The Great Salt Lake, located in a vast desert region of northern Utah, represents the largest saltwater lake in the Western Hemisphere. It is an endorheic basin, meaning it is a closed system where water flows in but has no natural surface outlet to the ocean, losing water only through evaporation. This unique hydrology makes the lake’s water level and volume highly sensitive to regional climate patterns and human activities within its watershed. The amount of water contained in this massive body is not static, fluctuating dramatically over decades and even within a single year.
Defining the Key Metrics of Measurement
Determining the “amount” of water in the Great Salt Lake requires tracking three distinct but interconnected metrics. The most frequently cited measure is the Surface Elevation, which is the height of the water surface measured in feet above sea level. This elevation is tracked at specific gauges, providing a daily, real-time snapshot of the lake’s condition.
The second metric is Surface Area, which measures the total square mileage of the lake’s footprint on the landscape. Due to the lake’s exceptionally shallow, flat basin, a minor change in surface elevation can result in a massive change to the surface area and shoreline. The final metric is Calculated Volume, typically expressed in acre-feet or cubic miles, representing the total quantity of water present.
Scientists derive the volume and surface area using detailed bathymetric surveys of the lakebed. Because the basin is so shallow, a drop of just a few feet in elevation can translate to a loss of millions of acre-feet of water. This relationship explains why Surface Elevation is the most practical and commonly reported figure, as it serves as the direct indicator for the other two metrics.
Current and Historical Water Volume and Surface Area
The Great Salt Lake has experienced historic extremes, but the recent trend has been overwhelmingly toward desiccation. Historically, the lake’s water level averaged around 4,200 feet above sea level, at which point it covered a surface area of approximately 1,700 square miles. At this average elevation, the lake held an estimated volume of about 16 million acre-feet of water.
The highest recorded level occurred in 1986, reaching a surface elevation of 4,211.65 feet and inundating 3,300 square miles of land. This record high was the result of a prolonged period of increased precipitation and runoff. In stark contrast, the lake reached its most recent record low in November 2022, when the surface elevation dropped to 4,188.5 feet.
The drop to the 2022 record low resulted in the lake covering only about 950 square miles, representing a 44% loss of surface area compared to its historical average. To illustrate the severe loss of volume, the lake was recorded at 4,191.6 feet in 1963, holding about 8.7 million acre-feet. The 2022 level, which was over three feet lower, signifies an unprecedented loss of water in the modern era.
Factors Driving Volume Fluctuation
The volume of the Great Salt Lake is intrinsically tied to a balance between water inflow and evaporation. Naturally, the lake level fluctuates with seasonal and multi-year climate cycles, driven by the volume of water provided by snowpack and precipitation. The three major tributaries—the Bear, Weber, and Jordan Rivers—deliver the vast majority of the lake’s water supply from the surrounding mountains.
The arid climate of the Great Basin region contributes to extremely high evaporation rates, which is the primary natural mechanism for water loss in this terminal lake. In a balanced system, annual inflow typically meets or exceeds the water lost to evaporation. However, human development has fundamentally altered this natural equilibrium.
The most significant factor driving the lake’s decline is the extensive diversion of water upstream from its tributaries. It is estimated that 62% of the water that would naturally flow into the lake is now diverted for human use and never reaches the basin. Agriculture accounts for the majority of this diversion, consuming between 70% and 82% of the total water withdrawn in the Great Salt Lake basin, primarily for irrigating crops like alfalfa and hay. This consumption exacerbates the natural deficit caused by drought, starving the lake of the inflow needed to counteract the high evaporation rate.
Ecological and Economic Consequences of Changing Volume
The physical loss of water volume has triggered a cascade of ecological and economic consequences, primarily through a spike in salinity. As the water level drops, the concentration of salt and minerals remaining in the reduced volume of water increases drastically. This hyper-salinity threatens the specialized organisms that form the base of the lake’s food web.
The most valuable of these organisms are brine shrimp and brine flies, which thrive in the lake’s saline environment. The brine shrimp industry harvests the shrimp cysts for use in global aquaculture. This industry is valued at up to $67 million annually and supplies nearly 45% of the world’s demand for these specialized eggs. The loss of brine shrimp habitat due to high salinity disrupts this global industry.
Ecologically, the millions of migratory birds that use the Great Salt Lake as a crucial stopover on the Pacific Flyway rely on the brine shrimp and flies as their main food source. The collapse of this food source due to hyper-salinity places stress on these bird populations.
Furthermore, the shrinking lake has exposed a massive expanse of lakebed, or playa, which becomes a source of toxic dust. This dust, when aerosolized by wind, contains accumulated heavy metals such as arsenic, copper, iron, and manganese, as well as combustion byproducts that have flowed into the lake over decades. This contaminated particulate matter poses a significant respiratory health risk to the millions of people living in the downwind communities along Utah’s Wasatch Front.