Water availability analysis for the upper
Indus, Ganges, Brahmaputra,
Salween and Mekong river basins
Arun Shrestha
International Centre for Integrated Mountain Development
Kathmandu, Nepal
LEG regional training workshop on national adaptation plans (NAPs) for
Asian countries
10-14 August 2015, Yangon, Myanmar
Acknowledgement
• HICAP Project
• Arthur Lutz, Future Water
• Walter Immerzeel, Future Water
& Utrecht University
Content
•
•
•
•
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The regional context
Major science questions
Global assessment - IPCC
Results
Conclusion
International Centre for Integrated
Mountain Development (ICIMOD)
Programmes
• Adaptation to
change
• Transboundary
Landscape
• River Basins
• Cryosphere and
Atmosphere
• Mount Information
System
•
•
Intergovernmental International organization working in the Hindu KushHimalayan Region
Established in 1983
The Hindu Kush Himalayan Region
“water tower”
Different sources of
moisture
(Shrestha, 2008)
Strong seasonality
Shrestha et al.,
Major science questions
30
THREE DECADES
1. What are the relative contributions of snow, ice, permafrost,
rainfall and groundwater to the hydrology of the sub-basins
and basin?
2. How will these contribution change and what will be the
impact of climate change?
3. What is the current water demand scenario and how will it
change in the future?
4. How can the scientific understanding linked with policy and
support planned and autonomous adaptation?
Global assessment – IPCC
AR5
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
Model domain
Upper Salween
Upper Mekong
103.497 km2
77.696 km2
Upper Brahmaputra
372.664 km2
(
( !
!
(
!
(
!
Upper Indus
437.201 km2
(
!
!
(
(
!
(
!
(
!
(
!
(
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(
(
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(
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Upper Ganges
169.162 km2
(
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Outflow locations to downstream models
(
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(
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(
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0
(!
!
(!
(
200
(
!!
(
400
(
(!
( !
!
(
!
600
800
(!
!
(
(
!
1000
km
Basin scale model set-up and
calibration
Input data
• Digital Elevation Model
(HydroSheds based on
NASA SRTM)
• APHRODITE and
Princeton gridded data
• Runoff from 12
measurements stns in
Nepal and Pakistan
• FAO Soil
• MERIS Land Use
Legend
> 7000 m
< 500 m
Soil types (FAO)
Land Use (GlobCover)
0
200
400
600
800
0
200
400
600
800
0
200
400
600
800
1000
km
1000
km
1000
km
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
Model input data
River runoff data 1998-2007 for calibration
• 12 locations with river flow
data series (not all
complete)
• Data provided by DHM
Nepal, IWMI, PMD, and
WAPDA Pakistan
Legend
River runoff data locations
0
200
400
600
800
1000
km
Glacier projections
1 km grid
cell scale
Fractional
glacier
cover
DEM
Basin-scale
Glacier
hypsometry
Classificatio
n glacier
size classes
Glacier
mass
balance
1 km grid
cell scale
VolumeAreascaling
Updated
fractional
glacier
cover per
cell
Contribution to stream flow
Contribution to total runoff (%)
Glacier
Snow
Rainfall-
Base
Basin
melt
melt
runoff
flow
UIB
41
22
27
10
UGB
12
9
66
13
UBB
16
10
59
15
USB
8
28
42
22
UMB
1
33
44
22
Glacier change
Changes in hydrological regime
RCP4.5
RCP8.5
No significant
change in water
availability
Changes in hydrological
regimes
Case study - Koshi
Tama
Koshi
Dudh
Koshi
RCP 4.5
RCP 8.5
Hydropower potential
Flow duration curves
Flow duration curves
Main results
•
Glaciers in the five river basins – Indus, Ganges, Brahmaputra, Salween and
Mekong –are likely to reduce by 20% to 55% by 2050.
•
Due to melting of glaciers and increased precipitation, the overall river flows are
likely to increase or remain unchanged in 2041-2050 compared to 1998-2007 for all
four river basins.
•
By 2050, total runoff is likely to change:
– -5% to +12% in the upper Indus basin,
– +1% to +27% in the upper Ganges,
–
0% to +13% in the upper Brahmaputra,
– + 3% to +19% in the upper Salween and
– + 2 to +20% in the upper Mekong.
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.
Thank you