Institute of Terrestrial Ecology, Swiss Federal Institute of Technology, ETH Zurich, Switzerland

School of Earth and Geographical Sciences, The University of Western Australia, Crawley, Australia

now at: Laboratory of Soil and Environmental Physics, EPF Lausanne, Switzerland

School of Earth and Geographical Sciences, The University of Western Australia, Crawley, Australia

School of Earth and Geographical Sciences, The University of Western Australia, Crawley, Australia

Simon Fraser University, Department of Geography, Burnaby BC, Canada

School of Architecture, Civil and Environmental Engineering, EPFL Lausanne, Switzerland

Water Resources Section, Delft University of Technology, Delft, The Netherlands

on leave from: Dept. of Forest Engineering, Oregon State University, Corvallis, USA