By Dave Sligh
Gathright Dam, which impounds Lake Moomaw, is located on the Jackson River, 43.4 miles upstream of its confluence with the Cowpasture River. This project is operated by the U.S. Army Corps of Engineers (COE) and was authorized by Congress to regulate river flows in the Jackson and James Rivers reduce flood damage downstream, to increase low flows for water quality improvement, and to provide recreational opportunities.
The dam's operation has a heavy impact on the Jackson River and on the James River for many miles downstream of its formation, where the Jackson and Cowpasture join. The COE is currently conducting a study authorized under Section 216 of the Rivers and Harbors and Flood Control Act of 1970 - a process in which JRA will be actively participating and in which we encourage interested citizens and businesses to do so also.
As part of this study the COE made what was termed a "pulse release" from the dam on August 17th. An abrupt rise in dam releases took flow levels in the River below the dam from 280 cubic feet per second (cfs) at 6 a.m. on that day to 3,000 cfs by 9 a.m. After maintaining the 3,000 cfs flows for two hours, the COE decreased releases over the next two hours until they again reached 280 cfs.
This test was done in cooperation with the Virginia Departments of Environmental Quality and Game and Inland Fisheries and was intended to test whether such pulses are effective at removing algae and improving water quality by simulating late-summer and early-fall storm events, a natural variability that's been reduced by the operation of Gathright Dam.
