Colorado River Basin Lags In Snow, Pushing Big Reservoirs Toward Critical Conditions
With a slim snowpack so far and, unless early conditions change significantly, the Colorado River Basin is expected to see poor runoff volumes this spring, which will have negative impacts on our water supply.
Snow water equivalent – a measure of how much water is contained within mountain snowpack – is below average across the Western Slope.
“I don’t have any good news on the forecast. The three-month outlook is tilting towards dry and warm,” said Colorado River District Deputy Chief Engineer Dave Kanzer.
According to the National Weather Service’s Climate Prediction Center, temperatures on the West Slope are forecast to be above normal, while precipitation is forecast to be below normal for the next one to two months.
Adding to the potentially bad outlook, dry conditions starting in April 2020 have decreased soil moisture in the Upper Colorado River Basin. This means that dry soils will soak up water as snow melts, meaning less water flows into rivers and ditches. Between Colorado’s so-far disappointing snowpack and dry soils, runoff forecasts are significantly below average across most of the Colorado River basin.
“Even if we were to get a good spring, we may not be able to recover, because a lot of that moisture will go into the ground and not runoff,” Kanzer said.
Looking at big river impacts, early season projections of inflow into Lake Powell is forecast to be 55% of the average for the water year. The water year runs from October 1 to September 30.
“Inflows across the [Upper Colorado River] Basin, top to bottom are well below average. In fact, we’re setting records for what is in the streams today,” Kanzer said. “The numbers in the statistics are startling.”
Low inflows into Lake Powell have broken records in the last 12 months. The six month period between April to December 2020 was the driest period on record, and the months September 2020, October 2020 and December 2020 were the driest respective months on record in terms of inflow into Lake Powell, Kanzer said.
“Right now, again we are tracking to be one of the four or five driest years for inflow into Lake Powell,” he said.
Current operational forecasts into the basin’s largest reservoirs, lakes Powell and Mead, indicate that low water levels could trigger Drought Contingency Plan actions in both the Lower and Upper Colorado River Basin. If the level of Lake Powell is projected to fall below 3,535 feet in elevation by October 2022 — which is currently within the worst-case scenario forecast — it would activate the Upper Basin Drought Contingency Plan. This would trigger coordinated releases into Lake Powell from Flaming Gorge Reservoir and other upstream reservoirs to protect reservoir levels and maintain power generation at Glen Canyon Dam. Under the most-probable forecast, Lake Mead is expected to fall below 1,075 feet in elevation later this year. If so, this would push the Lower Basin into Tier 1 shortage under the drought contingency plan, which requires Arizona, Nevada and Mexico to further reduce their use of water from Lake Mead.
Closer to home in the River District, Colorado’s largest reservoir, Blue Mesa Reservoir, is not expected to fill this summer, possibly reaching only 73% of its capacity by July. Although it is still early, other important reservoirs, including Taylor Park, Ridgway, Granby and Green Mountain reservoirs also may not fill to normal levels this year, according to operational projections.
