Peru · CLIMATE
Key Facts
- —Lakes flagged Peru’s glacial lake risk review rates 58 lakes very high and 94 high.
- —Regions Áncash, Cusco, Junín, Lima, Puno and Huánuco hold most of the flagged lakes.
- —Glacier loss A new national inventory puts Peru’s glacier loss at 59% over six decades.
- —El Niño The national disaster risk centre places over nine million people at very high risk.
- —Palcacocha Ten siphons operate above Huaraz, with maintenance funding still unresolved.
A national glacial lake risk review puts 152 lakes in the top two bands above Andean towns and farmland.
Peru’s glacier institute has put a number on the glacial lake risk hanging over its Andean valleys. Of 528 lakes judged capable of bursting, 152 sit in the two highest bands.
What the national review found
The Instituto Nacional de Investigación en Glaciares y Ecosistemas de Montana (INAIGEM) is Peru’s state glacier research body. Its national evaluation of lakes at risk of bursting is now the reference document.
INAIGEM counts 528 glacial lakes carrying some level of overflow risk. That is roughly 6% of all glacial lakes in the country.
Of those, 58 are rated very high risk and 94 are rated high risk. The combined 152 lakes define the current glacial lake risk picture.
Paola Moschella Miloslavich, INAIGEM’s director of glacier research, set out the figures this week. Most of the flagged lakes sit in Áncash and Cusco.
Where the danger is concentrated
The heaviest concentration runs through the central Andes. It lies between the Cordillera Blanca and the Cordillera Central.
INAIGEM’s ranking puts Upiscocha, in the Cordillera Vilcanota, at the top with a risk ratio of 0.99. An estimated 111 dwellings sit below it.
Palcacocha, above Huaraz in the Cordillera Blanca, scores 0.78 with 3,980 dwellings exposed. Tullparaju, also in Áncash, scores 0.75 with 4,198 dwellings exposed.
Across the 20 most dangerous lakes, INAIGEM counts more than 15,000 families in Áncash alone. That exposure is the core of the glacial lake risk problem.
How the high risk label is decided
The rating is not a forecast that any particular lake will burst. It combines physical susceptibility with the people and buildings downstream.
Moschella said the team weighed slope angles around each lake, lake size and the material holding the water back. Many Andean lakes are dammed only by moraine, the loose debris left by retreating ice.
A rock or ice fall into a lake can raise a wave that overtops or breaches that dam. The result is an aluvión, the Spanish term for a glacial mudflow.
Specialists call the same event a GLOF, or glacial lake outburst flood. INAIGEM’s report ranks Peru third in the world for exposure to it.
The nine million figure, and what it measures
A separate number has circulated alongside the glacial lake risk figures this week. It comes from the Centro Nacional de Estimación, Prevención y Reducción del Riesgo de Desastres (CENEPRED).
CENEPRED’s scenarios place 7,951,322 people at very high risk from flooding across 22 departments. Another 1.38 million face very high risk from landslides and huaicos, the local debris flows.
Together that clears nine million people, and the driver is El Niño rather than melting ice dams. It is a risk classification, not an alert level, and the two hazards are counted separately.
Response falls to the Instituto Nacional de Defensa Civil (INDECI), Peru’s national civil defence institute. INDECI estimates 1,248,412 people could be affected between October and March 2027.
El Niño is confirmed, not La Niña
The Comisión Multisectorial Encargada del Estudio Nacional del Fenómeno El Niño (ENFEN) reports every fortnight. Its technical report dated 26 August keeps the country on Alerta de El Niño Costero.
That is the top state in ENFEN’s five-level warm-phase alert system. The commission is vice-chaired by the Autoridad Nacional del Agua (ANA), Peru’s national water authority.
The Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI), the national weather service, sits on the same commission. SENAMHI grades its own warnings yellow, orange and red, with red the most severe.
ENFEN expects coastal El Niño to persist into the 2027 summer at extraordinary magnitude. Weekly sea surface anomalies off northern Peru ran near four degrees Celsius in late August.
Why 1941 and 1970 still frame the debate
On 13 December 1941 a lake dam in the Cojup valley above Huaraz gave way. The flood covered about 60% of the built-up city and killed roughly 1,800 people.
Palcacocha sits in that same Cojup valley, which is why it dominates local argument. Its volume grew roughly 34 times between 1972 and 2016 as the glacier withdrew.
On 31 May 1970 an earthquake offshore of Chimbote shook loose part of Huascarán. The rock and ice avalanche erased Yungay and a string of nearby villages.
Published Peruvian accounts put close to 4,000 people missing across those settlements. INAIGEM has since modelled how a comparable detachment would behave today.
The defences that exist, and the money
Palcacocha’s main physical defence is a set of ten siphons that draw the water level down. The regional government says all ten were working in late August.
Rafael Macedo Menacho, who runs disaster risk management for the Áncash regional government, put the volume below 15 million cubic metres. An alert level begins near 17 million cubic metres.
The early warning system above Huaraz has been the weak link. In April the provincial council said maintenance needed about S/700,000 (US$209,000) that never arrived.
Áncash general manager Marco La Rosa has since costed a full maintenance file at S/1.4 million (US$418,000). Conversions use the Banco Central de Reserva del Perú rate of S/3.348 per dollar on 27 August 2026.
Budget law blocks the region from transferring maintenance money to the two municipalities involved. The region therefore plans to take the system back and service it directly.
From siphons to permanent works
At a multisector El Niño meeting on 26 August, INAIGEM pressed one specific point. It urged authorities to move from temporary siphoning to permanent engineering works.
No funded national programme for those works has been announced. Local engineers have floated two containment dams above the Cojup valley, so far unstudied.
INAIGEM’s monitoring centre in Huaraz opened in May 2026 and watches three lakes live. Palcacocha, Upiscocha and Gangrajanca carry sensors and streaming cameras.
The institute also hands municipalities evacuation maps and marked safe zones. Macashca, near Huaraz, received its maps in July, and signage is still pending.
A new national glacier inventory is due for formal presentation shortly. It records about 4,500 glaciers left and a 59% loss of glacier cover in six decades.
Frequently Asked Questions
What is a GLOF?
A GLOF is a glacial lake outburst flood. It happens when a lake’s natural dam fails and releases water suddenly.
How many Peruvian lakes are rated dangerous?
INAIGEM lists 528 lakes with some overflow risk. Of those, 152 carry high or very high glacial lake risk.
Is the nine million figure about glacial lakes?
No, it is CENEPRED’s count of people facing very high risk from El Niño rains. Glacial lake risk is assessed separately by INAIGEM.
Connected Coverage
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Sources
- www.gob.pe
- www.gob.pe
- www.gob.pe
- enfen.imarpe.gob.pe
- gestion.pe
- gestion.pe
- www.infobae.com
- www.infobae.com
- larepublica.pe
- ancashnoticias.com
- ancashnoticias.com
- ancashnoticias.com
- estadisticas.bcrp.gob.pe
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