Water manager describes ‘perfect storm situation’ for spring runoff
“There is no sunshine that I see in the future – even when the sun does shine.”
That’s Bureau of Reclamation Wyoming Area Manager John Lawson’s opinion of what the next few weeks could hold for Wyoming in regard to the threat of unmanageable spring runoff.
On May 23 the Upper North Platte River Bain measured 220 percent of average, while last year on the same date it was 123 percent. In the lower reach, which also includes the Laramie River, snowpack had also increased dramatically, and on that same date measured 200 percent, where it was 143 percent a year ago.
Lawson says a couple things are happening to drive those averages up – the addition of fresh snow to existing snowpack, as well as cool temperatures that have prevented the snow from beginning to melt on its usual timeline.
One high-elevation site near Walden, Colo. in the headwaters of the North Platte measured 79.2 inches of water – not snowpack – on May 23, while the average is only 48.7 inches for that date. In Wyoming, a 10,000-foot site by Encampment, with an average of 31.7 inches, measured 59.8 inches of water that same day.
“That story continues on and on, but those are two sites that really reflect what the whole basin looks like,” says Lawson. “In the Lower North Platte Basin, the story isn’t much better, particularly the Laramie River, which is fed by high mountain snowpack that originates in Colorado. A site known as Fan Lake at 10,000 feet reads 59.8 inches of water, when its average is 31.7. We see a very consistent, familiar story here.”
Lawson says his office began to evacuate water early in the spring as soon as the ice came out of the river, and has been evacuating as much as possible ever since.
“Historically, there is no other year that we’ve released as much water through the March/April/May period,” says Lawson of his efforts to create space in the North Platte River system. “We got proactive on this way back in February, and it’s a good thing we did, but we’ll still face some high releases in the next 30 to 45 days, and people won’t be happy about it.”
As of midnight May 22, Seminoe Reservoir had been drawn down to 398,000 acre-feet, or 72 percent of the historic average for that day.
“We’ve got it way down, but that’s the good news,” says Lawson. “The bad news is Pathfinder, which started spilling May 23. It’s full. The reservoir starts spilling at 1,016,000 acre-feet, and on May 23 it was in excess of 1,118,000, and climbing.”
The reason behind spilling Pathfinder Reservoir so early in the season is to release more water downriver.
“We’ve been releasing the maximum amount possible, and the only way to increase releases was to get Pathfinder filled and spilled,” explains Lawson. “This is the earliest we could do it, because it’s been so cold and it continues to snow so we couldn’t get water out of Seminoe any faster – I’ve had the spillway gates at Seminoe Dam completely out of the water so they’ve just been a pass-through, trying to get water to Pathfinder.”
Lawson expected to begin to gradually increase rates of release through Casper the afternoon of May 23, but says he had to do it carefully, because at that time 5,400 cubic feet per second (cfs) was being released from Gray Reef Reservoir, while 6,300 cfs was flowing through Casper.
“In that short distance we were getting a gain of about 900 cfs because of the recent rainfall,” he says. “If the rain will stop, that gain will start dropping, but it’ll still take a few days.”
Lawson says the story in the Lower North Platte doesn’t get any better.
“We already estimate we’ll have to go into the flood pool at Glendo, and possibly go even higher than last year,” he says. “Last year we were within four feet of the spillway, and we definitely are not comfortable with that, because it takes away any flexibility if we have a big rain event like happened in Montana recently.”
Lawson describes it as a “perfect storm situation.”
“We’ve had three previous good years, and a tremendous year last year, that filled up the system. We evacuated 170,000 acre-feet last fall, and we still have a very full system. The same can be said on the Laramie River, with Gray Rocks Reservoir, which carried over a reasonable amount of water. There’s not a lot of space available, and we expect a lot of water will have to pass to the North Platte below us, and we’ll have a lot of pressure to cut back releases out of Glendo because of high flows from the Laramie River below it,” says Lawson.
“There’s no place to turn, but we’re still running scenarios, and we’ll talk with the emergency management people in Nebraska and Wyoming, because I believe we need to talk about greater releases out of Pathfinder than we’ve discussed so far, as well as greater releases out of Glendo,” he continues. “If we have the expected inflows, the longer we wait, the higher the releases will eventually be.”
“People need to prepare. We’re getting to a point where there’s nothing else we can do,” cautions Lawson.
Christy Martinez is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.