In 1941, thousands of people lost their lives in Huaraz, Peru, when a natural dam at a lake above the city collapsed. Today, melting glaciers are increasing the risk of such a disaster happening again.
Palcacocha Lake is located high in the Cordillera Blanca mountain range of the Andes in Peru, situated above the city of Huaraz at an altitude of approximately 4,500 meters. When the lake exceeds its large ice accumulations or natural dams, it can send nearly 10m3 of water and debris into the narrow valley below, reaching depths of 1,500 meters.
As a result, it was one of the most devastating glacial lake outburst floods ever recorded. The force of the water permanently altered the geography of the area and killed at least 1,800 people, with estimates going as high as 5,000.
Like all such lakes, Palcacocha was formed as glaciers retreated, filling the surrounding land with water. This process is natural; however, scientists now say that climate change is increasing the risk of another disaster.
Laguna Parón, at an altitude of 4,200 meters, is one of the largest glacial lakes in the Cordillera Blanca, Peru. (Source: The Guardian).
The Cordillera Blanca of Peru has the highest concentration of tropical glaciers in the world. While the Himalayas are considered to have a higher flood risk, the dense population of Huaraz significantly increases the threat to lives in the region.
When the disaster occurred in 1941, Huaraz had a population of 12,000; now it is a thriving city with 120,000 residents. Neil Glasser, a geography professor at Aberystwyth University, stated: “This is a unique example globally of a large city located right in front of the flood risk from a glacial lake.”
In the lower valley, the densely populated Nuevo Florida district would be the first area of Huaraz to be affected by flooding if it occurs. Saul Luciano Lliuya, a 43-year-old farmer and mountain guide, fears what might happen, as he has witnessed the glaciers and landscapes changing due to the climate crisis.
“The unpredictability of the issue means I don’t know what will happen to me and my family if that occurs. Older guides have told me stories about the mountains and how they are changing. As a farmer and a guide, I have noticed profound changes,” Lliuya said.
Glacial floods can occur in two ways. Glacial lakes form behind ice accumulations—natural dams formed by the accumulation of earth and rock left by a moving glacier. As glaciers melt, water levels can gradually rise, placing greater pressure on the ice accumulations, causing them to give way. Alternatively, an avalanche or earthquake can cause a change in water levels, leading to a breach of the ice accumulation and flooding the area below.
A study published in 2023 in the journal Nature Communications found that glacial floods threaten 15 million people worldwide. Last October, a glacial flood killed 92 people in Sikkim, a state in northeastern India bordering Nepal, Bhutan, and Tibet.
Scientists warn that the climate crisis is severely affecting glacial lakes. Wilson, an expert at the University of Huddersfield who has analyzed the lakes for the Peruvian government, stated: “If we look at the majority of scientific studies, we can see that glaciers globally are thinning significantly. This is particularly evident in the Andes and Peru.”
According to Wilson, those living downstream of such lakes need to be aware of the dangers. “We are facing a situation where more lakes are expanding and appearing. It is crucial to raise awareness and educate people, as these are very intense floods that can happen unexpectedly. They can travel several kilometers in 20 or 30 minutes, leaving little time to react,” he said.
While the Peruvian government is aware of the risks and has taken steps to mitigate them, local residents believe more needs to be done. Inés Yanac, director of the local environmental organization Wayintsik Peru in Quechua, stated: “People are very concerned about the risk of another flood. They worry about water shortages if a flood occurs and about securing water sources. Water is a vital resource for their livestock and crops.”
According to Yanac, the government needs to address this issue. Alarm systems are needed, but they have never been tested. Juan Torres Lázaro of Peru’s Inaigem Glaciology Institute believes that while the system has been tested, there are “serious procedural flaws.”
Victor Morales Moreno, who monitors water levels at Palcacocha Lake, has been tracking the lake’s water levels every two hours for the past nine years. He criticizes the approach to the issue, stating that the drainage pipes installed to lower the lake’s water levels are old and fragile, easily breaking under any signs of stress. An avalanche that struck Palcacocha in January of this year generated a wave 3 meters high across the lake. Fortunately, it did not cause a glacial flood, but all ten drainage pipes were damaged and need to be replaced.
However, Moreno remains fairly optimistic about the potential risks. “I am not worried about another flood because everything is under control,” he asserted.
Torres Lázaro is currently assessing the risks from the lakes, but progress has been slow. Four lakes were completed last year, with four more planned for 2024. According to Lázaro, everything was calm in 2022, but last year and this year, they have seen two avalanches, which has increased government interest. “Now, by definition, it is considered a risk,” Lázaro said.
