Great Salt Lake, Utah

Great Salt Lake, Utah Introduction • When did the lake first appear? Great Salt Lake, the shrunken remnant of Although as early as 30,000 years ago there • Why is the north part of the lake purplish- prehistoric Lake Bonneville, has no outlet. Dis- were alternating periods of saline lakes and pla- pink? solved salts accumulate in the lake by evapora- yas (salt flats) in the basin, Great Salt Lake is A railroad causeway separates the lake into tion. Salinity south of the causeway has ranged believed to have first formed about 11,000 years a north and south part. Most freshwater enters from 6 percent to 27 percent over a period of 22 ago when the lake rose from a smaller saline the south part, and water in the north part years (2 to 7 times saltier than the ocean). The body to about 4,250 to 4,275 feet at the Gilbert evaporates faster than it enters. The north part is high salinity supports a mineral industry that Level. At this time it was about three times as always much saltier than the south part. Several extracts about 2 million tons of salt from the large as present Great Salt Lake and was salty. species of purple salt-tolerant bacteria and an lake each year. The aquatic ecosystem consists The lake was less salty during the Stansbury alga with a red pigment live in the north part of more than 30 species of organisms. Harvest Level of Lake Bonneville. and cause the purplish-pink coloration, espe- of its best-known species, the brine shrimp, • Why is the lake salty? cially when the salinity is greater than about 25 annually supplies millions of pounds of food for percent. the aquaculture industry worldwide. The lake Because the lake does not have an outlet, is used extensively by millions of migratory water flows into the lake and then evaporates, • Are there any other large saline lakes? and nesting birds and is a place of solitude for leaving dissolved minerals behind as residue. Excluding Lake Eyre in Australia (3,100 people. All this occurs in On average, 2.9 million acre-feet of water square miles when flooded, but usually dry): a lake that is located at enters the lake each year from the Bear, Weber, and Jordan Rivers. The inflow carries about Water body Salinity Area the bottom of a 35,000- (parts per (square square-mile drainage 2.2 million tons of salt. About 4.3 billion tons thousand) miles) of salt are in the lake, and commercial removal basin that has a human Caspian Sea (Russia, Iran) 11 170,000 population of more than of the salt ranges from 1.6 to 2.5 million tons 1.5 million. annually. Aral Sea (Russia) 10 25,000 Lake Balkhash (Russia) 2.8 7,115 Frequently Asked Questions • What animals live in the lake? and Answers about Great Of the various animals, the most visible and Great Salt Lake (Utah) *140 1,700 famous is the brine shrimp (Artemia francis- Salton Sea (California) 44 380 Salt Lake cana). Two species of brine flies (genus Ephy- • How large is the lake? dra) also are very numerous but do not bite. Dead Sea (Israel) 220 390 At the average water-surface altitude of Numbers of these flies may reach 370 million * Measurement for Gilbert Bay, 1995. 4,200 feet, the lake is 75 miles long by 28 miles per mile of shoreline during summer. wide and covers about 1,700 square miles. At Two to five million shorebirds and hundreds this altitude, the maximum depth is about 33 of thousands of waterfowl use the lake season- feet. At its lowest altitude in 1963 (4,191 feet), ally. Wilson’s Phalarope and Eared Grebes often it was less than one-half the size it reached at its are present in summer. historic high peak during 1986–87 (4,211 feet). • How did brine shrimp get into the lake and • How was the lake formed? when did they first appear? The lake is a remnant of Lake Bonneville, a The shrimp likely arrived as cysts (eggs) on large Pleistocene-age lake that covered about the feet of migratory birds. Brine shrimp cysts 20,000 square miles (slightly smaller than West and fecal pellets in a deep sediment core have Virginia at 24,000 square miles) and was a been dated to be 15,000 years old. maximum of 325 miles long by 135 miles wide, with a maximum depth of 1,000 feet. Lake • How do brine shrimp live in the extremely Bonneville existed from about 30,000 years ago salty (hypersaline) environment of the lake? to 16,000 years ago. Four ancient shorelines The body cuticle prevents water loss and salt of Lake Bonneville are visible on the Wasatch entry. The shrimp drink large amounts of salt Mountains to the east. water and the gut takes up the water (and some salt). The branchia, or gills, then excrete the salt Adult actual size back into the water. Brine shrimp (Artemia franciscana) adults and cysts. Altitude Lake-level Years (feet) name before present • Have there ever been marine organisms or fish in the lake? History 4,500 Stansbury 23,000–20,000 Thirty thousand years ago, during the last ice In 1899, the U.S. Fisheries Service consid- 5,090 Bonneville 16,000–14,500 age, Lake Bonneville expanded from a small ered implanting oysters into the mouths of the saline lake to a freshwater lake that covered 4,740 Provo 14,500–13,500 larger rivers that enter the lake but decided that about 20,000 square miles and was about 1,000 oysters could not be raised commercially. 4,250 Gilbert 11,000–10,000 feet deep. About 16,000 years ago, the lake In 1986, killifish entered from Timpie (Curry and others, 1984) cut a massive outlet at its northern end and Springs on the south end when the lake was at a discharged a flood that reached the Snake River. salinity of about 5.5 percent. A dry period nearly eliminated any remnant of the lake about 500 years later, but increasing Water-Resources Investigations Report 1999–4189 April 2007 precipitation raised the water surface to about cies has been estimated at 32. These organisms 50 feet above the present lake level, creating interact to form a complex and highly produc- Great Salt Lake. tive ecosystem. Algae (25 species reported The Dominguez and Escalante expedition in 1979) provide the base for the food chain reached Utah Valley, 50 miles south of Great through photosynthesis. They serve as food for Salt Lake, in 1776. The indigenous Timpan- brine shrimp and brine flies, which in turn are gotzis Indians told them of a very salty lake consumed by birds or by the shrimp harvested in the valley to the north. The explorers were for the aquaculture industry. Bacteria, proto- anxious to return to Monterey and did not zoa, and brine flies recycle the organic material investigate this saline lake. In 1824, the French to release nutrients and keep energy flowing trapper Etienne Provost may have been among through the system. the first of the European trappers to see the Brine Shrimp lake, but other European trappers and explor- The invertebrate community ers also vie for the honors: Jim Bridger, Peter of Great Salt Lake undergoes Skene Ogden, and John H. Weber. An early large annual variations in timing scout and explorer, John C. Fremont, is cred- and abundance of life stages ited with making the first scientific measure- and is dominated by brine shrimp, Artemia ment of lake altitude in 1843 (4,200 feet). franciscana. The variations are partly the result The Stansbury expedition entered Salt Lake of changes in salinity, water temperature, Valley to make maps and describe the area in nutrients, and algal populations. The young 1849 under the direction of the U.S. Govern- artemia, called nauplii, typically appear ment. The expedition succeeded in mapping from over-wintering eggs (hard-walled cysts the entire shoreline of the lake by 1850. All of Union Pacific Railroad causeway viewed from containing an embryo in dormancy) from late the larger islands in the lake except Fremont Lakeside, Utah. Gunnison Bay on left, Gilbert Bay on right, January 1998. February to early March when water tempera- Island were named for members of this explo- tures are between 32 and 41 degrees Fahr- ration party: Stansbury Island (Howard Stans- ity of 25 percent or higher; water south of the enheit. Their appearance follows the winter bury), Carrington Island (Albert Carrington), causeway (Gilbert Bay) has varied from about 6 bloom of phytoplankton that provides food for Gunnison Island (J.W. Gunnison). to 27 percent salinity. The Bear, Weber, 30 Clarence King, a geologist with the U.S. and Jordan Rivers contribute about 27 Government survey of the Fortieth Parallel, 66 percent of the annual inflow of 2.9 million acre-feet (one acre-foot equals 24 Gunnison Bay surveyed the lake from 1869 to 1870. Addi- at Saline gage tional geologic and geographic surveys in the 325,851 gallons, or the amount of water 21 (north part) vicinity of Great Salt Lake were completed in that it would take to cover one acre to a 18 the next few years by F.V. Hayden, George M. depth of one foot) to the lake, precipita- 15 Measurements tion into the lake contributes about 31 made in non- Wheeler, and Grove C. Gilbert as part of the 12 consecutive great exploration of the percent, and ground-water inflow about years 9 West done by the U.S.

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