Sideways Outlook
Headwaters Snowpack and Hydrology
Read the complete board memo HERE
As we pass the seasonal peak for snowpack accumulation across the headwaters of the Colorado River, several confounding factors have lined up to cloud the water supply forecast: dust, heat and a fading El Nino.
For these reasons, the early reports of near to above average snowpack seem to have been premature, possibly even deceiving, as good snowpack measurements may not translate to above average snowmelt runoff across the region, especially down basin. Locally, at least, there is good news across the Colorado River District and points east, but the news gets less bright the closer one gets to Lake Powell and areas to the south.
This has been supported by the rapid decrease in snowpack conditions as reported by the SNOTEL sites across the District since mid-April. While indicators in the headwaters of the Colorado and Yampa Rivers are showing around 90% of average after a recent (4/27) storm, the numbers decline sharply the further south you look.
The measurement station at McClure Pass (Crystal River) shows a snowpack which dropped so rapidly that as of April 29, that it now sits at just 41% of average. Stations in the Uncompahgre and Gunnison River basins reflect a similar, precipitous decline.
“The stairstep on the snowpack is becoming the norm,” said Dave Kanzer, Director of Science and Interstate Matters for the River District. “This year we have been making and breaking temperature records. The winter was the hottest recorded average temperature in almost 130 years of observation. One storm will bump up the snowpack, then nothing.”
In addition to record heat, the West Slope has seen several dust on snow events along with above-average temperatures in late March. Climate forecasts are also identifying a shift in the larger patter from El Nino to La Nina as indicated by Pacific Ocean temperatures. While La Nina carries a great deal of uncertainty regarding its impacts on western Colorado, it is generally expected to bring drier than normal conditions to the southwest and the larger Colorado River Basin.
Looking towards a bright point in the seasonal water outlook, however, storage levels in western Colorado reservoirs remain in healthy condition due to carry-over storage from water year 2023. Most reservoirs on the West Slope are expected to fill, and some to spill this year.
Lakes Mead and Powell
In his board memo, Kanzer explains that early water supply forecasts across the Upper Basin and inflow forecasts into Lakes Powell and Mead are at or below average and represent a significant departure from the big flows of 2023, indicating that there is little chance of increasing large mainstream reservoir levels.
What does this look like in terms of releases from Lake Powell this year?
“We will likely be at the 3575’ threshold – just above where upper elevation balancing could occur in 2025,” said Kanzer. “This means that we could potentially see higher releases in 2025.”
The projected reservoir levels of Lakes Powell and Mead are generated by the Bureau of Reclamation based upon forecasts from the Colorado River Basin Forecast Center (CBRFC).
These figures show the cloud of forecasted traces for mainstream Colorado River reservoir elevations. The traces shown in grey were created using a probabilistic technique that simulates a range of different possible futures as reflected in projected reservoir elevation using an ensemble of 30 years of precipitation and temperature records as input data. This probability analysis shows the credible potential range of the water supply conditions over the next 24 months, using Reclamation’s current operating policies (i.e., 2007 Interim Guidelines along with Drought Response Operations, “DROA”).