Setting environmental flows in regulated rivers
There is a clear need for identifying simple relations between changes in flow and ecosystem response for the improved management of rivers and the implementation of the EU WFD. Despite this, it appears very difficult to identify widely applicable relations between hydrological/hydraulic parameters and ecosystem response, and one specific water flow target/methodology could hardly be found nor recommended. The review of management practices of setting environmental/minimum flows in selected European countries, rather revealed that a number of approaches are used, most of them, however, ending up in minimum flow/environmental flows in the range of 5-10% of mean annual flow. The authors would propose to use the building block methodology (BBM) as a conceptual framework for setting flow targets in regulated rivers. This would support the overall idea of the EU WFD of introducing ecosystem-based management with stakeholder involvement. This is in line with recommendations given to authorities in e.g. the UK where trials are currently undertaken. The authors believe the use of hydrological/hydraulic analysis still have an unleashed potential in the environmental management of regulated rivers in general and related to the EU WFD in particular, possibly supporting rapid assessment ecological status in rivers in the future.