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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
    Calibration of a groundwater model using pattern information from remote sensing data
    (2009-5-26)
    Li, H. T.
    ;
    Brunner, Philip 
    ;
    Kinzelbach, Wolfgang
    ;
    Li, W. P.
    ;
    Dong, X. G.
    Due to the chronic lack of verification data, hydrologic models are notoriously over-parameterized. If a large number of parameters are estimated, while few verification data are available, the calibrated model may have little predictive value. However, recent development in remote sensing (RS) techniques allows generation of spatially distributed data that can be used to construct and verify hydrological models. These additional data reduce the ambiguity of the calibration process and thus increase the predictive value of the model. An example for such remotely sensed data is the spatial distribution of phreatic evaporation. In this modeling approach, we use the spatial distribution of phreatic evaporation obtained by remote sensing images as verification data Compared to the usual limited amount of head data, the spatial distribution of evaporation data provides a complete areal coverage. However, the absolute values of the evaporation data are uncertain and therefore three ways of using the spatial distribution pattern of evaporation were tested and compared. The first way is to directly use the evaporation pattern defined in a relative manner by dividing the evaporation rate in a pixel by the total evaporation of a selected rectangular area of interest. Alternatively, the discrete fourier transform (DFT) or the discrete wavelet transform (DWT) are applied to the relative evaporation pattern in the space domain defined before. Seven different combinations of using hydraulic head data and/or evaporation pattern data as conditioning information have been tested. The code PEST, based on the least-squares method, was used as an automatic calibration tool. From the calibration results, we can conclude that the evaporation pattern can replace the head data in the model calibration process, independently of the way the evaporation pattern is introduced into the calibration procedure. (C) 2009 Elsevier B.V All rights reserved.
  • Publication
    Accès libre
    Extracting phreatic evaporation from remotely sensed maps of evapotranspiration
    (2008-5-26)
    Brunner, Philip 
    ;
    Li, H. T.
    ;
    Kinzelbach, Wolfgang
    ;
    Li, W. P.
    ;
    Dong, X. G.
    One of the most important parameters related to soil salinization is the direct evaporation from the groundwater (phreatic evaporation). If the groundwater table is sufficiently close to the surface, groundwater will evaporate through capillary rise. In recent years, several methods have been suggested to map evapotranspiration (ET) on the basis of remote sensing images. These maps represent the sum of both transpiration of vegetation and evaporation from the bare soil. However, identifying the amount of phreatic evaporation is important as it is the dominant flux in the salt balance of the soil. The interpretation of stable isotope profiles at nonirrigated areas in the unsaturated zone allows one to quantify phreatic evaporation independently of the transpiration of the vegetation. Such measurements were carried out at different locations with a different depth to groundwater. The benefit is twofold. (1) A relation between phreatic evaporation rates and the depth to groundwater can be established. (2) By subtracting the measured values of phreatic evaporation from remotely sensed values of ET, vadose ET consisting of transpiration and excess irrigation water in the unsaturated zone can be estimated at the sampling locations. A correlation between the normalized differential vegetation index and the calculated vadose ET rates could be established (R(2) = 0.89). With this correlation the contribution of phreatic evaporation can be estimated. This approach has been tested for the Yanqi basin located in western China. Finally, the distribution of phreatic evaporation was compared to a soil salinity map of the project area on a qualitative basis.