Paris, as many large cities built on aquifers, shows a disturbed hydrogeological environment.Land waterproofing reduces the natural recharge of the water table, then mainly driven by sewer network leakage. Underground intensive urbanisation covering more than 30 % of the Parisian surfaces (without Vincennes and Boulogne woods) influences groundwater flow. In addition, had to be taken in consideration the 20-30 millions cubic meters of water yearly pumped from the aquifer system.Parisian aquifers are surveyed by IGC (Inspection General des Carrières) from the city of Paris, thanks to a 305 piezometers network, in particular close to the Seine river, in order to monitor and anticipate a flood event. In order to appraise such events a hydrogeological model of the Parisian underground had to be setup, including anthropic specification.To achieve this model a 3D GIS of the Parisian underground has been done, integrating several topics:- Parisian geology, including Campanian chalk and tertiary formation. 20 000 geological drillings have been used.- Underground infrastructures: 20 000 residential car parks and cellars more than 140 public car parks conceded by the city of Paris, 197 km of underground subway and 46 km of RER.- Water pumping. Only declared samples (12 millions cubic meters)- Piezometric data from 669 piezometers over Paris and neighbouring townsBefore this thesis, no synthetic representation of Paris geology and underground has been done.In a second time a mathematical model including Paris and suburbs has been built. This multilayer model consists of 11 layers interbedding, 6 aquifers level and 5 semi-permeable discretized through 607 171 square mesh (50 m side). Until now, this mathematical model allowed exploratory simulation in steady state showing flow structure of the present day hydrogeological situation.
