Implementing ecological potential of lakes for the Water Framework Directive-Approach in Flanders (northern Belgium)

The European Water Framework Directive stipulates that artificial and heavily modified water bodies must reach good ecological potential, as opposed to good ecological status as required for natural water bodies, if certain hydrological and morphological pressures cannot be removed. We propose to obtain these objectives from the conditions expected once all feasible mitigating measures have been taken but relative to the internationally agreed quality goals for natural lakes. This allows a more objective, consistent and transparent definition of the possible deviation from the ultimate quality level than prevalent methods, in particular those considering the improvement expected from future measures. A level of functional integrity should be endeavored that minimizes the probability of undesired phenomena and negative consequences for biodiversity objectives embodied by the Habitats Directive. This remains a difficult exercise, but as a first approximation, constraints for the secondary alteration of lake hydrochemistry and the consequent potential for development of submerged vegetation can be considered. Six case studies illustrate possible procedures, which may be further refined to include additional relations between hydromorphological pressures, physical-chemical conditions and biota as knowledge develops or circumstances require. (C) 2013 Elsevier GmbH. All rights reserved.