Despite the recent torrential rain and flash flooding in portions of the D.C. region, the flow of the Potomac River is so low that local water suppliers are beginning to monitor for a drought.
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“Most of the rain, the accumulations occurred in the eastern portion of the (Potomac River) basin that’s downstream from the intakes for the D.C. water suppliers,” said Michael Nardolilli, executive director of the Interstate Commission on the Potomac River Basin. “A lot of places got a lot of rain, so gardens are going to pop back to life, but our focus is on the drinking water supply for the Washington, D.C. area.”
“The real question is: where did the rain fall? We need it to fall in the western part of the basin, which is upstream from the intakes for the D.C. area water suppliers,” Nardolilli said. The three local water suppliers are WSSC Water, the Washington Aqueduct and Fairfax Water.
Daily drought monitoring begins when the flow at the U.S. Geological Survey’s stream gauge at Point of Rocks, Maryland, falls below 2,000 cubic feet per second.
“The river is very low and it has been low — right now it’s at 1,720 cubic feet per second,” Nardolilli said. “We don’t think it’s a problem with the gauge. We think it’s a problem with the river.”
To illustrate, Nardolilli said the median for the date of Aug. 3, over 130 years of data collection, is 2,760 cubic feet per second: “We’re basically 1,000 cubic feet per second of the median for that date.”
While heavy rain is expected to continue this week, Nardolilli doesn’t think it will be enough to cause the cessation of the daily drought monitoring.
“Summertime is a traditional low part of the river flow, and we’re going into the fall, which really is the lowest part,” he said. “We’re pleased we’ve had so much rain, but it didn’t do much to dent the drought from our perspective, looking at drinking water supply.”
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