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Opening of the flood dam at Merikoski power plant

Fish left in the dam from Merikoski power plant diversions

31.07.2023 / Last updated 00:00

Videos have spread on social media taken during the Merikoski power plant diversion during week 28, where people are walking in the channel below the dam bridge and trying to move fish left in the pools formed in the rock basin onto the fish pass.

When a diversion is in progress, the gates are opened to allow the channel to open further and the fish to swim past the fish pass. When the water then drains, some individual fish may remain in the basin and pools. These fish will be able to move from these pools the next time the dam gates open.

In principle, the dam gates may be opened for various reasons and at any time. It may be necessary to open the gates, for example, during power plant system updates, maintenance, high flow rates, or faults. We comply with the permit requirements imposed on us by the authorities and use the diversions to prevent exceeding critical water level limits that could result in flood damage in the Oulujoki river above the dam.

Over the years, thousands of salmon have migrated up the fish pass, and it is rare for fish to be left in the pools, we are talking individual cases here. However, we understand people’s concerns for the migratory fish and will be looking into alternatives for how to prevent fish from being left in the basin and pools in the future. It is a complex whole for which we have to take into account issues relating to the operation, safety, and the environment of the power plant.

We would like to remind everyone that it is illegal and life-threatening to be in the dam. The gates usually open when an alarm sounds, after a 30-second delay, but in the event of a malfunction, the gates may open immediately. Up to 500 cubic metres of water per second can flow through the dam gates, which means that it is practically impossible to get out of the way of the flood in time.