Vignette d'image

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

Résultat de la recherche

Filtres

3
3
3
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 3 sur 3
  • Publication
    Accès libre
    Groundwater fluxes in a shallow seasonal wetland pond: The effect of bathymetric uncertainty on predicted water and solute balances
    (2014-5-18)
    Trigg, M. A.
    ;
    Cook, Peter G.
    ;
    Brunner, Philip 
    The successful management of groundwater dependent shallow seasonal wetlands requires a sound understanding of groundwater fluxes. However, such fluxes are hard to quantify. Water volume and solute mass balance models can be used in order to derive an estimate of groundwater fluxes within such systems. This approach is particularly attractive, as it can be undertaken using measurable environmental variables, such as; rainfall, evaporation, pond level and salinity. Groundwater fluxes estimated from such an approach are subject to uncertainty in the measured variables as well as in the process representation and in parameters within the model. However, the shallow nature of seasonal wetland ponds means water volume and surface area can change rapidly and non-linearly with depth, requiring an accurate representation of the wetland pond bathymetry. Unfortunately, detailed bathymetry is rarely available and simplifying assumptions regarding the bathymetry have to be made. However, the implications of these assumptions are typically not quantified. We systematically quantify the uncertainty implications for eight different representations of wetland bathymetry for a shallow seasonal wetland pond in South Australia. The predictive uncertainty estimation methods provided in the Model-Independent Parameter Estimation and Uncertainty Analysis software (PEST) are used to quantify the effect of bathymetric uncertainty on the modelled fluxes. We demonstrate that bathymetry can be successfully represented within the model in a simple parametric form using a cubic Sexier curve, allowing an assessment of bathymetric uncertainty due to measurement error and survey detail on the derived groundwater fluxes compared with the fixed bathymetry models. Findings show that different bathymetry conceptualisations can result in very different mass balance components and hence process conceptualisations, despite equally good fits to observed data, potentially leading to poor management decisions for the wetlands. Model predictive uncertainty increases with the crudity of the bathymetry representation, however, approximations that capture the general shape of the wetland pond such as a power law or Bezier curve show only a small increase in prediction uncertainty compared to the full dGPS surveyed bathymetry, implying these may be sufficient for most modelling purposes. (C) 2014 Elsevier B.V. All rights reserved.
  • Publication
    Accès libre
    Evaluation of outputs from automated baseflow separation methods against simulated baseflow from a physically based, surface water-groundwater flow model
    (2012-5-18)
    Joseph Partington, Daniel 
    ;
    Brunner, Philip 
    ;
    Simmons, Craig Trevor
    ;
    Werner, A. D.
    ;
    Therrien, René
    ;
    Maier, Holger Robert
    ;
    Dandy, Graeme Clyde
    Baseflow is often considered to be the groundwater discharge component of streamflow. It is commonly estimated using conceptual models, recursive filters or a combination of the two. However, it is difficult to validate these methods due to the current challenges of measuring baseflow in the field. In this study, simulation of a synthetic catchment's response to rainfall is carried out using a fully integrated surface water-groundwater flow model. A series of rainfall events with differing recovery periods and varied antecedent moisture conditions is considered to span a range of different streamflow generation dynamics. Baseflow is estimated for the outlet hydrograph of the synthetic catchment using a selection of commonly used automated baseflow separation methods. These estimates are compared to the baseflow signal obtained from the numerical model, which serves as the control experiment. Results from these comparisons show that depending on the method used, automated baseflow separation underestimates the simulated baseflow by as much as 28%, or overestimates it by up to 74%, during rainfall events. No separation method is found to be clearly superior to the others, as the performance of the various methods varies with different soil types, antecedent moisture conditions and rainfall events. The differences between the various approaches clearly demonstrate that the baseflow separation methods investigated are not universally applicable. (c) 2012 Elsevier B.V. All rights reserved.
  • Publication
    Accès libre
    Groundwater inflow to a shallow, poorly-mixed wetland estimated from a mass balance of radon
    (2008-5-26)
    Cook, Peter G.
    ;
    Wood, Cameron
    ;
    White, Troy
    ;
    Simmons, Craig Trevor
    ;
    Fass, T.
    ;
    Brunner, Philip 
    Radon activity within a shallow wetland in southern Australia has been measured on three occasions between May and October 2006. Measured activities within the surface water display a similar pattern of spatial variability on each occasion, suggesting that it is related to the locations of groundwater inflow and mixing processes. The mean groundwater inflow rate has been estimated from the mean radon activity using a mass balance approach. The components of the radon budget are (i) contribution from groundwater inflow, (ii) diffusive flux from wetland bottom sediments (iii) loss due to gas exchange, (iv) loss due to radioactive decay, (v) toss due to groundwater or surface water outflow. Also required to complete the water balance are the surface water inflow rate, direct precipitation on the wetland, and evaporation rate. The radon diffusive flux has been estimated from measurements of radon production within the sediments and a diffusive transport model., calibrated by measurements of radon activity in seated chambers that can receive radon only from diffusion and lose it only by radioactive decay. Radon loss due to gas exchange is inferred from the loss rate of SF6, following its injection into isolated areas of the wetland, while the rate of radioactive decay is known. The radon activity in groundwater inflow is measured from sampling piezometers surrounding the wetland. Steady state and transient mass balance approaches yield similar results, with groundwater inflow rates varying between 12 and 18 m(3)/day. Estimated groundwater inflow rates are most sensitive to the radon activity of groundwater inflow, the gas exchange velocity, surface water area and the accuracy with which the mean radon activity in the wetland can be, measured. Importantly, it is relatively insensitive to the surface water inflow rate, which is poorly known. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.