Hydrological response to climate extremes in mesoscale (pre-)Alpine basins at 0.5° and hyperresolution

Abstract. The response of key hydrological variables to climate extremes within five meso-scale basins in the Swiss Alps is investigated at two different resolutions using the distributed hydrological model Spatial Processes in Hydrology (SPHY). Based on elevation and presence of glaciers, three catchments are identified as Alpine and two as pre-Alpine. We run SPHY both at hyperresolution and at 0.5 × 0.5 degree, and aggregate simulated runoff and evapotranspiration per season. For four seasonal extremes representing flood and drought/heatwave conditions we investigate the simulated response at both model resolutions. Results from the high resolution model show that the within-basin response gets more complex with more extreme events. The response within each basin can be grouped per land use type, due to different dominant runoff generating processes. A comparison with the coarse resolution model results shows that there is a large discrepancy between the two simulated responses. The low resolution model is not able to correctly simulate the complex hydrological response as simulated with the distributed model, since both the complex topography and land use classes are not properly represented. We show that hydrological response simulated with a high resolution model can be a lot more extreme than a low resolution model might indicate, which has important implications for global assessments carried out at course resolution.