Wikipedia
Wölpe
The Wölpe is a left tributary of the river Aller in the German state of Lower Saxony and is about 22 km long. It has its source in a depression southeast of Erichshagen-Wölpe, a village in the borough of Nienburg/Weser and flows towards the northeast. In front of Rethem the Weiße Graben ("White Ditch") links the Wölpe with the Alpe. It then discharges into the Aller near Wohlendorf in the borough of Rethem. The waterway has been considerably straightened. It flows through woods, grassland and cultivated fields. According to the 2000 Water Quality Chart issued by the NLWKN it is critically polluted throughout ( quality class II−III).