[Evolution of the nitrate content of water collected in the Department of Aisne, and search for side basins permitting correlations between surface events and nitrate contents].

The aim of this study is to search for small underground side basins in order to propose them to agricultural businessmen. Those basins should be apt to a successful experiment of cultural techniques to reduce nitrogen leakages toward aquifers. They should allow to identify and try to quantify the reasons of nitrogen enrichment of the underground waters by a critical examination of the past of some reappearances and the use of their recharge basin. This work consisted, after drawing up evolution graphs of nitrate rates, in selecting springs at first according to their interannual variations amplitude with increasing nitrogen rates, secondly according to their moderate flow-having unimportant side basins and thin storage aquifer and therefore reacting rapidly to the surface attraction. Finally, the springs were selected according to their specified pollution so that the collected water should be a representative sample of the aquifer. Eleven spots were thus selected. We hope they will allow to draw an experiment over the 3 or 5 next years.