The relevance of preferential flow in catchment scale simulations: Calibrating a 3D dual‐permeability model using DREAM

• Published in: Hydrological processes Vol. 34; no. 5; pp. 1237 - 1254
• Main Authors: Hopp, Luisa, Glaser, Barbara, Klaus, Julian, Schramm, Thilo
• Format: Journal Article
• Language: English
• Published: Chichester Wiley Subscription Services, Inc 28.02.2020
• Subjects: Adaptive algorithms; Calibration; Catchment area; Catchment scale; Catchments; Computer applications; Computer simulation; Discharge; discharge simulation; Domains; dual‐permeability model; Evolutionary algorithms; Evolutionary computation; Field tests; Flow; Hydraulic properties; Hydraulics; HydroGeoSphere; Hydrologic models; Hydrology; model calibration; Optimization; optimization algorithm; Parameter identification; Parameters; Permeability; Physics; Preferential flow; Profiles; Ratios; Soil; Soil layers; Soil permeability; Soil properties; Soils; Three dimensional models; Tracers
• ISSN: 0885-6087; 1099-1085
• DOI: 10.1002/hyp.13672

The occurrence of preferential flow in the subsurface has often been shown in field experiments. However, preferential flow is rarely included in models simulating the hydrological response at the catchment scale. If it is considered, preferential flow parameters are typically determined at the plot scale and then transferred to larger‐scale simulations. Here, we successfully used the optimization algorithm DiffeRential Evolution Adaptive Metropolis (DREAM) to calibrate a 3D physics‐based dual‐permeability model directly at the catchment scale. In order to keep computational costs of the optimization routine at a reasonable level, we limited the number of parameters to be calibrated to the ones that had been shown before to be most influential for the simulation of discharge. We also calibrated parameters of the matrix domain and the macropore domain with a fixed parameter ratio between soil layers instead of calibrating every layer separately. These ratios reflected observed depth profiles of soil hydraulic properties at our study site. The dual‐permeability parameter sets identified during calibration were able to simulate observed discharge time series satisfactorily but did not outperform a calibrated single‐domain reference model scenario. Saturated hydraulic conductivities of the macropore domain were calibrated such that they became very similar to matrix saturated hydraulic conductivities, thereby effectively removing the effect of macropores. This suggests that the incorporation of vertical preferential flow as represented by the dual‐permeability approach was not relevant for reproducing the hydrometric response reasonably well in the studied catchment. We also tested the scale‐invariance of the calibrated dual‐permeability parameter sets by using the parameter sets performing best at catchment scale to simulate plot‐scale bromide depth profiles obtained from tracer irrigation experiments. This parameter transfer proved to be not successful, indicating that soil hydraulic parameters are scale‐variant, independent of the direction of parameter transfer. A 3D dual‐permeability model was successfully calibrated at the catchment scale, using the optimization algorithm DREAM. The calibration essentially removed the macropore domain, suggesting that vertical preferential flow was not relevant for simulating the hydrometric response at the catchment scale well.