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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
    When Can Inverted Water Tables Occur Beneath Streams?
    (2014-5-18)
    Xie, Y. Q.
    ;
    Cook, Peter G.
    ;
    Brunner, Philip 
    ;
    Irvine, Dylan J.
    ;
    Simmons, Craig Trevor
    Decline in regional water tables (RWT) can cause losing streams to disconnect from underlying aquifers. When this occurs, an inverted water table (IWT) will develop beneath the stream, and an unsaturated zone will be present between the IWT and the RWT. The IWT marks the base of the saturated zone beneath the stream. Although a few prior studies have suggested the likelihood of an IWT without a clogging layer, most of them have assumed that a low-permeability streambed is required to reduce infiltration from surface water to groundwater, and that the IWT only occurs at the bottom of the low-permeability layer. In this study, we use numerical simulations to show that the development of an IWT beneath an unclogged stream is theoretically possible under steady-state conditions. For a stream width of 1m above a homogeneous and isotropic sand aquifer with a 47m deep RWT (measured in an observation point 20m away from the center of the stream), an IWT will occur provided that the stream depth is less than a critical value of 4.1m. This critical stream depth is the maximum water depth in the stream to maintain the occurrence of an IWT. The critical stream depth decreases with stream width. For a stream width of 6 m, the critical stream depth is only 1mm. Thus while theoretically possible, an IWT is unlikely to occur at steady state without a clogging layer, unless a stream is very narrow or shallow and the RWT is very deep.
  • 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.