Storms this month have brought much-needed snow to the mountains above Lake Powell, but predictions for runoff into the reservoir this spring remain lackluster.
At the start of March, the Colorado Basin River Forecast Center reported that snow levels above Lake Powell were 87% of the median — the median snowpack in the area between 1991 and 2020. As of Monday, snowpack for the same region jumped to 95% of the median.
But runoff into Lake Powell between April and July of this year is predicted to be just 70% of 30-year average, hydrologists reported Monday. In terms of actual water, that translates to 4.5 million acre-feet of water. For reference, one acre-foot can support two Utah households for a year. The most recent forecast is a small increase from the early March forecast of 67%.
There are a few reasons why March’s boost in snowpack hasn’t drastically altered runoff predictions, said Paul Miller, a hydrologist at the Colorado Basin River Forecast Center.
“It’s not a one-to-one relationship between the amount of snowpack we have and the amount of runoff we get,” he said.
One factor is soil moisture. Low precipitation last summer and fall led to drier soils that will absorb more melting snow this spring, water that normally would flow into the Colorado River and its tributaries.
Utah’s soil moisture conditions are currently below normal and worse than they were a year ago, and “that’s definitely contributing to a more inefficient runoff from the snowpack,” Miller said.
Miller added that this winter hasn’t seen many big, snowpack-bolstering storms. “We’ve also had some warm weather where we’ve lost some of the snowpack we’ve accumulated over the course of the winter,” he said.
About 27% of water used in Utah comes from the Colorado River, and 60% of Utahns “benefit directly from the river,” according to the state Division of Water Resources.
Lake Powell is currently at its low point for the water year at just 32% full. Snowpack in the Colorado Basin is usually at its highest in early April before it melts into the Colorado River, which then flows downstream into Lake Powell. The reservoir peaked at 42% full last summer.
The federal Bureau of Reclamation, which operates Lake Powell, currently predicts the reservoir will be 35% full at the end of September, Miller said.
“This very persistent drought that we’ve been in,” he continued, “it’s going to take us more than one year to get us back on track.”
Lake Powell reached a record low of 22% full in 2023 due to drought and overuse, threatening water supplies for millions of people across the West and hydropower production at Glen Canyon Dam.
