The French long-term observation system H+ network was created in 2002 for hydrogeological research and has since been continuously funded by the National Institute of Earth Sciences and Astronomy of CNRS (INSU).


  • The primary mission of the H+ observation service is to maintain and coordinate a network of experimental sites capable of providing relevant data - including long-term chronicles or experiments - for the characterisation, quantification and modelling of water, element and energy transfers in underground aquifers. This experimental tool aims to be recognised as a real fundamental research tool of international level by bringing together and dynamising research in hydrogeology at national and, eventually, European level.


  • Specific and complementary scientific objectives are defined according to the instrumented sites: the impact of exploitation on the water cycle and the role of deep flows in the ecosystem operation (Ploemeur), the coupling between the porous matrix and highly localised structures (fractures or karsts) (S. E.H. Poitiers), flows in the unsaturated zone and the recharge of karst springs (LSBB), stock-flow relationships in karst aquifers (Larzac), contaminant transport at the water table-river interface (Auverwatch), the impact of overexploitation of resources in a monsoon context (Hyderabad), etc.


  • The H+ observation service also has the task of establishing a partnership between fundamental research, training and operational partners. This is already the case for one of the sites (Plœmeur) where the community of communes Lorient Agglomération acts as project manager. Training activities are organised on the exploitation of the resource and the prevention of environmental risks.


  • The coupling between measurements, theories and models is a fundamental mission of the H+ observation service. Modelling is an essential tool for prediction at all scales. The observatory aims to create a long-term relation between research teams interested in the theoretical, numerical or experimental aspects of transfers in heterogeneous media.