For Thurmond Lake fish, D-O is a G-O

Recently we received this comment about dissolved oxygen and pumpback at the Russell Dam:

“As I recall, the Russell project was initially accompanied by much debate over water quality and fish. Has the addition of underwater oxygen injection resolved the DO [dissolved oxygen] issues for the fish? Does the hydropower generated by Russell cover the cost of this oxygenation? Also, at startup there were serious fish-kill issues on Russell’s pump-back and it was stopped for a good while. Since it has resumed, I assume that changes made to protect more of the fish population. Can you or a fish and wildlife person comment? Thanks!”

Indeed, fish habitat and water quality were major issues surrounding the construction and environmental testing of the Richard B. Russell Pumped Storage Project in the 1980s and 1990s. Here’s a general explanation why:

Pumped storage has a direct impact on water quality downstream of the Russell Dam in the upper reaches of the Thurmond reservoir. Water quality—particularly dissolved oxygen and water temperature—directly relates to fish habitat. Many fish in the reservoir, especially striped bass, depend on cool, oxygenated water for essential habitat.

Pumped storage moves water from Thurmond Lake back into Russell Lake.  At the beginning of a pumped storage daily cycle, the water is cool in temperature because it was just released through the Russell Dam. But by the conclusion of the cycle, the water moved into the Russell tailwater and through the dam into Russell Lake will be warm surface waters from Thurmond Lake. The short-term effect is a warming of the Russell’s tailwater, an important Striped bass refuge in the summer months. A longer term effect over the entire summer is the gradual warming of Russell Lake’s water in the portion of the lake near the dam.

MODOC, S.C. – Workers install liquid oxygen tanks in April 2010 near Modoc, South Carolina, as part of the J. Strom Thurmond Lake dissolved oxygen injection system. Today, the system provides valuable habitat for Striped bass and other species in areas below the Russell Dam in the upper reaches of the Thurmond reservoir. USACE photo.

MODOC, S.C. – Workers install liquid oxygen tanks in April 2010 near Modoc, South Carolina, as part of the J. Strom Thurmond Lake dissolved oxygen injection system. Today, the system provides valuable habitat for Striped bass and other species in areas below the Russell Dam in the upper reaches of the Thurmond reservoir. USACE photo.

 

In the early years of pumped storage commercial operation from 2002 to 2010, the Corps could not operate more than two pumped storage units at a time during the summer due to these fish habitat impacts. But a solution was in the works. After several years of planning, engineering and awaiting funding, in 2011 the Corps completed construction of a dissolved oxygen (DO) injection system at the Thurmond reservoir, near Modoc, S.C.

The DO system is approximately 5.5 miles upstream of the Thurmond Dam and is designed to inject 20 to 200 tons per day of liquid oxygen. The oxygen travels through seven miles of perforated pipes, submerged 55 to 95 feet below the lake’s surface. This system creates a large refuge of well-oxygenated, cool water for a variety of fish and replaces the habitat which was altered in the area near the Russell Dam.

Due to the success of the DO system, the Corps can now operate all four pumpback units at the Russell Dam during the summer, when energy demands are highest. This is particularly beneficial during periods of drought, because we can reuse the same water to generate more electricity.

We continue to monitor the DO system to ensure it performs as intended. The Corps of Engineers partnered with the South Carolina Department of Natural Resources for a multi-year study to assess Striped bass movements in the Thurmond reservoir. So far, so good. Early results indicate that Striped bass, and other fish that require cool oxygenated water, are using the habitat created by the DO system—according to Jamie Sykes, fisheries biologist for the Corps’ Savannah District.

In addition to the construction of the DO system, the Corps of Engineers also implemented several measures to reduce the entrainment of fish during pumped storage operations, Sykes said. Pumped storage operations are limited to nighttime only. During fish spawning season (March through May) we further limit pumped storage to only one unit in March, zero units in April, and one unit in May.

MODOC, S.C. – Two 20,000 gallon liquid oxygen tanks installed near Modoc, South Carolina, supply pure oxygen to a series of underwater tubes in Thurmond Lake. The dissolved oxygen injection system creates a large refuge of well-oxygenated, cool water for a variety of fish and replaces the habitat which was altered in the area near the Russell Dam. USACE photo.

MODOC, S.C. – Two 20,000 gallon liquid oxygen tanks installed near Modoc, South Carolina, supply pure oxygen to a series of underwater tubes in Thurmond Lake. The dissolved oxygen injection system creates a large refuge of well-oxygenated, cool water for a variety of fish and replaces the habitat which was altered in the area near the Russell Dam. USACE photo.

The Corps also installed several physical fish protection measures including a high-frequency sound deterrent system, a light system to attract fish away from the intakes, and placed bar screens over each intake to exclude large fish from entering the pump units.

As for revenues, all hydropower monies are returned to the U.S. Treasury; they are not directly spent to cover the cost of the DO system. However, the return on investment for pumped storage operations is significant. The ability to store water during low-demand, low-priced energy periods and then use that water during high-demand, high-priced energy periods is favorable when comparing cost and benefit.

The Russell Pumped Storage Project is in its second year of a five-year monitoring effort to fully assess the impacts of four-unit pumped storage operations. The monitoring includes: water quality investigations, angler creel surveys, a Striped bass distribution telemetry study, and an assessment of entrainment during pump operations. Thus far, the results of these studies have been within the bounds of the predictions made during testing and monitoring conducted in the 1990s and documented in several environmental reports.

Oh, and anglers are enjoying the area, too.

~Tracy Robillard, public affairs specialist

About US Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multi-million dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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