Veneto’s lagoons, a unique environment

Veneto’s lagoons accompany the entire western arch of the Upper
Adriatic, from the Po Delta to the threshold of the Carso along the
main outlet mouths of the rivers of north eastern Italy, of which the
most important are the Adige, Brenta, Sile, Piave, Tagliamento and
Isonzo. Originally, the transition band between the dry land and sea
was composed of continuously evolving lagoon environments, due to
the constant deposition of alluvial material.

This dynamic was counter productive for human activity, particularly that regarding the largest body of water, the lagoon of Venice, the object of secular hydraulic work on both the sea front, with mighty systems providing protection from rough seas and that of the dry land, with the diversion of the affluent rivers and the creation of artificial canals.

All of this was performed to protect that fragile equilibrium that allowed urban settlement, maritime activities and fish farming inside. The Venice lagoon currently has a surface area of 550 km2 and an average depth of 1.2 meters and it is separated from the sea by an outer breakwater that develops for approximately 60 km from the mouth of the Adige to that of the Piave, interrupted by the port
mouths of Lido (800 m), Malamocco (400 m) and Chioggia (380
m). It is one of the vastest wet areas of the Mediterranean,
unparalleled worldwide as regards its environmental, historical and
economic value.

The lagoon basin is home to the cities of Venice and Chioggia and over 50 islands including Murano, Burano and Torcello.
The navigation network includes 1580 km of canals, which assure the changeover of the lagoon waters. On the surface there are approximately 70 km2 of sandbanks, land just below the surface of the water that plays a fundamental role in the lagoon’s hydraulic equilibrium and approximately 90 km2 of fisheries, banked basins equipped for fish farming, arranged along the lagoon border of the northern and central-southern area.

The upper Adriatic governs the lagoon’s ecosystem with its tides that twice a day sweep in and out of the lagoon through the port mouths, generating two maximum and two minimum levels; this phenomenon, which is regulated by a complex set of meteorological and astronomical events, is subject to an average variation of approximately 70 cm, between – 20 and + 50; the average volume of water exchanged every day is approximately 400 million m3, however in abnormal conditions, the ‘high water’ phenomenon may occur, the first consequence of which is the flooding of Venice city centre.