Future of the Simme weir: the key answers

In the Grimsel Dialogue, the Canton of Bern, Kraftwerke Oberhasli (KWO) and several environmental organisations agreed on a comprehensive package of compensation measures. The aim is to link the expansion projects in the Grimsel region with ecological improvements to bodies of water in the Canton of Bern. A possible dismantling of the Simme weir, which is owned by BKW, is a particular focus of public discussion.

BKW supports the path that has been taken. It is committed to ensuring that KWO's expansion projects can be implemented in a timely manner. The Simme weir plays a central role in this.

Legal obligation to remediate

The background to the project variant extends beyond the Grimsel Dialogue. Hydropower operators are legally obliged to ecologically remediate existing facilities. This includes, among other things, improving fish passability (further information). These measures are financed through an earmarked levy of 0.1 centimes per kilowatt hour, borne by electricity consumers. Whether a specific measure is considered proportionate and therefore eligible for this funding is decided by the Confederation, specifically the Federal Office for the Environment (FOEN).

Why the Simme weir in particular?

The Simme weir currently represents a migration barrier for fish and must therefore be remediated. BKW carried out a variant study on this several years ago. The result: from an ecological perspective, dismantling the weir, combined with an underground water pipeline between the Simmenfluh power plant and the water pipeline to the Spiezmoosweiher pond, is the most effective solution.

BKW submitted this project variant to FOEN in 2022. However, the cost estimate of around 55 million Swiss francs led FOEN to classify the measure as likely to be disproportionate. At the same time, it commissioned the Canton of Bern to prepare an overall assessment in order to examine possible synergies with further remediation projects on the Simme. This work is currently under way; BKW is actively accompanying and supporting it.

Funding and decision-making process

In the Grimsel Dialogue, the environmental organisations involved proposed – in the knowledge that funding remained unresolved – that KWO contribute to any remaining costs. KWO has earmarked a budget of around 6.5 million Swiss francs for this purpose. This contribution is intended to improve the basis for a positive assessment by the FOEN.

There is currently no specific timetable for dismantling. Numerous specialist, technical and financial questions still need to be clarified. The Canton of Bern is leading these clarifications, and the FOEN also plays a central role. Only after this can a decision be made on whether and when dismantling will be implemented. If this is not the case, compensatory measures defined in the Grimsel Dialogue with lower priority will come into play.

How the landscape and energy production would change

Dismantling would remove the weir and the impoundment. With the help of a block ramp made of stone blocks, the roughly 15-metre difference in height in the Simme is to be compensated for in a near-natural way. Excess water that cannot be channelled into the Spiezmoos pond would be fed back into the Simme. In this section, the river would take on a significantly more natural character.

Dismantling would also have an impact on electricity production, albeit to a limited extent. Since most of the water from the Simmenfluh power plant could be fed directly into the existing water pipeline between Wimmis and the Spiezmoos pond, production losses are estimated at around four to five gigawatt hours per year. This corresponds to about five per cent of the production of the Spiez hydropower plant.

Benefits for fish – open questions for the region

The dismantling of the Simme weir is considered a particularly effective aquatic measure. It would significantly improve fish passage in the Simme, particularly for the ascent of lake trout from Lake Thun to their spawning grounds. For this reason, BKW had already proposed this option at an early stage as the preferred solution for restoring fish passage. How far the fish will be able to migrate upstream in future also depends on further restoration work upstream.

It remains to be seen whether and in what form there could be impacts on road and rail connections into the Simmental. Various project variants exist, the details of which are currently still being developed. Reliable statements will only be possible once all outstanding questions have been clarified.

The forthcoming assessments will show whether and in what form the dismantling of the Simme weir can be implemented and how ecological improvements, energy production and regional interests can be reconciled in the best possible way.

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