The Ahauser Stausee, located below Attendorn in the Bigge valley, is a striking element of regional water management. It was built in 1938 to regulate the Bigge. With the commissioning of the Biggetal dam, its function was expanded to include that of an equalizing pond for the power plant. The construction comprises an earth dam and a weir system flanking an integrated power station. The weir system itself is equipped with two flap gates and two fixed weir fields.