The equalising pond of the Möhne dam will be emptied from the end of August
In the last week of August 2025, the Ruhrverband will empty the equalisation pond below the Möhne dam until probably the end of October. The reason for this is extensive construction work that is necessary to ensure the long-term safe and reliable operation of the Möhne Dam and its hydropower plants.
The Ruhrverband had already taken preparatory measures last year and upgraded an existing construction road when the equalisation pond was empty. However, due to persistently rainy weather conditions, the first major construction phase could not be realised and the pond has since been dammed up again.
This year, several measures are now being bundled together and carried out in an intensive construction window. The quarry stone masonry on the dam wall, on the walls of the gate houses and on the wing walls of the cascades will be repaired. At the same time, from 2 September, the culvert structure of the Westricher Bach, also known as the "Birkebach", will be completely rebuilt on the north side of the equalising pond. This will be replaced with a new steel mouth profile. The replacement is necessary as the existing structure is structurally damaged and no longer meets today's hydraulic requirements. The work is expected to last until 15 September. As part of this measure, the access road to the pond will be fully closed to car traffic from house number 11. A signposted diversions through the neighbouring woodland will be set up for pedestrians.
In addition, the cone nozzle on the bottom outlet pipe III will be dismantled and replaced by an auxiliary structure. This will make it possible to renew the corrosion protection in the end section of the bottom outlet pipe in the coming winter half-year when the pond is dammed up again. At the same time, the outlet area of the main power plant will be provided with a temporary elevation made of concrete blocks. In addition, a channel around 180 metres long will be built in the pond bed to ensure that water can be discharged in a controlled manner via the main power plant and an existing operating channel even when the pond is empty.
Extensive work is also due to be carried out at the secondary power station. Here, the two turbine inlet gates will be removed and thoroughly overhauled. These components date back to 1953, when the equalising pond was put into operation together with the current main and secondary power plants. In addition, the so-called minimum water discharge pipe was fitted with two new shut-off devices. This pipeline ensures that water can continue to be released into the lower reaches of the Möhne in the event of an unexpected failure of the turbines.
Work is also planned on the dam wall. There, inspection plugs will be installed on two bottom outlet inlets as part of diving operations. Inspection work and the repair of a defective hydraulic cylinder will then be carried out under their protection.
These measures mark the start of a multi-year renovation phase at the equalisation pond. In later construction phases, the cone nozzle on the bottom outlet pipe II, the bottom outlet gate and the dam gate on the secondary power station will be renovated or replaced with new components.
Restrictions for the public
Construction site traffic is to be expected during the work, particularly on the south side of the equalising pond. The paths around the pond will remain largely accessible to the public - apart from short-term closures for crane operations or similar work. The top of the wall of the Möhne dam will also remain accessible.
Important: It is strictly forbidden to enter or drive on the drained pond area. These areas harbour considerable dangers for unauthorised persons. The Ruhrverband is signposting this danger to life.