Reservoir management strategies consider river levels, fisheries
Casper – According to Bureau of Reclamation Wyoming Area Manager John Lawson, reservoir conditions are very important to fisheries, and his agency works closely with the Wyoming Game and Fish Department to manage that significant role.
“We could have a role both positively and negatively, and we understand that,” says Lawson, noting that some of the best fisheries in Wyoming are located below Reclamation reservoirs, like the Wind River Canyon, the Miracle Mile and the fishery below Gray Reef above Casper.
He says one strategy to ensure fishery success is a meeting with the WGFD twice a year to gain input and information. “The purpose is to see how we can operate the reservoirs and still meet our authorized purposes – storing water, meeting irrigation demands, supply power plants – and provide a river stream regime good for the fishery while not impacting the lake, because there’s a definite conflict there between the two types of fisheries.”
“We think we have some expertise in water operation, but not fisheries, so we work closely with Game and Fish to get management recommendations,” he adds.
He notes one significant success on the North Platte River has been a strategy involving flushing flows to clear sediment from gravel beds.
“When we started meeting with Game and Fish in 1993 they had graduate students working on the idea of cleaning gravel beds by alternating high and low flows and scouring the river,” says Lawson. “They asked if we were interested, and that was the initiation of flushing flows, which we’ve done ever since.”
Reclamation runs the flushing flows twice a year, in spring and fall before spawning. This fall’s is scheduled to run Oct. 12-16.
Currently the North Platte is running at winter releases of 500 cfs. Early on the first morning of the flushing flows the rate will be increased to 4,000 cfs at 12 a.m. “We’ll run 4,000 cfs until early morning, then cut back to 500 cfs by 10 a.m.,” explains Lawson, noting the early morning schedule is meant to avoid traffic on the river.
The increase is continued on the same schedule for four days in a row and completed by the end of the week.
“These surges scour the gravel beds, cleaning out the sediment,” says Lawson. “It’s been a great success, and we’ve had ups and downs, but after a couple years the poundage of fish per mile was measured and had dramatically increased, four- or five-fold.”
Boysen Reservoir and the Wind River Canyon have undergone the same treatment, increasing from 800 cfs to 5,000 cfs and back down.
Lawson says the technique works smoothly except when the weather steps in with an unexpected event, such as what happened Memorial Day Weekend 2008 when inflows in Glendo Reservoir increased from 3,000 cfs to 11,000 cfs in a matter of 72 hours.
“We were filling the reservoir in anticipation of irrigation season, and we didn’t have a lot of space,” says Lawson. “As a result, because we were in the exclusive flood control pool, the Corps of Engineers asked us to cut releases out of Gray Reef.”
The timing couldn’t have been worse for fisheries, as the agency had been releasing 1,500 to 2,000 cfs and the fish had spawned at that level. “All the sudden we had to cut to 500 cfs, exposing all those eggs, which had a detrimental effect on that year class that would have hatched that year,” he explains.
“We thought we had done a good job with flushing flows and the river level and good gravel beds for the fishery, but then we got into a pickle like that,” he adds. “We try to work with everybody to make sure we don’t do that, but sometimes we get caught in it.”
“Overall, I think people will have to admit that because we’ve had good water years things have improved significantly for everybody,” notes Lawson. “We’re balancing so many multipurposes – recreators want a reservoir that doesn’t fluctuate and the river people want minimum flows and a hydrograph that fluctuates. We have to find a way to do that, but also recognize the water is being released for a purpose – irrigation – and we don’t want to have a reservoir so full we have to bypass the power plants. Then you add in the flood control aspect. It’s all those aspects that weigh in on decisions.”
For the time being, Lawson says that because Wyoming’s been in a more wet cycle there will be good releases this winter, which will be good for the fisheries along with the rest of the water interests.
Christy Hemken is assistant editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.