A Wet Year

The Washington Post recently reported that due the very rainy few weeks we just had, the Potomac river hit its highest levels since March 2010 in areas all over the Washington, D.C. area. The Interstate Commission on the Potomac River Basin (ICPRB) reports that we have water and that there is a below normal probability of needing water from the Washington metropolitan area’s back-up water supply reservoirs for the 2018 summer and fall seasons.

Our backup water supply is held in the Jennings Randolph and Little Seneca reservoirs. The need to release water from the reservoirs is triggered by low river flows brought about by a combination of low summer precipitation and low groundwater levels.

This year the average precipitation in the Potomac basin has been significantly above normal for the month of May. Recent rainfall has caused flooding in many areas of the basin. Streamflow data from the U.S. Geological Survey shows that flows are above or much above normal. Their gauges reported that the flow rate of the Potomac at Goose Creek was over 4 times the long term median, and at Point of Rocks the flow of the Potomac River was over 3 times the long term median.

Groundwater levels are near normal. According to the Middle Atlantic River Forecast Center, the outlook for water resources and water supplies is good in the Potomac Basin. At present, there is sufficient flow in the Potomac River to meet the Washington metropolitan area’s water demands without augmentation from upstream reservoirs. The latest U.S. Drought Monitor did not report any areas of Virginia in drought or even dry.

Data from the National Weather Service’s Middle Atlantic River Forecast Center (MARFC) shows that the Potomac basin upstream of Washington, D.C. has received a precipitation total above normal for April, and that precipitation was abundant for the month of May. In the past week alone, heavy rain (generally 2-6 inches over the region, and locally much greater) fell across much of Virginia, Although southern Virginia did not receive the very heavy rainfall that was reported just to its north, it still received enough to eliminate any residual dryness. Finally, it looks like we’ve got your wet year to recharge the basin. 

The ICPRB, through its Section for Cooperative Water Supply Operations on the Potomac, coordinates water supply operations for the regional water utilities during times of drought and recommends releases of stored water. These operations ensure adequate water supplies for Washington metropolitan area water users and for environmental flow levels. The water supply outlooks are published on a monthly basis between April and October.