Climate change and related effects on water quality: examples from Lake Maggiore (Italy)

Lake Maggiore is the second largest lake in Italy, with a surface area, maximum depth and volume respectively of 212 km2, 370 m, and 37.5 km3. Politically, the catchment belongs in equal parts to Italy and Switzerland. Lake water is used for tourism, recreational-environmental activities, public and private navigation, professional and sport fishery, hydroelectric production, irrigation and drinking. Long-term studies provide a history of industrial pollution and eutrophication followed by successful re-oligotrophication. Thermal studies show an increase in the water temperature in the 0-30 m layer of about 1.4 °C during the last 45 years. The new physical conditions of the water column, coupled with an increase of recreational uses and the trade in exotic aquarium species, resulted in an increase of cyanobacteria blooms and alien species introduction (Dreissena polymorpha, Corbicula fluminea, Sinanodonta woodiana, Procambarus clarkii and Orconectes limosus). The water European Directive (2000/60/EC) classifies as "lowest quality" typology those lakes which have exotic species.