The Giona is a ‘torrent’, or intermittent stream, which rises on the slopes of Monte Tamaro

Monte Tamaro

The Monte Tamaro is a mountain in the Lepontine Alps in Switzerland.-External links:*...

, in the Swiss

Switzerland

Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 canton of Ticino. After about 2 km it enters the Italian

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

  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....

, foming the Val Veddasca before entering 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...

 at Maccagno

Maccagno

Maccagno is a comune of c. 2,000 inhabitants in the province of Varese in the Italian region Lombardy, located in the Val Veddasca about 70 km northwest of Milan and about 25 km northwest of Varese.-History:...

. Its course passes through the communes of Indemini

Indemini

Indemini is a former municipality in the district of Locarno in the canton of Ticino in Switzerland.On 25 April 2010, the former municipalities of Caviano, Contone, Gerra Gambarogno, Indemini, Magadino, Piazzogna, San Nazzaro, Sant'Abbondio and Vira Gambarogno merged in the new municipality of...

 in Switzerland and Veddasca

Veddasca

Veddasca is a comune in the Province of Varese in the Italian region Lombardy, located about 70 km northwest of Milan and about 30 km north of Varese in the Val Veddasca, on the border with Switzerland....

, Curiglia con Monteviasco

Curiglia con Monteviasco

Curiglia con Monteviasco is a comune in the Province of Varese in the Italian region Lombardy, located about 110 km northwest of Milan and about 70 km northwest of Varese in the Val Veddasca, on the border with Switzerland. The municipal seat is in Curiglia.-References:...

, Dumenza

Dumenza

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

 and Maccagno

Maccagno

Maccagno is a comune of c. 2,000 inhabitants in the province of Varese in the Italian region Lombardy, located in the Val Veddasca about 70 km northwest of Milan and about 25 km northwest of Varese.-History:...

 in Italy.

The fish found in the river are predominantly Salmonidae

Salmonidae

Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...

, Cyprinid

Cyprinid

The family Cyprinidae, from the Ancient Greek kyprînos , consists of the carps, the true minnows, and their relatives . Commonly called the carp family or the minnow family, its members are also known as cyprinids...

ae and Cottidae

Cottidae

The Cottidae is a family of demersal fish in the order Scorpaeniformes, suborder Cottoidei . There are about 300 species in 70 genera of Cottidae that are mostly marine and found in shallow coastal waters in the northern and arctic regions...

, in particular brown trout

Brown trout

The brown trout and the sea trout are fish of the same species....

, grayling, chub

European chub

The European chub , sometimes called the round chub, fat chub, chevin, pollard or simply "the" chub, is a freshwater fish of the family Cyprinidae...

, vairone

Souffia

The Souffia or Western Vairone is a species of ray-finned fish in the Cyprinidae family. It is found in Austria, Bulgaria, Czech Republic, France, Germany, Hungary, Italy, Romania, Russia, Serbia and Montenegro, Slovakia, and Switzerland.-References:* World Conservation Monitoring Centre 1996. . ...

 and European bullhead

European bullhead

The bullhead is a freshwater fish that is widely distributed in Europe, mainly in rivers. It is a member of the Cottidae family, a type of sculpin...

.

The river is put to use as a source of 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...

.