The search for environmental indicators is a descriptive approach but one which shows practical results fairly quickly. Its application to two Alpine lakes (Annecy and Le Bourget) is based on relating hydrobiological paramètres and socio-economic data. The comparative study of the two lakes leads to a global impression in which the purity of the water is of prime importance. It is possible to approach this through two hydro-biological variables : the colour and turbidness of the water. As for the various functions of water, there may be certain incompatibilities, which poses problems of spatial distribution and hence of planning. Four main functions (sport, ecology, social, and water to look at) have been set up and for each particular indicators are proposed.
