1. Technical University of Denmark, Institute of Environmental Science and Engineering, DK-2800 Lyngby, Denmark
2. Swiss Federal Institute for Aquatic Sciences, EAWAG, CH-8600 Dübendorf, Switzerland
3. University of Tokyo, Department of Urban Engineering, Hongo, Bunkyo-ku, Tokyo 113, Japan
4. University of Cape Town, Department of Civil Engineering, Rondebosch, 7700, South Africa