Abstract
Abstract. The transfer of parameter sets over different temporal and spatial resolutions is common practice in many large-domain hydrological modelling studies. The degree to which parameters are transferable across temporal and spatial resolutions is an indicator of how well spatial and temporal variability is represented in the models. A large degree of transferability may well indicate a poor representation of such variability in the employed models. To investigate parameter transferability over resolution in time and space we have set up a study in which the Variable Infiltration Capacity (VIC) model for the Thur basin in Switzerland was run with four different spatial resolutions (1 km × 1 km, 5 km × 5 km, 10 km × 10 km, lumped) and evaluated for three relevant temporal resolutions (hour, day, month), both applied with uniform and distributed forcing. The model was run 3150 times using the Hierarchical Latin Hypercube Sample and the best 1 % of the runs was selected as behavioural. The overlap in behavioural sets for different spatial and temporal resolutions was used as an indicator of parameter transferability. A key result from this study is that the overlap in parameter sets for different spatial resolutions was much larger than for different temporal resolutions, also when the forcing was applied in a distributed fashion. This result suggests that it is easier to transfer parameters across different spatial resolutions than across different temporal resolutions. However, the result also indicates a substantial underestimation in the spatial variability represented in the hydrological simulations, suggesting that the high spatial transferability may occur because the current generation of large-domain models has an inadequate representation of spatial variability and hydrologic connectivity. The results presented in this paper provide a strong motivation to further investigate and substantially improve the representation of spatial and temporal variability in large-domain hydrological models.
Highlights
The history of modern hydrological modelling dates back to halfway through the nineteenth century, starting with empirical models to predict peak flows (Todini, 2007)
The results of our study provide an indication of the current status of spatial and temporal representation in the Variable Infiltration Capacity (VIC) model, being representative of a larger group of land-surface models
The impact of temporal and spatial resolution on model performance is discussed for both uniform and distributed forcing, followed by a discussion of the impact of the temporal and spatial resolution on parameter distribution
Summary
The history of modern hydrological modelling dates back to halfway through the nineteenth century, starting with empirical models to predict peak flows (Todini, 2007). Hydrological models were developed only at the catchment scale, evolving from empirically based to more physically based. Computational power and increased data availability have driven the development of increasingly complex and distributed hydrological models (Boyle et al., 2001; Liu and Gupta, 2007). Distributed hydrological models can incorporate spatially varying parameters, including those reflecting land use and soil characteristics (Carpenter and Georgakakos, 2006), and spatially variable forcing. In 1989 the first global hydrological model (GHM) was presented (Vörösmarty et al, 1989; Sood and Smakhtin, 2015). Continuing improvements in computational power and data availability provide new opportunities for GHMs, for example expressed in the recent ambition to develop global models with a resolution of the order of ∼ 1 km and higher, the socalled hyper-resolution (Wood et al, 2011; Bierkens et al., 2014; Bierkens, 2015)
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