The Origin of Washington's Water Supply

 Tracing the route of the Washington Aqueduct. Google Earth image 

Tracing the route of the Washington Aqueduct. Google Earth image 

The Washington Aqueduct forms the central node in DC's water infrastructure. This marvel of engineering was designed before the Civil War and is still in use today.

In 1851 a terrible fire destroyed two-thirds of the Library of Congress collections and Congress tapped Montgomery Meigs and the Army Corps of Engineers to design a system to supply water to District residents and Capitol Hill firehouses.

Water enters the system far above Washington at Great Falls, Maryland. A diverting dam spans the river and draws gushing water into a set of parallel conduits. These gravity powered tunnels run under MacArthur Boulevard (formerly known as Conduit Road) and then soar 100 feet over Cabin John Creek inside the Union Arch Bridge. Nine miles down the line the water takes a stop at Dalecarlia Reservoir where settling basins allowed sediment and other unpleasants to drift to the bottom. (Today the settling basins also use chlorine and ammonia to disinfect the water). 

 Washington Aqueduct pipes. Library of Congress photo

Washington Aqueduct pipes. Library of Congress photo

The purified water continues on its way down the Reservoir Road toward the Georgetown Reservoir near Glover Archibald Park. An iconic gatehouse guards the entrance to the reservoir, its design was based on the blocky structure shown in the Army Corps of Engineers logo. 

Pennsylvania Avenue Aqueduct in 1859. Library of Congress photo

The aqueduct crosses Rock Creek Valley inside the Pennsylvania Avenue Bridge. This unique cast iron structure was structuraly supported by the two 48-inch arching water pipes. Meigs originally designed the span just to carry water. But according to the Historic American Engineering Record, “the urgent need for vehicles to traverse this route during the Civil War - just when the aqueduct was finished - spurred the Army Corps of Engineers to decide that this crossing be outfitted as a bridge.” 

Once the conduits are across Rock Creek they begin to branch out in a network of smaller and smaller pipes that eventually connect with individual houses. 

Map of the Washington Aqueduct. Library of Congress Map

The Washington Aqueduct was one of the first water systems of its type in the United States. It fits into a group of other City Beautiful Movement projects that increased public health and enhanced parkland and public spaces across the District. Two other subjects we have covered, the Senate bathtubs and the Temperance Fountain, wouldn't have been possible without it. 

Interested in learning more about Washington water infrastructure? Check out the behind the scenes tour below.