The water in the Rhine-Main metropolitan area could become scarce. The reason is not only global warming with mostly dry summers, but also the constant influx of people. They all need water. That is why more and more needs to be promoted. Bernd Petermann, head of the Offenbach water supply association (ZWO), is now calling for immediate reactions in order to secure the regional water supply for the coming decades. He is supported by Offenbach’s mayor Sabine Groß (Die Grünen).
The association supplies the city and district of Offenbach as well as the Hanau districts of Klein-Auheim and Mühlheim with water. Up to 20 million cubic meters per year go from the waterworks of the association to the 450,000 inhabitants of the catchment area. With an upward trend. The water is drawn from 121 wells, treated in six waterworks and distributed over 280 kilometers of pipelines within the city of Offenbach and a further 246 kilometers in the district.
The previous support is no longer sufficient
The water rights granted around 30 years ago for the pumping of groundwater are now in danger of being insufficient: the pumping of exactly 20.21 million cubic meters is permitted. While other counties exhaust their water rights to 70 to 80 percent per year, the ZWO is at the limit with 97 percent. That is why Petermann not only wants to renew the contracts concluded in the 1960s: he is also looking for new ways of supplying water and is counting on the state of Hesse, but also on the Hessian Ried and the Main.
Strictly monitored: The inflow and outflow as well as the filling level of the Bieberer Berg station in Offenbach are displayed on monitors in the control center of the Rodgau-Jügesheim waterworks. : Image: Frank Rumpenhorst
Petermann is aiming to join the Zweckverband im Ried, which treats Rhine water in Biebesheim in the Groß-Gerau district and then channels it back into the ground. This keeps the groundwater levels stable. Petermann could also imagine something similar for the ZWO, but then with water from the Main.
However, water could also be delivered to the ZWO from the reed. “We have to win additional amounts of water, but also reduce the demand for drinking water and rethink how we deal with water,” demands Petermann. This is already happening in Offenbach, says the mayor. For new buildings, cisterns would be required and more green would be required – for example on house roofs. Rock gardens should be banned.
For Petermann, however, cisterns are not the great solution. These are expensive, empty quickly in the summer and are refilled with precious water from the water pipes. Instead, the water expert calls for the abandonment of underground car parks: Instead, huge water collection tanks should be built under larger residential units, which collect the rainwater in heavy rain. From there it could be sent to waterworks for treatment or possibly even treated on site and used as drinking water. “We just have to think bigger,” emphasizes Petermann.
However, according to Petermann, it will be at least 2030 before Main water can be treated and returned to the groundwater. This is due to the lengthy bureaucratic processes, because an appropriate facility – similar to the one in Biebesheim – would first have to be built.
Treatment: The water is filtered in basins, its quality is constantly checked. : Image: Frank Rumpenhorst
Water traffic lights should regulate consumption in the event of a shortage
Petermann sees another difficulty for a secure water supply in the forecasts. “There are no reliable forecasts for the future.” Nobody knows how the groundwater situation will develop. Therefore, in the next few years, the use of drinking water must have absolute priority for the provision of services of general interest. The city of Offenbach is currently developing a water traffic light in order to be able to react accordingly in the event of a water shortage. When the traffic light switches from green to yellow or red, there should be bans: pools can no longer be filled and gardens can no longer be watered.
However, it is not an optimal solution: if gardens dry up, this damages the microclimate. For this reason, the ban on watering should initially be limited to lawns. “Because it will recover later,” says Groß, who wants to develop Offenbach into a “sponge city” that can store water in the long term.
Thorsten Winter, Hungen-Inheiden Published/Updated: , Recommendations: 19 Mark Fehr Published/Updated: , Recommendations: 59 Sebastian Balzter Published/Updated: , Recommendations: 33
The state of Hesse and the Darmstadt regional council are also working on concepts for groundwater management. In the Rodgau-Jügesheim waterworks, one of six of the ZWO, the two tanks on the factory premises, which hold around 6,500 cubic meters of water, are often quickly empty in the hot summer months. Then there are only five hours to refill them and ensure the supply.
#Offenbach #reaching #limits #water #supply
