The use of seawater will become a key component of Chilean mining, driven by water scarcity, new projects and growing sustainability requirements.
Seawater will be the primary water source for the mining industry over the next decade. Water demand is expected to grow by an average of 1% per year, driven by increased copper production, expansion of existing operations and the arrival of new projects. According to Pulso, Cochilco’s “Projection of Water Demand in Copper Mining in Chile” study for the 2025–2034 period estimates that total seawater consumption will rise from 41% in 2024 to 68% by 2034.
Overall, water demand in the mining sector will increase from 18.5 m³/s in 2024 to 20.6 m³/s in 2034.
Meanwhile, freshwater use is expected to continue declining over the coming years, dropping from 10.9 m³/s in 2024 to 6.7 m³/s in 2034. “The trend reflects the relative scarcity of freshwater in regions facing structural water shortages.” The study notes that “seawater use is the sector’s primary adaptive response and is projected to remain at the core of its water strategy over the next decade.”
Although demand will increase during this period, the growth will not be linear. A significant rise is anticipated between 2025 and 2027, followed by a decrease from 2028 to 2030.
The study highlights that the 2026–2027 period will be a significant milestone for water sustainability in large-scale mining, as several water-management projects will come online, including Collahuasi’s C20+ project, Codelco’s Northern District plant and the Aconcagua project.
However, the downward trend will reverse in 2031 when demand begins to grow again due to new projects and greater processing needs. According to Cochilco, this will occur due to a shift from oxidized to sulfide ores (from surface to underground mining), which generally requires more water.
The Antofagasta Region, the hub of Chile’s national mining industry, will account for 49% of the country’s water consumption by 2034. The Tarapacá, Antofagasta and Atacama regions will lead the way in seawater use, thanks to their strategic coastal
locations and the development of desalination and distribution infrastructure. The expansion of desalination plants requires regional planning.
Patricia Gamboa, Director of Research and Public Policy at Cochilco, remarked that reduced freshwater availability, the need to ensure operational continuity in the face of climate change and other factors have made seawater a strategic solution for the national mining industry.
“The investment is becoming increasingly viable from a strategic perspective, though costs remain significantly higher than those of freshwater, given the complexity of the required infrastructure,” she commented.
Although companies’ exact investment figures have not been quantified, Cochilco estimates that the average cost of desalination and pumping projects is US$4.45/m³, while for projects involving only direct seawater pumping, the cost is US$1.87/m³.
“In both cases, energy accounts for a significant portion of the total cost, so access to clean, competitive electricity is critical to the economic viability of these systems,” she said.
On the environmental front, Cochilco notes that while using seawater reduces pressure on freshwater sources, it is not without impacts. The primary long-term risks are concentrated in three areas: seawater intake; brine discharge, with effects that vary depending on local oceanographic conditions and the design of the discharge systems; and the energy footprint of the process, particularly when renewable sources are not used.
In Chile, oceanographic conditions tend to favor relatively rapid dilution of the brine, which can reduce the risk compared to other regions. However, the rapid expansion of the number of dedicated desalination plants highlights the need for more comprehensive territorial planning,” the agency concludes.
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