1. Estellus, 93 Blvd. de Sébastopol, 75002 Paris, France (corresponding author).
2. Director, LyRE, R&D Center of Lyonnaise des Eaux, 91 rue Paulin, 33029 Bordeaux, France.
3. Professor, Montpellier SupAgro, UMR G-EAU, 2 place Pierre Viala, 34060 Montpellier Cedex 1, France.
4. Irstea, UR HBAN, 1 rue Pierre-Gilles de Gennes, CS 10030, 92761 Antony Cedex, France.