Satellite photo of the Great Salt Lake in 2003. The line in the lake that divides blue water from reddish water is not a photographic artifact, but reflects a real difference in the chemical composition of the water in different arms of the lake. Details below.
The Great Salt Lake is a terminal lake located in northern Utah. It is the remnants of Lake Bonneville, a much larger lake that covered most of Utah (and parts of Idaho and Nevada) during the Pleistocene era. Its surface area and depth varies dramatically according to the amount of water that makes it into the lake. Its maximum depth can be anywhere from fourteen to thirty-three feet; its surface area can be as little as 1,000 square miles, or as much as 3,000. Much of Utah's wetland habitat is located where the lake's tributaries flow into the lake; these wetlands are an important habitat for migratory birds.
The lake is endorheic, meaning that it has no outlet. Water flows into the lake from several rivers and streams, but escapes only by evaporation. Like other endorheic lakes, the Great Salt Lake is highly sensitive to human involvement. The volume of the lake has been can be—and has been—significantly affected by any of the following factors:
- diversion of incoming rivers for agricultural and recreational use
- partitioning and pumping of water for industry and mining
- pumping water into the salt flats to alleviate flooding
An aerial view of MagCorp's magnesium mining facility on the shores of the Great Salt Lake. Click the image to go to this location on Google Maps.
But not only the volume of the lake is affected: its chemical composition is affected as well. The most dramatic example of this is the Lucin Cutoff, a causeway built across the length of the lake in 1959 for railroad use. The causeway effectively divides the lake into two separate bodies of water, a northern arm and a southern arm, joined only by a 300-foot culvert halfway along the length of the causeway. Because all of the lake's fresh water tributaries run into the southern arm, the northern arm has become progressively saltier than the southern arm. In 1999, the southern arm was 9% salt by weight, while the northern arm was 25%.
Southern Pacific Railroad claims that the Lucin Causeway helped defeat the Japanese in WWII. Click for full size image.
This partitioning of the lake is almost identical to the process of mining salt in evaporation ponds, except on a much larger scale. What makes this difference in salinity interesting is that it affects which types of algae and bacteria grow in the lake. This, in turn, affects the color of the water. In low salinity, the water is greenish; in high salinity, the water is red.
Salt evaporation ponds on the Great Salt Lake. Click to see the original image by Andrew Coulter Enright on Flickr.
A photograph of the Lucin Causeway in 1986. The south side of the lake is on the left, and the northern part is on the right. Click to see the image on the USGS web page.
Project description after the jump.
Continue reading "Site-Specific Site Analysis: Water/Wildlife of the Great Salt Lake" »
