How Meaningful are Plot‐Scale Observations and Simulations of Preferential Flow for Catchment Models?

Abstract

Core Ideas We tested a range of dual‐permeability parameterizations at plot and catchment scale. Well‐performing parameters at plot scale did not clearly improve catchment simulation. Vertical preferential flow was important for simulating plot‐scale observations. At catchment scale, it appeared more important to consider fast lateral subsurface flow. This showed that different nonuniform flow processes are critical at different scales. Despite ubiquitous field observations of nonuniform flow processes, preferential flow paths are rarely considered in hydrological models, especially at catchment scale. In this study, we investigated the extent to which plot‐scale observations of preferential flow paths are informative for rainfall–runoff simulations at larger scales. We used data from three plot‐scale irrigation experiments in the Weierbach catchment (Luxembourg) to identify preferential flow parameterizations via a Monte Carlo simulation with HydroGeoSphere. Subsequently, we tested whether these parameter sets could be used directly to simulate the hydrological response of the Weierbach headwater with a HydroGeoSphere catchment model. The Monte Carlo simulations showed that the different depth profiles of Br− tracer observed in irrigation experiments could be reproduced when vertical preferential flow was simulated with a dual‐permeability approach. However, it was not possible to identify unique parameter values for preferential flow. The direct transfer of a range of different dual‐permeability parameter sets to the catchment model revealed that the variability of simulated hydrometric catchment responses (discharge and soil moisture over 18 mo) was independent of the variability among the three irrigation experiments. More importantly, the dual‐permeability approach did not improve the match between simulated and observed discharge and soil moisture responses compared with the single‐domain reference model, where multiple soil layers with differing hydraulic conductivities had already been implemented. This suggests that including structures that allow nonuniform lateral flow was more important for reproducing the hydrological response in the Weierbach catchment than the vertical preferential flow observed at plot scale.

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

“…The results of our study corroborate the findings of Glaser et al (). They showed that the transfer of dual‐permeability parameters from plot to catchment scale simulations did not improve discharge simulations and reasoned that vertical preferential flow does not seem to be of major relevance for catchment scale runoff generation in the Weierbach catchment.…”

“…We carried out this study in a headwater section (6 ha) of the Weierbach catchment, located in western Luxembourg, where Glaser, Jackisch, Hopp, and Klaus () and Glaser et al () recently modelled the hydrological response using the 3D physically based model HydroGeoSphere (Therrien, McLaren, Sudicky, & Panday, ). The model reproduced the observed hydrograph well, but missed some specific features of the hydrograph, for example, peaks directly after dry conditions and the rise and recession of second, delayed peaks that are typical for the hydrological response at this site during wet conditions (Martínez‐Carreras et al, ).…”

Multimodal water age distributions and the challenge of complex hydrological landscapes

“…The importance of preferential flow in soils for catchment‐scale TTDs may be difficult to evaluate. Glaser, Jackisch, Hopp, and Klaus (2019) showed in the Weierbach catchment (Luxembourg) that rainfall‐runoff simulations were not improved by modelling vertical preferential flow at the catchment scale, using the soil preferential flow parameters deduced from plot‐scale tracer breakthrough experiments. However, non‐uniform lateral flow (similar to lateral preferential flow) appeared to be an important mechanism for discharge generation in this catchment, and it could be implemented in the model by using a highly conductive horizontal soil layer (Glaser et al, 2019).…”

“…Glaser, Jackisch, Hopp, and Klaus (2019) showed in the Weierbach catchment (Luxembourg) that rainfall‐runoff simulations were not improved by modelling vertical preferential flow at the catchment scale, using the soil preferential flow parameters deduced from plot‐scale tracer breakthrough experiments. However, non‐uniform lateral flow (similar to lateral preferential flow) appeared to be an important mechanism for discharge generation in this catchment, and it could be implemented in the model by using a highly conductive horizontal soil layer (Glaser et al, 2019). Different conclusions regarding preferential flow were found by van Schaik et al (2014), who highlighted its non‐negligible role for runoff simulations during extreme rainfall events in a semi‐arid catchment in Spain.…”

Testing the truncation of travel times with StorAge Selection functions using deuterium and tritium as tracers

“…This study is carried out in the Weierbach catchment, which has been the focus of an increasing number of investigations in the last few years about streamflow generation (Glaser et al, 2016(Glaser et al, , 2019bScaini et al, 2017Scaini et al, , 2018Carrer et al, 2019;Rodriguez and Klaus, in review), biogeochemistry (Moragues-Quiroga et al, 2017;Schwab et al, 2018), and pedology and geology (Juilleret et al, 2011;Gourdol et al, 2018). https://doi.org/10.5194/hess-2019-501 Preprint.…”