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.

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Observations of discharge, temperature and suspended sediment made at a gauging site established near the snout of the Dokriani glacier in the western Himalayan region are presented. These observations were made during a scientific expedition to this glacier over 21 days (23.8.1992-12.9.1992). Because of harsh weather conditions, observations could not be made for a longer period. The minimum streamflow in the glacier melt stream was observed at 0700 h whereas the maximum was observed at 1800 h. The ratio of maximum to minimum flow was computed to be 1.81 from the continuous hourly observations. Based on an analysis of the recession of the hydrograph, it was found that the meltwater time lag from the accumulation zone of the glacier was more than seven times higher than that from the ablation zone. No specific relationship was observed between suspended sediment and discharge. The average values of the suspended sediment concentration and load were found to be 350 ppm and 180 t day" 1 , respectively, for the study period. Weathering processes in different zones of the glacier were also studied to find out the source of the sediment transported by the meltwater into the melt stream. A high correlation coefficient (r = 0.89) was found between the glacier specific runoff and the air temperature at the gauging site. It showed that temperature alone can represent the melting of the glacier and may be considered for the hydrological modelling of glacier melt runoff. Based on observations over three days under clear weather conditions for isolated snow blocks, the average snowmelt factor was computed to be 5.4 mm /(°C. 6 h). Caractéristiques hydrologiques du glacier Dokriani, Garhwal Himalaya Résumé Les observations de débit, de température et de matières en suspension réalisées à la station de jaugeage établie près de la langue du glacier Dokriani dans l'Ouest de la région himalayenne sont présentées ici. Ces observations ont été réalisées dans le cadre d'une expédition scientifique d'une durée de 21 jours (23.8.1992-12.9.1992). En raison de rudes conditions météorologiques, il n'a pas été possible de poursuivre les observations plus longtemps. Le débit minimum de fonte a été observé à 0700 heures, cependant que le maximum de ce débit a été observé à 1800 heures. Le rapport du maximum de débit au minimum de débit a été estimé à 1.81 à partir d'observations horaires. L'analyse des Open for discussion until I October 1995

Diurnal and seasonal variations in particle size characteristics of suspended sediments of Dokriani glacier meltwater were studied during the 1994 ablation period (May-October). Diurnal suspended sediment concentration curves exhibit two prominent peaks from May to mid-August and only one peak during the rest of the ablation period. The first peak resulting from dominance of fine and medium sand contributed to the rising limb of the diurnal hydrograph, whereas the second peak was dominated by fine and medium silt which coincides with the diurnal discharge peak. The trends observed on the appearance of silts and sand particles on diurnal scales at various stages of the ablation period suggest that the subglacial drainage system comprises a diurnally-reversing hydraulic gradient between the channels and distributed system along with translatory flow through the distributed system. This study suggests that the subglacial zone is the major source of sediments in the Dokriani glacier meltwaters. However, high intensity monsoonal rainfall has contributed supraglacial sediments and resulted in bimodal distributions. Fines (clay to medium silt) are the dominant classes in the suspended sediments except during the spring event; the supraglacial sediments had coarsely skewed distributions. Caractéristiques granulométriques des matières en suspension et hydrologie du glacier Dokriani (Garhwal Himalaya, Inde)Résumé Les variations diurnes et saisonnières de la granulométrie des matières en suspension transportées par les eaux de fonte du glacier Dokriani ont été étudiées durant la période d'ablation de 1994 (mai-octobre). La courbe journalière de la concentration des matières en suspension présente deux extremums de mai à la miaoût et un seul extremum durant le reste de la période d'ablation. Le premier extremum résulte de la dominance des sables fins et moyens le long de la branche ascendante de l'hydrogramme journalier, alors que le second résulte de la présence de silts fins et moyens et coïncide avec le maximum journalier de débit. Les tendances observées concernant l'aspect des silts et des sables à l'échelle journalière pour différents moments de la période d'ablation suggèrent que le système de drainage sous-glaciaire subit tous les jours des renversements de gradient hydraulique entre ses chenaux allant de pair avec un flux d'eau transversal. Cette étude suggère que, en ce qui concerne les eaux de fonte du glacier Dokriani, le domaine sous-glaciaire est le principal fournisseur de sédiments. Les fortes intensités des pluies de mousson entraînent toutefois une contribution de sédiments du domaine supra-glaciaire et sont à l'origine de distributions bimodales. Les matières en suspension sont surtout constituées de fines (argiles à silts moyens) sauf au printemps et les sédiments supra-glaciaires sont distribués de façon très asymétrique.

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 melt water contributes to the river flow during the period of annual high flows produced by the monsoon. Other two major glacio-hydrological regimes of the Himalaya are winter snow dominated Alpine catchments of the Kashmir and Karakoram region and cold-arid regions of the Ladakh mountain range. 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. Discharge data generated from three hydrometric stations established at different altitudes of the Din Gad stream during the summer ablation period of 1998, 1999, 2000, 2001, 2003 and 2004. These data has been analysed along with winter/summer precipitation, temperature and mass balance data of the Dokriani glacier to study the role of the glacier and precipitation in determining the runoff variations along the stream continuum from the glacier snout to 2360 m a.s.l. Study shows that the inter-annual runoff variations in a ''Himalayan glacier catchment'' is directly linked with the precipitation rather than mass balance changes of the glacier. Study suggest that warming induced initial increase of glacier degraded runoff and subsequent decline is a glaciers mass balance response and cannot be translated as river flow response in a ''Himalayan catchment'' as suggested by the IPCC, 2007. Study also suggest that the glacier runoff critically influence the headwater river flows during the years of low summer discharge and proposes that the Himalayan catchment could experience higher river flows and positive glacier mass balance regime together in association with strong monsoon. This paper intended to highlight the importance of creating credible knowledge on the Himalayan cryospheric processes to develop a global outlook on river flow response to cryospheric change and locally sustainable water resources management strategies.