Rainfall and snowmelt contributions to discharge of the Ganges - A multi-model approach

The Himalayas supply large quantities of water to the major rivers of Asia, providing water resources to large populations in those basins. Timing and amount of water availability downstream depend on storage and melting of snow and ice in Himalayan headwaters and on summer monsoonal precipitation.

Quantitative determination of glacier ice and snowmelt proportions of runoff is highly uncertain. The magnitude of this contribution varies seasonally and inter-annually at a station, and with distance downstream. Most previous studies of snow and ice processes focus on highly glacierized tributary headwater mountain catchments. Few catchment-wide assessments of snow and glacier melt components of runoff are available.

In the HighNoon project, four hydrological models (VIC, JULES, LPJmL and SWAT) were used to provide estimates of the melt water contribution within the whole Ganges basin.

Contributions of snow and glacier melt along the Ganges and its tributaries are estimated at maximum 10% annual and 38% for the months of March – April – May, during which snow- and glaciermelt is at its peak and rainfall is largely absent. Analyses of the contribution of snow- and glaciermelt to runoff are important for assessing the impact of future climate change on water resources in the Ganges basin.