Impact assessment of climate change on the hydrological response of a snow and glacier melt runoff dominated Himalayan river

The effect of climate change on snow water equivalent, snowmelt runoff, glacier melt runoff and total streamflow and their distribution is examined for the Spiti river. This is a high altitude Himalayan river located in the western Himalayan region. The total streamflow of this fiver has a significant contribution from snow and glacier melt runoff. Plausible hypothetical scenarios of temperature and precipitation changes based on the simulation of climate change over the Indian subcontinent by the Hamburg climate model are adopted in the present study. The UBC watershed model was used to simulate the hydrological response of the basin under changed climatic scenarios. The adopted changes in temperature and precipitation covered a range from 1 to 3 degrees C and from -10 to +10%, respectively. Snow water equivalent reduces with an increase in air temperature. However, no significant change is found in the snow water equivalent of the Spiti basin by the projected increase in air temperature (T + 1 to T + 3 degrees C). An increase of 2 degrees C in air temperature reduced annual snow water equivalent in the range of 1 to 7%. Changes in precipitation caused proportional changes in snow water equivalent, It is found that annual snowmelt runoff, glacier melt runoff and total streamflow increase linearly with changes in temperature (1-3 degrees C), but the most prominent effect of increase in temperature has been noticed on glacier melt runoff for this high attitude basin. For example, an increase of 2 degrees C in air temperature has enhanced annual snowmelt runoff, glacier melt runoff and total streamflow in the range of 4-18%, 33-38% and 6-12% respectively. The effect of change in precipitation (P-10 to P+10%) suggests a linear increase in snowmelt runoff and total streamflow, while, in general, glacier melt runoff is inversely related to changes in precipitation. Snowmelt runoff is found more sensitive than glacier melt runoff to changes in precipitation (P-10 to P+10%). Under a warmer climate scenario, snowmelt runoff and glacier melt runoff cause an earlier response of total streamflow and a change in flow distribution. The seasonal analysis of total streamflow indicates that an increase in air temperature produces an increase in the pre-monsoon season followed by an increase in the monsoon season. implications of such seasonal changes are also briefly discussed. (C) 1997 Elsevier Science B.V.