Disproportionate costs in the EU Water Framework Directive—How to justify less stringent environmental objectives

The ambitious objective pursued by the European Water Framework Directive (WFD) is good status for all European waters. However, “less stringent environmental objectives” are permissible if the costs of achieving good status are disproportionately high. This exemption, if abused, carries the risk of watering down the ambitions of the Directive. Currently, no transparent, well-established, universally applicable method for routinely testing disproportionality exists throughout Europe. In this paper, such a method is developed for surface water bodies. The core idea is to determine a water body-specific disproportionality threshold which is then compared to the projected costs of achieving “good status/potential”. For the sake of practicability, the benchmark for disproportionality is estimated on the basis of prior expenditure on water quality enhancement. The paper argues that the proposed method combines both possible interpretations of (dis-)proportionality—affordability and cost-benefit considerations. Due to the method’s moderate data requirements it can be used readily in most German federal states and is transferable in principle to other EU Member States. The method was tested empirically for a river in the German federal state of Rhineland–Palatinate.