Flakavatn is probably Norway s largest high-alpine lake, situated in the remote Finse region, south central Norway. The unique character of the lake is a result of the long lasting annual freezing period, which affects nutrient status, gas exchange and drainage during the cold season and thaw. It s small periglacial watershed is probably underlain by continuous or discontinuous permafrost, and contains the glacier Flakavassfonn. Regional bedrock geology is heterogenic, and mostly barren rocks, boulders and gravel cover the area. Kaare Strøm investigated this lake and its catchments in 1933, so some historical data available. High mountain lakes are extremely responsive to climate change, as even slight warming results in appreciable changes in the catchment and lake processes. Remote mountain regions are hypersensitive ecosystems and therefore excellent indicators of environmental and climatic changes. Recent studies compared with historical records, suggest that there has been a marked change in Flakavatn catchment and lake processes. This study aims at understanding possible causes for these supposed changes trough investigation of: the ground conditions with geomorphologic mapping; the catchment geology; the melting glacier and snow beds; the lakes physical and chemical state; the watersheds drainage pattern; diatomé-analysis; and the climate in the area. To calculate permafrost thickness, maximum active layer, snow-accumulations, and water discharge, the geomorphologic features and climate-data was connected to a climate-model (VW4W) developed by Ole Humlum. The result from this study confirms that climate exerts a first-ordered influence on the catchment s change, as melting glacier and permafrost again affects the lake processes. The remoteness of this site indicates that the last decade s climate warming primarily drives changes in the lake, trough discharges from the catchments, lengthening of the summer growing season and related influences. There is still a lot of uncertainty about Flakavatn s limnological change since 1933, but the thermal response to the hot 2006 summer indicates that the lake also in the future may be an excellent indicator of environmental and climate change.