#Colorado’s statewide #drought “pretty dire.” It’ll take more than a season’s snowfall to get out of it — The Colorado Sun #snowpack (January 8, 2021)

From The Colorado Sun (Lucy Haggard):

Rehydrating would require at least 10 to 20 inches of good precipitation in the next 6 months, but this season’s snow totals are already well behind normal

More than a quarter of the state is in the worst level of drought, and with snowpack significantly below what’s expected this time of year — especially on the Western Slope — scientists are warning that it will take more than just a big snowstorm to alleviate this dry spell.

Colorado has been in drought to varying degrees since August, and this week is no different. Thursday’s U.S. Drought Monitor report found that all of Colorado is in at least “moderate” drought — the second lowest drought category — with 27.6% classified in the most intense category of “exceptional.” The past five weeks of reports have maintained that 27.6% figure; there hasn’t been less than a quarter of the state in “exceptional” drought since eight weeks ago.

US Drought Monitor June 25, 2002.

The last time Colorado saw drought this widespread was in 2002. On one hand, it’s good that the state’s drought status isn’t getting worse; on the other hand, it’s also not improving, and likely won’t anytime soon…

Colorado Drought Monitor January 5, 2021.

Much of Colorado’s water supply is banked up in winter snow, which, to be comparable in analyses, is converted to a liquid water equivalent. In a normal year, Colorado would have accumulated about 45% of its “normal” snowpack by now. Right now, the state has about 35% of its expected snowpack for the year, according to Karl Wetlaufer, hydrologist with the National Resources Conservation Service. Some areas are faring better than others, but across the board, the state is into month four of a concerningly dry water year.

Colorado snowpack basin-filled map January 8, 2021 via the NRCS.

It’s not just that the state isn’t getting much precipitation now; Colorado hasn’t had good precipitation for a long time. Nearly half of the NRCS snow telemetry sites saw their record lowest or second lowest precipitation measures on record from May to October last year, [Karl] Wetlaufer said. The telemetry sites have collected data for three to four decades, depending on the location.

“The drought situation now is pretty dire,” Wetlaufer said.

Even if the state meets or exceeds its snow-water-equivalent totals sometime this season, Wetlaufer noted that the lack of precipitation last year means that this year’s runoff will almost certainly be below average. Already, rivers across the state are reporting record-low streamflows.

A few factors influence how much water runs off into rivers and streams. For one, if soils are dry as they are now, any water that either melts from snow or falls from rain will first go into the ground, with soil soaking it up like a sponge. Plants will also absorb water as it falls or melts until they are satisfied, and right now the state’s vegetation is parched.

The ramifications of the current drought are wide-reaching, according to Wetlaufer; agricultural land is degrading, reservoirs are low, and scant stream flows are putting some wildlife and plant species at risk. The state recently activated its municipal drought response for the second time ever, after activating the agricultural portion of the plan last summer.

Based on the PHDI. PHDI is a primary measure of long-term drought but may not apply to all areas, including those with heavily managed surface water. No additional precipitation is needed for white areas. Map credit: NOAA (Screenshot)

It will take a lot to pull the state out of drought. According to a National Oceanic and Atmospheric Administration model, the state needs at least 10 inches of water-equivalent precipitation, and almost 20 inches on the Western Slope, in the next six months to emerge from its current drought.

It remains to be seen whether a good spring snow season is in the cards, but Wetlaufer said, “from all the outlooks I’ve seen, it’s not looking incredibly encouraging.”

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