In 2022, Great Salt Lake reached its lowest water volume in over 170 years of recorded history. The lake’s volume depends on three key variables: annual river flow into the lake, precipitation onto the water, and evaporation off the lake surface, but it was previously unknown which of these factors caused the lowest levels in nearly two centuries.
A study published last month in the journal Geophysical Research Letters suggests that low levels were caused by reduced stream flow and increased lake evaporation. Siiri Bigalke, first author of the study and a climate science PhD student at Portland State University, used historical data from 1950-2022 and computational modeling to simulate the lake’s volume in relation to stream flow, precipitation, and evaporation.
“What we found was that reduced stream flow accounts for about two thirds of the lake volume loss relative to a midcentury average volume, and increasing evaporation accounts for roughly one-third of the historic volume loss,” Bigalke said.
Bigalke explained that while evaporation off the lake water accounts for only a third of the volume loss, the historical data shows there has been a steady increase in the local evaporation rate since the 1950’s. She looked to see if this increasing evaporation is due to normal year-to-year variability or human-caused climate change.
“Our results indicate that random climate variability cannot explain the increase in local temperature, so therefore that increasing trend is due to climate change,” Bigalke said.
While these conclusions may seem bleak, Bigalke said one silver lining of the study’s results is that the lake volume responds most strongly to increases in river flow. This means that efforts to increase stream flow, such as decreased water diversion, would have rapid effects on replenishing lake volume.
