Potomac Flow to Show if Supply Is Adequate
By Jackie Spinner
Washington Post Staff Writer
Monday, October 8, 2007
In an extraordinary measure aimed at determining whether the Washington region truly is in a drought, the U.S. Army Corps of Engineers released a torrent of water yesterday from a dam in far Western Maryland to test how long it will take the water to reach this region.
The release of 200 million gallons of water a day through tomorrow from the Jennings Randolph reservoir will allow experts to fill in a crucial data point they say is missing from their drought predictions.
Despite the desiccated cornfields and front lawns, the declarations from political leaders and this fall's unseasonable heat, water experts remain uncertain whether the region's dry spell will ultimately lead to a drought for the water supply.
The Interstate Commission on the Potomac River Basin is predicting there is only a 1 percent chance that major water suppliers will have to tap backup sources through the end of the year. Without the water flow data from the dam, though, it doesn't know for certain.
"It's very rare to have full reservoirs late in the season with low flows [in the river], so we are taking advantage of it to test the time of travel from the reservoir to the intake," said Erik Hagen, the commission's director of operations.
In 1992, the last time the Corps of Engineers tested water flow from the reservoir, about 150 miles northwest of the District, it took nine long days to go downriver to the Potomac basin. That was one of the worst dry spells the region has experienced recently, a year when the water flow in the Potomac could not sustain the region's water supply needs. The nine days become something of a benchmark: If it takes longer for the water to get downstream this week, experts could decide that they have a problem.
Other indicators suggest that the region has not reached a "hydrological drought": The Potomac is coursing through Washington at about 700 million gallons a day, below normal but well above historic lows. Most major reservoirs have levels adequate for the region's drinking, washing and watering needs.
"The Washington area water supply is in excellent shape," Hagen said.
That is little solace to farmers across Virginia and Maryland who lost as much as 60 percent of their crops this summer, or to homeowners who have been asked to curtail lawn watering and shorten showers as the hot, dry weather continues in October.
Yesterday, the temperature reached 92 degrees at Reagan National Airport, the warmest day this month, according to the National Weather Service. It was one degree shy of the record for Oct. 7, set in 1941, and far above the average high of 72 degrees or last year's crisp 58 degrees. At Dulles International Airport, the temperature hit 91, breaking the 1963 record of 86 degrees.
Weather forecasters predict a hot day today, but a cold front should arrive tomorrow night and bring rain and cooler temperatures.
The conditions have prompted some public officials to impose water conservation measures, primarily in counties with heavy agricultural bases and with new development taxing the water supply. Some smaller reservoirs are at critical lows.
Loudoun County, for example, approved mandatory restrictions -- and $500 fines for excessive use -- for water customers in the county's eastern sector, citing, among other reasons, concerns about a depleted reservoir. Virginia Gov. Timothy M. Kaine (D) asked for a federal drought disaster declaration last week to help farmers statewide recover from crop losses, following similar action by Maryland Gov. Martin O'Malley (D).
Maryland officials put 15 counties, including Montgomery and Howard, on a "drought watch" last week, asking residents to conserve water. The Metropolitan Washington Council of Governments also issued a drought watch and urged residents to shorten showers, turn off the tap when they brush their teeth, curtail landscape watering and take other steps to conserve.
Forestry officials in both states say drought conditions are shortening the period of fall color for trees and increasing the threat of wildfires. But climatologists say that typically when the leaves start to fall and the first frost appears, reservoir levels start to rise.
To reconcile seemingly contradictory reports about weather, water supply and withered crops, experts say it helps to think of two kinds of drought: agricultural and hydrological. Sparse rainfall and hot weather feed both, but in different ways.
Summer rain totals in the region were about 40 percent below normal, and on many days, the temperature hit 90 or above. The combination proved lethal to corn -- overplanted this year because of high prices at the beginning of the season -- and other crops in Eastern Virginia, Eastern Maryland and Southern Maryland, leading to an agricultural drought, said Jerry Stenger, head of the University of Virginia Office of Climatology.
But Stenger and other experts said the region is not in a drought in terms of the water supply. "It's hard to predict what's going to happen," he said. "The months ahead will tell the story."
Terry Wagner, chairman of Virginia's Drought Monitoring Task Force, said the region "eked" by this summer. "But we're on the edge."
The Potomac, of course, is central to the region's water supply. The river has not been replenished this year by soaking tropical storms, but spotty rain showers and thunderstorms have provided enough saturation to keep its levels from dipping drastically. In September 1966, an unusually dry year, the river flow at Little Falls was measured at what experts called a low for the modern era: 388 million gallons a day. That's far lower than the current rate.
The region's major water agencies say most local reservoirs this fall have an ample supply.
The Fairfax County Water Authority, which serves nearly 1.5 million people in Northern Virginia, reports no shortages. Spokeswoman Jeanne Bailey said the Occoquan Reservoir on the Prince William-Fairfax county border is more than 50 percent full. The authority has drawn from the Potomac to keep reservoir levels from dipping further.
The Washington Suburban Sanitary Commission, which serves nearly 1.8 million people in Montgomery and Prince George's counties, also reports no shortages. Spokesman John C. White said the Triadelphia Reservoir is at 66 percent capacity, and the Rocky Gorge Reservoir is at 44 percent capacity.
"While we realize that some of the farmers are suffering," he said, "we believe these reservoirs and the Potomac River are adequate to meet our customers' needs."
The Washington Aqueduct, operated by the Corps of Engineers, provides water for about 1 million people in the District, Arlington County and Falls Church. "We're in no immediate crisis of any kind," said Tom Jacobus, aqueduct general manager.
Staff writer Delphine Schrank contributed to this report.
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