Great Salt Lake shrinking. From overuse, not climate change.
Since 1847, the Great Salt Lake has steadily shrunk, reaching its lowest recorded level in 2016. Today, the lake is 3.6 meters below its 1847 level and just half its original volume. Previously, many researchers thought the decline—here and in other saltwater lakes—was caused by wet and dry cycles related to climate change, says Wayne Wurtsbaugh, a limnologist at Utah State University in Logan.
To test that notion, Wurtsbaugh and his colleagues recreated the climate around the Great Salt Lake for 170 years, based on historical precipitation, stream level records, and tree ring data. The records showed that precipitation and temperature patterns had hardly fluctuated during the period, meaning that the amount of water flowing into the lake from nearby streams is likely the same today as it was in 1847.
Every year, people living in the region (which includes rapidly growing Salt Lake City) divert 3.3 trillion liters of water, not from the lake itself, but from the handful of streams feeding it. With climate staying relatively stable, the team concluded that humans are triggering the decline by consuming streamwater before it replenishes the lake, they reported last week in Nature Geoscience. Although some of that water returns to the lake (for example, by soaking into the ground after irrigation), Wurtsbaugh says the new calculations show that the overall amount fell 39% from 2003 to 2012. This, in addition to long-term stream records, suggests that climate change isn’t the culprit.