The Great Salt Lake (GSL) in Utah is the largest saltwater lake in the Western Hemisphere. It is a terminal lake, meaning water flows into it but does not flow out to the sea; evaporation is the only natural mechanism for water loss. Because of this unique hydrology and its relatively flat basin, the lake’s depth is inconsistent and highly variable.
Historical Average and Maximum Depth
Historically, the lake’s average depth typically ranges between 13 and 16 feet when the lake is at its long-term average surface elevation of 4,200 feet above sea level. Depth measurements are subject to fluctuations driven by long-term weather patterns. During periods of sustained high precipitation and runoff, the depth can increase dramatically. For instance, the maximum recorded water surface elevation occurred in the mid-1980s, seeing the maximum depth reach approximately 33 to 45 feet in the deepest sections of the basin.
Factors Driving Water Level Fluctuation
The water balance is determined solely by inflow versus evaporation. The GSL receives approximately 90% of its freshwater inflow from three major rivers: the Bear, the Weber, and the Jordan. The annual melting of the mountain snowpack drives this inflow, causing the lake level to rise by one to two feet each spring and summer. Conversely, the arid climate and the lake’s large surface area result in high rates of evaporation, which constantly draw the water level down, typically reaching its lowest point in the late fall.
Geographic Differences in Depth Across the Lake
The Great Salt Lake is split into two distinct arms by a 20-mile-long railroad causeway built in 1959. This structure severely restricts the exchange of water between the southern and northern portions. The South Arm (Gilbert Bay) receives nearly all the freshwater, making it less saline and usually deeper. Consequently, the water level in the South Arm is consistently higher than the North Arm, with a typical difference of 0.5 to 2 feet. The North Arm (Gunnison Bay) is often much shallower and has a significantly higher salinity, sometimes reaching saturation where salt precipitates onto the lakebed.
The Current Crisis of Record Low Levels
A prolonged period of drought and increased upstream water diversion has pushed the lake into a state of crisis. In November 2022, the Great Salt Lake reached its lowest recorded water surface elevation at 4,188.5 feet above sea level, breaking a record that had stood since 1963. This extreme shallowing meant that even the deepest parts of the lake were only about 22 feet deep. This historic decline has exposed vast stretches of the lakebed, which were previously submerged. The exposed sediment contains heavy metals and other particulate matter, leading to concerns about severe dust pollution that impacts local air quality.