Study blames fossil fuel emissions for significant loss of American West's water

A study published Tuesday in *Communications Earth & Environment* finds that emissions from the world’s 122 largest fossil‑fuel and cement companies have driven about half of the climate‑related water losses devastating the American West over the past decade. Between 2014 and 2024, climate change reduced the region’s April snowpack by roughly 36% and cut warm‑season streamflow by about 13%, with approximately half of those losses traceable to the so‑called “Carbon Majors.” Since 1950, those emissions have caused a loss of millions of acre‑feet of water — an amount comparable to the full capacity of Lake Mead, the nation’s largest reservoir. The Carbon Majors — including BP, Chevron, ExxonMobil and Shell — account for roughly 70% of global anthropogenic CO₂ emissions since 1854, with 97% occurring after 1950. Using climate and hydrological models, researchers determined that their post‑1950 emissions have produced a 15% reduction in April snowpack, a 6.1% change in warm‑season streamflow and a 2.4% increase in irrigation demand. Together, these shifts represent about half of the total disruption attributable to human‑caused climate change. In volumetric terms, the combined loss of April snowpack and warm‑season streamflow linked to Carbon Majors’ emissions exceeds 40 billion acre‑feet of water — roughly six times the annual water use of all California cities. On the demand side, the 2.4% rise in crop irrigation demand from higher temperatures equates to about 160% of the yearly water consumption of Los Angeles. The timing of flows is also shifting. In many western stream basins, the midpoint of yearly streamflow now arrives about six days earlier than it would have without those emissions; in some mountainous areas the advance reaches up to 30 days, widening the gap between when water is available and when it is needed for planting and harvesting. “People living in the western United States have been paying the price for climate‑change‑fueled droughts and fires with their health, livelihoods and wallets,” said Emily Williams, the study’s lead author and a postdoctoral researcher at UC Merced. “In particular, our dwindling snowpack and hotter, thirstier summers have spelled catastrophe for our water resources. These corporate climate emissions are bleeding us dry.” The study highlights California’s Central Valley as a case study. From 2003 to 2024, cumulative groundwater loss across the Sacramento River, San Joaquin River and Tulare Lake basins totaled about 34 million acre‑feet — more than 1.5 times the volume of Oregon’s Crater Lake. Roughly one‑fifth of that loss stems from climate change, with 10% specifically attributable to Carbon Majors emissions since 1950. The 2020‑2022 drought caused direct crop revenue losses of $2.7 billion, and idle irrigated cropland rose about 10% in 2021 and 2022. “Emissions traced to the Carbon Majors are intensifying an already dire water situation across the western United States,” said Angel Fernández‑Bou, a co‑author and bilingual senior climate scientist at the Union of Concerned Scientists. “Taxpayers, states, municipalities and communities are paying for the harms and costs associated with these climate impacts, and our study’s findings supply further technological grounds on how the fossil fuel industry is liable for those harms.” Nevada faces acute pressure because it draws about 90% of its drinking water from the Colorado River. The Bureau of Reclamation recently finalized a new 10‑year operating model for the river that requires Nevada, Arizona and California to collectively cut water use by about 20% over the next two years, with deeper cuts possible as conditions are reassessed every two years through 2036. As of Sunday, Lake Mead stood at roughly 1,039 feet above sea level — a record low since the reservoir was first filled in the 1930s and about 26.5% of capacity. John Entsminger, general manager of the Southern Nevada Water Authority, expressed frustration with stalled negotiations: “The river doesn’t care about legal interpretations, governmental comfort zones, or arguments about why a state can’t do much to conserve