Jonenbach flood retention basin

When it was commissioned, the Jonenbach flood retention basin, also known as the Jonental retention basin (German: Hochwasserrückhaltebecken Jonenbach, also Rückhaltebecken Jonental), was among 21 existing and six planned basins in the Zurich canton in Switzerland. It was built to safeguard the communities of Affoltern am Albis and Zwillikon against potential floods from the 17-kilometer-long Jonenbach.

Source: Wikipedia — Jonenbach flood retention basin (CC BY-SA 4.0)