Warm and Variable Water Year, Reservoirs Continue Decline
Dave Kanzer, Director of Science and Interstate Matters at the Colorado River District, provided the Board of Directors with a hydrologic summary of Water Year 2022 on Tuesday, October 18. Many of the Board’s decisions rely on a comprehensive understanding of reservoir and river levels, snowpack, and climate predictions.
According to Kanzer’s report, Water Year 2022 offered a little bit of everything. A slightly below-average snowpack led into a summer that was predicted to be hot and dry and devastating. Instead, a surprisingly robust monsoon cycle delivered consistent moisture throughout the months of July and August.
This moisture helped to suppress a potentially devasting wildfire season and aided agricultural producers across the West Slope. Two months of average moisture, however, were not enough to offset low reservoir levels and the basin-wide drought.
“The storage in our reservoir system, including Lakes Mead and Powell [and] the Upper Basin reservoirs,…sits around 24%,” said Kanzer. “It’s too early to say exactly what 2023 will look like, but no one expects it to be a ‘drought-busting’ year.”
Kanzer went on to explain that we are looking at the third La Niña cycle in a row, which promises another year of uncertainty. La Niña years, created by colder than normal conditions in the Pacific Ocean, historically lead to below-average precipitation with above-average temperatures in the Southwest.
“We’re hoping to maybe be surprised and find ourselves in a ’08-’09 kind of winter,” said Kanzer. “But right now, the operational forecasts are estimating that next year we will see 86% of average inflow into Powell and a Tier 2a shortage declaration from the levels in Lake Mead.”
Changing snow resources in the Colorado River Basin. Source: Talsma and Bennett, LANL, 2022
Across the southwest and the Colorado River Basin, recent studies have confirmed that average snowpack is decreasing. Warmer than average annual temperatures diminish the amount of water stored as snow, and hotter, drier summers deliver low soil moisture conditions to start the cycle over again. In fact, global models indicate that the Colorado River Basin could experience a 25-50% decline in snowpack by the end of the century.
“The climate is changing faster than our 30-year averages can account for,” Kanzer explained. “We are trying to plan in a world of deep uncertainty. We need to look at the lower half of the graphs and make a no-regrets plan.”
In the effort to collect data which will better forecast the amount of runoff into Powell and the availability of water in systems, the Board of Directors approved two new Community Funding Partnership projects, which will increase the accuracy of soil moisture and snowpack data on the western slope of Colorado.
In the District
Levels at Blue Mesa Reservoir in Water Year 2022.
Don Meyer, Sr. Water Resources Engineer, summarized the 2022 Water Year on the West Slope.
“Monthly precipitation maps indicate the huge amount of uncertainty even locally,” explained Meyer. “We had that snow-globe December, then a dry January. We did benefit from the monsoons, but no one is sure how much.”
Blue Mesa, the largest reservoir on the West Slope, received 68% of average inflow this year. Right now, according to Meyer, only around 100,000 acre-feet (af) of active storage remains. Active storage refers to the amount of water which could still be released to generate power. When the reservoir is full, Blue Mesa has an active storage capacity of 829,500 acre-feet, but 120,000 af of that storage is at a level below the intake for power generation.
During the month of July, high temperatures on the mainstem Colorado River again prompted months-long, voluntary fishing closures across the western slope. This is the second year in a row low water levels paired with higher-than-average temperatures created stressful conditions for native fish.
“Fishing is such a big economic driver for those communities in the summer,” Meyer said. “The [trans-mountain diverters] do contribute to the fisheries, but when it becomes really dry and hot, they need to become the solution.”
The River District made coordinated releases from Wolford Reservoir this summer to mitigate negative impacts to the eco-system.