing area on the Patapsco River is a 3.6-mile stretch from Daniels Dam downstream to Union Dam in the Hollofield Area of the State Park. This section was first stocked in 1995 and has a two-trout/day creel limit. With the reduced creel limit, more trout are available to anglers for a longer period of time than in the put-and-take sections. Spring and fall stockings provide great fishing for trout from October through early June. The Daniel's section has become very popular with fly anglers. With the rivers large size, there is plenty of room for fly casting. River temperatures become too warm during the summer months to expect trout survival. The trout are stocked with the intention that all will be harvested by anglers before the Patapsco River becomes too warm for their survival.
Smallmouth bass are a popular gamefish in the Patapsco River and provide angling recreation throughout the river.
The Patapsco River averages about 50 feet in width. The river is low in gradient, shallow and rocky with scattered deep pools and sandy runs. The many boulders provide pocket water that provide excellent habitat for the stocked trout and smallmouth bass. The large, slow pools are also attractive to trout, bass and sunfish.
Smallmouth bass, rock bass, redbreast sunfish, hog suckers and white suckers can be found throughout the river. Gizzard shad, hickory shad, American shad, river herring, striped bass and white perch migrate up the Patapsco River during early spring. Gizzard shad and river herring migrate up in the greatest numbers and can be seen swimming in the pool below Bloede Dam near the Denil fish ladder. Opening the river up to fish migration has helped the catadromous American eel. American eels can now be found throughout the Patapsco River. Biologists only found American eels below Bloede Dam prior to development of the Denil fish ladders. Stocked rainbow trout ranging from nine inches up to a few 20+ inch trophies can be found throughout the put-and-take and two-trout/day sections of the river from mid-October through early June and provide excellent fishing recreation for fly, lure and bait anglers. Occasionally, the Fisheries Service purchases and stocks brown trout from private hatcheries to provide another species of trout for angling recreation. A variety of minnow species can be found throughout the Patapsco River, which provide forage for smallmouth bass, trout and sunfishes. It would not be unusual for a fly angler fishing with a bead head nymph to catch trout, smallmouth bass, redbreast sunfish, rock bass, river chubs and spottail shiners during a day of fishing in early June. The Patapsco River, with its many angling opportunities, definitely deserves a place on your list of freshwater fishing hotspots.
The put-and-take sections of the Patapsco River allow for a five-trout/day creel limit with no size or bait restrictions. There are two closure periods in the spring to allow for stocking. During the two closure periods, no fishing is permitted within the designated put-and-take sections. There are no closure periods in the two-trout/day section of the river. The catch-and-return black bass section requires all bass to be immediately released to the water when caught. There are no bait restrictions, however; Fisheries recommends not using bait as higher bass mortality occurs with deep hooked fish than with artificial lures and flies.