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4 May 2021 | Cryosphere

Increasing risk of glacial lake outburst floods in Hunza River basin

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Passu Glacier. Photo: Muhammad Saifullah/MNSUET

The Hunza River basin is economically important for both China and Pakistan as the China-Pakistan Economic Corridor (CPEC) passes through it. The basin is highly glaciated and there is a great risk of glacial lake outburst floods (GLOFs).

A recent study that we were part of investigated the potential GLOF risk along the Karakoram highway. The study used both field-based data and remote sensing techniques to understand the formation and behaviour of moraine-dammed glacier lakes and recommends considering these risks in the formulation of future policies.

Based on 40 years of observation of the Karakoram glaciers, the study concludes that surging and debris-covered glaciers have a higher risk of causing GLOFs. It also concludes that surge-type and non-surge-type glaciers have behaved similarly with respect to recent mass changes.

Glacier surge is a common phenomenon in the region. The recent surge of Khurdopin Glacier in 2017 created the Khurdopin glacial lake in the Shimshal Valley of the Hunza River basin. Glacial lakes are a major source of freshwater in some areas but, when their dams suddenly breach, they can cause catastrophic floods and pose a great threat to the people and infrastructure in downstream areas.

The severity of damage from GLOFs increases as the elevation and volume of the glacial lakes increases, and if the settlements and infrastructure downstream is close in proximity. Many potential lakes in the study area have the capacity to damage infrastructure including roads and highways. In the past fifty years, several GLOF events in the area have been reported, especially in the eastern part of the CPEC region. The recent GLOF event triggered by the Shisper Glacier surge damaged the Karakoram Highway, causing it to shut down for some time.

Temperature rise is one of the main driving forces causing expansion of glacial lakes. Many glaciers are also retreating in this area. Closer investigation of Khurdopin Glacier’s surges revealed both that there is a presence of the thermal phenomenon – when the basal ice starts melting, it causes basal sliding that in turn causes these surges – and that the retreat of the glacier is leading to the expansion of Passu glacial lake. The study also revealed that a maximum increase in lake area occurred below 3500 masl, demonstrating a situation favourable for water resource management.

The CPEC initiative is expected to bring major changes in the lives of over 3 million people in this region. As the route is strategically important for both China and Pakistan, study of climate change impacts on glacier dynamics and lake formation in the vicinity of the corridor is crucial to ensure that the route is not vulnerable to future disasters.


Year Event date Glacier River Influencing factors
1973 Batura Hunza
1974 Batura Hunza
1977 Balt Bare Hunza
1978 September Darkot/Barados Gilgit
1994 July Sosot/Gupis lake Gilgit
1999 6 August Khalti/Gupis Gilgit Monsoon rainfall
2000 10 June Shimshal Hunza High temperature
2000 27 July Kand/Hushe Indus Monsoon rainfall
2005 July Sosot/Gupis lake Gilgit
2007 5 April Ghulkin Hunza Western disturbance
2008 6 January Passu Hunza Western disturbance
2008 2 April Ghulkin Hunza Western disturbance
2008 22 May Ghulkin Hunza Persistent rainfall
2008 24 May Ghulkin Hunza Persistent rainfall
2008 14/15 June Ghulkin Hunza Heat wave
2009 26 March Ghulkin Hunza Western disturbance
2018 17 July Barsuwat glacier Immit Heat wave
2019 23 June Shishper Hunza High temperature
2020 29 May Shishper Hunza High temperature

Major GLOF events reported in the CPEC region. (Source: Saif Ullah et al., 2020)

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