A Preliminary Assessment of the Snow Cover of the Upper Indus Basin and Contribution to

Water Resources

Richard Armstrong, CIRES/NSIDC, University of ColoradoAdina Racoviteanu, INSTAAR, University of ColoradoDonald Alford, Consulting Hydrologist, Billings MontanaMark Williams, INSTAAR, University of ColoradoSiri Jodha Singh Khalsa, CIRES/NSIDC, University of ColoradoAl Rasmussen, University of Washington, Seattle

Project Funding from World Bank, NASA , USAID

Eastern Himalayan Range - Nepal

- Digital elevation model (DEM) from the NASA Shuttle Radar Topography Mission (SRTM v.4)(90m spatial resolution).

- Glacier outlines for Nepal from topographic maps and satellite data (GLIMS/ICIMOD)

- Catchment basins from ICIMOD (basic topographic unit in water budget analysis)

-Runoff data from Department of Hydrology and Meteorology (DHM) Nepal

Data Sources

3

Estimating runoff from glacier ice melt in Nepal using area-altitude distributed models

Compute melt below 5400 m using a regional vertical mass balance gradient.

(from Alford et al. 2010, Glacier retreat in the Nepal Himalaya: An assessment of the role of glaciers in the hydrologic regime of the Nepal Himalaya. Report to SASDN, The World Bank.)

Estimated 0o C isotherm altitude

Area-elevation hypsometry and location of 0o isotherm for the glacier covered area of Dudh Kosi Basin, Nepal

= Approximately 5400 m

Compute runoff from melting glacier ice –

Accumulation area Ablation area

1.4m 2.8m 4.2m 5.6m

Runoff Volume = sum of the products of the specific net budget within the (100 m) elevation bands within the ablation zone and surface area of those elevation bands. In this study:VBG db/dz = 1.4 m/ 100m for probable maximum runoff volume from ice melt for the region.

Results of Nepal Study

The contribution of glacier ice melt to annual streamflow volume varies among the 9 sub-basins from approximately 2-30%.

This glacier ice melt contribution is estimated to be about 4% of the total mean annual streamflow volume of the rivers flowing out of Nepal.

Mass balance gradient and degree day melt models produce comparable results.

Similar results were reported by Thayyen and Gergan in The

Cryosphere 4, 2010 for the Dokriani glacier, Nepal.

6

Western Himalaya, Upper Indus Basin

0 10 20 30 40 50 600.000

20.000

40.000

60.000

80.000 Indus at Tarbela, Annual Flow

Years 1961-2009

Acr

efee

t, x

1000

Upper Indus Basin = catchment above Besham/Tarbela

Armstrong, NSIDC/U. of Colorado

Estimate Water Sources for the flow of the Upper Indus• Involve the relative percentages of rainfall, seasonal snow cover melt, and glacier ice melt. (infiltration, ground water, evaporation)• Although numerous publications address this pattern, there is limited agreement on the contribution from these individual sources:

• primary source is glacier ice and “semi-permanent snow cover”, with rainfall and seasonal snow being insignificant,

• runoff is equally divided between snow and glacier melt,

• two thirds from snow/ice but without a clear distinction between snow melt and glacier melt,

Armstrong, NSIDC/U. of Colorado

• in other examples, melt specifically from glaciers is

noted to be of lesser importance simply because glaciers only occupy a limited amount of area in the UIB.

One source of these differences is often the lack of consistent definitions for semi-permanent snow cover and seasonal snow cover.

The assessment presented here focuses on seasonal snow cover, defined as that snow cover that has accumulated during the previous winter, or snowfall season, prior to the current melt season.

Besham-Tarbela Dam340m AMSL

Besham

Approximately 107,000 sq. km are situated above Pangong Lake and its associated internal drainage.

Formerly, Pangong Lake had an outlet to Shyok River, a tributary of Indus River, but it was closed off due to natural damming.  

Defining the Upper Indus Basin

Some examples with a greater total area of approximately 200,000 to 273,000 sq. km include the region situated above Pangong Lake which we have considered to be internal drainage and therefore was not included in the map shownbelow which has an area of 166,101 sq. km above Besham. This is the basin polygon we have beenworking with for our snowcover and glaciermapping.

2000 20102009200820072006200520042001 20032002

MODIS Mean Monthly Snow Covered Area (SCA) km2

Departures from MODIS mean monthly snow covered area for Astore, Gilgit, Hunza, Shigar, and Shyok sub-basins, 2000-2010.

2000 2010

Departures from the MODIS mean snow covered area for the full UIB.

August – annual minimum,semi-permanent snow andglaciers

Upper Indus Basin Seasonal Snow Area

February – annual maximum seasonal snow cover

Armstrong, NSIDC/U. of Colorado

If snow present, and melt possible, (NCAR/NCEP upper air temperatures) apply PDD model to area-elevation data to generate local melt volumes (potential runoff).

Mean monthly area-elevations for seasonal snow cover in the UIB.

Armstrong, NSIDC/U. of Colorado

1 2 3 4 5 6

Series1 4.5 10.8 14.5 14 4.7 6

Series2 2.2 2.8 13.1 19.3 17 7.7

0

5

10

15

20

25

km3

Mean Snow Melt and Stream Flow UIB - Above Besham

Series1

Series2

Snow Melt

Stream Flow

April May June July August Sept

Snow MeltStream Flow

Average monthly values for snow melt and stream flow 2000-2010

Armstrong, NSIDC/U. of Colorado

Besham/TarbelaResevoir

Preliminary estimates of average contribution to annual flow at Besham:Snow Melt 75%Glacier Ice Melt 15%Rainfall 10% 20

Conclusions• Eastern Himalaya: river runoff dominated by summer

monsoon – snow/ice play minor role.• Western Himalaya, Karakoram, Hindu-Kush: seasonal snow

and glacier ice melt are major contributors to water resources.

• Snow and glacier cover in the west appears to be reasonable stable over the past decade.

• Well-planned management, conservation, and efficient use of water currently available – as important as any changes that may take place in the regional climate in the near future.

• Need remains for accurate estimates of potential impact of reduced seasonal snow or glacier melt contribution to downstream water resources in a warming climate.

GLIMS Database at NSIDC

• High resolution glacier outlines (shape files) derived primarily from Landsat, ASTER and SPOT

• Current content: 95,000 glaciers, 290,000 km2

• Coming soon: ESA GlobGlacier Project (European Alps, West Greenland, Sweden, Baffin Island)

• Svalbard, Argentina, Nepal, and China.• GLIMS database contains approximately 250,000

ASTER browse images.• http://glims.org

Richard L. ArmstrongCIRES/NSIDC, Univ of ColoradoBoulder, USA

The Glaciers of the Hindu Kush-Himalayan RegionA summary of the science regarding glacier melt/retreat in the Himalayan, Hindu Kush, Karakoram, Pamir, and Tien Shan mountain ranges

All ICIMOD Publications: http://www.icimod.org/publications

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