Expect more runoff: Utah’s not even halfway done melting
With lower-than-normal precipitation in April, Utah’s snowpack is steadily declining. But mountains around the Wasatch Back aren’t even a quarter of the way done melting.
Snowpack can be measured in snow water equivalent, the inches of water the snow contains.
Statewide, the snow water equivalent peaked at 30 inches April 8. As of May 5, the state still has 18.9 inches of water remaining. That’s 63% of the snow left to melt.
Locally, the snowpack is holding even firmer.
Parkite and Loughlin Water Associates hydrologist Matt Lindon says Thaynes Canyon and Trial Lake are some of the most important sites to look at for people in the Wasatch Back. Thaynes runs off to Park City, and Trial Lake’s snow ends up in the Weber and Provo rivers.
Snow at both sites is down from 40 to 33 inches of water right now. Both lost about 1 to 2 inches a day during last week’s warm weather.
“That's a good place to be because it gets us up to where we're starting to lose significant amounts of snow,” Lindon said. “But we're also not going so fast that we're going to be flooded.”
Some areas have flooded, such as Francis, Samak, parts of Heber City and neighborhoods near Willow Creek, but Lindon said it has not as bad as it could be.
He said if the Wasatch and Uinta mountains start to lose 3 or 4 inches of water a day, there could be trouble. So far, they’ve only lost about quarter of their snowpack.
The south and west-facing slopes melt first, and elevation plays a role too.
“We've taken care of the low snow, we've taken care of some of that South snow,” he said. “We're working our way up the mountain.”
The temperatures are cooling this week, which is going to give Summit and Wasatch counties a break from the runoff.
That gives officials time to prepare for the next big melt. One of the things they can do is controlled reservoir releases.
It’s kept most reservoir levels even with where they were last year, despite historic winter precipitation.
“That's mostly because they've seen this coming,” Lindon said. “They've been dumping water for several weeks to try to make some room in these reservoirs.”
Reservoirs are especially important in the springtime, because the soil is saturated and can’t absorb any more water.
Soil moisture levels are at or above 80% across the Wasatch Back, which Lindon said was normal once the snow starts melting. Still, it means that most of the water that melts or falls from the sky will stay on the surface.
Summit and Wasatch counties have seen some rain this week. If rain is in the forecast, Lindon said it’s ideal to have cool weather, as far as flooding is concerned.
There won’t be sheet flooding from heavy rain on snow and ice, and no extra moisture from any heat.
“If you get a warm rain on a warm snow snowpack, you can start precipitating a fair amount of moisture from that,” Lindon said.
For the amount of snow Utah saw this year, Summit and Wasatch counties have avoided the worst-case scenario of a 1983-style warm-up.
And fortunately, smaller reservoirs have been filling up. The largest reservoir locally, the Jordanelle, is also getting a boost.
“Usually this time of year it fills up pretty good pretty fast, and it has a good chance of filling up completely this year,” Lindon said.
In a drought-weary state that gets 95% of its water from snow, that’s welcome news.