The so-called imperial indulgences in Achau, located at the confluence of the Schwechat, Triesting and Mödlingbach rivers, date from the time of Emperor Karl VI. and Empress Maria Theresa. The weir system was rebuilt between 1998 and 2002 for flood protection. The client was the Republic of Austria.
The course of the many rivers and streams in this "water-rich" part of the Vienna Basin is quite complicated: Above is the Laxenburg Palace Park, the Laxenburg Canal, which branches off from the Triesting in Münchendorf, and from the Heidbach, which branches off the Schwechat in the Baden area - also called Badner Mühlbach - flows through. The Laxenburg canal culverts the Schwechat south-east of the palace gardens. In Achau, the Krottenbach, the Mödlingbach and the outflow from the pond in the Laxenburg Palace Park, the Lobenbach, first come together. The Schwechat - also called "Aubach" here - and the Triesting follow immediately afterwards. The Schwechat - the new name for all flowing waters - in turn has two rivers, the Mitterbach - the name for the Schwechat below the imperial indulgences to Schwechat - and the original Schwechat, i.e. the Schwechat-Werksbach. Only in Schwechat itself, at the confluence of the Liesingbach, do these waters unite again to form the Schwechat. (from a writing by SC Maria Lanzendorf)