Oulujoki basin

Oulujärvi () or Lake Oulu or Ule (), is a large lake in the Kainuu region of Finland. It is also historically known as Lake Cajania from a former name of Kainuu. With an area of it is the fifth largest lake in the country. The lake is drained by the Oulu River, which flows northwestward from the lake into the Gulf of Bothnia. Its nickname is the "Kainuu Sea", and it is bordered by the three municipalities of Vaala, Paltamo, and Kajaani. About 40 percent of the lake is in Vaala.

Oulujoki () is a river in North Ostrobothnia, Finland. Its name in Finnish literally means "Oulu River", originally in old Northern Ostrobothnian dialect literally "Flood River". Its origin is Oulujärvi, and its watershed area covers a significant part of Kainuu region. It flows into the Bothnian Bay at Oulu. Port of Oulu is located at the mouth of the river.

thumb|Illustration in Finland framstäldt i teckningar edited by [[Zacharias Topelius and published 1845-1852.]]

Kiantajärvi is a rather large lake in Finland, in the Oulujoki main catchment area. It is located in Suomussalmi municipality, in the region of Kainuu. It is the 24th biggest lake in Finland. The lake is narrow and 50 km long in north–south direction.

thumb|right|The Kiehimänjoki river Kiehimänjoki is a river of Finland. It flows for . The river begins from lake Iijärvi in Paltamo in Kainuu region and ends to the lake Oulujärvi, from which the waters flow through the Oulujoki River into the Gulf of Bothnia. The river drains a chain of lakes that originates in the municipalities of Suomussalmi and Hyrynsalmi in Kainuu ().

lake in Finland

Otermanjärvi is a medium-sized lake in Vaala municipality, in Finland. It belongs to the Oulujoki main catchment area.

Kivesjärvi is a medium-sized lake in Paltamo, Finland. The name Kivesjärvi literally means "testicle lake". Some say that the name derive from old giant-related folklore around the region, some say that the name originally related to the ancient word for gillnet weight, "kives", and only later became associated with the modern meaning of the word. Its average depth is four metres and the deepest point is sixteen metres deep. There is a village of the same name on the coast of the lake. The lake's area is 27 square kilometres. It is the 136th biggest lake in Finland. The lake has many islands a