Hållbar vattenkraft i Nissan
En förstudie och konsekvensutredning över förutsättningarna för ökade vandringsmöjligheter med nya fiskvägar.
The hydropower from Nissan River is of national interest and produces annually 230 GWh from the twelve power stations in the main flow. For modified waters a consideration between the power production and the biological values has to be made. This reports serves as a pre-study for Nissans Vattenråd. It tries to evaluate some of the biological values in the Nissan basin and map the power production in the area. And the size and value of lost power production from new fishways for the twelve stations in the main flow.The investment of new fishways is calculated using simplified templates with values from the business. The cost and loss of power due to new fishways are calculated for three cases: fish friendly grates for the power station inlet and bypass for migration. Fish friendly grate and vertical-slot fish passage for migration. The last case is called ?scenario? and is a combination with the most suited solution for each station. This includes a restoration of the creek, with maintained power production, for the two stations closest to the ocean.The cost for fish friendly grade and bypass for al stations is about 207 mskr and for vertical-slot fish passage 125 mskr. They both result in a loss of power production of 12 GWh/year, corresponding to a value of 3,2 mskr (NordSpot sale price only) annually. Case ?scenario? costs 177 mskr and loses additionally 4,2 GWh/year.In the overview, large parts of the Nissan runoff has difficulties reaching ?god ecological status? which is the goal set for 2021. This goal can be extended to 2027. The main problem is chemical effect of acidification and mercury in the ground, as well as connectivity issue caused by dams and culverts. Salmon and sea trout could earlier migrate to Nissafors and is limited to the lower parts of Nissan to Oskarström. Many of the tributary waters have high biological values. The existing fishways have questioned functionality and delays fish migration today. Before decisions are made about increasing fishways the advice is to do further studies about the breeding grounds. It?s also possible to identify positive cash flows from an increase in fish migration.