In the prior post, we examined the causes of the recent drought in southwest North America. Here we take a look at the Great Salt Lake, a terminal lake with no outlet that fluctuates in elevation and area depending on the water balance of the Great Salt Lake Basin.
New reports in recent days have highlighted that the elevation of the Great Salt Lake is near its historic low. Measuring the elevation of the Great Salt Lake turns out to be a tricky thing. Wind pushes water around and since the 1960s the lake has been divided by an earthen railroad causeway, so the north and south arms sometimes have slightly different elevations.
A news release issued by the USGS on July 16, 2021 indicates that the daily average lake elevation just prior to that news release was 2.4 inches above its historic low and that they expect water levels to continue to decline. The historical trace from the USGS web site is below and shows current levels near the previous 1963 minimum, so we are certainly close.
The Great Salt Lake is a remnant of Lake Bonneville. Geologic evidence suggests that Lake Bonneville began to form 30,000 years ago and at its highest level was over 900 feet deep and covered almost 20,000 square miles. Much of lowland western Utah was underwater.
|Source: Wikipedia (prepared by Oviatt, C. G., 2019)|
Ah, the good old days.
|Source: Oviatt (2015)|
As indicated in the first graph in this post, records of Great Salt Lake elevation extend back to 1847 when Salt Lake City was settled by Mormon pioneers. Since then, lake elevation has fluctuated from just under 4192 feet to just over 4211 feet. These fluctuations also affect lake area and salinity. Satellite imagery from yesterday well illustrates the current situation. The lake is confined primarily to Gunnison and Gilbert Bays, the north and south arms of the lake, respectively. The earthen railroad causeway limits mixing between these two bays, resulting in differences in salinity and halophilic bacteria that lead to the color contrast. At historical high stand, the Great Salt Lake would cover virtually all of the lighter playa surrounding it. Evidence suggests that during a prehistoric high around 1700 the lake also covered the playa area further west.