|Type||natural lake, reservoir|
|Primary outflows||Gudbrandsdalslågen, Rauma|
|Max. length||10 km (6.2 mi)|
|Surface area||4.34 km2 (1.68 sq mi)|
|Surface elevation||611 m (2,005 ft)|
The lake is unusual by having two outlets, one in each end: It flows both East into the Gudbrandsdalslågen and west into the Rauma river in the Romsdalen valley. The lake serves as the headwaters for two major rivers: Gudbrandsdalslågen (literally the Gudbrand Valley water course, flowing south/east) and for Rauma River (flowing west). Gudbrandsdalslågen (Lågen) flows through the Gudbrandsdalen valley floor, ending in lake Mjøsa. The lake sits on the watershed in the north-western corner of Glomma drainage system that includes large parts of eastern Norway.
The lake was dammed to serve the Lesja Iron Works in the 1660s. The east end was lifted 3 meters, the west end (Rauma) was lifted by a small stone wall. Earlier the lake was shorter and concentrated in what is now the west end of the lake. About 67% of the water flows to Rauma, at low water level about 80% flows to Rauma. Rotting plants and fish on the bottom produces gas that in winter is captured under the ice. The watershed has over thousands of years shifted east because rivers and glaciers to west dig more into the bedrock, notably in the upper part of Rauma river near Verma village..
Norwegian campaign 1940
No. 263 Squadron RAF operated with 18 Gloster Gladiator biplane fighters from a landing strip on the frozen Lesjaskogsvatnet in late April 1940 as part of the Norwegian campaign. The British air force chose Lesjaskogsvatnet because of the relatively short distance to the front line in the Gudbrandsdalen Valley as well as proximity to the British base at Åndalsnes. The British also planned to bring in large amounts of explosives from Scotland to blow up the railway tunnels at Dombås (this would block railway connections to Åndalsnes and Trondheim), but the German forces advanced too fast. The ice was covered by at least 40 cm snow and a few hundred locals cleared a 750 meter long and 70 meter wide runway. Snow clearing began on April 20 and the same day Norwegian Fokker C.V surveillance planes landed with skis. The workers on the ice were attacked by German fighter planes, and most snow clearing was then done during night. Some 100 ground crew arrived on April 23. The runway was used on April 24 and the 18 planes completed about 40 flights and attacked 37 enemy planes. That same night was extremely cold and engines did not start. Early morning April 25 the makeshift airfield was attacked by Heinkel 111 og Ju 88. Two British plane that were unharmed but unable to fly were burned by the crew. At the end only five planes survived and were moved to Setnesmoen camp at Veblungsnes on April 26.
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