1. Ph.D. Research Fellow, Dept. of Hydraulic and Environmental Engineering, Norwegian Univ. of Science and Technology, N-7491 Trondheim, Norway (corresponding author).
2. Professor, Dept. of Hydraulic and Environmental Engineering, Norwegian Univ. of Science and Technology, N-7491 Trondheim, Norway.
3. Senior Environmental Advisor, Statkraft AS, Lilleakerveien 6, P.O. Box 200 Lilleaker, N-0216 Oslo, Norway.
4. Manager, Tesaker Vann AS, Lerkevegen 8B, N-7072 Heimdal, Norway.