Largest tributaries
The Aa is the outflow of the Wägital Lake , a reservoir that has been located at 900 m above sea level since 1924. It is used by the electricity works of the city of Zurich and Axpo AG to generate electricity . The river follows the Wägital , which gives it its name, and passes the municipality of Vorderthal at 735 m above sea level.
There is another reservoir at 642 m above sea level. Shortly afterwards, the Wägital Aa takes in the Trepsenbach on the right. In the plain, it is channeled and forms the municipal boundary between Galgenen and Wangen . At Lachen, it flows into Lake Zurich .
