Abstract
Abstract. A large number of Himalayan glacier catchments are under the influence of humid climate with snowfall in winter (November–April) and south-west monsoon in summer (June–September) dominating the regional hydrology. Such catchments are defined as "Himalayan catchment", where the glacier meltwater contributes to the river flow during the period of annual high flows produced by the monsoon. The winter snow dominated Alpine catchments of the Kashmir and Karakoram region and cold-arid regions of the Ladakh mountain range are the other major glacio-hydrological regimes identified in the region. Factors influencing the river flow variations in a "Himalayan catchment" were studied in a micro-scale glacier catchment in the Garhwal Himalaya, covering an area of 77.8 km2. Three hydrometric stations were established at different altitudes along the Din Gad stream and discharge was monitored during the summer ablation period from 1998 to 2004, with an exception in 2002. These data have been analysed along with winter/summer precipitation, temperature and mass balance data of the Dokriani glacier to study the role of glacier and precipitation in determining runoff variations along the stream continuum from the glacier snout to 2360 m a.s.l. The study shows that the inter-annual runoff variation in a "Himalayan catchment" is linked with precipitation rather than mass balance changes of the glacier. This study also indicates that the warming induced an initial increase of glacier runoff and subsequent decline as suggested by the IPCC (2007) is restricted to the glacier degradation-derived component in a precipitation dominant Himalayan catchment and cannot be translated as river flow response. The preliminary assessment suggests that the "Himalayan catchment" could experience higher river flows and positive glacier mass balance regime together in association with strong monsoon. The important role of glaciers in this precipitation dominant system is to augment stream runoff during the years of low summer discharge. This paper intends to highlight the importance of creating credible knowledge on the Himalayan cryospheric processes to develop a more representative global view on river flow response to cryospheric changes and locally sustainable water resources management strategies.
Highlights
The role of high mountain areas of the world as an important source of freshwater for the population living in the adjacent lowlands has been highlighted by recent studies (Bandyopadhyay et al, 1997; Viviroli and Weingartner, 2004; Barnett et al, 2005; Viviroli et al, 2007)
This study focuses on the “Himalayan catchments” of the Western Himalayan region, mainly on the Din Gad catchment in the Ganga basin
A “Himalayan catchment” is defined as a glacier catchment that experiences snowfall in winter and monsoon precipitation in summer with peak discharge from the glacier contributing to the crest of the annual streamflow hydrograph
Summary
The role of high mountain areas of the world as an important source of freshwater for the population living in the adjacent lowlands has been highlighted by recent studies (Bandyopadhyay et al, 1997; Viviroli and Weingartner, 2004; Barnett et al, 2005; Viviroli et al, 2007). The Himalaya is one of the focal regions, both in terms of its cryospheric resources and the dependency of a huge population on rivers originating from this mighty mountain chain. The Himalaya nourish more than 12 000 glaciers (Kaul, 1999; ICIMOD, 2001) covering an area of about 33 000 km (Rai and Gurung, 2005). Snow and glacier melt together with monsoonal precipitation determines the headwater flow regimes of large parts of the Himalayas, including central and eastern Himalayan tributaries of River Ganga and Brahmaputra. Snow and glacier melt contribution are very significant in many of these Himalayan rivers. The annual snow and glacier melt contribution is estimated to be 60% in Satluj river at Bhakra dam (Singh and Jain, 2002), 49% in Chenab river at Published by Copernicus Publications on behalf of the European Geosciences Union
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