1. a Spatial Structures and Systems Joint Research Unit , Cemagref‐ENGREF, 500 rue Jean‐François Breton, 34093 Montpellier cedex 5, France
2. b Laboratory of Study of Interaction between Soil , Agrosystems and Hydrosystems Joint Research Unit , ENSAM‐INRA‐IRD, 2 place Viala, 34060 Montpellier cedex 1, France