TheriverTresaleavesLake Luganoat a point betweenLavena Ponte Tresain Italy andPonte Tresain Switzerland and flows intoLake MaggiorenearLuino,a few hundred metres after joining theMargorabbia.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.
| Tresa | |
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| Location | |
| Country | Switzerland |
| Canton | Ticino |
| Country | Italy |
| Region | Lombardy |
| Physical characteristics | |
| Source | |
| • location | Lake LuganobetweenPonte TresaandLavena Ponte Tresa |
| • elevation | 295 m (968 ft) |
| Mouth | |
• location | Lago MaggioreatLuino |
• coordinates | 45°59′48″N8°43′36″E/ 45.99667°N 8.72667°E |
• elevation | about 193 m (633 ft) |
| Length | 13 km (8 mi) |
| Basin features | |
| Progression | Lake Maggiore→Ticino→Po→Adriatic Sea |
| Tributaries | |
| • left | Margorabbia |
The river is about 13 kilometres (8 mi) long, and for most of its course marks the boundary between the ItalianProvince of Vareseand the SwisscantonTicino.It passes through the Swiss communes of Ponte Tresa,CroglioandMonteggio,and the Italian communes of Lavena Ponte Tresa,Cremenagaand Luino.
A dam on the river, known as the Creva dam serves two purposes: to use the difference in elevation between the lakes to producehydropower,and as far as possible to regulate the flow of water into Lake Maggiore in order to avoid or limit the dangers of flooding.
