Strong aquatic plant growth in ponds

Essen, Baldeneysee, July 1, 2026. The Baldeneysee is Essen's sporting heart, a training ground for rowers, sailors, and canoeists, a destination for families, and a stage for national and international competitions. However, the exceptionally strong growth of submerged macrophytes – especially hornwort – is increasingly pushing the ecosystem and the use of the lake to its limits. The 2026 German Junior and Age Group Rowing Championships, long planned by the Baldeneysee-Sportverband e.V., had to be moved just weeks before they were due to start. A technical conference, to which the Baldeneysee-Zweckverband had invited representatives from the NRW Ministry of Environment, the Weisse Flotte Baldeney, and the IG Baldeneysee, was intended to re-evaluate the situation and show ways out of the crisis. Baldeneysee.Ruhr summarizes the results.

The occasion was a landmark: the German Junior and Age Group Championships 2026 in rowing, originally planned for the end of June 2026 at Baldeneysee planned, had to be relocated at short notice to Elfrather See in Krefeld. The development of aquatic plants no longer allowed for safe execution and fair competition. A signal that alarmed all involved – and increased the pressure to prevent further cancellations.

Markus Rüdel, spokesperson for the Ruhrverbands, opened the meeting with a clear analysis. The plants growing underwater are currently in large parts of the lake from Hornwort dominates, while the Waterweed, which had caused problems in past years, now only occurs sporadically. However, the lower presence of Elodea is no reason to relax. „The morphological characteristics of the pondweed lead to considerable technical difficulties in mowing operations, as the cut material gets tangled and puts significantly more strain on the mowing boats“ systems.„ The challenge has therefore not become smaller - only different: “The current situation presents us with new challenges."

Dr. Christina Meinert-Berning, a microbiologist and expert on stagnant waters at the joint laboratory of Ruhrverband and EGLV, emphasized the ecological value of the plants. „Macrophytes are central components of a stable stagnant water ecosystem. At the same time, high biomass leads to pronounced conflicts of use, especially in performance-oriented Water sports.The expert conference made it clear: the lake needs the plants – but sports need open water surfaces. A classic conflict of objectives.

Aquatic ecologist Dr. Klaus van de Weyer from lanaplan presented an in-depth scientific assessment. The vegetation development was the result of a combination of particularly favorable environmental conditions in 2026: high temperatures, low water discharge, low turbidity, and a pronounced clear water phase in spring. „These conditions created optimal growth conditions for submerged aquatic plants.“ The dominant curled pondweed – a hybrid of Potamogeton crispus and Potamogeton friesii – also showed unusually high competitiveness. Why it has prevailed over the water milfoil with over 90 percent is still scientifically unexplained. „Predictions about the further course of growth would be unprofessional.“ A sentence that underscores the uncertainty of the coming season.

Steffen Quast, deputy head of reservoir operations at Trianel, reported on the ongoing mowing operations. Basically, pondweed can be mowed at slower speeds and with optimized conveying technology – however, it is significantly more demanding to handle than the previously dominant waterweed. This leads to increased maintenance effort and greater strain on the mowing boat technology. The cooperation with RWE functions very well. However, the existing infrastructure with two mowing boats and a mobile unloading point is largely utilized, and the logistical and personnel capacities are almost fully exhausted. Therefore, in the future, the mowing strategy is to be optimized through airborne monitoring, satellite-based recording of macrophytes, and data-based early detection systems, among other things.

The conference discussions made it clear that the development of aquatic plants at the Baldeneysee is not an isolated event, but part of a larger ecological change affecting many reservoirs and dams in Germany. Prof. Dr. Christoph Donner, Chairman of the Board of the Ruhrverband, placed this development in a broader context. Climate change, invasive species, and the return of native plant species are sustainably altering the waters and leading to new conflicts of use between water sports, recreation, nature conservation, and water management functions. Donner warned against hasty interventions that could jeopardize the lake's delicate balance. Sediment removal or relocation must be critically examined, as it could destabilize the system. The experience at Harkortsee in 2001 showed that even extensive sediment removal does not prevent the growth of aquatic plants. „We need to move more strongly from reactive.

For Essen, the Baldeneysee is not just a local recreation area, but a central building block of its sports infrastructure. Simone Raskob, Head of the Department for Environment, Transport and Sport, emphasized the urgency of a solution that considers both ecological and sporting requirements: „We need a short-term viable strategy to secure upcoming major sporting events.“ The postponement of the junior championships served as a warning signal that must be taken seriously. Essen wants to continue to be a venue for national and international competitions – reliable framework conditions are necessary for this.

In order to better understand the development and make informed decisions, further biological investigations are planned. These include dives in July 2026, which will document the spread of pondweed and the composition of macrophyte stands in detail. The planned monitoring measures – including satellite-based recording and airborne monitoring – are also intended to help recognize vegetation developments early on and plan mowing strategies more precisely in the future. All those involved emphasized their readiness for ongoing exchange. The conference was constructive and showed that Ruhrverband, Stadt Essen, Weisse Flotte, and IG Baldeney want to work together on solutions.

The lake is undoubtedly at a turning point. The exceptional vegetation development of previous years and of the year 2026 has shown how changeable the ecological balance is – and how quickly conflicts of use can arise as a result. At the same time, it has become clear that the lake cannot simply be controlled as an aquatic ecosystem. It reacts to environmental conditions, climate dynamics, and biological processes. The challenge therefore lies in preserving the ecological stability of the lake while simultaneously securing its importance as a sports and recreation location. The conference has shown that this path is demanding – but also that it can only succeed if we work together.

The Baldeneysee is a symbol of the modern, structurally transformed Ruhr area: a place where nature, leisure, sports, and city life come together. To ensure this remains the case, water management is needed that not only reacts but also thinks ahead. The coming months will be crucial and bring clarity. The results of the dives, the evaluation of monitoring data, and the coordination among stakeholders will determine what the 2027 season at the Baldeneysee will look like. One thing is certain: the Baldeneysee remains a complex, living ecosystem – and a body of water that requires attention, care, and shared responsibility. Baldeneysee.Ruhr will continue to follow the topic.