The Breitenauer See (Breitenau retention basin) is a reservoir and bathing lake in the Sulm valley in the area of Obersulm and Löwenstein in the Heilbronn district. After the devastating flood damage in the 1960s and 1970s, the Sulm Water Association, founded in 1973, built it between 1975 and 1980 to protect against flooding, especially for Neckarsulm and its industrial areas. The lake was named after the nearby Breitenauer Hof and is constantly partially dammed.
By damming the Sulm, a reservoir with a water capacity of 2.3 million m³ and a water surface area of 40 hectares was created. During floods, the lake surface area increases to around 47 hectares. 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 Stuttgart administrative district and is located on the northwest edge of the Swabian-Franconian Forest Nature Park in the Upper Sulmtal landscape conservation area. The Swabian Wine Route and the Swabian Poets' Route pass by it. It not only serves as a flood retention basin, but is also surrounded by a local recreation area.
It was opened to the public in 1986 and includes water sports facilities for sailors and surfers, a campsite and a 400 m long, fenced-off bathing bay with around 10 hectares of lawn. Rowing, paddling, pedal boating and fishing are also possible. There are 60 km of marked hiking and cycling trails in the area. Every year, 400,000 to 500,000 people visit the facilities maintained by the Breitenauer See local recreation association. The Heilbronn campsite, located on the lake, offers 400 pitches of 100 m² each and 70 tent pitches.
The lake is a fishing water of the Breitenauer See fishing club. Their stock has a total weight of ten to twelve tons and they reproduce independently to a small extent. All common native fish species are present, including carp, bream, crucian carp, perch, zander, catfish and pike. The lake is also home to several water turtles that were probably released. The Galician crayfish lives here in large numbers; in 2009, 2,500 specimens of this species of crayfish were caught there. Noble crayfish also lived in Breitenauer See, but fell victim to the crayfish plague that was introduced with the red American crayfish in 2013/2014 at the latest. As of 2016, according to estimates by the fishing club, thousands of red American crayfish live in the lake, but no noble crayfish.