The importance of internal validation in the assessment of physically based distributed models

As the use of physically based distributed models for solving environmental problems becomes more widespread it is important that we are satisfied with the manner in which they represent the processes operating within the modelled system. This paper seeks, with reference to three examples drawn from physical hydrology, to assess the utility of model internal validation to improve the analysis of distributed model behaviour. Obtaining a correct representation of physical process is particularly important in hydrology if the water movements simulated within a catchment will subsequently be used to drive simulations of solute and sediment transfers. We review current knowledge concerning catchment runoff processes to illustrate the range of physical mechanisms which physically based models may need to include. Examples of model applications of the SHE (Systhme Hydrologique Europben), the VSAS (Variable Source Area Simulator) and the RMA-2 models are then used to demonstrate the use of 'intemrnal' validation approaches to identify the extent to which model simulations can correspond to physical reality. It is argued that validation using measurements of internal model output values should form an essential part of any model evaluation scheme.

[1]  J. Hewlett.  Factors affecting the response of small watersheds to precipitation in humid areas , 1967 .

[2]  M. H. Diskin,et al.  A procedure for the selection of objective functions for hydrologic simulation models , 1977 .

[3]  M. Sklash,et al.  The Role Of Groundwater In Storm Runoff , 1979 .

[4]  K. Beven,et al.  A physically based, variable contributing area model of basin hydrology , 1979 .

[5]  P. Kneale,et al.  The influence of low-angled topography on hillslope soil-water convergence and stream discharge , 1982 .

[6]  S. Sorooshian,et al.  Automatic calibration of conceptual rainfall-runoff models: The question of parameter observability and uniqueness , 1983 .

[7]  D. Hughes.  An isolated event model based upon direct runoff calculations using an implicit source area concept , 1984 .

[8]  R. Gillham.  The capillary fringe and its effect on water-table response , 1984 .

[9]  P. Bernier.  Variable source areas and storm-flow generation: An update of the concept and a simulation effort , 1985 .

[10]  K. Beven,et al.  Shenandoah Watershed Study: Calibration of a Topography‐Based, Variable Contributing Area Hydrological Model to a Small Forested Catchment , 1985 .

[11]  P. Germann.  Rapid drainage response to precipitation , 1986 .

[12]  V. Klemeš,et al.  Operational Testing of Hydrological Simulation Models , 2022 .

[13]  D. R. Nielsen,et al.  Water flow and solute transport processes in the unsaturated zone , 1986 .

[14]  H. Rohdenburg,et al.  Deterministic hydrological site and catchment models for the analysis of agroecosystems , 1986 .

[15]  D. Stephenson,et al.  Criteria for comparison of single event models , 1986 .

[16]  A. Pearce,et al.  Storm runoff generation in humid headwater catchments 1 , 1986 .

[17]  Denis Isabel,et al.  Importance of the Convergence Criterion in the Automatic Calibration of Hydrological Models , 1986 .

[18]  Keith Beven,et al.  Changing ideas in hydrology — The case of physically-based models , 1989 .

[19]  J. A. V. D. Berg.  Measurements of hydraulic conductivity of silt loam soils using an infiltration method , 1989 .

[20]  K. Beven,et al.  A physically based model of heterogeneous hillslopes: 2. Effective hydraulic conductivities , 1989 .

[21]  M. Anderson,et al.  The application of a simple lumped river flow forecasting model to hillslope soil water storage estimation. , 1990 .

[22]  M. Bonell,et al.  The identification of runoff‐production mechanisms using environmental isotopes in a tussock grassland catchment, eastern otago, New Zealand , 1990 .

[23]  M. Anderson,et al.  Large‐scale floodplain modelling , 1990 .

[24]  K. Beven,et al.  Throughflow and solute transport in an isolated sloping soil block in a forested catchment , 1991 .

[25]  J. Nieber,et al.  Soil pipe contribution to steady subsurface stormflow , 1991 .

[26]  P. Bates,et al.  Modelling floodplain flows using a two-dimensional finite element model , 1992 .

[27]  J.-P. Jordan.  Spatial and temporal variability of stormflow generation processes on a Swiss catchment , 1994 .