Prolonged #drought results in record-low flows on #AnimasRiver — The Durango Herald #ColoradoRiver #COriver #aridification

From The Durango Herald (Jonathan Romeo):

All week, the Animas River has recorded record lows at a gauge station in Durango, which has been tracking flows on the river for 107 years.

On Thursday, for instance, the Animas River was reportedly running at 117 cubic feet per second – under the previous record low of 138 cfs in 1957 and far below the average of 447 cfs for this time of year.

The low flows on the Animas River come as no surprise as the region has been gripped by a prolonged drought.

Since January, a weather station at Durango-La Plata County Airport has recorded just 5 inches or so of precipitation, a 7-inch departure from historic averages at the site.

On Thursday, the U.S. Drought Monitor released a report that showed all of La Plata County engulfed in the “extreme” and “exceptional” drought categories, the center’s highest listings for dryness in a region.

West Drought Monitor October 6, 2020.

And, several weather stations in the headwaters of the Animas River recorded the lowest precipitation levels in August and September based on about 40 years of record keeping.

“The combination of an extremely dry spring, lack of a monsoon and above-average summer and fall temperatures has resulted in very low flows on the Animas River,” said Ashley Nielson, a senior hydrologist with the Colorado Basin River Forecast Center…

Becky Bollinger, a research associate with the Colorado Climate Center, said 2020’s water year was the third-driest on record, behind only the infamous drought years of 2002 and 2018…

The high country of the San Juan Mountains received about normal snowpack this winter, but it melted fast and early. On top of that, soils were so dry they absorbed more water than usual.

San Miguel, Dolores, Animas, and San Juan Basin High/Low graph May 14, 2020 via the NRCS.

One issue that concerns Bollinger is that the atmosphere is so dry, it is causing rapid evaporation of what little moisture there is – called evaporative demand…

Bollinger wonders whether a lack of monsoons in Colorado is the new normal.

“This is the fourth year in a row we have not gotten the benefits of monsoon moisture,” she said. “It’s concerning to think that might be a trend. Or is it just really bad luck? I don’t know the answer to that right now.”

[…]

As of this week, Vallecito and Lemon reservoirs were at about 24% and 27% capacity. Ken Beck, superintendent of the Pine River Irrigation District, said in an email to constituents that outflows were reduced to 5 cfs on Thursday…

The main concern for water managers is whether the upcoming winter will bring enough snowpack to replenish reservoirs. In previous drought years, such as 2018, the next winter brought heavy snowfall.

But meteorologists say the region may be stuck in a La Niña cycle, which typically means less snow for Southwest Colorado. That could result in less water for livestock and municipalities, and spell disaster for next year’s wildfire season.

San Juan River Basin. Graphic credit Wikipedia.

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