The Rhin-Meuse Water Agency regularly conducts studies on the ecological and chemical state of the lakes of Gerardmer, Longemer, and Retournemer. It consists of physicochemical monitoring of the water column and the sediments. The agency also applies a complementary paleolimnological-type approach. It is about identifying possible ecological dysfunctions and their probable causes by taking sediments samples. The waters of Gerardmer and Longemer lakes are weakly mineralized. It corresponds with the geological nature of their watershed, made of granite and gneiss.