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,
Lake Onega months. The highest water level is in June–August and the lowest is in March–April. Rivers bring of water per year to the lake, that is up to 74% of the water balance; the rest is provided by precipitation. Most of the lake water (84% or per year) outflows via a single River Svir, and the remaining 16% evaporates from the lake surface. There are frequent storms more characteristic of a sea than a lake; waves of are not uncommon and may even reach . The lake freezes near the coast and bays in late November and December and around mid-January