Great Salt Lake

Located in northwestern Utah within the Great Basin of the United States, Great Salt Lake is the largest terminal lake in North America. Having no outlet, this saline lake loses water through evaporation and leaves minerals and salts behind. As a relatively shallow lake (7-13 meters deep) with an expansive, low-gradient bottom, it varies widely in area as climatic and consumptive water-use conditions change. Since record keeping began in 1847, Great Salt Lake elevations have fluctuated 6.2 meters (20.3 feet) in depth. Correspondingly, the lake’s area fluctuated between 246,000 and 621,600 hectares (607,880 – 1,536,010 acres).

Rock-fill transportation causeways divide Great Salt Lake into five distinct bays, each with its own physical, chemical, and biological properties creating unique aquatic environments. Generally speaking, gradations of salinity among the five bays vary from freshwater areas to areas twice as salty as the ocean, and to areas completely saturated with salt. Fish and most other aquatic organisms cannot survive in the salty areas of the lake. Instead, two invertebrate halophiles, brine shrimp and brine flies, have complete reign in the saltwater ecosystem, providing incredibly abundant food resources for avian use. In the fresher-water bays, corixids (water boatman) and chironomids (midges) are important food sources.

Great Salt Lake lies within a cold desert environment characterized by sparse and low-lying drought and salt-tolerant plants. Surrounding the lake’s rocky shorelines, playas, salt marshes, and extensive mudflats, is over 162,000 hectares (400,000 acres) of freshwater wetlands – over 75% of Utah’s total.   These natural and constructed habitats consist of deep reservoirs, shallow ponds, wet meadows, flooded agricultural fields, and riparian corridors.

Wetlands concentrate around river and stream deltas extending along the eastern perimeter of Great Salt Lake wrapping around the northern and southern shores. Protected wetlands include Bear River Migratory Bird Refuge managed by the U.S. Fish and Wildlife Service; a Bureau of Land Management Wildlife Habitat Area; eleven state Wildlife Management Areas; three state parks; private refuges run by The Nature Conservancy, Audubon, and others; and numerous privately owned duck clubs.

Two main industries utilize the natural resources of Great Salt Lake . Mineral extraction companies own and lease large portions of the Great Salt Lake mudflats for evaporation ponds. These companies produce commodities like salt, deicing salts, sulfate of potash fertilizer, and magnesium metal.  Secondly, brine shrimp harvest companies skim cysts from the lake and sell them around the world for use as food in aquacultural production of fish and table shrimp.

Peak counts of shorebirds show that over 1.4 million use Great Salt Lake as breeding and staging areas. A single count of Wilson’s Phalaropes during fall migration exceeded 500,000, which is 30% of the global population. As many as 250,000 American Avocets and 65,000 Black-necked Stilts also stage on the shores of Great Salt Lake. Individually, each of these species qualify Great Salt Lake as a WHSRN Hemispheric Site, but several other shorebird species spend time at Great Salt Lake in large numbers: Snowy Plover (5,511), Marbled Godwit (44,000), Western Sandpiper (190,000), Long-billed Dowitcher (59,000), and Red-necked Phalarope (240,000).

Great Salt is also important to many other bird species.  Every fall, one to two million Eared Grebes (with some years numbers reaching close to 5 million) stage on the lake, fattening and molting while feeding almost solely on the abundant brine shrimp. One of the world’s largest populations of White-faced Ibis nest in the emergent marshes of the lake (27,000 breeding adults). Colonies of Franklin’s Gulls often nest with the ibis.

Several of the islands within the Great Salt Lake support breeding colonies of American White Pelicans, Double-crested Cormorants, Great Blue Herons, Caspian Terns, and California Gulls. At times, the pelican colony on Gunnison Island, with up to 20,000 breeding adults, ranks as one of the largest in North America. Great Salt Lake hosts the largest number of breeding California Gulls (160,000), including the world’s largest recorded, single colony. Breeding waterfowl are estimated to exceed 230,000 birds. Common Goldeneye, in numbers over 45,000, winter on the Great Salt Lake feeding on brine fly larvae when freshwater food sources freeze. Migrating fall Tundra Swans can range from 40,000 to 60,000 birds. Numerous other species depend upon the lake, such as Black-crowned Night Herons, egrets, terns, raptors (including Bald Eagles and Peregrine Falcons), swallows, and songbirds.

The health of the Great Salt Lake ecosystem is highly reliant on water supplies of sufficient quality and quantity. Great Salt Lake water levels are dependent on inputs from precipitation, natural springs, groundwater, and four water basins including—the Bear, Weber, Jordan and West Desert (For more information on sources of inflows: Final Great Salt Lake Comprehensive Management Plan and Record of Decision). Anthropogenic alterations to the Great Salt Lake watershed over the last century and a half – such as dams and diversions – have resulted in significant declines to Great Salt Lake’s freshwater inflows.  As one of the nation’s fastest growing states, Utah’s population growth and increased water demand will continue to put pressure on Great Salt Lake’s water sources.  Coupled with climate change, including increased temperatures and drought, these factors will further impact the amount of water reaching the lake.  Declining water flows resulting in lower lake levels and loss of shoreline and mudflat habitat is one of the largest threats to shorebirds at Great Salt Lake .

Since Great Salt Lake has no outlet, all the riverine and atmospheric inputs tend to stay within the lake. Historic and current contamination through industry, mining, urban runoff, and treated sewer discharges lead to increased concentrations of nutrients, heavy metals, and other emerging contaminants like pharmaceuticals, hormones, organic compounds, and detergents. The Utah Department of Environmental Quality’s Division of Water Quality is developing water quality standards for Great Salt Lake and its associated wetlands

The invasive species common reed (Phragmites australis), grows dense in vast expanses that choke out native plant species, which are more beneficial to shorebirds and other avian species. Labor and cost intensive programs are working to reduce this weed within many protected areas. Non-native predators reduce breeding success of shorebirds, and disease outbreaks of avian botulism in late summer produce high mortalities (1000s) for migrating shorebirds including American Avocets.