Elements of a flexible approach for conceptual hydrological modeling: 2. Application and experimental insights

Abstract

[1] In this article's companion paper, flexible approaches for conceptual hydrological modeling at the catchment scale were motivated, and the SUPERFLEX framework, based on generic model components, was introduced. In this article, the SUPERFLEX framework and the ''fixed structure'' GR4H model (an hourly version of the popular GR4J model) are applied to four hydrologically distinct experimental catchments in Europe and New Zealand. The estimated models are scrutinized using several diagnostic measures, ranging from statistical metrics, such as the statistical reliability and precision of the predictive distribution of streamflow, to more process-oriented diagnostics based on flow-duration curves and the correspondence between model states and groundwater piezometers. Model performance was clearly catchment specific, with a single fixed structure unable to accommodate intercatchment differences in hydrological behavior, including seasonality and thresholds. This highlights an important limitation of any ''fixed'' model structure. In the experimental catchments, the ability of competing model hypotheses to reproduce hydrological signatures of interest could be interpreted on the basis of independent fieldwork insights. The potential of flexible frameworks such as SUPERFLEX is then examined with respect to systematic and stringent hypothesis-testing in hydrological modeling, for characterizing catchment diversity, and, more generally, for aiding progress toward a more unified formulation of hydrological theory at the catchment scale. When interpreted in physical process-oriented terms, the flexible approach can also serve as a language for dialogue between modeler and experimentalist, facilitating the understanding, representation, and interpretation of catchment behavior.

Development of a large-sample watershed-scale hydrometeorological data set for the contiguous USA: data set characteristics and assessment of regional variability in hydrologic model performance

“…5c). This indicates that RMSE as an objective function may not be well suited for model calibration in basins with high flow autocorrelation (Kavetski and Fenicia, 2011;Evin et al, 2014). This is confirmed by comparing Fig.…”

“…Arid basins typically have few high flow events, which are generally subject to larger errors when minimizing the RMSE. Using advanced calibration methodologies that account for heteroscedasticity (Kavetski and Fenicia, 2011;Evin et al, 2014) may produce improved calibrations for arid basins in this basin set and provide different insights into model behavior using this type of analysis.…”

What can flux tracking teach us about water age distribution patterns and their temporal dynamics?

“…Further, plants require Cl − and thus take up Cl − stored in the root zone at varying rates (e.g. Kauffman et al, 2003;Lovett et al, 2005;Van der Velde et al, 2010). Here these combined imbalances in catchment Cl − budgets were accounted for by rescaling the input concentrations using lumped adjustment factors as successfully applied in earlier studies (e.g.…”

Impact of model structure on flow simulation and hydrological realism: from a lumped to a semi-distributed approach

“…More specifically, we investigate the relative importance of model equations and spatial discretization on flow simulation, snowpack representation and evapotranspiration estimation. This correspondence between model and "reality", often described as "working for the right reasons" (Kirchner, 2006;Kavetski and Fenicia, 2011;Euser et al, 2013), is essential if the model is to be used as a tool for improving the understanding of a hydrological system and/or used for prediction and extrapolation, such as simulating the impacts of land use change, variability in climatological forcing, etc.…”