Streamflow Modeling in a Highly Managed Mountainous Glacier Watershed Using SWAT: The Upper Rhone River Watershed Case in Switzerland

Abstract

Streamflow simulation is often challenging in mountainous watersheds because of irregular topography and complex hydrological processes. Rates of change in precipitation and temperature with respect to elevation often limit the ability to reproduce stream runoff by hydrological models. Anthropogenic influence, such as water transfers in high altitude hydro- power reservoirs increases the difficulty in modeling since the natural flow regime is altered by long term storage of water in the reservoirs. The Soil and Water Assessment Tool (SWAT) was used for simulating streamflow in the upper Rhone watershed located in the south western part of Switzerland. The catchment area covers 5220 km 2 , where most of the land cover is dominated by forest and 14 % is glacier. Streamflow calibration was done at daily time steps for theperiodof2001-2005,andvalidated for2006-2010.Twodifferent approaches wereused for simulating snow and glacier melt process, namely the temperature index approach with and without elevation bands. The hydropower network was implemented based on theintake points that form part of the inter-reservoir network. Subbasins were grouped into two major categories