Good ecological status in a heavily urbanised river: is it feasible?

In Germany, a national instructions sheet, BWK M3, sets out how the impact of sewer system discharges on receiving water bodies is to be analysed. When applying the simplified assessment procedure defined therein and relying on traditional measures only, it becomes evident that in heavily urbanised rivers a large number of retention facilities would be needed to improve the hydraulic and qualitative conditions. However, the associated economics make the feasibility of such an immission-based approach to river restoration doubtful. In response, the Bergisch Rheinischer Wasserverband and the Ruhrverband started a common research project to find out whether and how the Rinderbach River, a heavily modified water body in terms of morphology and flow dynamics, could achieve the good ecological status required under the European Water Framework Directive. The focus of the survey was on the elaboration of an inventory, the identification of potentially attainable ecological objectives, and the discussion of measures with regard to their benefits and feasibility. The results obtained clearly show that it is possible to achieve good ecological status in already heavily urbanised rivers by making use of all existing natural potential within the river basin. They also demonstrated that a good interactive co-operation of experts in the fields of biology, urban drainage and hydraulics is indispensable.