As water began to flow along a dry riverbed in central Chile last year, residents reacted with amazement and joy. People cheered and embraced – it had been a long time coming.
Petorca, a town in the central Valparaíso region some 220 km from Santiago, has become an emblem of water inequality in the country – severe drought over the past decade has dried up the Petorca River and left the town’s population reliant on water trucks. This lack of access to water has harmed small farmers, who for generations had depended on fruit harvests, including avocados. But on 24 June, heavy rains brought relief.
The joy that came with the rains was, however, a fleeting parenthesis amid years of high water stress caused by a mega-drought. Compromised water supplies plagued the region during the 2010s, aggravated by high levels of water use by the agricultural sector. Chile’s climate exhibits a high inter-annual variability of precipitation, with very wet years followed by very dry years. This pattern yields interspersed water surpluses. “The anomaly of the mega-drought is that we had many consecutive dry years,” says Camila Álvarez-Garretón, a hydrologist and researcher at the Center for Climate and Resilience Research (CR2).
She said that the country experienced extreme droughts in 2019 and 2021 and that this is part of a wider precipitation deficit. “This is due to two overlapping phenomena: inter-annual variability combined with the effect of anthropogenic climate change. The latter has manifested very clearly in Chile in the form of precipitation deficit trends,” she added.
The academic points out that, although the entire planet is warming, changes in precipitation are varying by region. There are areas in which global warming causes more rainfall, but in central-southern Chile there is a consistent downward trend. This is projected to continue for the rest of the century.
Although water availability at the national level is comparatively high, the realities are very different between the country’s regions. In the hyper-arid areas of the Atacama Desert in the north, there is virtually no rainfall, while in the southern Andes, more than three metres of rain can accumulate in a year.
Chile is more than 4,000 kilometres long, with a varied geography and climate influenced by the Pacific Ocean and large-scale natural phenomena, such as the El Niño and La Niña oscillations.
El Niño is a climate pattern in which the surface water of the east-central tropical Pacific Ocean warms to significantly above average temperatures. This affects rainfall patterns and weather across the world, raising temperatures globally for its duration.
El Niño is part of a phenomenon called the El Niño–Southern Oscillation (Enso). El Niño events do not occur on a regular schedule, but appear on average every two to seven years. The opposite, cooler phase is called La Niña.
During La Niña, cooler-than-average sea temperatures are present in the central and eastern equatorial Pacific. Like El Niño, it affects patterns of rainfall and atmospheric pressure worldwide.
“The La Niña phenomenon [which emerged in December] is already in retreat – it was short-lived and not very intense,” explains Roberto Rondanelli, a professor at the University of Chile’s geophysics department. “The good thing is that it happened in the season when it doesn’t rain in the central zone, so it doesn’t matter so much.
“When there is no El Niño and no La Niña, we are in a neutral situation. This does not mean that it will instantly rain more or less, but rather that anything can happen. What we see is that we are heading towards a neutral situation, or even a weak El Niño situation, which is favourable for precipitation in central Chile.”
Rondanelli also tells Dialogue Earth about Chile’s historic mega-droughts, including one in central Chile that lasted 12 years, between 1770 and 1782. These are not new phenomena, he says, but now they come with the added context of climate change.
A CR2 report on water security published in 2023, co-authored by Álvarez-Garretón, explains that trends over the past six decades indicate a significant increase in water-stress levels in central Chile. In this period, consumptive water uses have doubled, driven mainly by agricultural and forestry development.
Day Zero
In 2019, the journalists Tania Tamayo and Alejandra Carmona published the book ”El negocio del agua” (The Business of Water):
“The picture is grim. As the desert advances and water becomes scarce, an avocado tree in Chile, on average, consumes more water than a person in Petorca. The mining companies have advanced to such an extent that some places in the highlands have lost their inhabitants. Forestry companies do not appear in the water footprint figures, despite the fact that they have been consuming rainwater for years.”
The book alleges that, in Chile’s case, there are “selective droughts”, in a territory where water is “a market good”. It notes that water availability is also unequal in agriculture: “There are sectors that have greater access to water resources, a situation that is directly related to the economic capacity of the farmer.”
CR2’s water security report states that in central Chile, more groundwater is used than can be naturally replenished. This means aquifers (underground water deposits) are not able to recharge, which means the amount of available water gradually shrinks. Like taking water from a bucket without adding more, it will eventually be empty.
“This deepens the socio-economic and environmental impacts,” the report warns, and is leading the country towards an “absolute depletion” of water resources – a concept known as Day Zero. “The timing of Day Zero is uncertain, but, considering that the timeframe is in the range of decades to a few centuries, it poses an intergenerational problem in Chile,” it notes.
Álvarez-Garretón explains that Chile’s water consumption rate sticks close to the limits of what is naturally available. But despite the country’s inter-annual precipitation variations, she is concerned that very dry years are not synonymous with lower water consumption. Álvarez-Garretón says there are no policies or protocols in place to limit consumption and generate water reserves when precipitation declines.
The timing of when Day Zero will be reached is uncertain, but […] it poses an intergenerational problem in ChileCenter for Climate and Resilience Research (CR2)’s water security report
In 2018, Day Zero almost occurred in Cape Town, South Africa. Authorities utilised the term while alerting the population that taps would run dry within weeks without an extreme drop in water consumption. Fortunately, the city managed to avoid catastrophe. But Uruguay did not: the Montevideo metropolitan area was left without access to potable water in 2023 after a period of low rainfall. This led the city to draw saltwater from the Río de la Plata for part of its supply, with government ministers advising pregnant people and those with hypertension, kidney or heart problems to limit their consumption.
Solutions to the crisis
In the context of the climate emergency, industry, scientists and academics have been thinking about solutions to a possible mega-drought, and other problems caused by a lack of access to water.
Desalination plants are one tactic for easing water scarcity. They convert seawater into freshwater for human consumption, industry and irrigation. Desalination plants extract large quantities of water from the ocean at high speed, which is processed to remove oils, algae and other marine elements. It is then filtered by reverse osmosis, a water-purification process.
Chile currently has 24 desalination plants, 17 of which supply the mining sector. Latin America’s first desalination plant for drinking water opened in the northern Antofagasta region in 2003. In Atacama, Chile’s first state-owned desalination plant – and the largest to be built in the country for public water supplies – broke ground in 2018.
In December, the contract bidding process to build a desalination plant in the northern region of Coquimbo began; Chinese, European and domestic companies are all in the running. And in January, the Chilean government announced a further four desalination plants for both residential and industrial purposes.
The mechanical engineer Pedro Sariego, an academic at the Federico Santa María Technical University in Valparaíso, has proposed a large-scale solution: a solar-powered water desalination plant in Valparaíso (approximately 350km south of Coquimbo), designed to replace or complement the water generated by the proposed Catemu reservoir, which is intended to facilitate irrigation for nearly 26,600 hectares of land. His idea was conceived as a more sustainable way to produce drinking water that would also reduce water transportation costs.
“What we have to do, in the end, is reach some kind of agreement on water and energy,” says Sariego. “That’s the key. I talk a lot about bringing or moving large volumes of water at low cost through alternative energy synergy.”
Desalination drawbacks
The introduction of desalination plants is not without concern. Experts fear they could have negative environmental impacts on the coastline and threaten ecosystems.
A 2019 study warned of the environmental risks associated with desalination plants, particularly the high levels of hypersaline concentrate (brine) they produce. Most of this is returned to the sea, causing an increase in water salinity that affects and alters ecosystems and marine life. The researchers found it can have an impact upon the availability of nutrients in the water. It may even have an impact on ocean temperatures, since increasing salinity also increases water density and thus the circulation of ocean currents.
Meanwhile, climate change is an ever-growing complication. At the Desalination Latin America 2025 congress held in Santiago in March, Daniel Rojas – an engineering expert from Brugg Group, an infrastructure firm – warned that rising sea levels and more frequent storm surges caused by climate change are damaging infrastructure. They are also flooding areas where plants could be built and altering geological dynamics. During the event, Rojas recommended installing dams or marine sediment reservoirs, as well as rehabilitating wetlands, to cushion these effects.
Climate change also threatens the sustainability of the desalination plants themselves, because warmer water contains higher levels of salt, which will impact the plants’ operations.
Moreover, there is a lack of regulations for the construction and operation of desalination plants. But Sariego argues that the technology is more than proven worldwide, with some 20,000 desalination plants globally, and says he has no records of any ecological catastrophes. “It has to work rigorously well, following the standards. And in that respect, Chilean engineering – at least that linked to the mining industry – is quite rigorous, quite systematic, and all the standards are met.”
