Peru is a country recognized for its production of copper, silver, and gold, which is why the waters near abandoned mines often have a rusty color. However, in this case, the cause of this strange coloration is climate change.
In fact, the Cordillera Blanca, which houses the largest concentration of tropical glaciers in the world, has become especially vulnerable to rising temperatures, but what is most concerning is that it is a crucial source of freshwater for the country. For centuries, the glaciers were replenished with snow in winter, but since 1968 these huge ice masses have decreased by more than 40%, exposing rocks that, when exposed to the elements, trigger chemical reactions, releasing toxic metals into the water, in other words, acidifying it.
One of the most affected places is Lake Shallap, located in the heights of the Cordillera Blanca, which has high levels of heavy metals. In this sense, Raúl Loayza, a biologist at the Cayetano Heredia University, explained that this process, known as rock acid drainage, is a chain reaction that gradually poisons the water sources. “It is a very big problem and it is worsening,” warned the biologist.
On the other hand, the retreat of the glaciers in the Lake Shallap basin exposed more than 150 hectares of rocks rich in pyrite, an iron sulfide. When the meltwater passes over these rocks, the pyrite turns into iron hydroxide and sulfuric acid, releasing heavy metals such as lead, manganese, iron, and zinc, which contaminate the water. This is why the water pH of the lake, which should be neutral, dropped below 4, almost as acidic as vinegar.
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### Metales y acidez en el agua provocada por el cambio climático
According to the National Institute of Glacier Research and Mountain Ecosystems (Inaigem), the levels of metals in the water exceed environmental quality standards, so health authorities have declared that the Shallap River and several streams in the area are not suitable for human consumption.
However, many communities continue to use this water to irrigate their crops, even though they do not meet the requirements for agriculture. On the other hand, the higher areas of the Andes are the most affected by increased acidification and pollution with heavy metals, as the glaciers melt more rapidly.
This also harms indigenous villages living in these high-altitude areas, as they are more vulnerable to this situation due to their small size and lack of political influence to demand cleaner alternatives or support from authorities to face the crisis. As a result, Loayza warned that “these places in the Cordillera Blanca are a ticking time bomb for the high Andean communities, their ways of life, and the ecosystem.”
### ¿Cómo revertir la situación?
To mitigate the effects of acid drainage and reverse the situation, the town of Canrey Chico, located next to the Negro River, implemented a system of ponds and channels with native reeds to raise the water pH and reduce the concentration of heavy metals. However, the water quality remains a constant threat.
In other places, such as Lake Palcacocha, which supplies drinking water to Huaraz, the regional capital, scientists fear that water acidification will worsen as the glaciers continue to retreat. Although the lake’s pH remains alkaline for now, the other basins that feed the city are already becoming more acidic.
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