The Breitenauer See (retention basin Breitenau) is a reservoir and bathing lake in the valley of the Sulm in the area of Obersulm and Löwenstein in the district of Heilbronn. After the devastating flood damage of the 1960s and 1970s, the Wasserverband Sulm, founded in 1973, built it in the years 1975 to 1980 for flood protection especially for Neckarsulm and its industrial areas. The lake was named after the nearby Breitenauer Hof and is always partially dammed.
By damming the Sulm created a reservoir with 2.3 million m³ of water and 40 ha of water surface. At high tide, the lake area grows to approx. 47 ha. The lake is 1500 m long and between 200 and 500 m wide. The dam is 425 m long and 21 m high. The water depth at the dam is 16 m.
The Breitenauer See is the largest lake in the district of Stuttgart and is located on the northwest edge of the nature park Schwäbisch-Franconian Forest in the protected landscape area Upper Sulmtal. The Swabian Wine Route and the Schwäbische Dichterstraße pass by. It not only serves as a flood retention basin, but is also surrounded by a recreational area.
It was released in 1986 to the public and includes water sports facilities for sailors and surfers, a campsite and a 400 m long, demarcated bay with about 10 acres of lawn. Rowing, paddling, paddle boating and fishing are also possible. In the area there are 60 km of marked hiking and biking trails. Every year, 400,000 to 500,000 people visit the facilities maintained by the Breitenauer See recreational area association. The campsite Heilbronn offers 400 pitches of 100 m² each and 70 campsites.
The lake is angling waters of the fishing association Breitenauer See. Their stock has a total weight of ten to twelve tons and they increase to a small extent independently. All common domestic fish species are found, including carp, bream, crucians, perch, pike-perch, catfish and pike. The lake is also home to several presumably exposed turtles. The Galician Swamp Cancer lives here in large numbers; in 2009, 2500 specimens of this cancer were caught there. Also, crayfish lived in Lake Breitenau, but fell victim to the latest in 2013/2014 with the Red American marsh crab introduced crayfish plague. As of 2016, the Fisheries Association estimates that thousands of red American crayfish live in the lake, but no more crayfish.