A two-day surge in water releases from Gavins Point in southeastern South Dakota won't seriously reduce water levels on Lake Oahe heading into the crucial spring walleye spawning period, a state fisheries biologist said Wednesday.

Jim Riis, Missouri River fisheries program administrator for the state Game, Fish & Parks Department in Pierre, said the increased water releases are designed to help the endangered pallid sturgeon population in the Missouri River downstream from Gavins Point Dam without hurting sport fishing upstream.

"I think the spring pulse is a good thing," Riis said. "Really, it doesn't take much water out of storage to do it. What they're doing is matching the natural high flows that existed before the dams."

Tuesday night, the U.S. Army Corps of Engineers began a two-day "pulse" of water from Gavins Point Dam near Yankton, the last in a succession of four Missouri River dams in South Dakota. The increase of about 5,000 cubic feet per second from the dam is intended to mimic the natural spring rise that stimulated spawning movements for sturgeon and other native river fish before dam construction.

The pulse began after a federal court ruling in Missouri denied an attempt by state officials there to block the water release this spring. Central and eastern Missouri have already faced flooding problems this spring. Corps officials said those flooded areas would be well below flood stage by the time the additional water from the pulse arrived in central and eastern Missouri.

As downstream states worry about spring flooding, fisheries biologists in South Dakota, North Dakota and Montana are more often concerned about a shortage of water in the Missouri River reservoirs. They typically lobby the corps not to reduce water levels in reservoirs at a time when important fish species are spawning.

The corps estimates that the current pulse will reduce water levels in Oahe, Sakakawea in North Dakota and Fort Peck in Montana by less than a tenth of a foot over the course of the year. And Riis said it isn't likely to be a major problem when walleyes and other fish spawn in April, especially if forecasted rain and snow this week provides additional runoff into the system.

"I'm kind of excited about the storm being forecast. What might come in the next few days could be really important," he said. "That could put some wet snow on the plains around Oahe."

The biological plan for sturgeon recovery ideally would include two spring pulses: one in March, and one in May. But corps officials have determined that there isn't enough water in the Missouri River reservoirs for a second pulse this year.

During recent drought years, the corps has rotated management priorities among the three big river reservoirs in the Dakotas and Montana. This year, Sakakawea is scheduled to be favored.

Oahe is still troubled by drought. But it will go into the spring almost 10 feet above its 2007 spring level. Riis is hoping that water levels will hold stable or decline only slightly during the crucial spawn and egg-hatching period that follows.

"We've sort of asked them not to drop it like a rock," Riis said.

Apart from the spawning question, Riis said fishing for the popular salmon and walleye on Oahe - a widely known reservoir covering more than 300,000 acres when full - should be good again this year.

Contact Kevin Woster at 394-8413 or kevin.woster@rapidcityjournal.com