For the purpose of the formulation step, the representation of the system has to be simplified. The main simplifications are the following (see explanations in the scientific report): -the upstream activities sub-system will be reduced to a gross estimation as regards the regional demand for drinking water but it will contain a detailed representation of agriculture, -the hydrological system will be represented by two main blocks, the first one being defined as not salty and the second one as could be salty; between these two locations, wetlands and salt marshes are building a complex network submitted to opposite forces (river flow and tide), but in a first approach, no brackish water block will be built, -the ecosystems representation in the model will thus be reduced to the varying salinity of coastal waters, -the downstream activities sub-system will not consider non market uses on the coastal areas1 (ecological patrimony, aesthetic value or recreational activities) and it will focus on the uses (resource supply and support services) of freshwater by shellfish farming, -at last, the governance sub-system will focus on the water management measures implementation, the stakeholder participation and strategies toward management options being addressed through the deliberative part of the SSA work.