The Sierra Nevada snowpack, a major source of water for California, could largely disappear in 25 years if global warming continues unchecked, according to a recent study.
The worrisome findings, published Oct. 26 in the journal Nature Reviews Earth & Environment, have serious implications for California's water supply and add to a growing list of water woes in the western United States, which remains in the grips of a decadeslong megadrought.
Scientists at the Lawrence Berkeley National Laboratory used climate models of different warming scenarios to project when the Sierra Nevada snowpack could see dramatic changes. Previous studies have shown that increasing temperatures from human-caused climate change are shrinking snowpacks around the world and altering precipitation patterns.
The researchers found that the snowpack could experience "episodic low-to-no-snow" winters — when more than half of the mountain basin's accumulated snow vanishes for five consecutive years — by the late 2040s if greenhouse gas emissions continue unabated. The snowpack is then projected to experience "persistent low-to-no-snow" years (when those conditions linger for 10 consecutive winters) in 35 to 60 years, beginning in the late 2050s.
"A low-to-no-snow future has massive implications for where and when water is stored in the western U.S.," Erica Siirila-Woodburn, a hydrologist at the Lawrence Berkeley National Laboratory and one of the lead authors of the study, said in a statement.
She said that in addition to consequences for recreation in the region, a severely reduced snowpack could have domino effects for the broader ecosystem.
"So that’s anything ranging from increased wildfire occurrence to changes in groundwater and surface water patterns and changes in vegetation type and density," Siirila-Woodburn said.
The Sierra Nevada snowpack typically accounts for around 30 percent of California's fresh water supply and is a particularly crucial natural reservoir for the Central Valley and the northern reaches of the state.
Though the extent and depth of the Sierra Nevada snowpack waxes and wanes with drier or wetter winters, the region has seen overall declines in recent decades. Dry conditions persisted for several years beginning in 2007, before the snowpack was replenished by substantial snowfall in 2010 and 2011, according to the California Department of Water Resources. Drought conditions deepened, however, from 2012 to 2016, culminating in a 500-year record low level measured in 2015.
Wetter conditions returned in 2017 and 2019, but recent years have been characterized by below-average snowfalls. In April, when California's snowpack is typically the deepest, the department reported that conditions this year in the Sierra Nevada were "well below normal."
The projections for the Sierra Nevada snowpack add to concerns about the outlook for fresh water supplies in the United States. Earlier this year, water levels at Lake Mead, the nation's largest reservoir that supplies water to millions of people across Arizona, Nevada, California and parts of Mexico, hit their lowest levels in history.
The U.S. Bureau of Reclamation said in June that Lake Mead's declining water levels are the result of ongoing drought conditions and increased water demands across the southwestern United States. Strain on the reservoir's supply is expected to persist into 2022, and officials are closely monitoring the situation to determine any necessary water conservation measures.