By Saskia Kutscheidt // Translation: Maike Schröder
Since 1960, the dam near Geesthacht in Schleswig-Holstein has been adjusting the water level of the upper Elbe River. Fish, however, are not able to pass the dam without technical help. A new fish ladder consisting of 49 individual pools was built recently. In the 550 m long migration corridor, every pool is 16 m wide and 9 m long and connected with the neighboring pools via two slots. The size of these slots is not chosen randomly: “It always depends on the largest fish species that is expected to pass the ladder, in this case, the Atlantic sturgeon,” explains Dr. Boris Lehmann, Head of the Theodor Rehbock Water Management Laboratory (TRL) of the KIT Institute for Water and River Basin Management (IWG). For the double-slot passage to work equally for all species, the IWG scientists under the direction of Professor Franz Nestmann have now checked the extent to which the preliminary planning actually met the geometrical and hydraulic requirements. For this purpose, the water management engineers cooperated closely with biologists from the Hesse Institute of Applied Ecology.
The KIT scientists simulated hydraulic conditions in the planned ladder with the help of numerical computer models. They varied the slot geometry until simulation yielded an optimum flow pattern for the fish. This ladder geometry was then converted into a physical model at the TRL.
The new fish ladder was constructed on behalf of the Vattenfall Utility company. The project in the amount of EUR 20 million is an ecological compensation action for the construction of a coal-fired power plant planned by Vattenfall in Hamburg-Moorburg. After a construction period of about one year, the new fish ladder started operation on August 01, 2010. On some days, up to 20,000 fish pass the double-slot ladder.
