The Great Salt Lake in Utah is the largest saltwater lake in the Western Hemisphere. As a terminal lake, water leaves only through evaporation, concentrating its mineral content over time. This unique inland sea is currently experiencing a historic crisis, with its water level dropping to record lows in recent years. The exposed lakebed and diminishing water volume represent a significant ecological and economic threat to the region.
The Impact of Upstream Water Diversion
The largest factor driving the lake’s decline is the human diversion of water from its three main tributary rivers: the Bear, Weber, and Jordan. These rivers are the primary sources of fresh water replenishing the lake, but a vast network of canals and reservoirs intercepts this flow. Historically, human consumption accounts for an estimated 67% to 73% of the water loss contributing to the lake’s current low level.
Irrigation for agriculture is the dominant consumer of this diverted water, utilizing approximately two-thirds of the total water removed from the Great Salt Lake Basin. Much of this water is used to grow crops like alfalfa and hay, which are often exported out of the state. This practice effectively removes water from the local hydrological cycle, preventing it from returning to the lake.
The municipal and industrial sector is the second major user, accounting for about 18% to 25% of the diverted water. This includes water used by cities for residential and commercial purposes, as well as by mineral extraction operations. While some municipal water returns after treatment, the collective quantity diverted prevents the natural streamflow necessary to maintain the lake’s volume.
Over 2.1 million acre-feet of water is diverted annually from the watershed. This consistent, large-scale removal of inflow, primarily for irrigation, has lowered the lake’s elevation by an estimated 11 feet over the long term. Construction of reservoirs along these rivers ensures the water is captured and stored, fundamentally disrupting the natural replenishment process.
How Climate Change Accelerates Water Loss
The effects of climate change significantly accelerate the lake’s decline, compounding the water deficit caused by human diversion. Warmer regional temperatures contribute to increased evaporation, speeding up the natural process by which the lake loses water. This phenomenon is responsible for an additional 8% to 11% of the current lake-level decline, exacerbating the problem created by upstream use.
Higher air temperatures cause more water to evaporate directly from the lake’s surface, especially during summer. Rising temperatures also impact the winter snowpack that feeds the lake. The region relies on a slow, sustained release of water from melting snow to replenish rivers and streams during the spring runoff.
Warmer winters often result in less snow accumulation and more precipitation falling as rain. This shift reduces the total water stored in the mountains and causes faster, earlier runoff. This accelerated snowmelt is less effective at replenishing the lake and means less water is available to counteract the increased evaporation rates.
Dust deposited on the remaining snowpack, often originating from the exposed lakebed itself, also accelerates the melt. This darkening effect causes the snow to absorb more solar radiation, leading to quicker runoff and further reducing the amount of water that reaches the lake. Climate change thus acts as a force multiplier, speeding up water loss and diminishing inflow simultaneously.
Environmental and Economic Fallout
The dramatic shrinking of the Great Salt Lake has exposed vast stretches of lakebed, leading to a major air quality and public health crisis. This exposed playa contains fine silt rich in heavy metals and metalloids accumulated over centuries from natural sources, mining, and industrial activity. When this dry sediment is lofted by wind, it creates toxic dust storms known as “lake effect dust.”
Analyses of the dust reveal elevated concentrations of substances like arsenic, copper, lead, and manganese. The levels of arsenic and lithium in the exposed sediments exceed the U.S. Environmental Protection Agency’s residential regional screening levels. This bioavailable dust is linked to respiratory irritation, asthma, and a higher risk of heart and lung disease for millions of people living downwind.
The lake’s diminishing volume and resulting hypersalinity threaten several multi-million dollar industries. The brine shrimp harvesting industry, which supplies a significant portion of the global aquaculture feed market, is particularly vulnerable. As salinity levels rise, the lake becomes uninhabitable for the brine shrimp, disrupting the entire food web.
Mineral extraction operations, which harvest salt, magnesium, and other minerals, face economic collapse as the water recedes and mineral concentration changes. The potential cost of a drying Great Salt Lake to the state’s economy is estimated to be up to $2.17 billion per year, resulting in the loss of thousands of jobs. The loss of brine shrimp and brine flies also threatens millions of migratory birds that rely on the lake as a stopover on the Pacific Flyway.