On the testing of fully integrated surface–subsurface hydrological models

Abstract

Studies employing integrated surface-subsurface hydrological models (ISSHMs) have utilized a variety of test cases to demonstrate model accuracy and consistency between codes. Here, we review the current state of ISSHM testing and evaluate the most popular ISSHM test cases by comparing the hydrodynamic processes simulated in each case to the processes found in well-characterized, real-world catchments and by comparing their general attributes to those of successful benchmark problems from other fields of hydrogeology. The review reveals that (1) ISSHM testing and intercode comparison have not adopted specific test cases consistently; (2) despite the wide range of ISSHM metrics available for model testing, only two model performance diagnostics are typically adopted: the catchment outflow hydrograph and the catchment water balance; (3) in intercode comparisons, model performance is usually judged by evaluating only one performance diagnostic: the catchment outflow hydrograph; and (4) ISSHM test cases evaluate a small number of hydrodynamic processes that are largely uniform across the model domain, representing a limited selection of the processes of interest in well-characterized, real-world catchments. ISSHM testing would benefit from more intercode comparisons using a consistent set of test cases, aimed at evaluating more catchment processes (e.g. flooding) and using a wider range of simulation diagnostics (e.g. pressure head distributions). To achieve this, a suite of test case variations is required to capture the relevant catchment processes. Finally, there is a need for additional ISSHM test problems that compare model predictions with hydrological observations from intensively monitored field sites and controlled laboratory experiments.

Groundwater and Surface Water Interaction at the Regional-scale – A Review with Focus on Regional Integrated Models

“…Gaukroger and Werner 2011;Jolly and Rassam 2009;Rossman and Zlotnik 2013;Sebben et al 2013). "Integrated modelling^often has a much wider focus than GW-SW.…”

“…Overviews describing different coupling strategies are provided by Barthel et al (2008a), Ebel et al (2009), Furman (2008, Kollet and Maxwell (2006), Markstrom et al (2008), Levy and Xu (2012), Rossman and Zlotnik (2013), Sebben et al (2013), and Spanoudaki et al (2009).…”

“…The software packages mentioned most often in the literature include ParFlow (Kollet and Maxwell 2006), HydroGeoSphere (Therrien et al 2009), InHM (VanderKwaak 1999, and OpenGeoSys ). More examples are described in Sebben et al (2013), Shi et al (2013), Partington et al (2013), Maxwell et al (2014) and Bronstert et al (2005). These fully coupled schemes have in common the attempt to achieve a physics-based description of all processes involved in the saturated zone, unsaturated zone and surface waters and thus generally avoid implementing interfaces between separate model modules (e.g.…”

“…Maxwell et al (2014) report comparisons of larger and more complex cases. The performance of different fully coupled software packages was also investigated by Sebben et al (2013). They found that a lack of test cases and limited options for evaluating model performance (mainly river discharge only) hinder a meaningful comparison.…”

“…They found that a lack of test cases and limited options for evaluating model performance (mainly river discharge only) hinder a meaningful comparison. It is common to use only river discharge (and not groundwater heads) to evaluate model performance of integrated models (Hattermann et al 2004;Sebben et al 2013). Table 1 shows an overview of fully coupled models and their application to catchments within the range defined as regional in this article.…”