To simulate groundwater management negotiation, with a mediator and spatial argumentation, to reduce aquifer vulnerability using an example of gravel extraction in an alluvial aquifer How to make relevant decisions to preserve the quality of the hydrosystem and protect public health? Goals of this negotiation simulation are to design a cooperative solution where the participants must decide together : Where is the best new gravel pit location within a specified territory? What is the best method of rehabilitation after gravel extraction? Who is the most appropriate to manage the site after rehabilitation?