The river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 Tresa leaves Lake Lugano

Lake Lugano

Lake Lugano is a glacial lake in the south-east of Switzerland, at the border between Switzerland and Italy. The lake, named after the city of Lugano, is situated between Lake Como and Lago Maggiore...

 at a point between Lavena Ponte Tresa

Lavena Ponte Tresa

Lavena Ponte Tresa is a comune on Lake Lugano in the Province of Varese in the Italian region Lombardy, located about 60 km northwest of Milan and about 15 km north of Varese, on the border with Switzerland...

 in Italy and Ponte Tresa

Ponte Tresa

Ponte Tresa is a municipality in the district of Lugano in the canton of Ticino in Switzerland.-History:Ponte Tresa is first mentioned in 818 as ad Tresiae Pontem, though this comes from a 12th Century copy of the earlier document. In 875 it was mentioned as Ponte Tretia...

 in Switzerland and flows into Lake Maggiore

Lake Maggiore

Lake Maggiore is a large lake located on the south side of the Alps. It is the second largest of Italy and largest of southern Switzerland. Lake Maggiore is the most westerly of the three great prealpine lakes of Italy, it extends for about 70 km between Locarno and Arona.The climate is mild...

 near Luino

Luino

Luino is a small town and comune near the border with Switzerland on the eastern shore of Lake Maggiore, in the Province of Varese ....

, a few hundred metres after joining the Margorabbia

Margorabbia

The Margorabbia is a ‘torrent’—or intermittent stream—of the province of Varese in north Italy’s Lombardy, a tributary of the Tresa which it joins a few hundred metres upstream of Lake Maggiore.The source is near Valganna...

. At the outflow from Lake Lugano the river is crossed by a bridge which unites the Swiss and Italian parts of Ponte Tresa; a customs post divides them.

The river is about 13 km long and for most of its course marks the boundary between the Italian Province of Varese

Province of Varese

The Province of Varese is a province in the Lombardy region of Italy. Its capital is the city of Varese but its largest city is Busto Arsizio....

 and the Swiss canton Ticino

Ticino

Canton Ticino or Ticino is the southernmost canton of Switzerland. Named after the Ticino river, it is the only canton in which Italian is the sole official language...

. It passes through the Swiss communes of Ponte Tresa

Ponte Tresa

Ponte Tresa is a municipality in the district of Lugano in the canton of Ticino in Switzerland.-History:Ponte Tresa is first mentioned in 818 as ad Tresiae Pontem, though this comes from a 12th Century copy of the earlier document. In 875 it was mentioned as Ponte Tretia...

, Croglio

Croglio

Croglio is a municipality in the district of Lugano in the canton of Ticino in Switzerland.-Geography:Croglio has an area, , of . Of this area, or 20.3% is used for agricultural purposes, while or 70.5% is forested...

 and Monteggio

Monteggio

Monteggio is a municipality in the district of Lugano in the canton of Ticino in Switzerland.-History:Monteggio is first mentioned in 1466 as da Montegio. Until 1819 the current village core was called Albio. The name comes from the fortified seat of the Capitanei of Sessa, the ruins of which are...

, and the Italian communes of Lavena Ponte Tresa

Lavena Ponte Tresa

Lavena Ponte Tresa is a comune on Lake Lugano in the Province of Varese in the Italian region Lombardy, located about 60 km northwest of Milan and about 15 km north of Varese, on the border with Switzerland...

, Cremenaga

Cremenaga

Cremenaga is a comune in the Province of Varese in the Italian region Lombardy, located about 60 km northwest of Milan and about 20 km north of Varese, on the border with Switzerland...

 and Luino

Luino

Luino is a small town and comune near the border with Switzerland on the eastern shore of Lake Maggiore, in the Province of Varese ....

.

A dam on the river, known as the Creva dam serves two purposes: to use the difference in altitude between the lakes to produce hydropower

Hydropower

Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

, and as far as possible to regulate the flow of water into Lake Maggiore in order to avoid or limit the dangers of flooding.

External links

• Hydrological data of the Tresa at Ponte Tresa
  Ponte Tresa
  Ponte Tresa is a municipality in the district of Lugano in the canton of Ticino in Switzerland.-History:Ponte Tresa is first mentioned in 818 as ad Tresiae Pontem, though this comes from a 12th Century copy of the earlier document. In 875 it was mentioned as Ponte Tretia...