Wet year in Utah helps the Great Salt Lake

Note: Lake levels mentioned in this article are from the Saltair Boat Harbor, near I-80 Exit 104.

The last time the Great Salt Lake’s surface elevation was at its historical average of 4,200 feet above sea level was in the early 1990s. At that elevation, the lake is roughly 33 feet deep at its deepest point. In the 90s, the lake was coming down from a record elevation of 4,211.85 feet (putting the depth at 45 feet), but since then periodic droughts have kept the elevation significantly lower. It’s at about 4,200 feet that Antelope Island is actually an island.

The lake’s level is extremely variable throughout the year, as the entirety of the water it contains comes from runoff (both from snow and rain) coming into the rivers that flow into it from northern Utah as well as small parts of Idaho, Nevada, and Wyoming.

The runoff and the lake’s elevation are highest in the spring when snowmelt increases the amount of water coming into the lake and they are at their lowest in the fall after most of the snow has melted.

The fall of 2016 saw the lake level approach 4,192 feet, which is just above the historic low of 4,191.35 feet after unusually low winter snowfall as well as below average rainfall. While eight feet below average doesn’t seem to be that big of a deal, in a lake as shallow as the Great Salt Lake that value equates to the lake losing about 44% of its surface area.

This year, however, runoff from unusually high snowfall in the lake’s watershed helped to bring lake levels up again. Ski Utah reported (archive) that by February, snow depth values in the Wasatch were in excess of 150% of normal, with some areas even above 170%. At Snowbird, east of Sandy, the amount of snow on the ground was nearly double what had been seen in the five years previous, which had all been below average.

At the peak of the runoff in the spring, the lake elevation was (not including outliers) 4,196 feet above sea level. At its peak in 2016, the lake was a foot and a half lower. That foot and a half of more water added about 50 square miles to the lake surface, bringing it to approximately 1,100 square miles.

While the lake level has since receded, it is still higher than this time last year. On November 27, 2017, the surface elevation was 4194.21 feet above sea level. On the same day in 2016, the water level was 4192.5 feet.

Other lakes in the Great Basin have seen their water levels rise this year when compared to last. Near Reno, the waters of Lake Tahoe flow through the Truckee River to Pyramid Lake. Heavy snowfall in the Sierra Nevada last winter contributed to the lake raising by nearly 10 feet.

The lake level of the Great Salt Lake is important for several reasons. In the 1980s, when the lake was at its record level, the water began to erode away at the embankment for Interstate 80 causing the state to build pumps to divert the water. Today, the lake has about a third of the surface area.

The amount of water also affects how salty the lake is. Salinity varies from 3.5 to 8 times as salty as the ocean. When there is more water in the lake, it becomes less salty as the amount of salt in the lake becomes spread across a larger volume.

The Great Salt Lake plays a role in the climate of the Wasatch Front, where it is believed that 10% of annual precipitation comes from lake-effect storms. These storms form because the temperature of the lake differs from the temperature of the air surrounding it.

These storms are carried east toward the I-15 corridor and deposit significant amounts of precipitation, usually in the form of snow, along the Wasatch Front. When the lake is larger, the temperature varies less. On top of that, there is more area for water to evaporate from.

This year’s runoff is helping to bring the lake back to normal, but it will take at least one more year (probably more if we’re honest) of above-average precipitation to get the lake’s surface elevation up to 4,200 feet.