Presentation at ARRCC-CARISSA workshop 29 Jan 2019 to 31 Jan 2019

1. Arun B Shrestha
Using climate scenarios for understanding current and
future water availability of the Hindu Kush Himalaya
ICIMOD
ARRCC –CRISSA Workshop, 29 January 2019

2. • How much contributions of
snow and ice?
• What will happen to
Himalayan glaciers?
• What will happen to
Himalayan water?

3. Lutz, A. F., W. W. Immerzeel, A. B. Shrestha, and M. F. P. Bierkens,
2014: Consistent increase in High Asia's runoff due to increasing
glacier melt and precipitation. Nature Clim. Change, advance online
publication.
Himalayan Climate Change Adaptation
Programme (HICAP)

4. Approach
• High resolution (1 km) fully distributed model for
the upstream parts of the Indus, Ganges,
Brahmaputra, Salween and Mekong (HI-SPHY;
based on Immerzeel et al. 2010)
• Reference period from 1998 until 2007
• Calibration using observed runoff
• Climate change scenarios
• Ensemble of latest CMIP5 GCM output
• Downscaling ∆-change method
• Transient runs until 2050

5. Climate change scenarios
• Use two representative concentration
pathways (RCP)
• RCP8.5 (8.5 W/m2 in 2100)  extreme
• RCP4.5 (4.5 W/m2 in 2100)  less extreme
• Forcing regional and global circulation
models until 2050
• 4 GCMs for RCP4.5 and 4 GCMs for RCP 8.5
spanning entire range of possible futures:
• Dry & cold
• Dry & warm
• Wet & cold
• Wet & warm
• Total 2 RCPs x 4 models = 8 sets of climate
projections
• Downscaled using ∆-change method

6. Model domain
Upper Indus
437.201 km2
Upper Ganges
169.162 km2
Upper Brahmaputra
372.664 km2
Upper Salween
103.497 km2 Upper Mekong
77.696 km2

7. Basin-scale1 km grid
cell scale
Glacier projections
Fractional
glacier cover
Glacier
hypsometry
Classification
glacier size
classes
Glacier mass
balance
Volume-
Area-scaling
1 km grid
cell scale
Updated
fractional
glacier cover
per cellDEM

8. Impact on water availability
Present hydrology of the HKH rivers
• Indus: Glacier melt dominates including flow peak
during the summer season
• Brahamputra: glacier melt is important for the
most eastern tributaries
• Ganges: Rain runoff dominates the streamflow
Glacier melt
Snow melt
Rain runoff
Basin
Contribution to total runoff (%)
Glacier
melt
Snow
melt
Rainfall-
runoff
Base
flow
UIB 41 22 27 10
UGB 12 9 66 13
UBB 16 10 59 15
Shrestha et al., 2015 (HKH Climate and Water Atlas, ICIMOD; Lutz et al. 2014

9. Glacier change
Shrestha et al., 2015 (HKH Climate and Water Atlas, ICIMOD)

10. Changes in hydrological regime
RCP4.5
RCP8.5
No significant
change in water
availability
Shrestha et al., 2015 (HKH Climate and Water Atlas, ICIMOD)

11. Nang, Ladakh, India
Upstream communities dependent on glacier and snow
melt are feeling the impacts
Different story of middle mountains
• The middle mountains are fed by
rainfall and groundwater
• Springs are major source of water
• Springs are increasingly drying up
in the HKH

12. • High uncertainty in the precipitation forcing for
high altitudes and uncertainty in climate
projections
• First order assessment, recommendations for
more accurate assessments:
• Assessment of hydropower potential per subcatchment
• Include multiple potential dam heights and storage
volumes, or assessment of possible reservoir
morphology and possible dam height
• Not considered: extreme events, glacial hazards

13. The HI-AWARE Initiative
Himalayan Adaptation, Water and Resilience Research on
Glacier and Snowpack Dependent River Basins for Improving
Livelihoods
Lutz, A. F., ter Maat, H. W., Biemans, H., Shrestha, A. B., Wester, P., & Immerzeel, W.
W. (2016). Selecting representative climate models for climate change impact studies:
an advanced envelope-based selection approach. International Journal of
Climatology, 36, 3988–4005.
Lutz, A. F., Immerzeel, W. W., Kraaijenbrink, P. D. A., Shrestha, A. B., & Bierkens, M.
F. P. (2016). Climate Change Impacts on the Upper Indus Hydrology: Sources, Shifts
and Extremes. PLOS ONE, 11(11), e0165630.
Wijngaard, R., Lutz, A., Nepal, S., Khanal, S., Pradhananga, S., Shrestha, A., et al.
(2017). Future changes in hydro-climatic extremes in the Upper Indus, Ganges, and
Brahmaputra River basin, PLoS ONE, 12(12).

14. Climate model selection
Step1: changes in climatic means
Lutz et al., 2016, IJOC

15. Source: Wingaard et al. 2017, PlosOne
Changes in extremes: Floods
Extremes will increase
strongly during the 21st
century, almost
doubling in magnitude by the
end of the century
RCP 4.5
RCP 8.5
Change in 50-year
return period floods

16. Assessing climate change impacts on hydropower
Tamakoshi-III Khimti

17. Thank you