The past 30 days have at least temporarily erased hopes of above-average spring runoff in the Colorado River Basin, according to the February report from the National Oceanic and Atmospheric Administration’s Colorado Basin River Forecast Center.
“Very little precipitation during the last three weeks of January, especially across southern Utah and Southwest Colorado,” Cody Moser, a hydrologist with the NOAA forecast center, said Monday during a web briefing to review the agency’s latest monthly water-supply report.
The National Resources Conservation Service maintains snow telemetry (SNOTEL) sites across the Colorado River Basin, which automatically report snow depth and quality. Beginning in December, NOAA produces regular reports based on the SNOTEL data, detailing how that snow might translate into streamflow come spring.
Spring runoff is critical to irrigated agriculture, domestic water supplies and the recreation industry in Colorado and across the West. More than 36 million people rely on the Colorado River for drinking water; farmers and ranchers use water from the river to irrigate more than 3 million acres of farmland. Water managers have also been closely monitoring Glen Canyon Dam at Lake Powell, which delivers hydroelectric power to more than 3 million customers. If the Utah reservoir falls below the 3,525-foot elevation level, it threatens the dam’s ability to generate electricity.
Moser said that during the last three weeks of January many of the SNOTEL stations across the Colorado Basin, which includes the Colorado River and all the rivers and streams that feed into the Colorado, recorded either record- or near-record low precipitation.
“The wet weather that we saw come in the second week of December – that lasted the to first week of January,” Moser said. “The second week of January we had high pressure settle over the region that brought very dry weather.”
The February NOAA forecast predicts inflows at Lake Powell from April to July to be about 78% of average, based on 30 years of data from 1991 to 2020. The January NOAA prediction called for 98% of average inflows at Lake Powell during the same April to July period. Inflows at Powell have landed above average only four of the past 22 years.
Jeff Lukas, an independent water and climate researcher based in Lafayette, said the past 30 days have changed the spring runoff outlook quite a bit.
“Early in the season you can’t get too deflated or hopeful; I’m increasingly pessimistic now. We’ve got more than half the snow season behind us and we’re sitting on sort of average-ish snowpack,” he said. “If I had to put money down, I’d put it on us ending up statewide with below-normal runoff.”
The other significant factor playing into the most recent NOAA forecast, Lukas said, is the poor soil moisture statewide. Because Colorado was so dry and warm from July through the end of the year, a portion of this year’s spring runoff will seep into the dry ground, never making it into the rivers and streams.
“We know whatever the snow looks like, you have to subtract some amount,” Lukas said. “Basically, we were going into the snow season with a big tax – a pre-paid tax on the runoff.”
According to the latest map from the U.S. Drought Monitor, released Feb. 3, all of Colorado is experiencing some level of drought, with parts of south-central Colorado and the Eastern Plains facing “extreme drought.”
Lukas also noted that Colorado is in its second consecutive year of a La Niña weather pattern, which can lead to warmer and drier winters.
“La Niña is kind of the wildcard,” he said. “There is definitely a dry tendency for the spring with La Niña.”
What’s more, February looks to be dry for at least another week, Lukas said, if not longer.
“Could we recover? Sure.” he said. “Are we likely to? Probably not.”