Längentalspeicher

The Längentalspeicher is a pumped-storage reservoir high in the Sellrain valley, part of the Sellrain-Silz power group west of Innsbruck. It sits 400 metres below the larger Finstertal reservoir and collects water from thirteen mountain streams that drain the Stubai and Sellrain valleys. The dam, 45 metres high, was built mainly from excavated rock from the tunnels that link the power stations.

The site is worth visiting because Sellrain-Silz is one of Europe’s most powerful pumped-storage schemes. Water can be pumped from Längental up to Finstertal, gaining potential energy, then released down a 1 250-metre vertical drop through rock tunnels to drive turbines at the Silz power station. The Finstertal reservoir alone holds 60 million cubic metres and can release enough energy to generate 231 million kilowatt-hours.

Visitors find a stark alpine landscape dominated by the dark water of the reservoir and the grey dam wall. The power station itself is mostly underground, with only maintenance buildings visible at the surface. The surrounding peaks rise above 2 800 metres, and the reservoir is reached by a winding mountain road that climbs from the Inn valley through forests and pastures.