By 2050, the demand for water to sustain world agriculture will increase by seventy-five per cent in order to feed an estimated nine billion inhabitants. Increased amounts of water will be required for irrigation and for industrial and domestic use. Natural ecosystems will be threatened by the expansion of agricultural land and by a reduction in water availability, while climate change will exacerbate the situation. Management of available resources, particularly groundwater, will become more critical and aquifers will need to be managed for the benefit of all.These selected papers were first presented at the International Association of Hydrogeologists, Dijon 2006, and are divided into six themes: large aquifers, resource assessment; large aquifers, water salinity and evolution; karstic and carbonate aquifer systems; geothermal aquifer systems; aquifer contamination studies and aquifer monitoring systems and management. The volume also includes a short biography of Henry Darcy and illustrates his contribution to science. Five invited contributions describe modern methods for estimating the hydraulic conductivity of aquifers.