Lake Lacha Lake Lacha Lake Lacha () is a freshwater lake, located in the south of Kargopolsky District of Arkhangelsk Oblast in Russia, south of the town of Kargopol. It is the largest lake in Arkhangelsk Oblast, with a surface area of and a basin area of . Lake Lacha is the source of the Onega River, one of the major waterways of the White Sea basin. The etymological origin of the name is unclear. The river basin of Lake Lacha includes the southern and western parts of Kargopolsky District of Arkhangelsk Oblast, as well as north-west of Vologda Oblast. In particular,
Onega River of the Onega is notable for the rapids, spread everywhere between Kargopol and Gorodok, and also located downstream from Porog (the name "Porog" means "a rapid"). The Onega basin area has an important historical and cultural significance. Kargopol is one of the oldest cities in Russian North (the traditional foundation date in the 12th century, first mentioned in the 14th century), and it still contains a big number of architectural and historical monuments. Oshevensk on the left bank of the Onega is the location of the former Alexandro-Oshevensky Monastery. Another historically important monastery in the Onega basin is the Kozheozersky