Although the original project to build the reservoir dates back to 1931, work was not started on the Sau reservoir until 1942. It was completed in 1966, completely altering the landscape. One of the most well-known images of the reservoir is when the water level drops and the Sant Romà de Sau belfry appears.With the passing of time, it has become evident that, as well as producing electricity and storing and channelling the water of the Ter river, the reservoir is a first-rate tourism resource, as it attracts thousands of visitors every year, who come both to enjoy the Guilleries-Savassona Natural Area and to bathe or do watersports such as rowing, sailing or waterskiing.