Water managers see early runoff as a positive sign – The Durango Herald


As summer approaches, the forecast is not good, but it is slightly better than last year

The remaining snow is visible over the La Plata Mountains on Wednesday. Runoff in southwestern Colorado is two to three weeks earlier this year due to warmer temperatures and dust spells, said Susan Behery, a hydraulics engineer with the US Bureau of Reclamation. (Jerry McBride/Durango Herald)

As rivers begin to swell with spring runoff, water managers in southwestern Colorado are optimistic that this year will be better than last.

The water forecast remains below average, but above last year’s troubling lows – a positive sign for water managers adjusting to the region’s persistent drought. Yet much will depend on the impact of recent dust events and summer monsoons.

“We were showing that there had been snowmelt, but we were still quite well seated on the snowpack. Runoff estimates, depending on where you were looking, were 60 to 70 percent of average,” Southwestern Water Conservation District superintendent Steve Wolff said of the early April forecast.

According to SNOTEL data from the U.S. Department of Agriculture’s National Resource Conservation Service, just over half of the snowpack in the San Miguel, Dolores, Animas, and San Juan basins has melted so far. Snowpack is measured using the metric of snow water equivalent or snow water content.

The Animas River was flowing at 669 cubic feet per second at Durango Wednesday afternoon, the Dolores River at 556 cfs at Dolores and the San Juan River at 895 cfs, according to data from the Colorado Basin River Forecast Center.

Rivers in southwestern Colorado have slowed since Friday, but the Colorado Basin River Forecast Center predicts flows will increase again over the next week and a half.

Forecasts show the Animas River peaking at 3,100 cfs in late May or early June, slightly above last year’s peak of 2,910 cfs on June 7. Forecasts project peaks of 1,500 cfs for the Dolores River and 1,600 cfs for the San Juan River also in late May and early June.

A graph showing the snowpack in the San Miguel, Dolores, Animas and San Juan basins on Wednesday. The snowpack is just over half way through southwestern Colorado. (US Department of Agriculture/Natural Resources Conservation Service)

The snow is melting earlier than average this year, according to SNOTEL data, a trend Wolff and other water managers have noticed. Typically, snow accumulation would peak around April 1, and runoff would last from April through May and even into June, Wolff said.

“The runoff is coming earlier these days than we’ve been seeing before, so I’m not sure there’s more normalcy anymore,” he said. “We’re seeing snowmelt starting earlier in the season and I think that’s going to be a continuing trend.”

Although runoff will occur earlier this year, water supply forecasts suggest more optimism. The Animas, Dolores and San Juan rivers are hovering just above 70% of average, according to forecasts from the Colorado Basin River Forecast Center.

“It’s definitely better than last year. (We saw) a decent snowpack. We are seeing relatively decent water supplies,” Wolff said.

Forecasts also show below average reservoirs, ranging from 53% of average at McPhee Reservoir in Dolores to 72% at Vallecito Reservoir. But for McPhee Reservoir, it’s a clear departure from the all-time low of 32% projected last year.

Ken Curtis, district superintendent of the Dolores Water Conservancy, told Wolff the district hopes to get at least 70% of its average water.

“They got 10% last year. If they get 70%, or maybe even a little more than that this year, that’s really good news,” Wolff said.

Rob Genualdi, division engineer for the Colorado Water Resources Division’s Southwest Colorado Division 7, said none of the local reservoirs are likely to fill completely.

Kevin Hronich, president of the Pine River Conservation District, echoed that assessment for the Vallecito Reservoir, which he says will not meet its average. The Vallecito reservoir will reach about the same level as last year, when it was 71% of average, he said.

“If we can get some monsoon humidity, we’ll be about the same as last year. Still well below average, but at this point it’s better than not as good,” he said.

While the region’s water outlook is positive, Hronich, Wolff and Genualdi each said a successful summer will depend on monsoon rains to top up this year’s snowpack and maintain water supplies.

“We absolutely need rain this summer to get through,” Hronich said. “A reasonable goal for the Pine River Irrigation District in Vallecito is to be able to have irrigation water through September 15. We will simply run out of water by the first part of August if we don’t see monsoon humidity.

The other concern of water managers is the strong winds and dust episodes that have occurred in recent weeks.

Forecasts show the Animas River peaking at 3,100 cubic feet per second in late May or early June, slightly above last year’s peak of 2,910 cfs on June 7. Forecasts call for peaks of 1,500 cfs for the Dolores River and 1,600 cfs for the San Juan River also in late May and early June. (Jerry McBride/Durango Herald file)

Wolff said he was curious about the impact of recent dust-on-snow events on runoff, but he didn’t have a good idea how quickly those dust events would melt the snowpack.

In his latest update released Monday, Jeff Derry, executive director of the Center of Snow and Avalanche Studies and head of the Colorado Dust-on-Snow program, documented a 17% one-day decrease in snow albedo. during a monitoring site at Red Mountain Pass.

Lower albedo, a measure of snow reflectance, leads to faster snowmelt, and southwestern Colorado will likely see snowmelt earlier this year due to dust events, Derry said. .

Southwestern Colorado has seen seven dust events so far this season, according to Derry’s update.

“It just got windy all over the state more than the usual spring winds, and that really did a lot for the wildfires and the dust,” he said.

Susan Behery, a hydraulics engineer with the U.S. Bureau of Reclamation, attributed the early snowmelt this year in part to dust.

“We had what I would consider an average snow year, but all the SNOTELs are melting two to three weeks earlier,” Behery said. “A lot of that is due to the warm temperatures and then partly to the really intense and severe dust episodes that we’ve been experiencing lately.”

The dry soils of the drought years also resulted in less runoff, she said.

“Even if we had an average snowpack, we’re probably looking at a well below average influx season,” she said.

While water managers maintain hope that the early-season forecast for southwestern Colorado will result in a hydrological year comparable to or better than 2021, elsewhere in the upper Colorado River basin, forecasts are less promising.

“It’s pretty grim. There may be a few sites in Upper Colorado that should be near normal, but almost everywhere we are forecasting and expecting below normal runoff,” said Cody Moser, senior hydrologist at the Colorado Basin River Forecast Center.

On Wednesday, the entire southwestern Colorado was in drought conditions, ranging from moderate in La Plata, Archuleta, Hinsdale, Dolores, San Juan, San Miguel and Ouray counties to severe and extreme in parts of Montezuma County.

“I think we’re going to fight another drought year,” Behery said. “I hope for a good monsoon season because we really need sustained above average monsoons to overcome the soil moisture deficit.”

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