Spring weather to dictate threat of runoff floods
Area authorities are still in wait-and-see rather than worry mode when it comes to the potential for flooding resulting from the high snowpack in the Colorado mountains.
That’s because while more winter snow means an increased potential for flooding, the weather during spring runoff season has a lot to say about whether stream banks are topped as a result.
“It’s not a matter of how much snow. It’s just a matter of how fast it comes off,” said Barry Smith, emergency management director in Eagle County.
A week of well-above-average temperatures during runoff could enhance melting and cause flooding problems, whereas shorter, alternating stretches of warmer and cooler days could make runoff much more manageable, said Aldis Strautins, a hydrologist with the National Weather Service in Grand Junction.
The latter happened during another year of heavy snowpack, 2011, which included some record snow in the Yampa River Basin, Strautins said.
“Yes, we had some flooding issues but it could have been worse,” he said.
The difficulty of predicting now what the weather might do in May and June makes it hard to forecast the flood threat this soon.
The National Weather Service’s Climate Prediction Center has forecast above-average temperatures for the next three months in the West, including southern Colorado.
“Take it for what it is because that’s a couple of months out and that’s hard to predict,” Strautins said.
While that forecast has its uses, it also still doesn’t indicate what the day-to-day weather might be like, he said.
Nevertheless, more snow does equal greater flooding potential, so authorities are keeping an eye on the situation.
“We have a heightened awareness of the potential and so we’re monitoring it because of the snowpack,” Strautins said.
He pointed specifically to the Upper Colorado River Basin, which Monday was at 126 percent of median, according to the Natural Resources Conservation Service, and the Yampa/White River basins, which are at 124 percent.
The Laramie/North Platte (138 percent) and South Platte (136) are the leading basins for snowpack. The Gunnison is at 108 percent, the Arkansas at 99, and southwest Colorado continues to lag at 83 percent for the Upper Rio Grande and 88 percent for the San Miguel, Dolores, Animas and San Juan basins.
Lt. John Hutchins, emergency manager for the Rio Blanco County Sheriff’s Office, said emergency managers in northwest Colorado plan to meet with the National Weather Service in April to see where things stand.
“We’re keeping our eye on the snowpack right now, knowing full well that it’s above-average in part of the high country above us,” he said.
He said that even with above-average snowpack, runoff occurs generally without too much problem as long as there aren’t aggravating factors such as a fast warm-up and possibly rain on top of that.
High-country snowmelt also is moderated by cooler nights, but lingering valley snow can compound things because it melts with less of a nighttime slowdown, Hutchins said. He said area valleys for the most part don’t have much snow.
“At this point it doesn’t look like there’s too bit a worry (about flooding) right now, but of course it’s springtime — everything can change,” he said.
Hutchins said Rio Blanco County generally doesn’t suffer much flooding damage even when banks overflow because there’s not much housing and usually only rural agricultural land is affected, in valleys where the water spreads out fairly quickly.
In Eagle County, Smith said officials will be taking a closer look at the situation in later April. He said while the upper Colorado River Basin as a whole has high snowpack, that appears to be thanks to conditions in areas such as the Colorado’s headwaters. Snowpack in tributaries in Eagle County is closer to average, he said. And in Eagle County, the Colorado typically is better able to handle the extra water, he said.
“It’s the tributaries that usually create most of our problems,” he said.
In anticipation of a healthy runoff season, the U.S. Bureau of Reclamation has increased the amount of water being released from Green Mountain Reservoir in Summit County and Ruedi Reservoir above Basalt.
Neither reservoir was authorized by Congress for flood control, but they were designed to fill with snowmelt, said bureau spokeswoman Kara Lamb.
“We just want to make sure that we’ve got as much room as we can provide for that melting snow,” she said.
Strautins said one of the benefits of this winter’s snowpack is that it can recharge some reservoirs that have been low, such as Blue Mesa Reservoir outside Gunnison.
If anything, he’s less worried about flooding than he is anxious about seeing a big drop-off in snowfall the remainder of the snowpack accumulation season, which would reduce badly needed runoff.
“I don’t want enough (runoff) that we flood, but it sure would be nice to have enough in the reservoirs that they all fill up, and we have a good water supply the rest of the year,” he said.