An updated runoff forecast from the Corps of Engineers has fishery managers in North Dakota and South Dakota nervous.
The recently-released forecast is for high summer water releases that haven't been seen for at least 14 years. In 1997, the last time releases were that high, fishing took a huge nosedive on Lake Oahe and took years to recover.
Greg Power, fisheries chief for the North Dakota Game and Fish Department, said as much as two months ago, there was discussion that the corps miscalculated mountain and plains snowpack runoff.
The runoff is coming and will continue to come this spring, but the three upper basin reservoirs - Fort Peck, Lake Sakakawea and Lake Oahe - are all but full.
Mike Swenson of the corps district office in Omaha said normally snowpack in the mountains peaks in mid-April, but that has not been the case this year.
"We've seen a lot of change in the snowpack in the last half of April" because of continued precipiation, Swenson said.
In early April, he said, the forecast for snowpack between Fort Peck and Garrsion was 112 percent above normal.
The May forecast came in at 136 percent above normal, Swenson said.
In April, Lake Sakakawea rose more than 7 feet and Oahe 3 feet, while Fort Peck came up about 2 feet.
Downstream, Fort Randall, Big Bend and Gavins Point remained steady.
Swenson said there are no flooding issues downstream now, but this will be a year the river runs higher as officials evacuate water from upstream, limiting the ability to cut flows downstream in the event of major precipitation events.
Power said the concern is two-fold: Higher releases mean more bank erosion and also could threaten the rainbow smelt population as it did in 1997.
Garrison Dam is projected to see summer releases of 49,000 cubic feet per second, while Oahe releases are projected to top out at more than 52,000 cfs in June and 54,000 cfs in July.
Only in 1975 and 1997, the year water was over the spillway, were releases higher on Garrison, Power said.
"Biologically speaking, we are very concerned about Oahe's summer releases, which are forecasted to be over 50,000 cfs," Power said.
"In 1997, summer releases were in the upper 50s," he said, "and a very large proportion of Oahe's rainbow smelt population were lost downstream."
The end result was a huge hit to the fishery in both states. The systems took five to eight years to recover from the loss of the main forage source for game fish like walleyes.
"Hopefully, we won't have a repeat," he said.
In South Dakota, the effect was more pronounced.
John Lott is the fisheries chief for the South Dakota Department of Game, Fish and Parks. He said with the volume of water projected to run through the dam at Pierre, there is a good chance that smelt could again be flushed through the dam.
The setup of the intakes is different on Garrison Dam and Oahe Dam.
Water is drawn off the bottom of Garrison Dam to activate the turbines that generate electricity, while on Oahe, the intakes are higher off the bottom.
This area is where the smelt tend to run near the thermocline, the layer of water between the shallow warmer water and cold water near the bottom.
Lott said a couple of different methods have been tried in cooperation with South Dakota State University to use stimuli to keep smelt away from the intake structure.
He said strobe lights and sound were used, and while the strobe lights proved effective, the unknown is how far away from the intake the strobes should be located to be effective.
Also questioned is the expense and how often the lights would need to be used.
The loss of the smelt base in 1997 took a year to hit home, Lott said.
"By the spring of 1998, we were seeing a lot of skinny fish," he said.
By 1999, South Dakota removed the 14-inch minimum for walleyes and by 2001, adopted a daily limit of 14 walleyes in an effort to remove the smaller fish from the system.
Today, Lott said, Oahe has a more diverse forage base with perch, white bass, drum and gizzard shad but still retains a four walleye daily limit with only one keeper longer than 20 inches.
"We are still trying to restore balance," he said.
Still, he said, angler use and harvest on Lake Oahe has been down since then. Lott said anglers who had fished Oahe for years turned to other lakes, like those in the northeast part of the state and in large degree, have not come back.
"It certainly was a destination," Lott said.
For Power, there are concerns for both the loss of smelt and further bank erosion. He said Sakakawea is forecast to reach an elevation slightly above 1,852 feet.
"Last year, it peaked at 1851.4 feet, which was the fourth highest summer elevation on record and caused very significant erosion on the adjoining uplands," he said.
(Reach reporter Brian Gehring at 250-8254 or email@example.com.)