Hegauer Aach

Learning for Lakes: Wetland Restoration Case Study Title: Restoration of the Lake Constance Tributary Hegauer Aach Location: Germany Period: 1988 – now Organisations: AK WÖK Budget: over €10 million for 39 measures Location and Background The Hegauer Aach (also kown as Radolfzeller Aach) is an exceptional river. It originates from the Aachtopf, the largest karst spring in Germany, which is mainly fed by water from the Danube. The river flows for some 35km before pouring into a vast flood plain between Radolfzell and Moos, which discharges into the Untersee of Lake Constance. With numerous hydroelectric plants alongside its shores, the river plays an important role in generating power for the region. Origin: Aachtopf in the city of Aach, a small town in the German state of Baden-Württemberg Location: district of Constance, Baden-Württemberg, Germany Length: 35km Mouth: into the Untersee of Lake Constance between Radolfzell and Moos Average discharge at mouth: 10m 3/s Catchment area: 261km 2 Problems/Issues and Causes of Issue Originally, the Aach was characterised by a large number of meanders flowing through a gravel and sand valley formed by the melt water of the Rhine Glacier during the last glacial period. Frequent floods and large-scale groundwater outlets created a magnificent fluvial topography with numerous reeds. In the second half of the 19 th century human beings began straightening the Aach, in order to improve the use of the river’s flood plains and to protect adjacent settlements from floods. Its highly meandering middle reaches were, for instance, shortened by around 40%, whereas other river sections were even shortened up to 50%. Along with the intensification of all land uses after the Second World War, the straightening of the river led to a strong decline in natural water routes and wetlands and, consequently, to a huge loss of biodiversity. This environmental degradation also had a negative effect on the region’s reputation as a recreational area. Organisations Involved In 1989, a river basin management plan was initiated by the Freiburg government office (Regierungspräsidium Freiburg), in order to foster a nature-oriented watercourse development of the Aach. This project, which is called “WÖK” in German, is carried out by the local water, nature conservation, agriculture, and fishery authorities. Local communities as well as nature conservation and fishery organisations are actively involved in the implementation of the different measures and the District Office of Constance dynamically supports the project. Furthermore, a working group called “AK WÖK” was created for the supervision of the project. This working group includes the following members: • the Freiburg regional government office (Regierungspräsidium Freiburg) • the District Office Constance • the City of Aach • the Municipality of Steißlingen • the City of Singen/Hohentwiel • the Municipality of Rielasingen-Worblingen • the Municipality of Moss • the City of Radolfzell • the local agricultural federation (Badischer Landwirtschaftlicher Hauptverband, BLHV) • Friends of the Earth Germany (BUND) • the Nature and Biodiversity Conservation Union (NABU) • the local fishing community (Hegegemeinschaft Hegauer Aach) Actions Taken During a winter flood in February 1988, the Aach broke its levees and flooded the surrounding landscape. This event shaped the future of the river: instead of repairing the old dams, the shores of the river were only provisionally fortified. Alternatively, the above mentioned development plan (WÖK) was initiated in 1989 as a pilot project for sustainable and nature-oriented watercourse development. The aim of this long-term project is to protect the river and its valley from further pressures and to fully restore the river’s ecological functions. Based on a detailed ecological assessment an action plan for the sustainable management of the Aach was designed. The project is characterised by a very comprehensive and integrative approach based on the following guidelines: • Allow the river’s intrinsically dynamic development Without human interference, the Aach will gradually create a natural riverbed on its own. • Stimulate the river’s intrinsically dynamic development In areas with a low gradient or man-made river banks, the natural flow of the Aach can be supported by means of flow diversion and dismantling of the banks. • Reconnect severed river bends In areas where severed meanders have not been filled up with gravel, the natural river bends can be reconnected. • Nature-oriented hydraulic engineering In areas with little space for development, the natural flow and structure of the watercourse can only be restored by means of nature-oriented hydraulic engineering. • Ecological passageways With the help of fish ladders, bypass channels, etc., the habitats of fish and other aquatic life forms, including important food sources for fish, are reconnected. • Improve water quality The water quality can be improved by means of river bank restoration, the introduction of adequate stream margins as well as the elimination of discharges into the river. • Conversion of arable land into grassland For centuries, humid grasslands shaped the landscape surrounding the river Aach. Animals and plants are adapted to this environment. • Restoration and maintenance of wetlands By mowing and scattering the grass of the wetlands once or twice a year without fertilisation, the typical species of the region can be preserved. • Extensive grazing of humid grasslands Extensive grazing with cattle represents a cost-effective complement or alternative to mowing the humid grasslands. Grazing with cattle was already widely used in the Aach valley around 1800. Maintenance and Monitoring The working group “AK WÖK” meets regularly to discuss the progress and the necessary maintenance measures of the restoration project. Thanks to a strong involvement of the public, local people help to monitor the project and sometimes even carry out maintenance measures together with the AK WÖK. Results and Benefits By involving numerous different stakeholders the concept became a well-functioning community project and functions as a “best practice example” for nature friendly restoration activities. The continuous implementation of 39 measures within the last 20 years led to the following results: • Ecological passageways for fish and other aquatic life were established • In Weitenried, the natural creation of meanders was allowed • Between Beuren and Hausen, the intrinsically dynamic development of meanders was stimulated • In Weitenried, water grasslands were rehabilitated • Severed river bends were reconnected in the Radolfzeller Aachried, which enhanced the habitats for fish and other aquatic life forms • In numerous residential areas, the Aach was reconstructed in a near-natural way Lessons Learnt Bulding blocks for successful action include: • Strong commitment from individuals • Public participation • Assertiveness • Prominent advocates • Staff continuity (for instance the project managers of the Water Management Administration) • Clear project goals • Links to other funded projects References: Regierungspräsidium Freiburg (2012) 20 Jahre WÖK Wasserwirtschaftlich-ökologisches Entwicklungskonzept Hegauer Aach , available at: http://www.bund- bawue.de/fileadmin/bawue/themen_projekte/radolfzeller_aach/HegauerAach_Faltblatt.pdf Credits: Kai Steffen Frank, BUND; Greta Link, Global Nature Fund; Dr. Thomas Schaefer, Global Nature Fund; Nina Bastian, Global Nature Fund .

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