Water authority inspects Klaus flood tunnel as inflows hit historic low

Austria’s water authority has inspected a flood-control tunnel at the Klaus hydroelectric plant in the Kirchdorf district this week, ORF reports. The tunnel, operated by Ennskraft, helps regulate the Steyr River when flooding threatens.

The plant has been operating on the Steyr for more than 50 years. During high water, water can be released either over the dam or through a bottom outlet tunnel running 300 metres through the mountain. The concrete-lined tunnel is six metres in diameter and lies 40 metres underground.

The tunnel can release up to 400,000 litres of water per second through its outlet structure, Ennskraft department head Gerhard Zarfl said. That is equivalent to about 20 swimming-pool fills a second. During heavy rain, water can be directed downstream; in larger floods, some water can also be held back.

Water inflow to the plant is currently at a historic low, said Ennskraft plant manager Reinhard Burgholzer. The level in front of the plant is being kept constant, but the plant can release only as much water as flows in. Low flows can also cause cavitation, in which small vapour bubbles collapse and damage turbine runners.

The tunnel, which is normally full of water, was refilled from Wednesday and is expected to be ready for operation again by the end of the week.