Did much-needed rain from Debby alleviate drought conditions in DC area?

Debby brought much-needed rain to the D.C. area, but not enough to pull it out of the ongoing drought.

“It’s a mix of 1 to 2 (inches) farther to the southeast, toward Southern Maryland. All the way up to anywhere between 6 to 9 inches through the Shenandoah Valley up through northern Maryland,” said Jeremy Geiger, senior service hydrologist at the National Weather Service Baltimore-Washington office.

He told WTOP he expects general improvement of drought conditions across the region, but not as much as people might think.

NWS is one of the agencies that provides input for the U.S. Drought Monitor, which is one of the main indicators for drought. Geiger said areas in D3 (extreme) drought will probably be improved to D2 (severe) drought. And across the region, there will likely be a “one category” improvement.

The U.S. Drought Monitor is updated every Thursday.

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“We have been in a pretty deep drought for the past six months, and also we had a drought last year,” Geiger said. “Although we got widespread rain, we will likely need further rain to really end the deep drought.”

Debby brought heavy rain to the area, which often runs off into the rivers instead of soaking into the ground.

“Although we did get a lot of rain, not all of it went to the groundwater. Some of the wells are still relatively low,” Geiger said. “We need multiple 2- to 3-inch storms over the next month and a half to really help us get rid of this drought.”

Debby improved river levels and stream flows, which is what the Interstate Commission on the Potomac River Basin expected. Executive Director Michael Nardolilli said the drinking water supply of the nation’s capital and the surrounding areas is now in good shape.

“We were really concerned,” he said. “Last few months, it’s been extremely dry upstream from Washington, D.C. And that’s the source water for the District of Columbia, Arlington and then the surrounding areas in the Maryland and Virginia suburbs.”

Nardolilli said the gauges registered a significant increase in flow because of Debby. At the Point of Rocks gauge, the ICPRB monitored a threshold of 1,740 cubic feet per second right before the storm.

Whenever it drops to below 2,000 cubic feet per second, the commission goes into daily drought monitoring.

However, that threshold surged to 61,000 cubic feet per second during the peak of the storm, and has now subsided to about 18,000 cubic feet per second.

“There’s plenty of water coming downstream,” he said. “We have three major reservoirs that are on the river and they’re now full, and so we’re in pretty good shape going into the fall.”

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