Sousbach hydropower plant supplies electricity for 6,700 households

At a glance

Project facts

Project location

Lauterbrunnen Valley, Bernese Oberland, Switzerland

Project status

in operation

Project type

new construction and operation

Construction period

2019–2025

Commissioning

2025

Technology area

Hydropower

Total installed capacity:

11.4 MW

Expected annual production

around 30.6 GWh

Turbine type

Pelton turbine

Gross head

917 m

Headrace

2,980 m

Operator

BKW

BKW shareholding

100%

Key figures

installed capacity

annual production

households supplied arithmetically

long headwater supply conduit

construction period

From the project idea to the use of hydropower

The idea of using the hydropower of the Sousbach in the Lauterbrunnen Valley for regional electricity production dates back to 2008. Extensive planning and approval procedures were required before this idea became a feasible power plant project.

The location in alpine terrain placed particular demands on the project. What was therefore needed was a solution that took account of the technical and geological conditions of the site as well as the requirements for protecting the surrounding environment. A long-term approach was required from the initial project idea through to implementation.

Three kilometres through the mountain

Various sites for the water intake and different routes for the headrace were already examined during the feasibility study. The decision ultimately fell on a technically demanding solution: the water is conveyed entirely within the mountain from the intake to the powerhouse through a system of tunnels and shafts just under three kilometres long. There were two key reasons for choosing this route. On the one hand, an above-ground pipeline route would have posed geological risks due to possible landslides. On the other hand, trenching and pipe-laying work on the surface would have meant interventions in the partially protected flora and fauna.

The underground solution therefore takes account of both the geological conditions and the requirements for protecting the surrounding environment. In addition, monitoring, replacement and enhancement measures, among others, were defined together with the cantonal specialist authorities in a two-stage environmental impact assessment process.

From mountain stream to turbine

After many years of project development, construction work on the Sousbach hydropower plant began in 2019. Tunnels and shafts were built for the underground headrace system, carrying the captured water to the power station located further downstream. There, the water drives a Pelton turbine. With a gross head of 917 metres, the power plant achieves an installed capacity of 11.4 MW. After around six years of construction, the hydropower plant was completed in 2025.

30.6 GWh for the regional electricity supply

With the Sousbach hydropower plant, BKW produces around 30.6 GWh of electricity from domestic hydropower every year. This is equivalent, in purely arithmetical terms, to the annual consumption of around 6,700 four-person households. In this way, the hydropower potential of the Sousbach is being used for regional electricity production over the long term. Sousbach also shows how a hydropower project can be implemented under challenging topographical and ecological conditions. After a long project development phase, a production facility designed for long-term operation has been created in the Lauterbrunnen Valley.