Abstract:
Climate change has significant implications for glaciers and water resources in
the Himalayan region. There is an urgent need to improve our current knowledge and methods
in quantifying changes in water resources in this region. This study uses an integrated
approach that couples a hydrological model and a glacier retreat model to assess the future
water resources for two Himalayan basins. They are the Chamkhar Chhu basin in Bhutan
(Eastern Himalayas) and the Beas basin in India (Western Himalayas). The future climate is
simulated by two Regional Climate Models (RCMs) for south Asia under three Representative
Concentration Pathways (Rcp2.6, Rcp4.5 and Rcp8.5). The six climate projections for
the period 2010–2100 indicate significant warming effects; however, projected changes in
precipitation are not consistent. Discrepancies in precipitation are noteworthy between the
RCMs and greenhouse gases emissions scenarios. The glaciers in the Chamkhar Chhu basin
are predicted to disappear or reduce to a small size before the 2050s, whereas the glaciers in
the Beas basin are expected to lose mass before the 2060s, and afterwards to gain mass under
Rcp2.6 and Rcp4.5, or to melt at a high rate under Rcp8.5. The available water resources
per capita of two basins are projected to decrease in the period 2010–2050. The decreasing
water resources are jointly induced by climate change and population growth. The latter is responsible for roughly 40 % of the water declines. Both basins are facing water shortages
at present and the water shortages will intensify in the future.
