Rainfall severely insufficient in upper western basin of Potomac River... Emergency in drinking water supply for capital region
Flow rate plummets to 1,720 cfs... Falls 1,000 cfs below 130-year average, triggering daily monitoring
Experts warn: "Entering 'autumn dry period' past summer peak... Urgent need for residents to conserve water for prolonged drought"
Although sudden heavy downpours accompanied by thunder and lightning have recently struck the Washington Metropolitan Area (DMV), including Virginia, triggering road flooding and flash flood warnings, they have proved far from enough to relieve the drought in the Potomac River—the primary lifeline for 6 million area residents. Despite daily rain showers, concerns over drinking water shortages in the Washington area appear to be worsening into an ongoing crisis.
The main cause of the large gap between the "heavy rain" felt by residents and the actual "water supply flow rate" lies in the hydrological imbalance of the rainfall areas.
An official from the Interstate Commission on the Potomac River Basin (ICPRB) explained, "Most of the rain that recently fell on the capital region was concentrated in the eastern basin, downstream from the primary drinking water intakes in the Washington, D.C. area." The official added, "While the heavy rain may have temporarily revived gardens and plants, it virtually did nothing to increase the upstream water flow feeding into the intake stations."
According to experts, ensuring a stable drinking water supply for the Washington metropolitan area requires continuous and sufficient rainfall in the western and uppermost mountainous basins of the Potomac River, where the intake facilities are located. Currently, drinking water for D.C. and nearby areas in Maryland and Virginia is supplied by three major water utilities—WSSC Water, Washington Aqueduct, and Fairfax Water—which withdraw water from the upper Potomac River, treat it, and distribute it.
Currently, the water level and flow rate of the Potomac River have dropped to levels that threaten safety margins.
According to measurements from the U.S. Geological Survey (USGS) Maryland monitoring station, the Potomac River's flow rate recently fell to 1,720 cubic feet per second (cfs), well below the threshold of 2,000 cfs that triggers daily drought monitoring.
An analysis of 130 years of hydrological data shows that the average flow rate for the Potomac River in early August is around 2,760 cfs. In other words, the river's current flow rate has reached a serious 'drought warning' state, sitting a staggering 1,000 cfs below the historical average. Consequently, authorities have entered emergency mode and significantly stepped up daily flow and intake monitoring.
The problem is that the outlook ahead is also not bright. Water resource authorities expect that although localized showers are forecasted for this week, they will be insufficient to reverse the current significantly low flow trend.
In particular, summer is seasonally a period when the Potomac River's flow naturally declines due to increased evaporation from high temperatures and a surge in water demand. Furthermore, as the region enters the "autumn dry period"—the time of year when the Potomac's flow is at its lowest—water authorities are reportedly carefully considering emergency releases from backup reservoirs, such as Jennings Randolph and Little Seneca reservoirs.
A water resources official warned, "Residents should not be complacent about news of rain showers. Voluntary water conservation efforts in daily life and gardens, such as refraining from watering lawns and washing cars less frequently, are desperately needed right now." The official added, "If the drought continues to persist, staged mandatory water restriction measures could be issued across the entire metropolitan area."