Lister dam: Ruhrverband starts deep water aeration

As has been the case at the Möhne Dam since the beginning of September, the Ruhrverband is also aerating the deep water of the Lister Dam from this week in order to prevent possible fish mortality. This is a purely precautionary measure that has been successfully implemented at various Ruhrverband dams in recent years. 

The mobile oxygen enrichment plant will be set up tomorrow, Wednesday 1 October, in the small car park next to the Lister dam. This car park will therefore be closed to visitor traffic for the duration of the aeration work, which is expected to last several weeks. The larger car park directly on Listertalstraße can still be used during the project, but will be temporarily closed tomorrow, Wednesday, as the area is required for the installation and refuelling of the oxygen system. 

As soon as the oxygen enrichment system has been installed, fishing will be prohibited in the entire area around the system. Mooring boats to marker buoys or parts of the plant is strictly prohibited. 

Another road closure that is currently in force at the Lister dam is not related to deep aeration. Repair work is being carried out on the tarmac on the Listerrandweg between the dam wall and Kalberschnacke. The work is expected to be completed at the beginning of next week, when the edge path can be reopened to leisure traffic. 

Background: Why there is a lack of oxygen 
Stable temperature layers form in the reservoir between spring and autumn: cold (heavy) water at the bottom of the reservoir and water that has been warmed by summer temperatures and sunlight (i.e. lighter) at the surface, with a so-called thermocline in between. In the thermocline layer, decomposition processes of dead phytoplankton and zooplankton consume a lot of oxygen. This creates an almost oxygen-free "bar" that traps the cold-loving fish species at the bottom of the lake. If the oxygen content there falls below three milligrams per litre, the fish stocks are at risk. 

To prevent this, the reservoir operator, the cooperation laboratory and the Ruhrverband's fisheries management team monitor the values closely from the end of the summer. Targeted aeration has successfully prevented fish mortality in recent years. The stable temperature stratification dissolves by itself due to stronger autumn winds, cooler air temperatures and increased inflows to the dam. The low oxygen levels measured are a natural phenomenon and are not related to the water quality. This remains at a high level in all other Ruhrverband reservoirs