It was created to deposit the sludge from the wet mechanical iron ore processing in Calbecht and was in operation from May 1944 to 1952.

When wet washing ceased in 1976, the surrounding area and banks were recultivated and an attractive water area was created, which was also accepted by many water birds.

Located 195 meters above sea level, the former sewage pond 2 is 52 hectares in size. The water inflow comes from a relatively large catchment area and the artificial outlet prevents it from absorbing too much water and the risk of a dam bursting. The Reihersee is now considered an insider tip among nature lovers.