Is the Achievement of “Good Status” for German Surface Waters Disproportionately Expensive?—Comparing Two Approaches to Assess Disproportionately High Costs in the Context of the European Water Framework Directive

Currently only 8.2% of German surface water bodies have reached the goal of the European Water Framework Directive to bring all water into a “good status”. For all water bodies that presumably will not achieve the objective by 2027, the member states have to justify an exemption by 2021, for example, by arguing that the costs of achieving “good status“ would be “disproportionately high”. In this paper, two approaches for assessing cost-disproportionality of surface water bodies are empirically tested and compared on a set of real-world data from a German federal state. In the first approach, called average cost approach, costs are considered as being disproportionately high if they are significantly higher than what would be a “relatively normal effort”. The core idea of the second, the benchmark approach, is to take the past public expenditures on water management as a basis for comparison. Both approaches include generated utility for determination of a water-body-specific disproportionality threshold. While the benchmarking approach needs less data, the empirical tests indicate that both approaches yield comparable results and are suitable to support authorities in the decision as to which water bodies are to be considered disproportionately expensive such that exemptions are justified