Arno

Source and route

The river originates on Monte Falterona in the Casentino area of the Apennines, and initially takes a southward curve. The river turns to the west near Arezzo passing through Florence, Empoli and Pisa, flowing into the Ligurian Sea at Marina di Pisa.

With a length of 241 km, it is the largest river in the region. It has many tributaries: Sieve at 60 km long, Bisenzio at 49 km, Ombrone Pistoiese at 47 km, and the Era, Elsa, Pesa, and Pescia. The drainage basin amounts to more than 8200 sqkm and drains the waters of the following subbasins:

• The Casentino, in the province of Arezzo, formed by the upper course of the river until its confluence with the Maestro della Chiana channel.
• The Val di Chiana, a plain drained in the 18th century, which until then had been a marshy area tributary of the Tiber.
• The upper Valdarno, a long valley bordered on the east by the Pratomagno massif and on the west by the hills around Siena.
• The Sieve's basin, which flows into the Arno immediately before Florence.
• The middle Valdarno, with the plain including Florence, Sesto Fiorentino, Prato, and Pistoia.
• The lower Valdarno, with the valley of important tributaries such as the Pesa, Elsa, and Era and in which, after Pontedera, the Arno flows into the Ligurian Sea. The river has a very variable discharge, ranging from about 6 m3/s to more than 2000 m3/s. The mouth of the river was once near Pisa but is now several kilometres westwards.

It crosses Florence, where it passes below the Ponte Vecchio and the Santa Trinita bridge (built by Bartolomeo Ammannati but inspired by Michelangelo). The river flooded this city regularly in historical times, most recently in 1966, with 4500 m3/s after rainfall of 437.2 mm in Badia Agnano and 190 mm in Florence, in only 24 hours.

Before Pisa, the Arno is crossed by the Imperial Canal at La Botte. This water channel passes under the Arno through a tunnel, and serves to drain the former area of the Lago di Bientina, which was once the largest lake in Tuscany before its reclamation.

The flow rate of the Arno is irregular. It is sometimes described as having a torrentlike behaviour, because it can easily go from almost dry to near flood in a few days. At the point where the Arno leaves the Apennines, flow measurements can vary between 0.56 and. New dams built upstream of Florence have greatly alleviated the problem in recent years.

The flood on November 4, 1966 collapsed the embankment in Florence, killing at least 41 people and damaging or destroying millions of works of art and rare books. New conservation techniques were inspired by the disaster, but even decades later hundreds of works still await restoration.

Etymology

From Latin Arnus (Pliny, Natural History 3.50). 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 (river).

Ecology

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.

Uses and human impacts

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.

Gallery

File:Arno_river.jpg|The Arno in Florence File:Arno River in Pisa.honeydew.jpg|The Arno in Pisa, near the Ponte della Fortezza (Fortress Bridge) File:Firenze.Arno.jpg|Banks of the Arno, seen from the Ponte Vecchio (Old Bridge), Florence File:Arno_Mouth_Italy_aerial_view.jpg|Mouth of the Arno in Marina di Pisa File:Florence Arno 180.jpg|The Arno in Florence, 180 degree view: the Uffizi Gallery is straight across and the Ponte Vecchio is to the left File:Florence at night.jpg|The Arno in Florence at night File:Ponte amerigo vespucci.JPG|The Ponte Amerigo Vespucci (Amerigo Vespucci Bridge)

References

References

1. (16 March 2023). "Arno River - WorldAtlas".
2. (11 September 2023). "The River Arno/ Tuscany's life force – PILOT GUIDES".
3. Parco Nazionale delle Foreste Casentinesi. (1999-01-01). "Environmental restoration of the area of the river Arno offsprings". European Climate, Infrastructure and Environment Executive Agency.
4. (July 20, 1998). "Arno River".
5. (August 24, 2018). "Like a Reverse Atlantis, This Legendary Harbor Ended When Its Sea Route Dried Up".
6. (March 12, 1965). "Interesting facts about the Arno River".
7. (November 3, 2023). "Marina di Pisa, la mareggiata si porta via lo storico retone di Bocca d'Arno".
8. (November 3, 2023). "Mareggiata Marina di Pisa".
9. Alison McLean. (November 2006). "This Month in History". Smithsonian.
10. Edelmiro Bascuas, ''Hidronimia y léxico de origen paleoeuropeo en Galicia'' (page 41)
11. (2021). "Two centuries for an almost complete community turnover from native to non-native species in a riverine ecosystem". Global Change Biology.
12. (2020). "When alien catfish meet—Resource overlap between the North American Ictalurus punctatus and immature European Silurus glanis in the Arno River (Italy)". Ecology of Freshwater Fish.
13. (2020). "Overlapping niches between two co-occurring invasive fish: the topmouth gudgeon Pseudorasbora parva and the common bleak Alburnus alburnus". Journal of Fish Biology.
14. (2015-11-18). "The low basin of the Arno River (Tuscany, Italy) as alien species hotspot: first data about Rhithropanopeus harrisii (Crustacea, Panopeidae)". Transitional Waters Bulletin.
15. (2020-11-01). "Water Values: Participatory Water Ecosystem Services Assessment in the Arno River Basin, Italy". Water Resources Management.
16. (2018-02-01). "Flood risk assessment of environmental pollution hotspots". Environmental Modelling & Software.