Water releases at river in Arkansas helping make stressed fish cool

Trout in the White River don't use electricity, but they benefit from hydroelectric power generation at Beaver Dam.

The fish are having to do without it -- at least temporarily.

Hydroelectric generation releases cool, fresh water into the river. Without it, temperatures rise and oxygen drops, according to the manager of the Arkansas Game and Fish Commission trout program.

The U.S. Army Corps of Engineers stopped one of the dam's two main power generators for long-scheduled repair. Then the other developed problems last month, according to a July 31 statement by the Corps. The broken generator is down for evaluation of the problem and repairs -- with no certain finishing date, the Corps confirmed Friday.

The Corps immediately notified the Game and Fish agency, spokesmen said. The commission stepped up monitoring water temperature and oxygen downstream of the dam.

No generation means no regular, large release of cooler water at the height of summer. By the end of July, biologists confirmed reports of dead fish such as freshwater shad, which feed larger fish, downstream of the dam where U.S. 62 crosses the White.

Further checks showed dissolved oxygen dropped to critically low levels while water temperatures climbed near the top of tolerable limits, said Christy Graham, trout management supervisor for the state Game and Fish Commission.

So the Corps made large, unscheduled, releases of cooler water and more will take place as needed, officials said. There is a plan for such a situation, it is in effect and it is working, the Corps and Game and Fish said Friday.

"This is not the first time we've lost both units for a while," said Steve Bays, former chief engineer for the Corps' White River system. Bays retired last year, but still works with the Corps part time.

The Corps notified Game and Fish before the scheduled repair to the first generator. It also sent notice as soon as the problem with the second generator developed, said both Bays and Eric Krebs, a hydrology engineer for the Corps. Graham said Friday that she received an email July 19 about the problem with the second generator.

That day the commission checked both water temperature and the amount of dissolved oxygen in the river every half mile for 7 miles downstream from the dam, Graham said. The commission kept up the monitoring.

It found the temperatures and oxygen levels remained within tolerable limits for trout. Continued monitoring found the fish later sought out cool spots in deeper water in some sections of the river, she said. Those cool spots are called "thermal refuges" in biology parlance, she said.

Then the dead shad surfaced. Checks confirmed dissolved oxygen dropped to critically low levels while water temperatures climbed near the top of tolerable limits, Graham said.

The Corps planned a water release the next day, but chose a rarely used method to do it.

The spillway starting at the dam's top is the normal release method when Beaver Lake's water is high or water is needed downstream. But releasing water through spillway gates would do little good, the engineers and Graham said.

"The water at the surface is about 75 degrees," Krebs said, bumping the upper limit of what trout can tolerate. Even though top-layer water would replenish oxygen, temperatures would remain close to critical at best after a release from there.

Releasing cooler water through the generator outlets was impossible with repair under way, Krebs and Bays said. The small outlet that kept an in-house generator running for the dam's own electrical needs was too small to make an impact.

But a conduit built during construction remains. The Corps used the conduit to release water while the dam was under construction so the site wouldn't flood in heavy rain. It remained in place as the dam was built above it. The outlet can be opened mechanically if needed, but is usually only opened to make sure it is still in working order, Krebs and Bays said. The dam was completed in 1966.

The deep water released through the conduit is cool and is refreshed with dissolved oxygen by turbulence as it flows from the dam into the river, Graham said.

Carl Caso works at the Beaver Dam Store downriver from the dam. He said Friday the fishing in the river is good near the dam, but fishermen who usually fish downriver have had to move closer to the dam. Downriver water temperatures are just too high, he said, and the release from the conduit -- "the tube," he called it -- is too limited to lower water temperatures far from the dam. Also, the water released by the conduit isn't rich enough in oxygen to do much good downriver, he said.

The Corps released about 5,170 cubic feet a second of water through the opening for an hour Tuesday, according to a statement by the Corps. That figures to about 18.6 million gallons or about 70,000 metric tons.

The Corps released more water Thursday and will continue to use the old opening until at least one of the power units is back, its spokesmen said.

The length of time the conduit can remain open is limited, Bays said.

"It was never designed to release large amounts of water over a long period," he said.

Recent rain in the White River basin didn't help much with temperatures in the river, Graham said. The rainwater's warm temperature nearly matched the river water's temperature before, although the cooler air temperature brought with the rain helped, she said.

The Buffalo River is a tributary of the White that joins it 30 miles below the last Corps dam, so the river's condition had no effect on the recent outbreak of blue algae on the scenic Buffalo, Graham said.

Metro on 08/06/2018

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