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What to expect from an above-average spring runoff

Area reservoirs are likely to fill; meanwhile, rapid snowmelt could result in flooding
The snowpack in the San Juan Mountains on April 1 is well above-average for this time of year. A sudden spike in temperatures, which isn’t in the area’s immediate forecast, could cause flooding in lower elevations. (Jerry McBride/Durango Herald)

A strong snowpack this winter coupled with a wet summer in 2022 bodes well for water conservationists, the agricultural industry and reservoir operators. But La Plata County officials are keeping a wary eye on weather forecasts in case temperatures spike too quickly, causing rapid snowmelt and increased risk of flooding.

The Colorado River Basin Forecast Center stationed in Salt Lake City forecasts 153% of average runoff for the Animas River Basin through July, said Paul Miller, service coordination hydrologist and spokesman.

That level of runoff hasn’t been seen in the basin since 2019, which has the most comparable conditions of recent years to this spring. But one key difference is the snow started melting earlier in 2019 than it has this year, he said. Rapid snowmelt began in early April 2019, but that isn’t expected to happen this year for at least another 10 to 14 days, or longer.

Steve Wolff, general manager at Southwest Water Conservancy District, said he hasn’t seen any runoff into rivers yet despite above-average winter snowpack. Last year didn’t have nearly as much snowpack, but what was present melted quickly as a result of warm, windy weather.

“This year, across the Colorado River Basin, I think people are expecting some significant runoff,” he said. “And it’ll just depend on how fast it warms up.”

He said Bureau of Reclamation forecasts show most area reservoirs are expected to “fill and spill,” meaning they will fill up and release excess water. Some reservoirs, such as Vallecito, are already performing early releases to make room for the spring runoff.

“We’ve been in a long, dry period and we haven’t seen reservoirs filled in a while,” Wolff said. “So I think that’s great. Based on some of the rains we had last year, our soil moisture is in pretty good shape.”

The Animas River flows into Durango on Thursday. An above-average snowpack in the mountains could push the river out of its banks if the area experiences a sudden rise temperature. So far, spring is off to a slow start with cool temperatures, which is good news for La Plata County officials who are ever watchful of flood conditions. (Jerry McBride/Durango Herald)

According to the National Weather Service, soil moisture is an important component for runoff. If the soil is dry, it will absorb water, which results in less runoff reaching streams, rivers and reservoirs. But when soil moisture is high and the soil can’t retain more water, the water will continue to flow downhill.

“Right now it’s looking like a good year,” Wolff said. “The one thing we don’t want to see is a lot of damage from flooding.”

Miller said current streamflow forecasts for reservoirs near the San Juan Mountains are 150% of average through July. Lemon Reservoir almost 18 miles northeast of Durango is forecast to receive 160%, or 77,000 acre feet, of what it does on average. Vallecito Reservoir, 24 miles northwest of Durango, is forecast to receive 144% of its average supply, or 255,000 acre feet.

McPhee Reservoir, 62 miles northwest of Durango, is forecast to receive an impressive 202% of its average supply, 515,000 acre feet, more than what was achieved in 2019, he said.

Historically, if predictions come true, this would be the second wettest runoff season on record for McPhee Reservoir, he said. And the water supply would only be about 4,000 acre feet behind the record set in 1993.

“We could definitely see the wettest on record,” Miller said. “It’s definitely within the realm of possibilities.”

Emergency preparedness
Sgt. Chris Burke, with the La Plata County Sheriff’s Office, opens the department’s Terradyne MPV tactical vehicle that, thanks to its ground clearance and weight, can be used to rescue people during floods and debris flows. The Sherrif’s Office had previously used an older tactical vehicle to rescue people during flooding after the 416 Fire. (Jerry McBride/Durango Herald)

Clogged culverts, rockslides and flooded roads are just a few of the possibilities that can result with a rapid spring runoff. But when to expect what can be a complex question to answer.

Shawna Legarza, director of La Plata County emergency management, said she tunes into National Weather Service forecasts about every two weeks to keep up with evolving weather conditions.

The National Weather Service predicts a slow warmup leading into the summer, which is good news because it reduces the threat of a rapid runoff, Legarza said.

La Plata County’s Office of Emergency Management has been monitoring areas that are prone to flooding, she said.

After rains in March, the county opened its Emergency Operations Center and met with area fire chiefs to strategize where to store sandbags for use by residents in case of flooding.

The Colorado River Basin Forecast Center stationed in Salt Lake City forecasts 153% of average runoff for the Animas River Basin through July. (Jerry McBride/Durango Herald)

Increased moisture is good for vegetation and helping grasses grow, Legarza said, but eventually those grasses will dry out, which can help fuel wildfires.

La Plata County Sheriff Sean Smith said 2023 will be an interesting year because of significant winter snowpack after years of drought.

Most of the flooding events he has dealt with as sheriff stemmed from the 416 Fire of 2018. He said flash-flooding can be a “terrifying” experience.

“We burned for 37 days during the fire and didn’t lose a structure,” he said. “On the first day of flooding, we lost three (structures from) mudslides and debris flows,” he said.


An earlier version of this story misattributed a quote. Paul Miller of the Colorado River Basin Forecast Center said: “We could definitely see the wettest on record. It’s definitely within the realm of possibilities.”

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