Despite Historic Monsoon Season, Drought Continues On The Western Slope
“Everywhere is Hurting” – A Bleak Water Year
Closing out on September 30, Water Year 2021 was officially the second driest year on record for the Colorado River Basin, just behind water year 2002 at 31% of average.
“Hydrological conditions across the Colorado River District have been dismal,” said Dave Kanzer, the District’s Director of Science and Interstate Matters. “It’s the combination of well-below average precipitation, above-average temperatures, and the extremely dry soils, all sustained over the past two years [to] create the perfect recipe for drought. Everywhere is hurting.”
According to the hydrology report presented to the River District Board of Directors on Tuesday, October 19, the only water-delivery measurements within the Upper Colorado River Basin to exceed 70% of average were those of trans-mountain diversions in the Colorado-Big Thompson (CBT) and Fraser (Moffat) Collection Systems. Some water supply volumes in the Yampa and the lower Gunnison were even less than 30% of average, including Elkhead Creek and the Dolores River.
These extreme conditions have resulted in plummeting levels in Lakes Powell and Mead, which, along with the information provided by long-term forecasting, has led the Bureau of Reclamation to declare the first-ever Tier 1 shortage in the Lower Basin. In addition to the Colorado River Basin, much of the western portion of the continental United States set records for high temperatures, low inflows, and near-empty reservoirs. Many climatic records were broken for elevated temperatures and decreased stream flows in the region.
Within the District, well below average runoff, a hot, dry climate, and multiple diversions in the Upper Colorado River Basin caused spiking water temperatures, resulting in stressful conditions for fish. The summer progressed with multiple reports of fish kills alongside fishing closures imposed by Colorado Parks and Wildlife, from the Colorado River below Kremmling to Rifle.
In late July, an unexpected crash in stream flows triggered a call on the Yampa River for several days – the earliest call ever placed, and only the third on record. All three Yampa River calls have occurred during the last three years. The Colorado River District, with support from partners and the State of Colorado, took action to release water stored in Elkhead Reservoir for agricultural producers impacted along the Yampa. The releases, along with some help from Mother Nature, staved off the early-season call.
Monsoonal Impacts Minimal
One hydrologic bright spot came in the form of a historical monsoon season for the Mountain West. Within the Upper Colorado River Basin (UCRB), intense rains did bring some temporary relief to water temperature and streamflow, but came with a cost. Powerful, localized rain events in late summer mobilized debris in fire-scarred areas of Glenwood Canyon and on the Roan Plateau, causing damage to infrastructure, closures to I-70, and fish kills below Roan Creek.
“Rain like that has no way to be absorbed by soil as dry as ours has been,” River District Director of Technical Advocacy Brendon Langenhuizen said. “All it can do is run downhill as fast as possible, and in the burn scar areas, this meant that a ton of debris was coming with it.”
Overall, the positive effects of the monsoon season were short-lived, and the vast majority of the Western Slope returned to severe, extreme, and exceptional drought conditions by the end of September.
Big River Conditions and Long-Term Projections
The majority of the Colorado River Basin continues to suffer below-average water supply conditions as well, with both local and regional reservoir facilities continuing to decline until next runoff season. There are even increasing chances that Lake Powell water levels could drop below 3,490 feet, where the large power-generating turbines can no longer function safely. To prop up Powell, Upper Basin Storage Project reservoirs Blue Mesa, Flaming Gorge, and Navajo, released a total of 181 acre-feet of water as per the Drought Operations Agreement in the Drought Contingency Plan. The releases ran from August to October and are now completed.
Looking ahead, the three-month outlooks from NOAA Climate Prediction Center suggest a continuation of warm and dry conditions, as shown in the image below, especially in the southern portions of the Colorado River Basin (published September 16th, 2021). This pattern is typical of the cold ‘La Niña’ phase of the often-discussed ENSO (El Niño Southern Oscillation) that is being forecasted.
Currently, Reclamation has convened a series of workgroups of basin states’ representatives to investigate the issues related to the 2021 DROA emergency releases and to discuss if and how to plan for potential future DROA releases. There are a lot of unanswered questions related to transit losses, water rights accounting, and legal protection of such flow releases. River District Staff have thus far not been asked to the table.