Snowpack across the Upper Colorado River Basin is much lower than average for this time of year. Researchers say the lack of accumulation is due to warmer temperatures in November.
"If you look throughout the region during October, temperatures were two to four degrees above average for much of the Upper Colorado River Basin," said Seth Arens, a research scientist with the Western Water Assessment, adding that November got even warmer.
"(Temperatures) have been running six to 12 degrees above normal, some places even as much as 15 degrees," he said. "So little bits of snow that maybe had fallen in October, some of those have melted out."
SNOTEL monitoring data across the region shows many sites recording snow-water equivalent, or the amount of water that's stored in snowpack, as being below 50% of average for this time of year. The notable exceptions are in the southern parts of Colorado and Utah. The SNOTEL site near Mancos, Colorado, for instance, is recording snow-water equivalent at over 130% of average for this time of year, and sites in southwestern Utah, near Cedar City, are recording between 120-170% of normal.
The remnants of hurricanes in the Pacific Ocean brought rain to much of Colorado and massive floods to the southwestern part of the state, which eased ongoing drought conditions at the end of October. Currently, about 66% of Colorado is experiencing what the U.S. Drought Monitor classifies as "abnormally dry conditions," and only about 1.2% is experiencing the second-worst category of drought: "extreme drought." That's a sharp decline from the beginning of October, when 14% of the state was in extreme drought.
Arens said those rains increased water levels at some reservoirs, like Navajo Lake, which is on the state line between New Mexico and Colorado on the San Juan River. The reservoir saw an increase of over 100,000 acre feet of water, which Arens said is about 10% of its total capacity.
Lake Powell, which is much bigger than Navajo Lake, also got an increase of over 100,000 acre feet of water, but that only represents about a fraction of one percent of its capacity.
"Nonetheless, this is often a time of year where we're seeing steadily decreasing reservoir levels," Arens said. "So seeing any increase? Ultimately, that just buys a little bit more time before any critical elevations of reservoir storage might be reached."
The other positive aspect of the October rainfall, Arens said, was that it increased soil moisture across the region.
"We don't have a good sense of how much it's going to rain or snow throughout the course of the winter," he said. "However, we do know that the soils were a little wetter than they were before."
Having increased soil moisture going into the winter season is important because that means the ground will already be wet when snow starts to fall and snowpack really starts to accumulate. Looking ahead to spring, when that snow melts, most of that water will flow straight into rivers and streams, rather than being absorbed by dry soils.
Arens said soil moisture is also a key component when considering whether water stored in the Colorado River Basin's snowpack actually makes it into rivers and streams. When soils are dry at the beginning of the season, a portion of the snowpack is absorbed into the ground during spring snowmelt. But if they're already saturated, most of the spring snowmelt will runoff into rivers and streams, which is referred to as efficient runoff.
Much of the basin saw the opposite of that this past winter, when snowpack was around 80% of average for much of the basin above Lake Powell, but during the peak runoff season between April and July, streamflows were at about 40% of average. That inefficient runoff threw off water forecasters and impacted water users' ability to make plans for irrigation and municipal use, among other uses.
"If we had super dry soils right now, I would say we're having an inefficient runoff no matter how the winter happens, no matter how the melt happens," Arens said. "So now we have the stage set so we could have an efficient runoff."
Human-caused climate change contributes to conditions that lead to inefficient runoff. One example, which the Rocky Mountains also experienced in last winter, was an early melt in March, followed by a cold April and a fast melt.
As the seven states that use the Colorado River attempt to reach an agreement onr how that water will be allocated after 2026, this winter season will be critical in assessing how much water is actually available, especially when it comes to the system's biggest reservoirs: Lake Powell and Lake Mead.
"We are at the same point that we were in fall of 2021, essentially, where (Lake Powell) was low, not quite to those really dangerous levels that trigger like turning off power generation, but not far," Arens said. "By the time we got to spring of 2022, we had hit the lowest level ever at Lake Powell, and that was only 30 feet above minimum power pool."
"If we have a winter just like last year, that we end up with less than 50% runoff into Lake Powell, we're probably going to hit minimum power pool next year."
Copyright 2025 Rocky Mountain Community Radio. This story was shared via Rocky Mountain Community Radio, a network of public media stations in Colorado, Wyoming, Utah, and New Mexico, including KSJD.
