Main strands of Werra, Fulda and Weser are already impounded by weirs since a long time ago. The construction reached its peak by the end of the 19th and at the beginning of the 20th century. Further construction on the Middle Weser was then continued in the 1950’s.

Hydraulic barriers were constructed during the last centuries not only in the large navigation waterways, but also in the springs and tributaries, with a view to energy production, agricultural use or discharge control. Currently there are approx. 4.700 hydraulic barriers on approx. 16.600 km of water courses in the Weser river catchment area. Many hydraulic barriers  are only partly or not at all passable for the aquatic fauna, which has caused deterioration of animal and plant species in many water courses. This has affected the migratory fish species in particular.

The information about the number and location of the hydraulic barriers, as well as their actual continuity are therefore of particular importance for the development of a strategy at federal level. Hereto, the data from the databases of all lands were compiled. Altogether 212 hydraulic barriers on the transregional migration routes could be located.