Day 1 - arun bhakta shrestha, arrcc-carissa workshop
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1) The document discusses using climate change scenarios to understand current and future water availability in the Hindu Kush Himalaya region. 2) A fully distributed hydrological model was used to simulate river flows under different climate change scenarios through 2050. The scenarios project increases in precipitation and glacier melt that result in mostly stable or increased water availability across the basins. 3) However, communities dependent on glacier and snow melt could be negatively impacted as glaciers recede. Springs that supply water in mountain areas are also drying up in some locations. The document calls for more accurate assessments of climate change impacts.
Day 1 - arun bhakta shrestha, arrcc-carissa workshop
- 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