Optimization of conditions for fish and power production in Surna, Moere and Romsdal. Report from phase 1 concerning development and employment of simulation tool from Rinna to Skei

A documentation of the current and previous physical conditions in the regulated part of the river Surna (Norway) is provided. Focus is on power production's negative impact on young salmon. Recommendations are addressed to Statkraft in order to reduce the negative impact. Four problems significant for the salmon habitat are identified: 1. Swift water level dips, especially early in growth season and daytime in the middle of the winter, cause a significant amount of stranded fish. 2. A change in the temperature regime downstream in Trollheim power plant because of bottom drainage of Follsjoe, lowering the water temperature in large parts of Surna in the summer and increasing it in the winter. 3. Periodical low water and marginal habitat conditions in Surna above the discharge of the power plant. 4. Reduction of hiding places and tightening of cavities because of reduced intensity and duration of floods. Proposed actions and sketches for solutions are provided in the analysis (ml)