The Great Salt Lake has lost more than 15 billion cubic yards of water over the past three decades, is getting shallower at the rate of 4 inches a year, and an analysis of its water budget suggests reducing irrigation is necessary for saving it.

The study published in Environmental Challenges shows that 62% of the river water bound for the lake is diverted for human uses, with agricultural activities responsible for nearly three-quarters of that percentage.

"The research highlights the alarming role of water consumption for feeding livestock in driving the lake's rapid depletion," said co-author William Ripple, distinguished professor of ecology at Oregon State University, who notes that 80% of agricultural water use is for irrigating alfalfa and hay crops.

To stabilize the lake and begin refilling it, the authors propose cutting human water consumption in the Great Salt Lake watershed by 35%, including a reduction in irrigated alfalfa production, a fallowing of much of the region's irrigated grass hay fields and compensation for farmers and ranchers who lose income.

"The lake is of tremendous ecological, economic, cultural and spiritual significance in the region and beyond," said Ripple, a member of OSU's College of Forestry. "All of those values are in severe jeopardy because of the lake's dramatic depletion over the last few decades."

The authors used data from the Utah Division of Water Resources to build a detailed water budget for the Great Salt Lake basin for the years 1989 through 2022. On average, inputs to the lake—river inflows and precipitation—during the study period lagged behind consumption and evaporation at the rate of 500 million cubic yards per year.

The water budget has been in a deficit situation for much of the past 100 years and the numbers have worsened with climate change and drought, the authors say.

"Abnormally large snowmelt inflow during the 1980s and 1990s served to temporarily obscure the long-term decline in lake levels, and the lake actually reached its highest level in more than a century in 1987," Ripple said. "But it has been dropping by roughly 4 inches per year on average since then."

The Great Salt Lake, which has no outlet, is the largest saline lake in the Western Hemisphere and the eighth largest in the world. Its 21,000-square-mile drainage basin includes the Wasatch Mountains, whose snowfall accounts for much of the basin's water replenishment.

A biodiversity hotspot, the lake sustains more than 10 million migratory birds and 350 bird species. Declining lake levels threaten critical habitats and could disrupt food webs, Ripple said.

The lake directly supports 9,000 jobs and annually fuels $2.5 billion in economic activity in the form of recreation, mining and brine shrimp harvesting, the paper points out. It's the world's largest supplier of brine shrimp eggs, a food source that underpins global aquaculture, but as the lake shrinks and salinity increases, the shrimp become physiologically stressed and don't produce as well.

Also, as the lake gets smaller, human health risk grows in the form of wind-carried dust from the exposed saline lakebed, or playa. Five percent of the Great Salt Lake playa is fine particulate matter that can enter the lungs and cause a range of pulmonary problems, and particularly troublesome, the scientists say, is the presence of toxic heavy metals, residues of the region's history of mining, smelting and oil refining.

Depending on which conservation measures are deployed—including crop shifting, reducing municipal and industrial use, and leasing water rights from irrigators—the authors propose that farmers and ranchers who lose income from using less water could be compensated at a cost ranging from $29 to $124 per Utah resident per year. The state's population is 3.4 million.

"Revenues from growing both irrigated alfalfa and grass hay cattle feed in the Great Salt Lake basin account for less than 0.1% of Utah's gross domestic product," Ripple said. "But our potential solutions would mean lifestyle changes for as many as 20,000 farmers and ranchers in the basin."

In that regard, he adds, the Great Salt Lake area exemplifies the socio-cultural changes facing many river basin communities in the West and around the world, where climate change is sending many water budgets into deficit status.

"The economic and cultural adjustments required are significant but not insurmountable," said Ripple. "With the right policies and public support, we can secure a sustainable future for the Great Salt Lake and set a precedent for addressing water scarcity globally."

Collaborating with Ripple on the paper was an interdisciplinary team of scientists from Northern Arizona University, Utah State University and Virginia Tech; the Utah Agricultural Experiment Station; and Sustainable Waters, a New Mexico-based nonprofit focusing on global water education.