Too expensive to be worth it? A methodology to identify disproportionate costs of environmental measures as applied to the Middle Tagus River, Spain

[EN] The European Union (EU) Water Framework Directive (WFD) established in 2000 that EU Member States should achieve good status for all their water bodies by 2027 at the latest. The competent authorities are obliged to commit the necessary resources to achieve this goal. In water bodies where the costs are deemed disproportionate, the Directive foresees the definition of exemptions. Two decades after approval of the WFD, however, there is no common method across the EU to evaluate the disproportionality of costs and define the associated exemptions. We propose a methodology based on WFD indicators of water body status and economic variables that are common to all the EU countries. The method uses data that is already available in Eurostat and European Environment Agency databases, thus minimizing data collection costs. The method is applied to the Middle Tagus (Spain), where currently there are several water bodies with declared exemptions for disproportionate costs.