The main tributary of Lake Constance is the Alpine Rhine. The Alpine Rhine and the Seerhein do not mix greatly with the waters of the lake and flow through the lakes along courses that change relatively little. There are also numerous smaller tributaries (236 in all). The most important tributaries of the Obersee are (counterclockwise) the Dornbirner Ach, Bregenzer Ach, Leiblach, Argen, Schussen, Rotach, Seefelder Aach, Stockacher Aach, Salmsacher Aach, the Aach near Arbon, Steinach, Goldach and the Old Rhine. The outflow of the Obersee is the Seerhein, which in turn is the main tributary of the Untersee. The most important tributary of the Untersee is the Radolfzeller Aach.