June water forecasts increase dramatically

Casper – With regard to water and river conditions in Wyoming as of June 9, Bureau of Reclamation (BuRec) Wyoming Area Manager John Lawson says it’s come to a be a situation of “top this.”
The recent June forecast, predicting 1,950,000 acre-feet of water in the North Platte system this year, will match quantities not seen since 1917.
“The highest inflows since 1917 were in 1983 and 1984, when we had 1,550,000 acre-feet in 1984,” explains Lawson.
As a result of rainfall and increased snow levels, BuRec’s forecast has jumped dramatically. On the North Platte, Seminoe Reservoir is forecast to receive inflows 273 percent above average, while the stretch between Pathfinder and Glendo reservoirs is forecast at 198 percent of average.
Boysen Reservoir in Fremont County is 211 percent above average in its forecast.
“The forecast for Boysen inflows from April through July has increased significantly to 1,175,000, and, worse yet, only 125,000 of that came in April and May,” says Lawson. “That means there’s 1,050,000 yet to come in June and July.”
Buffalo Bill Reservoir west of Cody shares a similar story, with an April through July forecast that’s increased to 1,110,000 – one of the highest in recent history at 168 percent of average.
“The problem is that only 183,000 acre-feet of that came in April and May, so we still expect the remaining 927,000 acre-feet in June and July,” says Lawson.
Of river flows in the North Platte’s upper basin, Lawson says he doesn’t think the river has peaked.
“It’ll be an interesting 30 days,” he says. “We have such a large snowpack, and hopefully it’ll come out in a good way.”
Lawson notes that snowmelt is occurring at 9,000 feet in elevation and below, while there’s still a lot of snow sitting above 10,000 feet.
“That higher country is melting out, but slowly, because night temperatures are still below freezing,” he says. “We hope both high and low elevations don’t come at the same time.”
Currently runoff is approaching 16,000 cubic feet per second (cfs) into Seminoe Reservoir – the first one on the North Platte system.
“And that’s going up,” says Lawson of the inflow. “The Medicine Bow is running about 1,800 cfs, so we’ll probably have 18,000 cfs coming into Seminoe before the weekend.”
He says all data indicates that Seminoe inflows will continue to climb, and he looks to exceed last year’s record of just under 20,000 cfs.
Of flows through the Miracle Mile, between Seminoe and Pathfinder, Lawson says they won’t be as high as last year.
“Last year we were surprised and needed to get Pathfinder up to a spill as quickly as possible, but this year we started planning as early as late February, although we weren’t planning on this much,” notes Lawson. “Now we’ve been spilling Pathfinder for some time, because we moved a lot of water out of Seminoe in April and May, getting it down to 40 percent full. At this point we hope to hold our releases out of Seminoe in the neighborhood of 8,500 cfs.”
Farther down the system, Lawson says his agency is releasing 8,000 cfs out of Gray Reef Reservoir below Alcova, and, with the gains along the way, 8,300 cfs is running through Casper.
“Those are the highest releases since 1983,” says Lawson. “All our modeling and estimates tell us it’ll be tight, but, with the space we made in Seminoe, we don’t project to go above that.”
However, he adds that depends on rain events that could push the river higher.
“There’s no absolute certainty in this. If it comes out the way we’re projecting, the system will be a pass-through, with 8,500 cfs out of Seminoe, 8,300 out of Pathfinder and 8,000 cfs coming down the river, after 300 cfs is diverted by Casper/Alcova Irrigation District,” he explains.
Even farther down the system, below Glendo Reservoir, Lawson says the Laramie River has been a surprise, in that Gray Rocks Reservoir’s releases have been lower than anticipated. He says that’s due, in part, to the Wheatland Irrigation District’s actions to attenuate some flow.
“At this point it’s good we haven’t had those high flows, but we know they’re coming, and how soon the irrigation district runs out of room is something we’re watching,” says Lawson, noting that two gauging stations above Laramie near Centennial have been steadily climbing.
Meanwhile, Lawson says his office has sought to get as much water out of Glendo as possible before the Laramie River reaches its peak contribution to the North Platte.
In northwest Wyoming, Lawson says his office continues to closely coordinate with Montana water managers, and that Buffalo Bill is now at 68 percent of average for this time of year, and Boysen is at 75 percent.
Lawson says he would let more go from Boysen, but the reservoir is already at its maximum releases.
“Right now the reservoir’s only five feet higher than the spillway, so we’re releasing as much as we can between the hydro plants, the discharge valves and the spillway,” he states. “I’d like to release about 7,000 cfs, but right now we’re at something less than 5,000.”
“There’s good news out there, but I still have to sit here with cautious optimism, because we project we’ll be at 8,000 cfs at Gray Reef for at least the next 35 days, and there is a lot of opportunity for big rainstorms,” says Lawson.
“It will be a long summer, and the next 35 to 45 days will be critical,” he adds.
Christy Martinez is managing editor of the Wyoming Livestock Roundup and can be reached at christy@wylr.net.