1. Institute for Chemical and Bioengineering, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland, Laboratory of Hydraulics, Hydrology, and Glaciology, ETH Zurich, Gloriastrasse 37/39, CH-8092 Zürich, Switzerland, and Nestlé Research Center, Vers-chez-les-Blancs, 1000 Lausanne 26, Switzerland