Sog is the largest freshwater 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...

 in Iceland in terms of water volume. Average flow is 110 m³/s

Cubic metres per second

A cubic metre per second is a derived SI unit of flow rate equal to that of a stere or cube with sides of one metre in length exchanged or moving each second...

. It runs from Lake Þingvallavatn

Þingvallavatn

Þingvallavatn is a lake in south-western Iceland. With a surface of 84 km² it is the largest natural lake in Iceland. Its greatest depth is at 114 m. At the northern shore of the lake, at Þingvellir , the Alþingi, the national parliament, was founded in the year 930.The lake is part of the...

 for 21.9km to its confluence with the river Hvítá, forming the river Ölfusá

Ölfusá

The Ölfusá is a river in Iceland. It is formed when the rivers Hvítá and Sog combine, just north of the town of Selfoss and flows for 25 km into the Atlantic ocean. It is Iceland's largest river with an average flow of 423 m³/s. Its discharge area is 5760 km². The Ölfusá has a strong salmon...

 which then runs for another 25 km into the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

.

There are three hydroelectric power stations in the river: Ljósafossstöð (15 MW), Írafossstöð(48 MW) and Steingrímsstöð(27 MW).

Sog River runs through two lakes, Lake Úlfljótsvatn and Lake Álftavatn.

The river has a healthy stock of arctic char

Salvelinus

Salvelinus is a genus of salmonid fish often called char or charr; some species are called "trout". Salvelinus is a member of the Salmoninae subfamily of the Salmonidae family. Charr may be identified by light cream pink or red spots over a darker body. Scales tend to be small, with 115-200 along...

 and Atlantic salmon

Salmon

Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...

. The size of the char can be anywhere from 0.5 pounds up the 5.0 pounds with an average size of 1.0 pound. The most common weight for salmon is 5.0 to 10.0 pounds with a few fish caught each year from 20.0 to 30.0 pounds. There are also sea-run brown trout

Trout

Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

in the Sog River.