River continuity under difficult boundary conditions–useful steps and practical hints for designing a fish way

Abstract

Most large and medium sized river basins in Germany have, over time, been affected by anthropogenic changes due to navigation, hydropower generation, and straightening and shortening of river courses for land reclamation. Consequently, there are many weirs inhibiting fish migration. The Ruhr River is affected by several such barriers or obstacles of which Baldeney Weir is the biggest. The search for an appropriate fish pass structure has not been easy given that the location is embedded in urban surroundings and used for traffic or recreation. This situation led to the establishment of an expert working group chaired by the Ruhrverband to discuss the problems and find a common solution. In a step by step approach, all necessary basic information was elaborated and evaluated, including consideration of diverse fish pass types. Setting up a working group of experts and responsible decision makers was found to be an appropriate method of overcoming differing opinions, sometimes based only on subjective, one-sided assessments, and reaching a mutually acceptable solution.