A climate-resilient water supply needs resilient infrastructures

Insight into a spectacular construction phase for the Neue Riedbahn: tunnelling under the Riedbahn line and laying a casing pipe under the railway tracks. Here, the opportunity was taken that the railway line was also closed for renovation work

Water management and water protection are facing major challenges: Climate change brings with it more frequent, stronger or longer-lasting extreme weather events that affect the availability and quality of our water resources. The uncontrolled entry of undesirable substances into our water bodies and aquifers, particularly from agriculture or air pollutants, makes it more difficult and expensive to obtain and treat drinking water. Last but not least, geographical change is putting pressure on water suppliers, especially in urban centres.

Action plans of the federal government and the associations

The German government's Nationale Wasserstrategie and the joint Roadmap 2030 of Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V. (DWA) and Deutscher Verein des Gas- und Wasserfaches e.V. (DVGW) are intended to meet these challenges.

In the Nationale Wasserstrategie, a total of 78 different measures, divided into ten strategic topics, are to be implemented by 2030 in order to ensure the sustainable use of water beyond 2050. One of these strategic topics is „Wasserinfrastrukturen klimaangepasst weiterentwickeln – vor Extremereignissen schützen und Versorgung gewährleisten“. [1]

In the Roadmap 2030, the actions that now urgently need to be tackled or have already begun in some cases are described in six fields of action. Field of action 4 – Resilient supply and disposal infrastructures deals with both the structural infrastructure for water supply and wastewater disposal and the digital infrastructure. Principles for water management planning are to be adapted and developed for both areas of infrastructure, this planning and implementation is to be initiated throughout Germany and all the necessary legal and personnel requirements are to be created.

Construction of a water conduct. A double thread of large diameter water pipe is laid through plain fields

Water supply in Germany according to the current status

In Germany, around 6200 water supply companies supply their customers with a total of around 5.1 billion litres of drinking water per year. 70 % of this water comes from groundwater reservoirs and 15 % from lakes, reservoirs or rivers. A further 15 % is taken from the bank filtrate of rivers or artificially enriched groundwater. The DVGW puts the total length of the supply network in Germany at 530,000 km [1]. Its maintenance is very complex and involves high costs. Water suppliers invest over one billion euros in their drinking water networks every year. The average lifespan of drinking water pipes in Germany, taking all materials into account, is around 40 years [3].

Plastic pipes for drinking water pipelines

Maintaining security of supply: The example of the Rhine-Main region

Prolonged dry weather conditions, such as in the years 2018 to 2020, but also competition for use between drinking water consumers, industry and agriculture can lead to shortages. Population growth in urban centres increases the demand for water there, often at the expense of the surrounding area. Water has to be transported from greater distances.

The Rhine-Main region is an important example of a large regional water supply where drinking water is brought into the cities from a greater distance. Hessenwasser's supply area stretches from the Hessian Ried through the Frankfurt metropolitan region to the Taunus. The technical centrepiece of the regional water supply is the network of 337 km of drinking water pipelines. This network connects a total of 21 waterworks with their extraction and treatment systems, which are distributed throughout the region. 300 pumps provide the necessary water pressure to bring the water to every house connection. Drinking water tanks with a total storage volume of 338,000 m3 serve as a buffer and to equalise volumes in the event of changing water demand. Around 40 % of the drinking water required by the Rhine metropolis of Frankfurt comes from the Hessian Ried.

The failure of one of the largest transport pipelines in this network, the Riedleitung, which is over 50 years old, is not an option. This is why Hessenwasser has been working for some time on its largest infrastructure project for the coming years: the construction of the new Ried pipeline. This new pipeline, a good 41 km long and realised in four individual construction phases, will connect the Allmendfeld waterworks in the southern Hessian Ried with the Hattersheim-Eddersheim connection point, which is located on the Main to the west of Frankfurt Airport, once it is fully completed in 2030.

Planning and construction will take place in four sections. The first to be completed was the
4 km long northern section, which went into operation in 2018, as this was the most urgent section. This was because the old pipeline, which supplies the towns of Rüsselheim and Raunheim from a group of storage tanks with a total capacity of 40,000 m3, had already been damaged in the past [4]. The old Ried pipeline is made of prestressed concrete, a material that is no longer used for drinking water pipes. For the new pipeline, steel pipes are used that are coated with polyethylene on the outside and lined with cement mortar on the inside. The experts at Hessenwasser expect this material to have a very long service life, longer than the service life of the old pipeline.

Replacing a water pipe in a residential area

Redundancy and expansion of the interconnected system

„The main motivation behind the project is redundancy: if one pipeline fails, we have to be able to stand on the other leg“, says Silvan Großklaus, the overall project manager responsible for the construction of the Neue Riedleitung at Hessenwasser. However, the new pipeline, the second section of which, the longest construction section south at 18 km, was started in summer 2024, is not intended to replace the old Ried pipeline after its completion, but to be operated in parallel with it. However, double pipelines do not mean double the amount of water, as the maximum amount of water that Hessenwasser is permitted to pump in its extraction facilities will not increase as a result, but is limited by the extraction rights. However, it does give the operator more flexibility if a higher volume of drinking water needs to be supplied within a short period of time, for example in hot and dry periods with increased water demand.

The Neue Riedleitung only runs parallel to the old pipeline in the northern section; in the south, it takes a slightly different route. This is not only due to the fact that the route of the new pipeline should be such that all human and nature concerns are equally taken into account, but the new pipeline also enables an expansion of the interconnected system. This is achieved by connecting an additional waterworks that supplies the city of Darmstadt and the neighbouring communities. This increases the security of supply for all partners, as drinking water pipelines are not one-way streets.

Literatur:
[1] Bundesministerium für Umwelt, Naturschutz, nukleare Sicherheit und Verbraucherschutz (BMUV): Nationale Wasserstrategie, Kabinettsbeschluss vom 15. März 2023. www.bmuv.de/publikationen.

[2] Roadmap 2030 – Handlungsagenda für die Zukunft der Wasserwirtschaft. Deutscher Verein des Gas- und Wasserfaches e.V. (DVGW) und Deutsche Vereinigung für Wasser, Abwasser und Abfall e.V. (DWA), Bonn, Hennef, Dezember 2023. www.roadmap-zukunft-wasser.de/

[3] P. Maler, M. Wagner, A. Schwigon, S. Kochendörfer: Netz- und Schadesstatistik Wasser – Ergebnisse aus den Jahren 2018 – 2022 energie|wasser-praxis 6+7/2024, S. 40 – 49.

[4] Neue Riedleitung: Sicherung der Trinkwasserversorgung der Metropolregion Rhein-Main. Interview mit Silvan Großklaus, Gesamtprojektleiter bei Hessenwasser. gwf Wasser|Abwasser 9/2024, S. 20 – 23.