Little Falls Branch

Little Falls Branch, a 3.8-mile-long (6.1 km)tributary stream of the Potomac River, is located in Montgomery County, Maryland. In the 19th century, the stream was also called Powder Mill Branch. It drains portions of Bethesda, Somerset, Friendship Heights, and the District of Columbia, flows under the Chesapeake and Ohio Canal, and empties into the Potomac at Little Falls rapids, which marks the upper end of the tidal Potomac.

In the mid-19th century, the stream served as an interim water source for Washington, D.C. The Dalecarlia Reservoir was built on the D.C.-Maryland border next to Little Falls Branch. A dam was built on the stream, and water was diverted into the reservoir starting in 1859. In 1864, with the completion of the Washington Aqueduct, the Potomac River became the city's principal water source. However, muddy water from Little Falls Branch continued to flow into the reservoir, and a bypass pipe was built to channel the aqueduct water to another city reservoir, the Georgetown Reservoir. In 1895 construction was completed to fully divert the stream from the Dalecarlia Reservoir.

Today Little Falls Branch flows through a highly urbanized area, and parts of the stream have been altered through construction of underground pipes, culverts and open concrete channels. Portions of the stream flow through Little Falls Stream Valley Park in Bethesda and next to the Capital Crescent Trail. The stream runs near the Dalecarlia drinking water treatment plant in Washington and occasionally has received overflow discharges from the plant.

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