Press Release: Drought Exercise

Drought Exercise a Key to Protecting Metropolitan Drinking Water

Rockville, MD

Although the region’s streamflows currently are above normal, the region’s major water suppliers and the Interstate Commission on the Potomac River Basin Section for Water Supply Operations on the Potomac (CO-OP) will exercise their ability to respond to severe drought conditions during a multi-day exercise beginning November 16-18, 2020.

The exercises are a way to practice operations under severe drought conditions, when the normally independent utilities work cooperatively with CO-OP so that each utility can meet the demands of their customers while minimizing the need for restrictions. The three major water suppliers draw the bulk of their raw water from the Potomac. A drought of record could drop the flow of the river below what is needed to meet high summertime drinking water demands. When riverflow and other data indicate a coming shortage, CO-OP can guide Potomac use among the utilities and manage releases of stored water to meet demands. The Jennings Randolph reservoir on the North Branch Potomac holds billions of gallons of water that can be released downstream to meet utility demands and environmental flow concerns. The much smaller Little Seneca Reservoir in Montgomery County, Md., is used to adjust river flow in the short term as a release from Randolph Reservoir can take about nine days to reach the metropolitan suppliers’ intakes.

The exercise uses simulated low flows that allow all parties to practice daily reporting procedures, internal communications, and releases of stored water.

This year’s exercise will focus on honing the communications channels between the utilities, CO-OP, and the U.S. Army Corps of Engineers, divisions of which operate both as a metropolitan water supplier and operator of Randolph Reservoir. Another focus is the modeling that incorporates drinking water demand data and forecasts from utilities, precipitation, and stream flow data to determine the timing and volume of reservoir releases. In addition, the exercise will include an actual release from Little Seneca Reservoir, and improved data reporting systems.

These procedures are honed by the annual exercise, and have resulted in a very resilient drinking water system for the Washington metropolitan area’s more than four-million residents who rely on the Potomac as their primary drinking source. More information about the metropolitan water supply system and CO-OP are available on the ICPRB WEBSITE .

For more information on the exercise, contact Curtis Dalpra,; 301.274.8107