The Wirri Guild considers the “Aarauer Bachfischet” to be Switzerland's oldest living tradition. The cleaning of the Aarau city stream is first mentioned in writing in the Aarau council minutes of September 3, 1526. From the 13th to the end of the 19th century, the city stream was an important lifeline for the city. The stream provided drinking water, water for domestic use and firefighting, as well as hydraulic power for industry. The annual cleaning of the open stream bed to remove debris and sand, known as “Rumen,” was therefore essential. Since the 17th century, there has been evidence of a “Bachfischet Festival” following the “Bachrumete.” In 1923, the newly founded Guild “Heinerich Wirri-Zunft zue Arau der Stadt”, whose goal was, among other things, “the preservation of old customs and traditions,” took over the patronage of the festival.
Today, the city's public works department is responsible for clearing the Aarau city stream. The return of the water is celebrated on the penultimate Friday before the autumn holidays with a procession of schoolchildren carrying homemade lanterns through the dark old town of Aarau. During the procession, the children sing the traditional “Bachfischet song.” Afterwards, they are rewarded with free food and drink. The festival ends with fireworks and the “Mordschlapf,” the traditional final bang.
