The Hohenfelder Mühlenau is a stream, about 10 km long, in the district of Plön in northeast part of the North German state of Schleswig-Holstein. The Hohenfelder Mühlenau is classified as a gravel-bedded stream. It begins at the Selenter See in Holstein and, together with the Salzau / Hagener Au, is one of its natural tailwaters. The course of the stream has an incline of about 4%, a length of 10 km, a width of generally between 2 and 4 m and a depth of 0.1 to 1.5 m. It is interrupted by two barriers, the mill at Köhn, which has fallen into ruins leaving just a foundation behind, and poses an obstacle of 2 to 3 m. This hurdle will now be bypassed, in line with the EU Water Framework Directive, using a drop structure (Sohlgleite) which will be built next to the existing building. The Hohenfelde Mill is another obstacle of about 4 m, which is partly bypassed with a fish pass. The existing 50 hp Francis turbine is still an obstacle however. At the end of its course the Hohenfelder Mühlenau discharges into the Baltic Sea with a water quality class of I-II.