Drought: Ruhrverband utilises new water flow limits

From tomorrow, 1 July 2025, the Ruhrverband will for the first time make use of the option to manage its interconnected reservoir system in accordance with the lower legal limits for minimum discharges in the Ruhr. An amendment to the Ruhr Association Act came into force in December 2024 that allows this. As a result, up to 259,200 cubic metres of water per day can be retained in the reservoirs in the Sauerland region during dry summer periods such as the current one, which would have to be released into the Ruhr under the higher limits of the old version of the law. Due to the largely dry and warm weather, the discharges in the Ruhr catchment area have been in the low water discharge range for weeks and must be supported with water releases from the Ruhrverband reservoirs.

The amendment to the law is thus having the desired effect of increasing the climate resilience of the reservoir system from the earliest possible point in time. As the months of April to June are excluded from the new limits in consideration of the spawning phase of the bullhead and the brook lamprey, the minimum water flow from the previous version of the law will still apply until 30 June 2025 and the Ruhrverband will only be allowed to go below these old limits with its dam management from tomorrow.

However, the lower water flow that will occur in the Ruhr as a result is not entirely new, as the NRW Ministry of the Environment has repeatedly authorised lower minimum flows in the past in dry summers on a case-by-case basis. Each time, however, the Ruhrverband had to apply for an exceptional authorisation in order to conserve the heavily used water supplies in the reservoirs, and this was only granted for a limited period of time. This high administrative effort on both sides is now a thing of the past.

"The fact that we have to make use of our new room for manoeuvre on the very first day that it is permitted shows impressively how essential this change in the law was," says Prof. Christoph Donner, Chairman of the Ruhrverband. "I know how intensively my predecessor Norbert Jardin, together with the AWWR, the working group of waterworks on the Ruhr, and the NRW Ministry of the Environment, campaigned for this for years and how much persuasion was necessary at a political level. Not forgetting the immense interdisciplinary and cross-institutional work carried out by numerous experts in the run-up to the project. Thanks to these efforts, we are now in a position to take better precautions for long dry periods."

The considerable saving in water that does not have to be released into the river system thanks to the lower limits can add up to 42 million cubic metres by March next year - depending on the development of precipitation and temperatures. This corresponds to slightly more than the capacity of the Henne dam. "We're talking about water here," emphasises Christoph Donner, "which is invaluable for river ecology and for all user groups that rely on water from the Ruhr in the face of climate change." 

Background: With the largest interconnected reservoir system in Germany, the Ruhrverband ensures the minimum water supply in the Ruhr and thus the water supply for 4.6 million people. The Ruhr Association Act regulates the minimum amount of water that the Ruhr must carry in each watercourse cross-section. The new limits stipulate that the average discharge on five consecutive days in the months of July to March must never be lower than 12.0 m3/s in the section of water from the Hattingen gauge to the mouth of the Ruhr and 5.4 m3/s at the Villigst gauge. From April to June, the limit values are 3 m³/s higher, corresponding to the previous version of the law.