Great Salt Lake

The Great Salt Lake, situated in northern Utah, is the largest salt lake in the Western Hemisphere and one of the world’s most significant endorheic water bodies. As the remnant of the prehistoric Lake Bonneville, it exerts a major influence on the region’s climate, economy and ecology. Its shallow depth, high salinity and fluctuating water levels make it a distinctive natural feature that continues to shape settlement patterns, environmental challenges and scientific research in the Great Basin.
Fluctuations in the lake’s area and depth are dramatic due to its closed-basin nature. Since it has no outlet other than evaporation, minerals accumulate, giving the lake salinity levels far exceeding those of the ocean. Its mineral-rich waters support diverse bird species, brine shrimp and specialised shoreline ecosystems. Periods of intense drought, water diversion and climate change have recently caused the lake to reach record lows, sparking concerns about public health, biodiversity loss and the future of the surrounding environment.

Geological Origins and Prehistoric Context

The Great Salt Lake is the successor of Lake Bonneville, a vast Pleistocene-era lake that once covered much of present-day Utah and parts of Idaho and Nevada. At its maximum, Lake Bonneville approached the size of modern Lake Michigan and reached depths of around 300 metres. Roughly 16,800 years ago, the lake experienced a dramatic outflow through Red Rock Pass in Idaho, known as the Bonneville Flood, after which climatic warming caused the lake to recede gradually.
As Lake Bonneville shrank, several isolated water bodies remained. Among these, the Great Salt Lake is the largest, with Utah Lake, Sevier Lake and Rush Lake representing additional remnants. The current lake lies in a structural basin within the Great Basin, where low precipitation and high evaporation rates maintain its saline conditions.

Historical Discovery and Exploration

Maps from the late sixteenth and seventeenth centuries depicted a large inland lake in the region, although early cartographers often confused the Great Salt Lake with Utah Lake and other water bodies. Indigenous peoples, particularly the Timpanogos Ute, were familiar with the lake long before European contact, and they conveyed its existence to Spanish explorers in 1776.
Early nineteenth-century trappers such as Jim Bridger and Étienne Provost independently reported the lake, though their accounts varied. Scientific exploration began in earnest with John C. Frémont’s 1843 expedition, whose reports influenced the decision of Mormon settlers to locate in the Salt Lake Valley. Brigham Young visited the lake shortly after arriving in 1847, and local settlers soon developed small-scale salt production.
The first systematic survey was conducted in 1850 by Howard Stansbury, whose work led to the naming of Stansbury Island and the Stansbury Range. His published report became widely read and contributed to broader geographic and cultural understanding of the region. Later, writers such as Alfred Lambourne documented life around the lake, including the isolation of Gunnison Island in the late nineteenth century.

Infrastructure, Engineering and Water Management

The Great Salt Lake’s changing water levels have prompted several major engineering interventions. In the early 1930s, proposals to create a freshwater reservoir by diking off part of the lake were considered but never completed. More significant developments occurred in the twentieth century:

• Lucin Cutoff and Causeway: Constructed in the 1950s to replace a wooden trestle, the rock-fill causeway altered the lake’s natural circulation by restricting water exchange between the northern and southern arms. This created distinct salinity zones. In 2016 a breach was opened to restore some water flow.
• Willard Bay Reservoir: Completed in 1964 on the lake’s northeastern arm, this freshwater reservoir was created by isolating and draining a shallow bay and refilling it with water from the Weber River.
• West Desert Pumping Project: Constructed in the mid-1980s in response to record-high lake levels, this large-scale project pumped lake water into the Newfoundland Evaporation Basin to increase evaporation and reduce flooding. Operating between 1987 and 1989, it removed vast quantities of water and was instrumental in lowering lake levels. Although dormant today, the pumps remain intact for potential future use.

Environmental Change and Lake Shrinkage

In recent decades, climate change, prolonged drought and heavy upstream water consumption have significantly reduced the lake’s size. The lake reached a historic low in 2021, surpassing the previous record set in 1963. Water diversions from its tributaries—the Jordan, Weber and Bear rivers—combined with reduced snowmelt have accelerated the decline. As of the early 2020s, the lake occupies a fraction of its 1980s extent.
Scientific studies have warned that without substantial policy changes, the lake could face ecological collapse within the decade. Increasing salinity threatens brine shrimp populations, migratory bird habitats and local industries reliant on mineral extraction. Exposed lakebed sediments risk transforming into airborne toxic dust, posing health dangers to millions of residents in the Salt Lake Valley.
Policy proposals have included establishing minimum lake levels, altering agricultural water use, enhancing river inflows and reducing consumption. Disagreements among policymakers, however, have hindered the adoption of consistent water-level targets. The debate underscores the challenge of balancing ecological needs with economic and political constraints.

Hydrology and Tributary System

The Great Salt Lake receives most of its inflow from the Bear, Weber and Jordan rivers. These rivers collectively supply around eleven million tonnes of dissolved minerals annually. Because the lake has no natural outlet, these minerals accumulate until precipitation and inflow dilute them. This process contributes to the lake’s exceptional salinity, which can vary widely between its arms due to circulation patterns and evaporation rates.
High salinity enhances water density, allowing swimmers to float easily—leading to comparisons with the Dead Sea. Salinity also affects the distribution of microbial and invertebrate life, resulting in distinct ecological zones across the lake.

Ecology, Wildlife and Environmental Significance

Despite its extreme salinity, the Great Salt Lake supports abundant life. Brine shrimp and brine flies thrive in the nutrient-rich waters, forming a critical food source for millions of migratory birds. The lake is a major hemispheric stopover for species such as Wilson’s phalarope, avocets, stilts and various species of ducks and shorebirds. Its wetlands and islands form vital habitat networks within the Pacific Flyway.
Fluctuating water levels influence ecological conditions. Lower levels reduce wetland areas, increase salinity and stress populations of invertebrates and birds. The lake is therefore closely monitored by ecologists, conservation groups and governmental agencies.

Cultural and Regional Influence

The lake lends its name to Salt Lake City, originally called “Great Salt Lake City”. It has shaped regional identity, recreation, mineral industries and climate patterns. The lake-effect snowfall generated by moist air crossing the lake contributes significantly to winter snow accumulations in the Wasatch Range, supporting world-renowned ski conditions.