The Rhine-Weser watershed runs over the Totenkopf. So while the waters of the Großen Aa and Kleine Aa, which are impounded a few kilometers north of the hill by the Aabach Dam to form the Aabach Reservoir, drain via the Aabach, Afte, Alme and Lippe in a predominantly northwesterly direction into the Rhine, the shorter streams that rise south of the Totenkopf drain via the Hoppecke and Diemel, or from the Momeke and Dütlingsbach straight into the Diemel, in a mainly northeasterly direction into the Weser.