Gathright Dam 'test pulse' to increase Jackson River water flow

Posted September 21, 2011
By Norfolk District Public Affairs

09/21/2011 - NORFOLK, Va. — State and federal agencies will use Gathright Dam near Covington, Va., to simulate a storm event on the Jackson River Sept. 28.

The test pulse, conducted by the Norfolk District, U.S. Army Corps of Engineers, in cooperation with the Virginia Department of Environmental Quality and the Virginia Department of Game and Inland Fisheries, will begin at approximately 6 a.m. and peak at 3,500 cubic feet per second.

The agencies advise people to be aware of the river fluctuations that will be caused by the test pulse. The pulse is expected to raise the water level downstream in the Jackson River by up to five feet in some sections and up to three feet in the upper James River, but will remain several feet below flood stage. In some areas, the rate of the river rise may exceed two feet per hour.

The river is normally at a constant height and flow during this time of year.

Gathright Dam will gradually increase water releases from 240 cfs to a maximum of 3,500 cfs by 9 a.m. The maximum surge will last two hours, and at 11 a.m. releases will begin to gradually decrease, and return to 240 cfs by 2 p.m.

The controlled release will test whether the pulses effectively remove algae and improve water quality by simulating natural storm events that occur during the late summer and early fall. This natural variability is reduced by the operation of Gathright Dam.

A 3,000-cfs test pulse in August 2010 showed that the pulse raised dissolved oxygen levels in the river, scoured excess oxygen-consuming algae and "slightly improved" aquatic habitat of the Jackson River below Covington.

The pulses are part of a continuing Army Corps of Engineers feasibility study at the dam. The study will determine whether a change to current low-flow augmentation operations at the dam can improve the overall water quality and ecological resources in the lower Jackson River without affecting the existing fisheries in Lake Moomaw and the trout fishery below the dam.