Environmental Flow and Habitat Mitigation in Mandal River, Norway
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Stockholm, 4. juni 2018 Environmental flow and habitat mitigation in Mandal River, Norway Svein Haugland [email protected] Agder Energi Ownwership: 30 Agder municipalities: 54.5 % Statkraft: 45.5 % Mandal river • 6 power plants • Average annual production 1,7 TWh • Acid rain led to extinction of salmon population • Liming in 1997 • Salmon reestablished • Annual catches from 5-12 tons • 146 GWh Laudal- run of river power plant • Intake in lake Manflåvatn • Outlet; physical barrier • Two ways migration • Weirs; built for landscape measures • Rules of maneuvering from 1980 – 1993: 250 l/sec ( ~1 GWh) • Rules of maneuvering from 1993-2013: 3 m3/s during summer and 1,5 during winter (~ 10 GWh) Mandal Outlet Laudal «Multiple lakes» From outlet to intake Bjelland og Åseral Rules of maneuvering 2013-2018 Smoltperiod Number of smolt at Hesså increase: start of the period 1. October - 1. May: Up to 20 m3/s- everything pass the plant 6 m3/s 20 and 50 m3/s at least 20 m3/s to pass, and After smolt: maximum 25 m3/s through the plant 8-12 m3/s everything pass the plant 50 and 70 m3/s at least 30 m3/s, and maximum 30 m3/s .. 12-30 m3/s 12 m3/s passing 70 and 105; 70 m3/s, and 50.. 30-50 m3/s 15 m3/s passing 105 and 150; 80 m3/s, and 105.. 50-80 m3/s 20 m3/s passing 3 > 80 m3/s 25 m3/s passing 150 and 210; 80 m /s, and 105 .. >210 ; full production (~25-30 GWh) Removal of weirs and other mitigation measures Potential and excisting spawning areas Water velocity, depth and shelter Diagnosis and measures • An Environmental design project was established in 2014 • Project goal: Reduce the loss of salmon production from regulation to minimum, and sustain or increase power production • The scientists recommended to remove the weirs • The advicory group recommended to remove the weirs (stakeholders and authorities) • AEVK initiated an application process • NVE gave permission to remove the weirs «Spunt» and the weir was removed in two operations- important to avoid the grey water from flooding the river Big rocks Shelter Fishing Fishpassage Big rocks Variation in velocity and depth Ripping Removal of silt and clogging Shelter Spawning areas Before and after removal of weir 6 m3/sec Before and after Vannføring 6 m3/sek After… Terskel 4 Terskel 3 A f t 15m³/sec e r … Terskel 2 Summary • Evironmental design approach seems to give acceptable solutions both for the owner of the power plant and the environment • The river is now a river and not multiple lakes • AEVK will apply for a new rules of manouvering, and we hope that the project goal will be achieved- both for salmon and power production.