Peru faces the risk of glacial lake floods

In 1941, thousands of people died in Huaraz (Peru) when the natural dam on the lake above the city broke. Now, melting glaciers are increasing the risk of that happening again.

Lake Palcacocha is located high in the Cordillera Blanca range of the Peruvian Andes, above the city of Huaraz at an altitude of about 4,500m. As the lake crossed vast moraines, or natural dams, it sent nearly 10 cubic meters ^of water and debris into the narrow valley toward the city, at a depth of 1,500 meters.

The result was one of the most destructive glacial lake outbursts on record. The force of the water changed the geography of the area forever and killed at least 1,800 people and possibly as many as 5,000.

Like all such lakes, Palcacocha was formed when glaciers receded, water filling the empty land around it. This process is natural, but now, scientists say, the climate crisis is increasing the risk of disaster happening again.

Laguna Parón, at an altitude of 4,200m, is one of the largest glacial lakes in the Cordillera Blanca mountain range, Peru. (Source: The Guardian).

Peru's Cordillera Blanca range has the highest density of tropical glaciers in the world. While the Himalayas are considered to pose a more significant flood risk, Huaraz's large population makes the threat to life in this area much greater.

When the disaster occurred in 1941, Huaraz had a population of 12,000, and now it is a prosperous city of 120,000 people. Neil Glasser, professor of geography at Aberystwyth University, said: 'This is the only example in the world of a major city located directly at risk of flooding from a glacial lake.'

Down in the valley, the populous Nuevo Florida district would be the first area of ​​Huaraz to be hit by flooding if it occurs. Saul Luciano Lliuya, a 43-year-old farmer and mountain guide, fears what might happen, because he has seen glaciers and landscapes change due to the climate crisis.

'The problem is unpredictable so I don't know what my family and I will do if that happens. The older guides told me about the mountains and how they were changing. As a farmer and a tour guide, I have noticed profound changes' - said Mr. Lliuya.

Glacial lake flooding can occur in two ways. Glacial lakes form behind moraines - natural dams formed by the accumulation of soil and rock left behind by a moving glacier. As glaciers melt, water levels can gradually rise and put greater pressure on the moraines, causing them to give way. Or an avalanche or earthquake could create a change in water level and cause it to overflow the moraine, flooding the area below.

A study published in 2023 in the journal Nature Communications showed that glacial lake floods threaten 15 million people globally. Last October, glacial lake floods killed 92 people in Sikkim, a state in northeastern India bordering Nepal, Bhutan and Tibet.

Scientists warn that the climate crisis is seriously affecting glacial lakes . Mr Wilson, an expert at the University of Huddersfield who has analyzed lakes for the Peruvian government, said: 'If we look at the majority of scientific studies, we can see that glaciers globally are thinning. go significantly. That happens especially in the Andes and Peru'.

According to Mr. Wilson, people 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 important to propagate and make people understand, because these are floods of great intensity that can happen suddenly. They can move kilometers in 20 or 30 minutes and don't have much time to react ,' Mr. Wilson said.

While Peruvian authorities are aware of the risks and have taken steps to mitigate them, locals say more needs to be done. Ms. Inés Yanac - Director of local environmental organization Wayintsik Peru in Quechua, said: 'People are very worried about the risk of another flood. They worry about water shortages if there is a flood and worry about ensuring the security of the lake. Water is an important resource for their livestock and crops.'

According to Ms. Yanac, the government must solve this problem. There should be some alarm system, but it has never been tested. Mr. Juan Torres Lázaro of Peru's Inaigem Institute of Glaciology said that this system has been tested but has 'serious procedural shortcomings'.

Mr. Victor Morales Moreno - the person in charge of monitoring the water level at Palcacocha Lake has monitored the water level in the lake every 2 hours for the past 9 years. He criticized the way the problem was handled, saying the drainage pipes installed to lower the lake's water level were old and brittle, prone to breaking at any sign of stress. The avalanche that hit Palcacocha Lake in January this year sent a 3m high wave across the lake. Fortunately, it did not cause a glacial lake flood, but all 10 drainage pipes were damaged and needed to be replaced.

However, Mr. Moreno is quite optimistic about possible risks. ' I'm not worried about another flood because everything is under control' - Mr. Moreno affirmed.

Mr. Torres Lázaro is currently assessing risks from the lakes but progress is quite slow. 4 lakes were completed last year and another 4 lakes are planned for 2024. According to Mr. Lázaro, things remained calm in 2022, but last year and this year, they saw 2 avalanches, this has increased government interest. 'Now, according to the limit, it is considered a risk' - Mr. Lázaro said.