The Great Salt Lake, located in northern Utah, is a remarkable natural feature. It is the largest saltwater lake in the Western Hemisphere and ranks among the most saline inland bodies of water globally. Its unique characteristics prompt a deeper look into its composition and behavior.
Understanding the Salt Content
The Great Salt Lake contains an estimated 4.5 to 5 billion tons of salt in its waters. Salinity, which describes the concentration of dissolved salts, varies considerably across its sections and with water levels. While the average salinity for the lake can range from 5% to 27%, the southern arm typically maintains 8% to 16% salinity, whereas the northern arm is significantly saltier, often reaching 25% to 29% due to restricted water flow. For context, the world’s oceans average about 3.5% salinity, making the Great Salt Lake many times saltier.
The predominant dissolved solid in the lake is sodium chloride, commonly known as table salt, making up about 99% of the salt crust that can form on the lakebed. Beyond sodium chloride, the lake’s waters also contain substantial amounts of other minerals. These include sulfate, magnesium, calcium, and potassium. These diverse mineral components contribute to the lake’s unique chemical properties and its value for mineral extraction industries.
Why the Lake is So Salty
Its extreme salinity results from unique geographical and hydrological characteristics. As an endorheic basin, it is a terminal lake with no natural outlet. Water flows into the lake from rivers and streams, but the only way water leaves is through evaporation. This process continuously concentrates the dissolved salts and minerals.
Rivers such as the Bear, Weber, and Jordan continuously transport dissolved minerals and salts from the surrounding landscape into the lake. Annually, these rivers contribute millions of tons of dissolved solids, including 1.1 to 2.2 million tons of salt. Over millennia, as water evaporated, salt accumulated. The Great Salt Lake is also a remnant of the ancient, much larger Lake Bonneville, which, despite being less saline, left behind a legacy of concentrated salts as it receded.
How Salt Levels Change and What It Means
Salt concentration in the Great Salt Lake is not static; it fluctuates with water levels. When the lake’s water level rises, the same amount of salt is diluted by a greater volume of water, leading to lower salinity. Conversely, as water levels fall, the salt becomes more concentrated, increasing the overall salinity. This dynamic is directly influenced by precipitation, snowmelt runoff, and evaporation rates.
These shifts impact the lake’s ecosystem and human activities. High salt levels restrict life to specialized organisms like brine shrimp, brine flies, and certain algae. It also provides habitat for millions of migratory shorebirds and waterfowl, which rely on these species for food. Additionally, the variable salinity impacts mineral extraction operations, which harvest salts and minerals, and recreation, as the dense, salty water allows people to float with ease.