The Oglio (Italian: [ˈɔʎʎo]; Latin Ollius, or Olius; Lombard Òi; Cremonese Ùi) is a left-side tributary of the Po River in Lombardy, Italy. It is 280 kilometres (170 mi) long. In the hierarchy of the Po's tributaries, with its 280 kilometres (170 mi) of length, it occupies the 2nd place per length (after the river Adda), while it is the 4th per basin surface (after Tanaro, Adda and Ticino), and the 3rd per average discharge at the mouth (after Ticino and Adda).

The river between Soncino and Orzinuovi
Course of the river Oglio
provincesBrescia, Bergamo, Cremona, Mantua
Physical characteristics
SourceValle delle Messi, as Frigidolfo branch
  locationnear Punta Valmalza, Sobretta-Gavia Group, Ortler Alps, Lombardy
  coordinates46°20′31.5″N 10°27′03.5″E
  elevation3,035 m (9,957 ft)
2nd sourceLake Ercavallo, Valle di Viso, as Arcanello branch
  locationat the slopes of Cima di Caione, Ortler Alps, Lombardy
  coordinates46°20′21.1″N 10°31′35.5″E
  elevation2,621 m (8,599 ft)
3rd sourceLake Pisgana, as Narcanello branch
  locationNarcanello Valley, near Vedretta di Pisgana, Presena glacier, Adamello-Presanella Alps, Lombardy
  coordinates46°12′22″N 10°31′49″E
  elevation2,500 m (8,200 ft)
4th sourceOgliolo branch
  locationCorteno Valley, on the provincial border between Corteno Golgi, province of Brescia and Aprica, province of Sondrio, Lombardy, near Zappello dell'Asino
  coordinates46°08′52″N 10°09′54.2″E
  elevation1,172 m (3,845 ft)
Source confluenceconfluence of Frigidolfo and Narcanello branches
  locationPonte di Legno, province of Brescia, Lombardy
  coordinates46°15′32.7″N 10°30′28.7″E
  elevation1,253 m (4,111 ft)
at the municipal border between Marcaria and Viadana, province of Mantua, Lombardy
45°02′40″N 10°39′37″E
Length280 km (170 mi)
Basin size6,649 km2 (2,567 sq mi)
  average137 m3/s (4,800 cu ft/s)


The Oglio is formed from the confluence of two mountain streams, the Narcanello branch from the Presena Glacier, in the Adamello group and the Frigidolfo branch, in the Corno dei Tre Signori, part of the Stelvio National Park. The streams merge near Pezzo di Ponte di Legno, both the streams have an average discharge of 1.5 m3/s (53 cu ft/s). The Frigidolfo branch, before merging with Narcanello branch, receives the Arcanello branch, which have an average discharge of 0.5 m3/s (18 cu ft/s), which receives a minor branch originating from Lake Ercavallo. The Ogliolo stream, with an average discharge of 2.5 m3/s (88 cu ft/s) and a length of 20 kilometres (12 mi) (similar to the length of the main branch between the Frigidolfo-Narcanello merge at Ponte Di Legno and the Oglio-Ogliolo merge at Edolo) is sometimes considered as a de facto fourth branch of the Oglio river.

It flows in a southwest direction, through Valcamonica and enters into the Lake Iseo at Costa Volpino. It leaves Lake Iseo at Sarnico and, after traveling a zone of moraine deposits, it joins the Po river at Torredoglio, not far from Cesole and Scorzarolo, in the province of Mantua. Its drainage basin, which corresponds to the region of Valle Camonica, covers 6,649 square kilometres (2,567 sq mi). It is part of the larger Po-Adige basin.

The course of the river main branch

Camonica Valley section

The river in the Camonica Valley flows almost exclusively in the province of Brescia, entering in the province of Bergamo only at 45°51′38.2″N 10°08′56″E, on the border between Artogne, Brescia and Rogno, Bergamo.

The following is a list (incomplete) of the tributaries in the Camonica Valley:

Lake Iseo section

At Costa Volpino, the Oglio river enters the Iseo lake with a mixed delta-estuary mouth.

The tributaries of the Iseo lake
Brescia side: Bergamo side:

Po Valley section

The Oglio main branch leaves the lake at the provincial border between Sarnico, Bergamo and Paratico, Brescia 45°39′56.5″N 09°57′24″E and begins to follow (approximately) this provincial border. At the triple provincial border between Torre Pallavicina (Bergamo), Roccafranca (Brescia) and Soncino (Cremona) 45°25′40.5″N 09°53′07.5″E the Oglio begins to follow (approximately) the provincial border between the Brescia-Cremona provincial border.

The major tributaries in the Po valley are the following:

At this triple provincial border the Oglio river begins following the Mantua-Cremona provincial border, which leaves at the triple municipal border between Acquanegra sul Chiese (Mantua), Calvatone (Cremona) and Bozzolo (Mantua) 45°07′57″N 10°29′32″E where the river enters entirely in the Mantua province.

At the municipal border between Marcaria and Viadana 45°02′40″N 10°39′37″E, the Oglio river enters the Po river.

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