Great Salt Lake, a saltwater lake in northwestern Utah, is the largest lake in the western United States. It is three to eight times as salty as the ocean. The Great Salt Lake is fed by precipitation and by inflowing streams. It has no outflowing streams. The inflowing streams carry salts, which are left behind when the water evaporates.
At its deepest point, the Great Salt Lake is only 33 feet (10 meters) deep. Because it is so shallow, it varies in size according to climate conditions. On average, the lake covers about 1,600 square miles (4,200 square kilometers). It averages about 75 miles (120 kilometers) long and about 35 miles (56 kilometers) wide. During warm, dry weather, reduced inflows of water and increased evaporation shrink the lake’s size. In the early 1960’s and the early 2020’s, for example, the lake covered less than 1,000 square miles (2,600 square kilometers). At times, heavy snowfall in the nearby mountains has led to an increase in the water flowing into the lake. In the mid-1980’s, the lake grew to one of its largest sizes, about 2,300 square miles (6,000 square kilometers). It expanded across public and private lands and caused millions of dollars of damage.
The concentration of salt varies, depending on the amount of water in the lake at any given time. The saltiness also varies from one end of the lake to the other. An earthen railroad causeway, constructed in 1959, divides the lake into north and south sections. The salt content of the south end ranges from about 5 to 14 percent. The north end, which has fewer inflows than the south end, ranges from about 16 to 28 percent salt.
The salt in the Great Salt Lake comes from minerals dissolved in the creeks and rivers that flow into the lake. Sodium and chloride—which make up salt—account for about 80 percent of the lake’s mineral content. Other minerals include magnesium, potassium, and sulfate.
Bathers and boaters enjoy using the lake. Swimmers float easily in the salty water. Many visitors go to Antelope Island, which is the lake’s largest island and a state park. A herd of wild buffalo lives there. At times of low lake levels, the island becomes a peninsula.
The wetlands around the lake make it an important stopover for migrating birds. The birds feed on the lake’s small brine shrimp and on the tiny brine flies that live in the lake during their grub stage. Carp and some Utah chub live near the lake’s freshwater inflows. In the salty waters at the north end, only salt-loving bacteria can live. At certain times of the year, these organisms give the lake a pinkish-purple color.
Scientists believe a lake has existed on the Great Salt Lake’s site for millions of years. The Great Salt Lake was once part of an ancient freshwater lake called Lake Bonneville. The lake drained away thousands of years ago in a great flood, leaving a few isolated lakes. The Great Salt Lake is the largest of these lakes.
Since the early 2000’s, a decades-long drought and increased regional water usage have led to historically low water levels in the Great Salt Lake. Scientists have warned of the dangers that a dry lake bed could pose for air quality in the Salt Lake City area. Winds over the lake bed can stir up dust that contains toxic pollutants. Officials have considered taking steps to reduce the diversion of water from streams flowing into the lake.
