From mountains to the Great Salt Lake: The secrets of snowmelt

May 10, 2024, Banner photo above: Creator: Scott MarkeCredit: Scott Markewitz

Utah’s snowpack has been smashing records. The combined totals for the 2022-24 winter seasons were 1,531 inches, the highest two-year snowfall in the state’s history.

Paul Brooks

What does that mean for water levels in the Great Salt Lake?

On April 24, 2024, University of Utah hydrologist and biogeochemist Paul Brooks spoke on the topic to a packed room at Alta Ski Area for the Friends of Alta lecture series. He discussed the importance of snowmelt to Utah, the western U.S. and semi-arid regions around the world. An affiliate of the U’s Peak Water Engine, Brooks’ research group focuses on the interactions between climate, water, ecosystems and society. In particular, he aims to improve models to give water managers earlier and better predictions of the season’s water availability, based on the year’s snowpack totals.

Brooks spoke with science writer Lisa Potter about the multi-year journey for water molecules from mountain snowfall to the Great Salt Lake.

Q: Does a big snow year guarantee lots of water will flow into the Great Salt Lake?

It certainly helps, but it isn’t a guarantee. That is because the relationship between the amount of snow and amount of streamflow is highly variable. We tend to think that the snow falls and then just sort of sits there and waits until spring, but it doesn’t. Snow evaporates or sublimates over the course of the winter, so we lose a fraction of water to the atmosphere. How much we lose depends on things like aspect and elevation, but also year-to-year variability in winter and spring weather. One thing that surprises many people is that when winters are warmer and snow starts melting earlier, we often see greater evaporation, which reduces streamflow.

Once snow starts melting, very little of it runs off directly to the stream—almost all of it goes into the ground.

Historically, we thought only a small volume of melt went into soils, and once those shallow soils were saturated, the remaining melt water quickly ran off the surface and into streams. That’s an assumption that many water management prediction models still rely on. We now know that the ground can hold much more water, which means a large fraction of snowmelt goes into the subsurface and from there takes months or years to get to the stream. That’s a fundamental change in how we think about water resources and an area that my group works on—how much water goes into the ground and, ultimately, to surface streams? How long does it take to get there?

Access the full interview in @The U.