Hydrology Report: ‘Weather Whiplash’ Kicks Off 2022
At the opening of his hydrology report to the Colorado River District Board of Directors on February 8, Director of Science and Interstate Matters Dave “DK” Kanzer used the term ‘weather whiplash’ to describe the first few months of Water Year 2022.
The past four months have been a study in extreme weather behavior and frequently changing expectations, he said. A snowy October led to a record-dry November, and December culminated in a series of storms which sent snowpack across the Colorado River Basin soaring to well over 100% of average. The precipitation pendulum swung back this January, however, producing no significant precipitation. In fact, SNOTEL observation graphs showed an almost flat line for snowpack accumulation across the Colorado River Basin.
“We’re back where we started, and it’s not the best place to be. We are reaching 100% from the wrong direction,” said Kanzer.
Even the precipitation from East to West within the state of Colorado has experienced significant re-alignments. “We had a role reversal from last year, which put the East Slope into extreme drought.”
While the West Slope was enjoying feet of snow during the last few weeks of 2021, the Front Range was experiencing abnormally dry conditions. This allowed the Marshall Fire to sweep through the suburban community of Superior. Yet the January that dried out the West Slope produced multiple snowstorms on the Front Range, putting the South Platte drainage at about 106% of average.
Don Meyer, Senior Water Resources Engineer at the District, summarized the upcoming weather outlook for the region. A ridge of high pressure off the western coast of California continues to divert moisture away from the Central Rockies, so the precipitation outlook for the foreseeable future is looking well below average.
Kanzer noted that when we see river basins snowpack statistics at over 100% of average, it doesn’t mean we can expect above average streamflow. Before it can fill the river, melting snowpack must first meet a considerable soil-moisture deficit and answer to a thirsty atmosphere.
“The Millennial Drought has been going on for 22 years now, and it is affecting not just Colorado, but the entire West. 100% of the Colorado River Basin is abnormally dry or worse, despite the fact that our current SWE (snow-water equivalent) is 100% or better.”
Downstream, forecasts from the Colorado Basin River Forecast Center (CBRFC) are predicting well-below average inflow to Lake Powell.
The Powell inflow forecast is an essential part of the District’s resource management planning. Organizations like CBRFC provide updated predictions for the flows of the Colorado River every month based on recent weather events and drought conditions. Current models now indicate that the Colorado River will provide only 78% of average inflow into Lake Powell.
In fact, every day is setting a record low for streamflow into Lake Powell. To protect the Power Pool (the water level necessary to allow continued hydro-power production at Glen Canyon Dam), the Bureau of Reclamation has reduced releases from the dam until spring runoff begins. Their plan involves ‘borrowing’ against the higher inflows of runoff season to secure power-production in Lake Powell. After last year’s Drought Response Operations Agreement triggered nearly 181 million acre-feet from Upper Basin reservoirs, the Bureau of Reclamation has few other options. Most reservoirs in the Colorado River Storage Project now sit at or below 30%, except Flaming Gorge at 74% of full storage on the Green River.
Kanzer’s assessment of these Big River issues was not optimistic. “We have a high likelihood that we will be below Power Pool this spring before runoff begins, because it depends largely on the weather and two more months of snow banking.”
Below Lake Mead, the Lower Basin states of Arizona, Nevada, and California are preparing for the impacts of a Tier 1 Shortage Declaration from the Bureau of Reclamation. Despite the historic ‘500 plus’ plan agreement, signed by these four states last December, storage in Lake Mead also remains at or below 30% of average.
One more unique factor to consider when looking at upcoming spring hydrology is the National Oceanic and Atmospheric Administration’s adjustment of the 30-year average. As of 2022, ‘average’ will be calculated from observed conditions between 1991 and 2020, instead of their previous average which came from 1981-2010.
“This is a well-accepted practice to change the frame of reference every ten years to reflect more recent atmospheric and hydrological norms,” Kanzer said.
It does mean, however, that ‘77% of average’ this year would have been only ‘68% of average’ last year. The previous 30-year average included the 1980s, holding some of the highest inflow to Lake Powell on record, while the ‘new normal’ now reflects an average calculated from a multi-decadal drought.