Mining giants Rio Tinto and BHP Billiton will spend $US3 billion ($A3.26 billion) to support the world's largest copper mine, Escondida in Chile.
BHP Billiton, the mine's operator, will put in $US1.97 billion ($A2.14 billion) for a new seawater desalination plant at the mine, and Rio, with a 30 per cent stake in the mine, will contribute $US1.03 billion ($A1.13 billion).
The companies say the 2,500-litre-per-second facility will ensure continued water supply to Escondida and minimise its reliance on regional aquifers.
"Securing a sustainable water supply in the Atacama Desert is a major priority for all Chilean copper producers, so the approval of the Escondida Water Supply project is a significant milestone for our business," BHP Copper president Peter Beaven said.
Construction will start this month with commissioning scheduled for 2017.
The project will include two pipelines, four high pressure pump stations, a reservoir at the mine site and high voltage infrastructure to support the system.
The remaining stakeholder in the Escondida mine, located 3,100 metres above sea level and 170 kilometres southeast of the City of Antofagasta, is Japan's JECO Corporation.
Rio said its investment will be funded through the company's share of Escondida's cash flows.
BHP gave no details on its funding source.