Site-Specific Site Analysis: Water/Wildlife of the Great Salt Lake
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
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%.
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.
Project description after the jump.
Engineering projects undertaken by both industry and government have unintentionally used the lake as a canvas, creating sometimes spectacular colors and shapes that virtually define the visual aspect of the lake when viewed from above. The ecology of the lake has rarely been taken into account when planning these engineering projects; the aesthetics of the lake are taken into account even more rarely.
My project idea for the lake is to take advantage of its unusual properties—its shallowness, its biology, and the fact that public policy makers virtually ignore its fragile ecosystem—to create an aquatic, geographical display. This display would take the form of a ten-by-ten grid of artificial evaporation pools, constructed along the shores of the lake (or along the already existing Lucin Cutoff causeway). These evaporation pools would be individually connected to the lake by means of a sluice gate. This sluice gate could be adjusted to either trap water inside the pool for evaporation, or let water in from the surrounding lake.
Together, these evaporation pools would form a pixel-based display, although with an enormously slow refresh rate—a matter of months, maybe, or however long it takes for the water to evaporate and for the microorganisms in the water to adjust to the salinity levels. The display could be used to show arbitrary images or data. A mock-up of how this display might look from a satellite view is below (click here if the embedded applet below doesn't work). The satellite imagery is from 2003, and the data being displayed is a monthly record of the lake's levels from 1966 to the present.