Abstract
Abstract. Hydrological models are being applied for impact assessment across a wide range of resolutions. In this study, we quantify the effect of model resolution on the simulated hydrological response in five mesoscale basins in the Swiss Alps using the distributed hydrological model Spatial Processes in Hydrology (SPHY). We introduce a new metric to compare a range of values resulting from a distributed model with a single value: the density-weighted distance (DWD). Model simulations are performed at two different spatial resolutions, matching common practices in hydrology: 500 m × 500 m matching regional-scale models, and 40 km × 40 km matching global-scale modeling. We investigate both the intra-basin response in seasonal streamflow and evapotranspiration from the high-resolution model and the difference induced by the two different spatial resolutions, with a focus on four seasonal extremes, selected based on temperature and precipitation. Results from the high-resolution model show that the intra-basin response covers a surprisingly large range of anomalies and show that it is not uncommon to have both extreme positive and negative flux anomalies occurring simultaneously within a catchment. The intra-basin response was grouped by land cover, where different dominant runoff-generating processes are driving the differences between these groups. The low-resolution model failed to capture the diverse and contrasting response from the high-resolution model, since neither the complex topography nor land cover classes were properly represented. DWD values show that, locally, the 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 or continental scale assessments carried out at coarse grids of 0.5∘×0.5∘ or 0.25∘×0.25∘ resolution.
Highlights
In current distributed hydrological modeling, we identify two approaches at opposite ends of the scale of application
Our study presents a new metric to quantify the difference between a range of values with a single value: the density-weighted distance (DWD)
We investigated the hydrological response anomalies in five catchments in the Swiss Alps at two different spatial resolutions
Summary
In current distributed hydrological modeling, we identify two approaches at opposite ends of the scale of application. Most global studies are run at rather coarse spatial resolutions (often at 0.5◦ × 0.5◦) to investigate trends in the terrestrial water cycle as result of recent and projected changes in climate conditions (e.g., Luterbacher et al, 2004; Sánchez et al, 2004; Barnett et al, 2005; Beniston et al, 2007; Sheffield and Wood, 2008; Adam et al, 2009; Sheffield et al, 2012; Van Huijgevoort et al, 2014; Jacob et al, 2014) These studies often rely on standardized values such as the standardized precipitation index (SPI) or standardized runoff index (SRI) in order to quantify differences between different climatic regions across the globe. Even when global modeling at hyperresolution becomes state of the art, the question remains as to how we should deal with simulations at these fine spatial scales, since the models pa-
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