Dirk Hoffman: Comparison of recently formed glacial lakes in Bolivia and New Zealand

High Mountain Glacial Watershed Program - Glacial Flooding and Disaster Risk Management Knowledge Exchange and Field Training July 11 – 24, 2013 – Huaraz, Ancash, Peru

Comparison of recently formed glacial lakes in the Bolivian Andes and the Southern Alps of New Zealand - Differences and similarities Dirk Hoffmann Bolivian Mountain Institute

Instituto Boliviano de la Montaña - BMI

Outline • • • • •

Introduction Glacier retreat and glacial lakes in Bolivia Glacier retreat and glacial lakes in New Zealand Similarities and differences Conclusions

Introduction

Aim of this study • Comparison of glacial lakes in two very different mountain regions of the Southern hemisphere: - What is similar?

- What is different, and why?

- What follows for glacial lake management?

Glacier retreat and glacial lakes in Bolivia

Glacier retreat across the tropical Andes

Cumulative length evolution (m)

-200

-50000

-400

-100000

-600

-150000

antizana 15A antizana15b

-800

-200000

yanam arey broggi

-1000

-250000

pastoruri uruashraju

-1200

Cajap

-300000

Cumulative area evolution (m²)

0

0

Zongo (area)

-1400

Charquini-S (area)

-350000

Chacaltaya (area)

-1600 1930

-400000

1940

1950

1960

1970

1980

1990

2000

Edson Ramírez, Instituto de Hidráulica e Hidrología (IHH)

Glacier retreat in Bolivia • Bolivia was home 566 km² of glaciated area (World Glacier Monitoring Service, WGMS; data from 80s); and about 2,500 glaciers.

• The accelerated melting of glaciers commenced around 1980.

• Based on Soruco et al. (2009): Cordillera Real: 50 % reduction in surface area and volume over the last 35 years.

• This has led to the formation of hundreds of glacial lakes.

Formation of glacial lakes Apolobamba (Cololo region)

Glacier lake Ulla Khaya

Glacier lake Laguna Isquillani

Keara GLOF incident November, 2009

GLOF Keara, 2009

Fotos: MartĂ­n Apaza Ticona

Keara glacial lake today

Glacier retreat and glacial lakes in New Zealand

New Zealand glaciers • Temperature rise between 1-2 °C in the Southern Alps.

• Total ice loss from 54.53 km³ in 1976 to 46.12 km³ in 2008 (equals 15%)

Large valley glaciers • There are 12 large valley glaciers.

• Low gradients and heavily debris-covered.

• They remained areal extent until the 1970s (long response time).

• New dynamic with forming of supra-glacial lakes in the 1980s.

Dykes et al. 2010

Glacial lakes in New Zealand • Rapid lake expansion starting in 1990s.

• New dynamic of glacial recession once lakes have formed.

• Glacial lakes dammed by alluvial outwash gravel fan heads (not by moraines).

Hooker and Mueller glaciers

Ice level dynamics

Alluvial gravel outwash

Source: T. Chinn

Ice loss by downwasting

Source: T. Chinn

Similarities and Differences

Lake Tasman, NZ

Similarities • There is a clear trend of glacial recession in both regions.

• A number of glacial lakes have formed during the last 2-3 decades at the snouts of glaciers.

• These lakes have notably, sometimes dramatically increased in size.

• Formation of glacial lakes is an ongoing phenomenon.

Moro Khala

Muelller and Hooker

Differences • Ice loss in Bolivia (45-50%) was about three times that of New Zealand (15%).

• Glacial lakes in Bolivia are more numerous.

• Glacial lakes in New Zealand are much larger in size and water volume.

• Some of the lakes in Bolivia are to be considered dangerous; There was a first recorded GLOF incident in 2009.

• New Zealand´s lakes are not posing any danger; glacial lakes as a new tourist attraction.

Differences (cont.)

• Bolivia: mining and agricultural activities close to glaciers • New Zealand: no native population in high mountain areas • Differences in mountain topography: long valley glaciers in New Zealand (absent in Bolivia).

• Lake levels lower over time.

• Very high rates of uplift in Southern Alps: 10 mm/yr • Alluvial outwash gravel fan heads instead of moraine dams

Conclusions

Conclusions • Differences are more significant than similarities.

• They are based mainly on the characteristics of the mountain ranges and its glaciers.

• In Bolivia, there is a need for inventories of other mountain regions, to expand monitoring, and to realize on-site technical expert surveys.

• In New Zealand, there is no need for managemente of glacial lakes; it might be good to take another close look at topography higher up to make sure no dangerous glacial lakes would form there in the future.

Thank you for your attention!

Contact: dirk.hoffmann@bolivian-mountains.org

Additional information

Bolivian Mountain Institute - BMI

Klimablog „Cambio Climático Bolivia“

„Bolivia in a 4 degree warmer world“ • Supposes

a 4° C global average temperatrure increase by 2100 • Estimas the regional temperature increase for the Northern Altiplano region • Visualizes two time horizons: • 2030 – our lives • 2060 – the lives of our children and grandchildren • Develops sociopolitical scenarios, which are possible futures