With heavy rain in recent days in northwestern New Mexico and Southwest Colorado, rivers in the Four Corners are flowing at increased levels, and residents should expect higher peak flows and some flooding in San Juan County.
Cody Moser, a civil engineer with National Oceanic and Atmospheric Administration’s Colorado Basin River Forecast Center, said a couple of warm days and increased snowmelt followed by a storm could create flooding hazards.
Spring peak flows are expected to be higher compared with the past few years in the San Juan River Basin. Many SNOTEL sites in the basin are near or above the annual peak snow-water equivalent that typically occurs in April/May. Both water year precipitation and March 1 snow water equivalent are above average, according to flood potential data.
“We’re certainly above normal,” he said, adding that although some SNOTELS indicate unusually high levels, he did not see “widespread record snowpack.”
“Seasonal peak flow of the region’s rivers is expected to be higher than the last few years,” Moser said.
According to U.S. Geological Survey, the Animas River in Farmington is flowing slightly above a gauge height of 5.6 feet while the San Juan is at 2.27 feet.
According to the Weather Underground, precipitation level Thursday in Farmington was 0.26 inches in the past 24 hours, with the historic level at 5.10 inches. With snowfall in the high country near Durango receiving near-record snowfall, rivers are expected to flow higher than usual.
According to NOAA, the San Juan mountain range is at 130% to 150% of average snowfall level.
But if there’s a “seven- to 10-day – just huge warmup – you’re gonna expect higher likelihood of flooding,” Moser said.
“If we see a kind of an extended period of, you know, above-normal temperatures and sunnier weather, then we typically likely see some higher runoff efficiencies in that scenario, versus you know, if it runs off a little bit and then it cools down and then it really kind of comes in waves,” Moser said.
“That would be kind of ideal for, you know, hazards and keeping the flood impacts down if it was to come off kind of smaller waves throughout the spring,” he said.
Peak flows because of snowmelt are expected to be near average or above average this spring in the San Juan River Basin. But because snow typically accumulates into April, conditions could change.