In 2020 the Maipo River carried a surplus of 46 m³/s over demand, according to the climate science center CR2, but only 25 m³/s once ecological flows are protected. Agriculture draws about 40 m³/s from the same river, and Aguas Andinas, which serves Greater Santiago, owns about 28% of its water rights.
A city that depends on one river
More than 80% of the Metropolitan Region's drinking water demand is met from the Maipo. Aguas Andinas produced 775.1 million m³ of drinking water in 2025, about 24.6 m³/s on average, and groundwater supplied 19% of that total.
The river's reliability is falling. CR2 finds Maipo flows nearly 25% below their 20-year average and more than 800 glaciers in the basin retreating, and projects the glacier contribution to December–March flows to fall by about 75% by the end of the century.
Two systems run the water
Chile separates water services from water rights. The sanitation regulator, the SISS, sets Aguas Andinas' tariffs every five years; the 2025–2030 tariffs were fixed by Decree No. 47 of May 15, 2025. Water rights and basins sit with the Dirección General de Aguas, which raised its online monitoring stations by 15% to 1,581 and handled 50,000 water rights registrations in 2023.
Holding a minority of the rights, the operator secures dry-year water through transfers and agreements with irrigators, alongside its own wells and reservoirs. The company plans to raise groundwater to about 40% of supply under its Biociudad roadmap to 2035.
Which institutions decide Santiago's water security, how the network and treatment system performs, and which projects and risks will define the next decade are set out in the full report. The full report, Water Systems Overview: Aguas Andinas, is available for USD 499. For a free overview, read the Aguas Andinas Utility Snapshot.