23 research outputs found
Applied tracers for the observation of subsurface stormflow at the hillslope scale
Rainfall-runoff response in temperate humid headwater catchments is mainly controlled by hydrological processes at the hillslope scale. Applied tracer experiments with fluorescent dye and salt tracers are well known tools in groundwater studies at the large scale and vadose zone studies at the plot scale, where they provide a means to characterise subsurface flow. We extend this approach to the hillslope scale to investigate saturated and unsaturated flow paths concertedly at a forested hillslope in the Austrian Alps. Dye staining experiments at the plot scale revealed that cracks and soil pipes function as preferential flow paths in the fine-textured soils of the study area, and these preferential flow structures were active in fast subsurface transport of tracers at the hillslope scale. Breakthrough curves obtained under steady flow conditions could be fitted well to a one-dimensional convection-dispersion model. Under natural rainfall a positive correlation of tracer concentrations to the transient flows was observed. The results of this study demonstrate qualitative and quantitative effects of preferential flow features on subsurface stormflow in a temperate humid headwater catchment. It turns out that, at the hillslope scale, the interactions of structures and processes are intrinsically complex, which implies that attempts to model such a hillslope satisfactorily require detailed investigations of effective structures and parameters at the scale of interest
Morphological controls on surface runoff: an interpretation of steady-state energy patterns, maximum power states and dissipation regimes within a thermodynamic framework
Picturing and modeling catchments by representative hillslopes
This study explores the suitability of a single hillslope as a parsimonious representation of a catchment in a physically based model. We test this hypothesis by picturing two distinctly different catchments in perceptual models and translating these pictures into parametric setups of 2-D physically based hillslope models. The model parametrizations are based on a comprehensive field data set, expert knowledge and process-based reasoning. Evaluation against streamflow data highlights that both models predicted the annual pattern of streamflow generation as well as the hydrographs acceptably. However, a look beyond performance measures revealed deficiencies in streamflow simulations during the summer season and during individual rainfall–runoff events as well as a mismatch between observed and simulated soil water dynamics. Some of these shortcomings can be related to our perception of the systems and to the chosen hydrological model, while others point to limitations of the representative hillslope concept itself. Nevertheless, our results confirm that representative hillslope models are a suitable tool to assess the importance of different data sources as well as to challenge our perception of the dominant hydrological processes we want to represent therein. Consequently, these models are a promising step forward in the search for the optimal representation of catchments in physically based models
Picturing and modeling catchments by representative hillslopes
This study explores the suitability of a single hillslope as a parsimonious
representation of a catchment in a physically based model. We test this
hypothesis by picturing two distinctly different catchments in perceptual
models and translating these pictures into parametric setups of 2-D
physically based hillslope models. The model parametrizations are based on a
comprehensive field data set, expert knowledge and process-based reasoning.
Evaluation against streamflow data highlights that both models predicted the
annual pattern of streamflow generation as well as the hydrographs
acceptably. However, a look beyond performance measures revealed deficiencies
in streamflow simulations during the summer season and during individual
rainfall–runoff events as well as a mismatch between observed and simulated soil water dynamics. Some of these shortcomings can be related to our
perception of the systems and to the chosen hydrological model, while others
point to limitations of the representative hillslope concept itself.
Nevertheless, our results confirm that representative hillslope models are a
suitable tool to assess the importance of different data sources as well as
to challenge our perception of the dominant hydrological processes we want to
represent therein. Consequently, these models are a promising step forward in
the search for the optimal representation of catchments in physically based
models
Where should hydrology go? An early-career perspective on the next IAHS Scientific Decade: 2023–2032
Regional analysis of parameter sensitivity for simulation of streamflow and hydrological fingerprints
Diagnostics of hydrological models are pivotal for a better understanding of
catchment functioning, and the analysis of dominating model parameters plays
a key role for region-specific calibration or parameter transfer. A major
challenge in the analysis of parameter sensitivity is the assessment of both
temporal and spatial differences of parameter influences on simulated
streamflow response. We present a methodological approach for global
sensitivity analysis of hydrological models. The multilevel approach is
geared towards complementary forms of streamflow response targets, and
combines sensitivity analysis directed to hydrological fingerprints, i.e.
temporally independent and temporally aggregated characteristics of
streamflow (INDPAS), with the conventional analysis of the temporal dynamics
of parameter sensitivity (TEDPAS).The approach was tested in 14 mesoscale headwater catchments of the
Ruhr River in western Germany using simulations with the spatially distributed
hydrological model mHM. The multilevel analysis with diverse response
characteristics allowed us to pinpoint parameter sensitivity patterns much more
clearly as compared to using TEDPAS alone. It was not only possible to
identify two dominating parameters, for soil moisture dynamics and
evapotranspiration, but we could also disentangle the role of these and other
parameters with reference to different streamflow characteristics. The
combination of TEDPAS and INDPAS further allowed us to detect regional
differences in parameter sensitivity and in simulated hydrological
functioning, despite the rather small differences in the hydroclimatic and
topographic setting of the Ruhr headwaters
Picturing and modeling catchments by representative hillslopes
This study explores the suitability of a single hillslope as a parsimonious
representation of a catchment in a physically based model. We test this
hypothesis by picturing two distinctly different catchments in perceptual
models and translating these pictures into parametric setups of 2-D
physically based hillslope models. The model parametrizations are based on a
comprehensive field data set, expert knowledge and process-based reasoning.
Evaluation against streamflow data highlights that both models predicted the
annual pattern of streamflow generation as well as the hydrographs
acceptably. However, a look beyond performance measures revealed deficiencies
in streamflow simulations during the summer season and during individual
rainfall–runoff events as well as a mismatch between observed and simulated soil water dynamics. Some of these shortcomings can be related to our
perception of the systems and to the chosen hydrological model, while others
point to limitations of the representative hillslope concept itself.
Nevertheless, our results confirm that representative hillslope models are a
suitable tool to assess the importance of different data sources as well as
to challenge our perception of the dominant hydrological processes we want to
represent therein. Consequently, these models are a promising step forward in
the search for the optimal representation of catchments in physically based
models