The river Suhre is a 34 kilometer long tributary of the river Aare in the Swiss cantons of Lucerne and Aargau. The river rises in Sempachersee (or Lake Sempach) at an elevation of 504 meters above sea level, and joins the Aare east of the town Aarau at an elevation of 362 meters. The most important side valley is the Ruedertal, which joins the Suhretal (or Suhre Valley) at Schöftland. In the medieval age, the river had several names: Suron (1036), Suranum flumen (1210), Sure (1241). Today, the name is written without "h" in the canton of Lucerne, and with "h" in the canton of Aargau. The most important tributaries are the Ruederchen joining at Schöftland, the Ürke joining at Unterentfelden and the Wyna joining at Suhr. River and valley The Suhre flows from the Sempachersee in Oberkirch (LU) north of the lake just next to medieval town of Sursee, which it traverses afterwards. After the underpass of the A2 motorway the creek Ron from the Mauesee joins the Suhre in the Sursiwald from the west (forest; left, Sursee). Chommlibach joins the Suhre right afterwards (right, Sursee). Then it runs further north between the villages Knutwil and Büron in the distance. Then it continues west of Triengen and east of the village Winikon in the middle of the valley and the last one in canton of Lucerne passing in the distance of the now Aargovian villages (Winikon, Reitnau, Attelwil, Moosleerau, Kirchleerau) situated at the bottom of the enclosing hills (about 650 m to 850 m a.s.l.) on each side of the flat, about 2 km wide valley. Just before Staffelbach, the Suhre traverses at 471 m the end moraine (up to 519 m a.s.l.) of the glacier that formed the upper Suhre Valley and flows then through Staffelbach. Still running north it passes Wittwil in the east before entering Schöftland, where in the middle of this larger village the Ruederchen joins from the east (right, Schöftland). Ruederchen is a larger creek which forms the Ruedertal, which in itself divides from north-west to south-east the north–south mountain range between the Suhretal and the Wynetal in the east. After Schöftland the Suhre runs west of Hirschthal ad further away from Holziken in the east. Holziken is at the northern bottom end of the eastern mountain range of the upper two-thirds of Suhre Valley. East of Holziken the Ürketal with its Ürke joins