Snowmelt season is in full swing, but one may not know that by looking at the Animas River, which this week more closely resembles a slow trickle through Durango than a roaring, muddy torrent more common for this time of year.
The river’s flow Monday was about 328 cubic feet per second, according to the U.S. Geological Survey. By comparison, the average flow for April 26, based on 109 years of data, is 1,180 cfs. For reference, 1 cfs equals about 7.5 gallons flowing by a particular point in one second.
The Animas River’s peak runoff is still to come, but on average, the river’s flow is expected to be lower than usual through July, according to the National Weather Service. In fact, the river is expected to see about 45% of the volume it normally sees between April and July, said Aldis Strautins, National Weather Service hydrologist.
“That’s really significant,” Strautins said. “That would be the seventh lowest volume out of 110 years, if the forecast is correct.”
The Animas River already saw record low flows in recent months. In December, the river dipped below its historic low, 94 cubic feet per second, dropping to 79.6 cfs. Then, in February, it beat its own record and briefly fell to 71.4 cfs.
There are multiple reasons why the river is lower than average and projected to stay that way, Strautins said.
First, the region is in drought. Almost all of La Plata County was categorized as “extreme” or “exceptional” drought as of April 22, according to the U.S. Drought Monitor. Those are the most severe of five drought rankings.
Below-average precipitation and a poor monsoon season contributed to a dry summer and fall for Southwest Colorado, Strautins said.
Dry conditions led to low soil moistures. What precipitation the region did receive was immediately absorbed into the soil instead of running off.
“The soil moisture was so dry it’s going to take a lot of moisture to get it back to normal,” he said.
The region’s snowpack is also below average – another cause for the low flows, Strautins said.
As of Tuesday, the snowpack was at 57% of the basin’s average. It also peaked earlier than usual, March 28 instead of April 6, according to provisional Snotel data from the U.S. Department of Agriculture.
The snowpack started melting after a warm spell in early April, then the melt slowed because of winter storms and some cloudy, cool days.
“That would also contribute to why we have less runoff now,” he said.
Looking ahead, he said the river would see some higher-volume peaks over the next three months. But they would not last as long because there is not as much snowpack to feed them.
The weather outlook also shows a higher probability of below-normal precipitation for spring into early summer and a higher probability for above-average temperature for that time period, Strautins said.
smullane@durangoherald.com