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Brunner, Philip

Nom
Brunner, Philip
Affiliation principale
Fonction
Professeur ordinaire
Email
philip.brunner@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/165
_
0000-0001-6304-6274

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  • Publication
    Accès libre
    Uncertainty assessment and implications for data acquisition in support of integrated hydrologic models
    Brunner, Philip 
    ;
    Doherty, J
    ;
    Simmons, Craig T
    The data set used for calibration of regional numerical models which simulate groundwater flow and vadose zone processes is often dominated by head observations. It is to be expected therefore, that parameters describing vadose zone processes are poorly constrained. A number of studies on small spatial scales explored how additional data types used in calibration constrain vadose zone parameters or reduce predictive uncertainty. However, available studies focused on subsets of observation types and did not jointly account for different measurement accuracies or different hydrologic conditions. In this study, parameter identifiability and predictive uncertainty are quantified in simulation of a 1-D vadose zone soil system driven by infiltration, evaporation and transpiration. The worth of different types of observation data (employed individually, in combination, and with different measurement accuracies) is evaluated by using a linear methodology and a nonlinear Pareto-based methodology under different hydrological conditions. Our main conclusions are (1) Linear analysis provides valuable information on comparative parameter and predictive uncertainty reduction accrued through acquisition of different data types. Its use can be supplemented by nonlinear methods. (2) Measurements of water table elevation can support future water table predictions, even if such measurements inform the individual parameters of vadose zone models to only a small degree. (3) The benefits of including ET and soil moisture observations in the calibration data set are heavily dependent on depth to groundwater. (4) Measurements of groundwater levels, measurements of vadose ET or soil moisture poorly constrain regional groundwater system forcing functions.
  • Publication
    Accès libre
    Using tree ring data as a proxy for transpiration to reduce predictive uncertainty of a model simulating groundwater–surface water–vegetation interactions
    Schilling, O. S
    ;
    Doherty, J
    ;
    Kinzelbach, W
    ;
    Wang, H
    ;
    Yang, P. N
    ;
    Brunner, Philip 
    Summary The interactions between surface water, the vadose zone, groundwater, and vegetation are governed by complex feedback mechanisms. Numerical models simulating these interactions are essential in quantifying these processes. However, the notorious lack of field observations results in highly uncertain parameterizations. We suggest a new type of observation data to be included in the calibration data set for hydrological models simulating interactions with vegetation: Tree rings as a proxy for transpiration. We use the lower Tarim River as an example site for our approach. In order to forestall the loss of riparian ecosystems from reduced flow over a 300 km reach of the lower Tarim River, the Chinese government initiated periodical, ecological water releases. The water exchange processes in this region were simulated for a cross-section on the lower reaches of the Tarim River using a numerical model (Hydro-GeoSphere) calibrated against observations of water tables, as well as transpiration estimated from tree ring growth. A predictive uncertainty analysis quantifying the worth of different components of the observation dataset in reducing the uncertainty of model predictions was carried out. The flow of information from elements of the calibration dataset to the different parameters employed by the model was also evaluated. The flow of information and the uncertainty analysis demonstrate that tree ring records can significantly improve confidence in modeling ecosystem dynamics, even if these transpiration estimates are uncertain. To use the full potential of the historical information encapsulated in the Tarim River tree rings, however, the relationship between tree ring growth and transpiration rates has to be studied further.