International Centre for Integrated Mountain Development

Kathmandu, Nepal

Sustained hydropower potential in the

Hindu Kush Himalaya river basins due to

increasing glacier melt and precipitation

International Conference on Climate Change Innovation and

Resilience for Sustainable Livelihood

12-14 January 2015, Kathmandu

Arun B Shrestha arun.shrestha@icimod.org

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)

The “Third Pole”

Largest reserve of snow and ice outside the polar regions

• Contributions of snow

and ice?

• Impact of cc on

glaciers?

• Impact on the water

availability and

infrastructure?

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

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!( Outflow locations to downstream models0 200 400 600 800 1000

km

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

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 m0 200 400 600 800 1000

km

Soil types (FAO)0 200 400 600 800 1000

km

Land Use (GlobCover)0 200 400 600 800 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

Legend

River runoff data locations0 200 400 600 800 1000

km

• 12 locations with river flow

data series (not all

complete)

• Data provided by DHM

Nepal, IWMI, PMD, and

WAPDA Pakistan

Basin-scale

1 km grid

cell scale

Glacier projections

Fractional

glacier

cover

Glacier

hypsometry

Classificatio

n glacier

size classes

Glacier

mass

balance

Volume-

Area-

scaling

1 km grid

cell scale

Updated

fractional

glacier

cover per

cell DEM

Contribution to stream flow

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

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

RCP 4.5

RCP 8.5

Tama

Koshi Dudh

Koshi

Hydropower potential Flow duration curves

Flow duration curves

Hydropower potential

• First order estimate using Water

Evaluation and Planning Tool

(WEAP)

• Hypothetical reservoir at catchment

outlet – Reservoir storage capacity - half the annual

inflow during the reference period (1998-

2007).

– Reservoir initial storage - 80% of the total

storage capacity.

– A volume-elevation curve typical for mountain

reservior

– Evaporation and infiltration to groundwater

are neglected.

– Top buffer - 50% of the total storage capacity.

Below this level releases constrained by a

buffer coefficient which is assumed to be 50%

– The hydropower generation is assumed to be

not constrained by a maximum turbine flow.

Expected increase in Nepalese energy

demand (NEA, 2012)

2041-2050

Conclusions

• Hydrological model provides insight into

stream flow composition

• Glacier changes ranging from 25 – 50%

• Changes in outflow to downstream areas:

overall remains the same or increases

• Glacier melt contribution decreases

• Rainfall-runoff increases

• No negative impacts on hydropower potentials

• 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

Thank you