SURFACE

Study: Lithium mining not cause of water loss in Salar de Atacama

There has been a real lack of understanding about the hydrology of the salar

Scientists have completed a new study on the Salar de Atacama.

Scientists have completed a new study on the Salar de Atacama.

A new study has been completed on the hydrological environment in the Salas de Atacama, which hosts 40% of the world's lithium deposits.

"We need to understand the hydrology of where lithium is found," lead author of the paper and postdoctoral researcher at University of Massachusetts Amherst Brendan Moran told Mining Magazine.

The Salar de Atacama is one of the most important lithium mining deposits in the world, with Chile's Sociedad Quimica y Minera (SQM) and American company Albemarle currently mining the salar for lithium.

Copper producers on the Salar de Atacama include Antofagasta at its Zaldivar mine and BHP at Escondida.

There has been a real lack of understanding about the hydrology of the salar, Moran said. Studies up to this point have been inadequate and has "looked at the small things and are not looking at the big picture."

The main goal of the study, which was conducted in collaboration with the University of Alaska Anchorage, is to ensure that increases in lithium and copper production can happen "efficiently and without damage," Moran said.

The scientists completed a rigorous analysis of the hydrologic system of the salar, to determine where the water is coming from, how much water is being used, and how much water is being stored in the earth.

"A lot of water managers and other agencies that have tried to assess the available water for [mine] allocation have over-allocated the water," Moran said. "They are basing the inputs on the outputs [of water] that we measure. From what we've been studying, the inputs now are not nearly as high as they thought."

Water managers assumed that the salars are internally drained basins, where all the water leaves via evaporation, Moran said.

"They assumed that you can measure the water coming out easier than the water coming in, and assume that's in balance," he said. "But we show in this study that it's actually not even close to the amount that's coming in."

Study also determined age of water

Scientists have also determined the relative age of the water, which provides details on the water table and how the ecosystem is refreshed.

The team used remote sensing to measure the relative of the water in the salar by working with tridium, a radioactive isotope of hydrogen. This allowed scientists to conclude that the average age of the water contained in the salar is older than 65 years old.

"Almost all of the groundwater is really old," Moran said.

It's for this reason that the scientists have concluded that meteorological conditions, and not mining, is the root cause for changes to water levels in the water table.

"Rainfall is critically important" for this ecosystem, he said, adding that it took researchers by surprise because rainfall is so rare in this climate.

"This area is one of the driest places on earth, and it sometimes doesn't rain for years. But when it does rain, it rains for three to four days, a few times a year, and that's about it."

The team determined that about one-third of the salar comes from rainfall overall, not groundwater as scientists initially expected.

The scientists determined this by observing a major impact on the salar due to a major drought in the area from 2012 to 2013.

"If the lagoons were fed by groundwater, [these impacts] wouldn't have shown up. But the change was very observable."

Once the rain resumed, the wetlands surpassed its water levels, further pointing to the effect of the drought on the salar, he added.

Many local communities blamed mining for the drop in water levels, but it appears to be due to the drought, Moran said.

When it comes to water usage by mines, copper mines are using a lot of fresh water, Moran said. "But lithium companies use less than the 10% of freshwater that's allocated."

The Chilean government launched a lawsuit in April against mines operated by BHP and Antofagasta, accusing them of overdrawing the amount of water from the salar.

Droughts will likely not affect the brine, as it sits at the bottom of the salar, and doesn't fluctuate in levels very much, he said.

The study was funded by the BMW Group and BASF.

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