Lake Trasimeno (/ˌtrɑːzɪˈmeɪnoʊ/ TRAH-zim-AY-noh,[1][2] also US: /-ˈmiːnoʊ, ˌtræz-/ -⁠EE-, TRAZ-im-;[2] Italian: Lago Trasimeno [ˈlaːɡo traziˈmɛːno]; Latin: Trasumennus; Etruscan: Tarśmina[3]), also referred to as Trasimene (/ˈtræzɪmiːn/ TRAZ-im-een) or Thrasimene in English, is a lake in the province of Perugia, in the Umbria region of Italy on the border with Tuscany.

However, the Romans dug an artificial drainage tunnel in the San Savino area, which was restored in the Renaissance; a modern canal, the Emissario del Trasimeno, was built in 1898,[4] flowing into the Caina, the Nestore, and eventually the Tiber.

The lake's water quality is still very good, as a study by conservation group Italia Nostra showed in 2005.

Historically, Trasimeno was known as the Lake of Perugia, being important for northwestern Umbria and for the Tuscan Chiana district.

The water level of the lake is very dependent on the amount of seasonal rain and can change significantly from one year to the other.

Trasimeno has high hills to the east, which help to capture rain and partially protect the lake from cold eastern winds.

During the following five years rain was insufficient (especially in 2006 and 2007 winters were very dry and summers hot) so by October 2012 the water level was -1.51 m vs the reference.

[5] A channel from the reservoir at Montedoglio in Tuscany to supply agriculture and lakeside towns (and thereby eliminate the need to draw water from the lake) was opened in 2012.

[6] The inhabitants of the communes around Trasimeno and the Umbrian people have successfully protected their lake, whose waters are fit for swimming and whose valleys and islands are intact environments.

The impact of non-native species in the lake has been heightened by the effects of climate change, which consist primarily of decreasing water levels due to lowered precipitation and increased evaporation rates, alongside reduced transparency, less dissolved oxygen and higher salinization caused by the gradual warming and shrinking of the lake.

[7] Commercially important native species include southern pike, tench, and European eel.

Efforts to counteract the southern pike's decline include a ban on its fishing, which has been in effect since 2011, and controlled restocking of juvenile specimens.

Eels are also considered to be locally at risk due the presence of artificial dams and weirs impeding their ability to migrate between the lake and the Mediterranean Sea; restocking programs have been implemented in response to this.

[7] The rovella and the spined loach have historically been native to the lake, but have not been recorded in modern samplings and are considered to be locally extinct.

The extinction of the rovella is linked to the introduction of non-native pumpkinseed, which competed with it for food and habitat, and to decreasing rates in dissolve oxygen in the water.

Other introduced species include the largemouth bass, European perch, big-scale sand smelt, topmouth gudgeon and common carp.

The growing populations of goldfish, carp and gudgeon are linked to their greater tolerance for more turbid, higher-temperature water with less dissolved oxygen.

Pumpkinseed has been introduced to the lake and was recorded in large numbers in 1966, but is considered to be a locally rare species in the present.

The local airport, the Eleuteri, near Castiglione del Lago, was once one of the main aviation schools in Italy, with elegant buildings that were destroyed by retreating German troops in the summer of 1944.

It was founded around 80 years ago and the buildings still exist near the Passignano sul Trasimeno railway station.

Eleuteri was also used as test center for the Ambrosini SS.4, advanced canard aircraft, which crashed in the second flight and the project was abandoned.

Exceptions apply to authorised boats propelled by motor only in the water in front of port areas or authorized landing places.

[8] There are ferryboats, 3 small, 2 medium, and two big (two decks) called Perusia and Agilla II, based in Passignano Port, also two dredges.

There are ports in Castiglione del Lago (recently totally rebuilt), S. Arcangelo, S. Feliciano, Tuoro, and several minor anchorages.

Maggiore is a 'hill', whereas Polvese is a more complex structure with plains and hills, and Minore resembles a sloped table.

The castle still remains, and the ruins of the church and the monastery are almost totally preserved, despite the abandonment in the 17th century due to malaria.

Minore Isle, near Maggiore, is now uninhabited, totally covered by local vegetation except for a small anchorage.

This complex system consisted of a wooden trap in the water and a circular structure to hold the net around it.

The Guglielmi castle in Maggiore Isle was built in the late 19th century on the foundation of an old Franciscan church, and for many years was a popular place in the Trasimeno area.

To avoid its collapse, a steel reinforcement was recently added, with plates and wires as thick as 2 to 3 cm (0.8 to 1.2 in).