Arno

The Arno is a river in the Tuscany region of Italy. It is the most important river of central Italy after the Tiber.

Etymology

From Latin Arnus. The philologist Hans Krahe related this toponym on a paleo-European basis *Ar-n-, derived from the Proto-Indo-European root *er-, "flow, move". The hydronym is closely akin to another nearby hydronym, for the Reno.

The Arno river has been strongly affected by non-native species: over 90% of fish species and 70% of macroinvertebrate species in the area around Florence are alien species. These include the European catfish, channel catfish, Crucian carp, common bleak, topmouth gudgeon, New Zealand mud snail, and killer shrimp. The mud crab has been found in the river near Pisa.

Water from the Arno drainage basin is used for drinking water, irrigation, and firefighting. Citizens in the central part of the drainage basin also identified flood control, support for biodiversity, fisheries, and cultural value as other services that the river provides. There is the risk that flooding will jeopardize these ecosystem services, as 9% of wastewater treatment plants, 10% of landfills or other waste sites, and 4.5% of contaminated sites are at high risk of flooding, which would produce hotspots of pollution.