Growing water scarcity could hamper the expansion of lithium mining in the U.S., deepening its reliance on foreign imports over the coming decades, a new study finds.Lithium is used in electric-vehicle and energy-storage batteries due to its high energy density and low weight compared with other minerals, but mining it requires a huge amount of water. Currently, the U.S. has only one active lithium mine, in Nevada, and with demand for the metal projected to explode over the next few years, the government and private companies are planning to open at least 115 new mines across the country, according to the study.However, most of the proposed mines that are in advanced stages of development overlap with water-stressed areas, specifically in the western U.S. In the new study, published May 28 in the journal Communications Earth & Environment, scientists found that if lithium mines start operating in these regions, they will compete for water not only with households, agriculture and industry, but also with one another and with other proposed mineral mines."Future water availability under climate change may constrain whether new lithium mines will have sufficient water to operate," study senior author Jennifer Dunn, a professor of chemical and biological engineering and the director of the Center for Engineering Sustainability and Resilience at Northwestern University in Illinois, told Live Science in an email.The U.S. imports more than 50% of its lithium, mostly from Chile and Argentina. Policymakers and corporations want to reduce this dependence, but even with the existing Nevada mine and the 22 proposed mines that are the closest to coming online, the U.S. won't have enough lithium to meet domestic demand, Dunn said."Every mine produces a different amount of lithium depending on its deposit type, lithium grade, and final product so we are unable to determine how many mines exactly would be needed," she said. "Our analysis estimated that if all 22 advanced [stage] proposed mines and the sole operating mine continued operation into 2050, 0.14 [to] 0.25 million metric tons [0.15 to 0.28 million tons] of lithium content in products could be produced per year."This range falls short of the 0.83 million to 1.9 million tons (0.75 million to 1.7 million metric tons) of lithium per year that other researchers previously estimated the U.S. would need to cover its own demand.However, the water demand to produce more lithium would be astronomical. That's because lithium is typically extracted from brines and rocks known as pegmatites, which require large-scale evaporation and aggressive processing with fresh water, respectively.To find out if the U.S. would have enough water to support additional lithium mines under intensifying climate change, the researchers calculated the future water use of the 23 lithium mines most likely to be active in 2050, using data from mining companies. Then, they layered this projected water use on top of projected water uses from other sectors, such as agriculture and manufacturing, under four modeled socioeconomic-climate scenarios between 2040 and 2060.The researchers found that the available water supply will, in most cases, be insufficient to support new lithium mines. The starkest example was Southern California's Salton Sea, which contains roughly 4.5 million tons (4.1 million metric tons) of lithium. The Salton Sea is fed by the Colorado River and showed the least water available to support lithium mining and other water demands, owing to the river's dwindling flow.Southern California's Salton Sea has been shrinking for decades, partly because inflow from the Colorado River has declined. A deposit of geothermal brine beneath the sea area is believed to hold one of the planets largest reserves of lithium. (Image credit: Mario Tama via Getty Images)Lithium deposits in the U.S. are clustered in Nevada, Arizona and California. These are also some of the most arid and water-stressed states. Although the study found an increase in rainfall under a high emissions, "business as usual" climate scenario, these regions likely won't have enough water to support other activities, let alone additional lithium mining, Dunn said.There were four exceptions in the study, including lithium-rich sites in North Carolina and Arkansas, which may have enough water to support future mines. However, there are other concerns related to lithium mining."Many of the lithium deposits in the United States reside near federally-recognized Indigenous and Tribal reservations, and the mines could violate Indigenous rights," Dunn said. "Lithium mining could also disturb sensitive ecosystems and biodiversity. And, like many other mineral mines, pollution, soil erosion, and water contamination are concerns."Together, the findings highlight a catch-22 in the quest to source lithium: Lithium is essential to support a green energy transition and curb climate change, but shrinking water availability due to global warming is making it harder to extract lithium.RELATED STORIESScientists just discovered an enormous lithium reservoir under PennsylvaniaDays numbered for 'risky' lithium-ion batteries, scientists say, after fast-charging breakthrough in sodium-ion alternativeSalar de Uyuni: The world's largest salt desert and lithium reservoir surrounded by volcanoesThe study did not explore potential improvements to water-use efficiency that could reduce the pressure on some water resources and increase the availability for activities such as lithium mining. Nor did the researchers include water exchanges known as interbasin transfers (IBTs) in their analysis, due to the lack of studies about these transfers under climate change."IBTs could help supply water to arid or water-stressed regions," Dunn said.Still, there is likely an upper limit on how much water can be allocated to lithium mining in a warming world, according to the study. This means the U.S. will probably continue to partially rely on foreign supply chains for lithium and other critical minerals.