The role of artificial recharge in active groundwater management

Lyonnaise des Eaux (LE), is a leading private French environmental design and water resource management group employing over 110,000 staff with sales in excess of US$ 18 billion. LE has used artificial recharge (AR) techniques for more than 30 years in the Paris area. Artificial recharge applies in the two largest groundwater treatment plants in the Paris area: Croissy-sur-Seine (300,000 m(3) per day) and Flins-Aubergenville (150,000 m(3) per day). The recharge process has been in operation in Croissy-sur-Seine with infiltration basins since 1959, allowing a large number of quality, quantity and ecological surveys. The water is drawn from the Seine river and undergoes treatment processes including clarification, settling and sand filtration. It is then sent to 15 hectares (37 acres) of infiltration basins where it undergoes cascade aeration before gradually reaching the aquifer, Infiltration capacity ranges from 1 to 3 m per day, Altogether 54 million m(3) thus reach the aquifer every year. Through two real examples, the authors analyses the nature of the problem, the methodology and results obtained for groundwater resource management using AR techniques in the Paris area, They explain the site procedures, experimentation carried out and the numerical approach. A statement of the various surveys is proposed, which outlines the programmes carried out: hydrogeochemical survey, ecological survey, groundwater modelling, aquifer recharge optimization in term of quantity, quality (including microbiology and parasitology survey), age of the water and economic aspects. The experience gained over the past ten years has made it possible to develop innovative techniques to optimize management and maintenance of infiltration processes according to physicochemical and biological clogging phenomena. The authors also present the advantages and disadvantages of various recharge techniques using basins in the light of comprehensive water ecosystem management policies. Issues related to groundwater protection, intake maintenance, continuous water quality monitoring stations, alert systems and crisis management are also addressed.