The reservoir was built by the United States Army Corps of Engineers as part of the Washington Aqueduct project. It was partially completed by 1858 and began operation while construction continued. Additional construction and modifications to the reservoir were carried out through the 1860s and 1870s.
Water from the Dalecarlia Reservoir is pumped to the Georgetown Reservoir for further desedimentation before being treated. The Georgetown Reservoir and the nearby Dalecarlia water treatment plant are operated by the Army Corps of Engineers. The treated water is distributed throughout the city in water mains managed by the D.C. Water and Sewer Authority.
At the outlet of the Georgetown facility is a sluice gate building that controls the flow of water into a distribution tunnel. This structure, called the Georgetown Castle Gatehouse, was built by the Army (c. 1901) in the shape of a castle.