Arun Shrestha. Water availability analysis for the upper Indus, Ganges, Brahmaputra, Salween and Mekong river basins

Transcription

1 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 August 2015, Yangon, Myanmar

2 Acknowledgement HICAP Project Arthur Lutz, Future Water Walter Immerzeel, Future Water & Utrecht University

3 Content The regional context Major science questions Global assessment - IPCC Results Conclusion

4 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 Kush- Himalayan Region Established in 1983

5 The Hindu Kush Himalayan Region water tower

6 Different sources of moisture (Shrestha, 2008)

7 Strong seasonality Shrestha et al.,

8 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?

9 Global assessment IPCC AR5

10 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

11 Model domain Upper Salween km 2 Upper Mekong km 2 Upper Brahmaputra km 2 Upper Indus km 2 Upper Ganges km 2 Outflow locations to downstream models km

12 Basin scale model set-up and calibration

13 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) km km Land Use (GlobCover) km

14 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 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

15 Model input data River runoff data 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 km

16 Glacier projections 1 km grid cell scale Fractional glacier cover DEM Glacier hypsometry Classificatio n glacier size classes Basin-scale Glacier mass balance Volume- Areascaling 1 km grid cell scale Updated fractional glacier cover per cell

17 Contribution to stream flow Contribution to total runoff (%) Glacier Snow Rainfall- Base Basin melt melt runoff flow UIB UGB UBB USB UMB

18 Glacier change

19 Changes in hydrological regime RCP4.5 RCP8.5 No significant change in water availability

20 Changes in hydrological regimes

21 Case study - Koshi Tama Koshi Dudh Koshi RCP 4.5 RCP 8.5

22 Hydropower potential Flow duration curves

23 Flow duration curves

24 Main results Glaciers in the five river basins Indus, Ganges, Brahmaputra, Salween and Mekong are likely to reduce by 20% to 55% by Due to melting of glaciers and increased precipitation, the overall river flows are likely to increase or remain unchanged in compared to 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.

25 Thank you