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Picture of USGS employee on the Great Salt Lake.

GREAT SALT LAKE

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Great Salt Lake, Utah

Great Salt Lake Facts

  • The largest U.S. lake west of the Mississippi River
  • The 4th largest terminal lake (no outlet) in the world
  • A remnant of Lake Bonneville, a prehistoric freshwater lake that was 10 times larger than GSL
  • About 75 miles long, and 28 miles wide, and covers 1,700 square miles
  • Has a maximum depth of about 35 feet
  • Typically 3 to 5 times saltier than the ocean
  • Fish free, the largest aquatic critters are brine shrimp and brine flies
  • One of the largest migratory bird magnets in Western North America
Satellite image of Great Salt Lake (click for larger image.

Great Salt Lake is located on a shallow playa. Consequently, small changes in the water-surface elevation result in large changes in the surface area of the lake. This is particularly evident when the lake spills into the west desert at an elevation of about 4,215 feet, greatly increasing its area. The satellite imagery shows changes in the area of the lake from 1972, through the high-runoff period of 1983-87, and ending in 1996. At the historic average (1847-1986) surface elevation of 4,200 feet (1975 is an "average year" shown in the images), the lake covers an area of about 1,700 square miles. At the historic low elevation of 4,191.35 in 1963, the lake covered only 950 square miles. The drop of about 8.5 feet in elevation resulted in a loss of about 44 percent in surface area. During 1986 and again in 1987, the lake reached an elevation of 4,211.6 feet and had a surface area of about 3,300 square miles. The relation between water-surface elevation and corresponding surface area and volume of the lake is shown on an elevation-area-volume curve, also called a hypsographic curve (from the Greek, hypsos, meaning height).

 Satellite images of Great Salt Lake, from USGS EarthShots.

Great Salt Lake and vicinity, Utah

Map of Tooele and Salt Lake City (Click for larger image.)The U.S. Geological Survey (USGS) has measured the elevation of Great Salt Lake since 1875 and conducted many studies on the hydrology, salinity, water quality, and ecology of the lake. Currently, the USGS operates lake elevation gages at Saltair Marina, Saline (north arm), and on the railroad causeway near Promontory Point. The USGS is studying the ecology of brine shrimp in the lake in cooperation with the Utah Division of Wildlife Resources and researchers from the Department of Fisheries and Wildlife at Utah State University.

The map to the left shows Tooele and Salt Lake City. A larger image is available.


Hydrology

In addition to measuring changes in lake elevation, since the early 1960s the USGS has conducted detailed studies of the physical and chemical hydrology of the lake. These have included investigations of the prehistory of the lake, general hydrology of closed-basin lakes, effects of human activities on the lake, and a detailed accounting of the water budget.

Salinity and water quality

Salt industry

The salts of the lake are primarily sodium chloride (common salt), although small amounts of other elements and salts are also present, including magnesium, potassium, sulfate, and carbonate. There are about 4.5 to 4.9 billion tons of salt in the lake, and about 2.2 million tons of salt enter the lake annually from surface- and ground-water flow. The salt industries extract about 2.5 million tons of sodium chloride and other salts and elements from the lake annually.

The picture to the left shows salt ponds. A larger image is available.

Industries extracting salt and other minerals from the lake:

Ecology

Brine shrimp

Brine shrimp are not only the most visible inhabitants of Great Salt Lake and are very important to the ecology of the lake, serving as a major source of food for migratory birds. They are also valuable for the hard-walled eggs they produce, which are commercially harvested and used worldwide in the aquaculture industry.

Birds

Birds: Great Salt Lake supports between 2 and 5 million shorebirds, as many as 1.7 million eared grebes, and hundreds of thousands of waterfowl during spring and fall migration. Because of its importance to migratory birds, the lake was designated a part of the Western Hemisphere Shorebird Reserve Network in 1992. The lake and its marshes provide a resting and staging area for the birds, as well as an abundance of brine shrimp and brine flies that serve as food.

Planktonic and benthic habitats

The planktonic and benthic habitatin Great Salt Lake consists of the open water inhabited by brine shrimp, phytoplankton (algae), bacteria, and other small zooplankton. These organisms are all free-swimming or float in the water. The benthic habitat consists of the bottom substrate of the lake and its associated organisms. These organisms are primarily brine-fly larvae and benthic algae.

USGS publications about the ecology of Great Salt Lake

Other interests on Great Salt Lake

Boating and recreation

This is a brief explanation and listing of boating and recreation on Great Salt Lake.

Organizations involved with Great Salt Lake

  • Friends of Great Salt Lake
    The mission of Friends of Great Salt Lake is to increase public awareness and appreciation of the lake through education, research, and advocacy.
  • The Utah Wetlands and Riparian center
  • International Society for Salt Lake Research

    The International Conference on Salt Lake Research, held at the University of Utah, Salt Lake City, Utah, USA, May 1116, 2008, in conjunction with the 2008 FRIENDS of Great Salt Lake Issues Forum, brought together over 200 scientists, managers, and students from 18 countries, who discussed all possible aspects of salt lake research, including physics, chemistry, biology of plants, animals and microorganisms, biogeochemistry, history, economical utilization, conservation, and others. This symposium was the tenth in a series of salt lake symposia held every three years. The book, Saline Lakes Around the World: Unique Systems with Unique Values, clearly shows the diversity of interest in salt lakes, with 51 chapters. Of the 51 chapters, 12 are devoted to research done on Great Salt Lake, Utah.

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