2011 inflows break historic records, begin to subside

“I always look forward to August,” says Bureau of Reclamation (BuRec) Wyoming Area Manager John Lawson as 2011’s record inflows into the state’s river systems begin to come to an end.
“We’re in the throes of reducing our releases above Pathfinder Reservoir, and we’re also attempting to reduce releases below Pathfinder, because inflows have dropped off to the extent that we’re comfortable reducing,” says Lawson.
Pathfinder’s level was beginning to come down in late July, and Lawson says he expects its spill to cease by July 31.
“We’re lowering the reservoir’s level, and it’ll be the longest we’ve ever spilled,” says Lawson. “We started spilling in May, and spilled through the entire months of June and July.”
The Pathfinder spill in 2010 stopped by mid-July.
“Compared to what we were getting, today’s inflows aren’t significant, but we’re still getting a considerable amount,” notes Lawson. “Today’s inflows are a lot higher than we’d normally expect, and they’re still coming at a pretty good rate.”
Natural Resources Conservation Service Water Supply Specialist Lee Hackleman says that he continued the Monday Morning Snow Reports several weeks longer than usual, just to show people the changes in snow water equivalent, or SWE.
As of late July, Hackleman says all the NRCS SNOTEL sites are melted out.         “Grand Targhee melted out over the weekend of July 23, and that was the last one to go, but there’s still considerable snow above those sites, and some of that probably won’t melt out this year,” he says, adding that some of the glacier areas might build this year.
“We were projecting some 300-percent runoffs in some places, and I’m not sure if we’ll end up getting that or not,” says Hackleman. “Time will tell, but we’re definitely getting 200-plus in a lot of places.”
Of navigating the challenging situation indicated by Hackleman’s office beginning in February, Lawson says his office managed through it very well, and Glendo Reservoir, in the North Platte River’s lower reach, didn’t reach the levels anticipated by BuRec.
“This year Glendo was about four feet lower than last year, and a lot of that is attributed to two things – we didn’t get the inflow in the lower reach that we were afraid we might, and actions taken by the Wheatland Irrigation District early on made room in their reservoirs for Laramie River runoff, which allowed us to continue to release higher flows out of Glendo during June than we did last year,” explains Lawson. “We benefitted on both ends.”
Lawson says last year’s inflows between Pathfinder and Glendo were 300,000 acre-feet, while this year they were in the neighborhood of 190,000 acre-feet.
Of the happy ending to record snowpack in the region and its flooding potential, Lawson says the early decisions made by BuRec paid off, and weather conditions also helped.
“We had record inflow into Seminoe Reservoir – we forecast 1,950,000 acre-feet, and it looks like we’ll have over 1,970,000 acre-feet this year,” says Lawson, noting the previous record was 1,550,000 acre-feet. “We exceeded the record from 1983/1984 by over 400,000 acre-feet.”
“We really didn’t have as high of a peak flow as last year, but we had a lot more,” he adds. “By coming out slower, that gave us more time to keep evacuating, so we were helped there. We had good decisions made by Reclamation, and Mother Nature did cooperate, considering what she was trying to do to us.”
“We’re feeling pretty good about it, particularly for all those people who could have been affected,” he notes.
Of the other major reservoirs in the state, Lawson says Buffalo Bill in Park County also exceeded all inflow records.
“We’re anticipating we’ll probably have an inflow around 1,240,000 acre-feet, which far exceeds anything in our recent history,” says Lawson. “We managed to get through that without any flooding downstream on the Shoshone River.”
Lawson says avoiding the flooding was a result of keeping Buffalo Bill and Boysen reservoirs at levels the public though were too extremely low early on.
“We got input from people implying we were mis-operating and would never fill those reservoirs. Fortunately they were down, because we needed every bit of space,” says Lawson. “We got up to releases of 8,400 cubic feet per second out of Buffalo Bill, and that’s the highest release we’ve made since modification in 1994.”
Lawson says Boysen was in the flood control pool, but levels are now starting to subside.
“We’re now on the downside, and we’re reducing releases out of both Boysen and Buffalo Bill, and we anticipate getting out of the flood control pool at Boysen no later than the second week of August,” he explains. “Things turned out rather well, considering the kind of inflows and snowpack we had.”
Planning for the 2011 inflows began in Fall 2010, after the agency was surprised by record inflows the previous spring.
“We went into this year with far better planning for something like this, and last year we made the decision to reduce our total storage in the North Platte system down to two million acre-feet, and that required us to evacuate water toward the end of the water year in September,” explains Lawson. He says his office will take the same approach this fall. “We’re targeting two million acre-feet again as the ending amount, and we’re on track for that.”
Beginning in February again, BuRec will start to watch and evaluate the snowpack conditions very closely to decide how soon to begin to release water from the system, much like they did earlier this year.
Of whether or not the last two springs indicate any sort of a trend, Lawson says he doesn’t know that anybody is willing to step off that cliff and make a prediction.
Christy Martinez is managing editor of the Wyoming Livestock Roundup and can be reached at christy@wylr.net.