Status of the Great Salt Lake

Several media outlets are reporting this week that the Great Salt Lake appears to have crested for the summer.  For example, the Salt Lake Tribune reported today that the lake entered the week at 4,193.8 feet elevation at the Great Salt Lake State Park Marina, which is 3.5 feet higher than last year at this time and 5 feet above the record low in November.  

That is of course good news.  However, it is somewhat misleading.  A rock-fill causeway has divided the lake for decades.  Essentially, the Great Salt Lake is two lakes, and that is especially true today because the berm in the causeway between the north and south arms of the lake was raised in February.  Most of the freshwater inflow to the lake enters the south half, so this has helped to lower the salinity in the south arm (important for brine shrimp), but it has also enabled the south arm to rise more rapidly since the flow to the north arm has been reduced.  

We can see this in lake-elevation data collected by the USGS.  At Saltair in the south arm, the lake elevation currently sits at 4193.9 feet, which is more than 5 feet higher than last November.

Source: USGS

However, at Saline in the north arm, the lake elevation currently sits at 4189.4 feet, 4.5 feet lower than in the south arm.  Lake levels have only climbed about a foot over where they were last fall and winter (note scale change).  

This contrast can be seen in Landsat imagery from last week.  Note how coverage of water to the south of the causeway, which extends westward from the southern tip of Promontory Point, is greater than to the north side.  This is especially noticeable on the west shore.  Note also that the coverage of water has improved quite a bit, although there is still considerable lake-bed exposed in the Farmington Bay area immediately north of Salt Lake City.  

Source: https://glovis.usgs.gov/app

From an ecosystem management perspective and perhaps local dust sources, there are good reasons to have captured most of the water in the south arm.  It is possible that if the lake continues to remain low, that a decision may eventually be made to let the north arm whither and focus on saving the south arm (there are also disadvantages to doing this).  

That said, I'm not a fan of using the Saltair elevation in isolation as a measure of lake changes.  It only tells half the story (perhaps a bit more than half since the south arm is larger than the north arm).  We are very fortunate to have had a big snowpack this year, but my view is that the lake is still in critical condition and the elevation of the south arm paints a picture that is rosier than reality.