Climate Change in Nepal and its Impact on Himalayan Glaciers

1
Climate Change in Nepal and its Impact on
Himalayan Glaciers

• Arun B. Shrestha
• Department of Hydrology Meteorology
• PO Box 406, Kathmandu, Nepal
• arun_at_dhm.gov.np

29 June 2005 Kathmandu
2
Outline of the Presentation

• What is the likely climate change scenario in
  Himalayan Region (climate model)
• What are the observed climate trends in Nepal
  Himalaya (network data)
• Impact of climate change on Himalayan glaciers
• Glacier fluctuation
• River flows
• Glacier lakes

3

• What is likely to happen to the climate of the
  Himalayas in the future?

4
Temperature Change Projection
Period from 2071 to 2100 relative to the period
1961 to 1990 according to nine AOGCMs (IPCC ,
2001)
5
Precipitation Change Projection
IPCC , 2001
6
MAGICC/SCENGEN Analysis for Nepal
GCM Estimates for temperature and precipitation
changes in Nepal
OECD, 2003
7
Annual runoff change (mm yr-1) by 2050
Annual runoff by 2050 relative to the year 1961
to 1990 based on AOGCMs (a) HadCM2 and (b)
HadCM3 IPCC , 2001
8
How does observations compare?
9
Observed Temperature Trends
IPCC , 2001
10
Spatial Distribution of Temperature Trends
Spatial Distribution of max. Temperature Trends
Shrestha et al., 1999
11
Regional Temperature Trends
Temperature Fluctuations (sigma units)
Shrestha et al., 1999
12
Comparison with Global Trend
Shrestha et al., 1999
13
Temperature changes in Tibetan Plateau
Spring
Summer
Autumn
Winter
Annual
Liu and Chen, 2000
14
Observed Precipitation Trends
IPCC , 2001
15
Regional Precipitation Time Series
Shrestha et al, 2000
16
Precipitation, some comparisons
Shrestha et al, 2000
17
Precipitation, more comparisons
Shrestha et al, 2000
18
Impact on Glaciers?
19
Impact on GlaciersMap of Glaciers and Glacier
Lakes Distribution
ICIMOD/UNEP (2000)
20
Area decrease of AX010
SOURCE GEN AND OTHER RESEARCH
21
General Glacier Condition in Nepal

• AX 010 This small clean glacier is shrinking at
  an alarming rate. If it continues to shrink at
  the same rate it will disappear by 2060.
• Rika Samba The terminus of this glacier is
  retreating by 10 m per year
• Other glaciers in Hidden Valley, Dhaulagiri
  Region are also retreating at the rate of 1.5 to
  3 m per year
• Lirung About 4 m of surface lowering in one year
• Khumbu This large debris covered glacier the
  surface lowering between 1978 and 1995 was 10 to
  30 m (max 2 m/yr). This glacier might divide into
  two at 5000 m
• Majority of glaciers in Kanchenjunga area are
  also retreating

22
Consequences of Glacier Retreat !

• Variations in runoff is related to percentage of
  glaciated area.
• Variability in runoff is inversely proportional
  to percentage of glaciation
• Decrease in the glaciated area will cause extreme
  flow conditions, i.e., floods and droughts
• Initially the discharge will increase due to
  higher rate of melting, but later it will
  decrease as ice mass is depleted
• Glacier lake formation
• Glacier Lake Outburst Flood (GLOF)

23
Rivers of Nepal

• The glaciers and seasonal snow feeds several
  river systems of Nepal. They help maintain the
  flow of these rivers long after the monsoon
  precipitation ceases.
• These perennial rivers are source of lives of
  millions of people not only in Nepal but also in
  India, because all Nepalese rivers flows into the
  Ganges

Karnali
Narayani
Sapta Kosi
24
Discharge Time Series of Large Rivers of Nepal
Karnali
Narayani
Sapta Kosi
25
Discharge Time Series of Southern Rivers of Nepal
Babai
Rapti
Kankai Mai
26
Discharge Time Series of Largely Snow-fed Rivers
of Nepal
Dudh Kosi
Kali Gandaki
Tamur
27
Other Variations

• Extremes seems to be increasing
• Dry season flow decreasing and wet season flows
  increasing
• Hydrograph shift
• However the observed variations are not
  consistent and are not statistically significant
  to be considered conclusive

28
Formation and Growth of Glacier Lakes

• Valley glaciers generally contain supra-glacial
  ponds
• Due to warming climate, these ponds grow bigger
  and merge.
• During Little ice Age (1550-1850 AD) the glaciers
  were much longer than today. As the glacier
  retreat they leave a large void behind. The ponds
  occupy the depression earlier occupied by glacier
  ice
• These glacier lakes are very unstable and may
  outbreak causing catastrophic flood called
  Glacier Lake Outburst Flood (GLOF)

29
Past GLOF in Nepal
Source Yamada, 1998 DHM, ICIMOD
30
Past GLOF in Nepal contd.
Source Yamada, 1998 DHM, ICIMOD
31
Potentially Dangerous Lakes

• Tsho Rolpa (Rolwaling)
• Imja (Khumbu)
• Thulagi (Manang)
• Barun (Makalu)
• ICIMOD/UNEP (2001) 20 lakes dangerous

ICIMOD/UNEP (2001)
32
Tsho Rolpa Lake
SOURCE DHM
33
Imja Lake
SOURCE WECS
SOURCE DHM
34
Summary

• Climate Model results are highly variable
• More or less consistent and significant for
  temperature with projected mean temperature
  increase of 1.2 and 3 oC by 2050 and 2100 and 2.3
  to 4.3 oC at 2CO2
• Overall increase in precipitation but not very
  significant
• Runoff change projection generally follows
  precipitation although highly variable with model
• Observation
• Temperature changes generally agree with climate
  model results
• Generally more warming in high altitudes compared
  to low land
• No significant trends in precipitation
• Both temperature and precipitation related to
  large scale climatological phenomenon.
• Hydrology
• There is no consistent trends in river flow
• There is an overwhelming evidence of deglaciation
  in the Himalayas.
• Numerous glacier lakes have formed, and are in
  risk of outburst in the future.

35
Conclusion

• As runoff variation is directly related to
  glacier condition, continued deglaciation is
  certain to have impact on runoff in the future
• However runoff increase or degrease is dependent
  on the stage of deglaciation and we do not know
  in which stage we are in. It is therefore wise to
  prepare for the worse.
• There is no doubt that GLOF is a problem to water
  resource development.
• It is timely to make vulnerability assessment of
  different development sectors and devise
  Adaptation Plans
• But we also know very well that there is a
  limitation to what we can adapt to, so mitigation
  is inevitable

36
Thank You !