When people in the Patagonian village of El Chaltén saw untreated waste flowing into waterways and found the sewage plant was faulty, they grew increasingly concerned about the health risks from pollution in two glacier-fed rivers, the Fitz Roy and Las Vueltas.
The incident in 2016 led Marie Anière Martínez, a conservationist with the Patagonian environmental organisation Boana, and Lorena Martínez, a Los Glaciares national park official, to form a group to investigate water contamination at the Unesco world heritage site.
The park is the heritage of ‘all humanity’, says Marie Anière Martínez. Photograph: Natali Ormazabal
Last year, they secured a landmark court ruling against water pollution in the Argentinian national park. Supported by the Escazú agreement, a regional treaty on environmental rights, residents filed a collective lawsuit, forcing authorities to acknowledge failures in waste management and commit to upgrading systems by January 2025.
Yet despite this victory, the pollution persists and activists are still calling for more robust enforcement. “What have the authorities done to prevent environmental damage?” asks Marie Anière Martínez.
Nestled in a 135-hectare (330-acre) valley in the shadow of Mount Fitz Roy, El Chaltén is home to up to 2,900 people during high season in the area, which is a paradise for hikers exploring Patagonia’s spectacular trails.
Los Glaciares protects part of the southern Patagonian ice field – a massive freshwater reservoir in South America. Spanning 600,000 hectares of lakes, forests and glacier-fed rivers, the national park includes the Las Vueltas River sub-basin, where 231 ice bodies feed the watercourses running through El Chaltén.
Waste from a sewage outlet is discharged into the Fitz Roy River. Photograph: Natali Ormazabal
But environmental problems escalate during the peak tourist season, from November to April, when the village hosts up to 10,000 people a day, putting pressure on sanitation infrastructure.
Complaints were first filed in 2022 by the community in El Chaltén, concerned about the sewage system’s collapse and the lack of clean energy. “In 2019, the Los Glaciares national park guidelines plan was developed with input from residents and experts,” says Lorena Martínez. “We had already warned about the lack of data and water monitoring.”
We don’t know how, over time, sewage discharges into the river can impact ecosystemsPaula Chaparro, guide
In 2023, 21 residents sought an injunction to defend their constitutional right to a healthy environment. “We gathered previous studies, which already indicated that sewage effluent from the treatment plant of the public utility were reaching the Vueltas and Fitz Roy rivers without proper treatment,” she says.
Local residents together with Martínez’s group, called Guardians of the El Chaltén Basin, proved that untreated sewage and resistant bacteria from overflowing treatment plants were contaminating waterways, threatening public health, according to judges. But still residents are waiting for action.
Sewage along the Fitz Roy River, which flows through El Chalten. Photograph: Natali Ormazabal
Like many in the village, Paula Chaparro, a mountain guide, has been involved in monitoring the water and public advocacy over pollution for more than a decade. “We don’t know how, over time, sewage discharges into the river can impact ecosystems,” she says. “The pollution goes beyond the village and affects the entire course of the Las Vueltas River to Lake Viedma.”
The activists are now supporting new legal action against the national parks administration for roadworks and other projects carried out in protected areas without environmental assessments.
During the legal process, Karina Soledad Esquius and fellow biologists from the National University of Mar del Plata sampled water from 82 watercourses in the north of Los Glaciares park.
A Nasa satellite image of the south Patagonian icefield, which straddles Chile and Argentina. Much ice is being lost from the 60 glaciers that run off the peaks. Photograph: Terra/Modis/Nasa
In November 2023, they found multiresistant bacteria in the water. “In most of the environments sampled, the water quality is very good, but we found multiresistant Escherichia coli [E coli] near the confluence of the Vueltas and Fitz Roy rivers, close to the sewage treatment plant,” says María Soledad Domínguez, the biologist responsible for the analysis. “Of 27 isolates, five showed resistance to three different families of commonly used antibiotics.”
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Carolina Codo, a local doctor, joined the lawsuit after seeing test results. Photograph: N Ormazabal
The results shocked Carolina Codó, a doctor at the community health centre, and pushed her to join the lawsuit. “Upon learning about the bacteria in the water, we took on a greater commitment to monitoring and demanding answers from the company and the authorities,” she says.
The findings revealed serious failures in sewage management. A court in Comodoro Rivadavia found that, according to a 2019 audit, the state utilities company was operating the treatment plant without monitoring liquid waste or assessing environmental or public health effects.
The company acknowledged that the two treatment plants could not handle the number of visitors during high season. “The system collapses when the population jumps from under 3,000 to more than 14,000,” says Melina Lorenti, the residents’ lawyer. “The public utilities state company committed to having the modules fully operational by mid-January 2025 and launched a public tender – now under evaluation – to expand the plant.”
The company says it has two treatment plants with a third under construction, and is increasing capacity. On 1 July last year, it invited bids for a grease and oil separation system to be added to the El Chaltén plant.
The big mistake is that El Chaltén expanded rapidly without an environmental framework in placeMelina Lorenti, lawyer
According to Adrián Alonso Durán, municipal director of environmental policy, the study on pollution in Las Vueltas River is inconclusive and needs more data. But he acknowledges the treatment plant’s limitations. “It has a fairly small capacity and does not operate at full capacity during the high season,” he says.
He highlights less visible sources of pollution related to overtourism. “In restaurants, oil is often poured down the sink, which builds up and eventually clogs the pipes,” he says. “A municipal ordinance now requires the installation of grease traps in restaurants and hotels, which are mandatory for renewing commercial permits.”
The confluence of the Las Vueltas and Fitz Roy rivers. Photograph: Natali Ormazabal
The utilities company says it has worked with the municipality to better regulate wastewater discharges, especially from laundries, restaurants and hotels.
The national parks administration, a federal agency under the authority of the climate-change denier president, Javier Milei, did not respond to a request for an interview.
With campaigners saying their concerns have not been fully addressed, the Guardians of the El Chaltén Basin have set up a committee to ensure public oversight and access to technical information, a sustainable governance initiative supported by the OECD and UN Water. “The big mistake is that El Chaltén expanded rapidly without an environmental framework in place,” says Lorenti.
The conservationists in this Patagonian valley remain vigilant. “We must continue raising awareness about the water,” says Marie Anière Martínez. “This national park is a natural heritage site for all humanity.”