Présentation des bassins versants ateliers (Coët-Dan et Kerharo) et de la baie de Douarnenez

The transmission of several contaminants from agricultural land to the shoreline has been studied within the scope of this programme, both by general research and by field investigations. The field investigations took place in two test catchment areas (fig. 1). One of them, Coët-Dan, has been fitted out with various measuring devices since the year 1971 and has been monitored since that date. The other one, Kerharo, has never been studied until now. The research topics were distributed between these two catchment areas in the following way. At Coët-Dan, what was handled were the transfer of pesticides and bacteria of sanitary interest, the nitrogen and phosphorus supplied to the fields by farms, the transfer of these nutrients into the surface horizons and the transfer of nitrogen into the deep soil. At Kerharo, what was handled were modelling of the nitrogen transfer in ground levels not saturated with water, denitrification in damp areas (natural and artificial), hydrogeology and underground transfers of nitrogen as well as deep denitrification bacteria, the relationship between springtime nitrogenous streams to the coast and the green tides on the beaches of Douarnenez Bay.