Comparing global and local calibration schemes from a differential split-sample test perspective

Abstract

This work explores the performances of the hydrologic model Hydrotel, applied to 36 catchments located in the Province of Quebec, Canada. A local calibration (each catchment taken individually) scheme and a global calibration (a single parameter set sought for all catchments) scheme are compared in a differential split-sample test perspective. Such a methodology is useful to gain insights on a model’s skills under different climatic conditions, in view of its use for climate change impact studies. The model was calibrated using both schemes on five non-continuous dry and cold years and then evaluated on five dissimilar humid and warm years. Results indicate that, as expected, local calibration leads to better performances than the global one. However, global calibration achieves satisfactory simulations while producing a better temporal robustness (i.e., model transposability to periods with different climatic conditions). Global calibration, in opposition to local calibration, thus imposes spatial consistency to the calibrated parameter values, while locally adjusted parameter sets can significantly vary from one catchment to another due to equifinality. It is hence stated that a global calibration scheme represents a good trade-off between local performance, temporal robustness, and the spatial consistency of parameter values, which is, for example, of interest in the context of ungauged catchments’ simulation, climate change impact studies, or even simply large-scale modeling.

A hydrological prediction system based on the SVS land-surface scheme: efficient calibration of GEM-Hydro for streamflow simulation over the Lake Ontario basin

“…The potential benefits of global calibration have been demonstrated here, as for a previous Hydrotel application (Gaborit et al, 2015). It achieves satisfactory performances for a large area with a unique calibration and favors temporal robustness, spatial consistency and parameter transferability.…”

“…Sensitivity tests (Gaborit et al, 2016) revealed that 2 and 10 arcmin resolutions for SVS lead to quite similar performance in terms of streamflow at the outlet, while a substantial amount of computation time is saved when running the coarser resolution (see Fig. 1).…”

“…GEM-Hydro is very similar to MESH, but is tied to the LSSs available in GEM: ISBA and SVS. A previous study on the same basin demonstrated the clear superiority of SVS over ISBA, especially in regard to the baseflow component of the streamflow (see Gaborit et al, 2016). We thus only use SVS with GEM-Hydro in this paper.…”

“…The global calibration of GEM-Hydro-UH consists in finding a unique trade-off parameter set that allows for simultaneous improvement in performances for all subbasins (Ajami et al, 2004;Haghnegahdar et al, 2014;Gaborit et al, 2015), whereas local calibration consists in finding each subbasin's optimal parameter set. Local calibration logically leads to the optimal performances for a given subbasin, but global calibration may lead to temporal robustness (Gaborit et al, 2015) and spatial consistency of the parameter values, because they are either fixed or adjusted the same way over the whole area under study. Local calibration, on the other hand, because of equifinality and experiment imperfections (model processes, forcing data, observed flows, etc.…”

Simultaneous calibration of hydrological models in geographical space

“…Parajka et al (2007) indicate that the iterative regional calibration indeed reduced the uncertainty of most parameters. Regional calibration can result in a better temporal robustness than normal individual calibration (Gaborit et al, 2015) and it provides an effective approach in large-scale hydrological assessments (Ricard et al, 2012).…”