Chapter 3 notes that management is needed to tackle externalities and points out that multiple policy options can help address these issues, acknowledging that specific responses will need to be tailored to hydrogeological and environmental conditions. Chapter 4 provides an overview of management approaches in OECD countries that vary widely, with weak evidence of a constraint-response correspondence. Only four of the 20 responding OECD countries (Austria, Czech Republic, Slovenia and the Netherlands - national and regional) and five of the 20 regions (the Jeju volcanic island region in Korea and the four Spanish regions) report conducting regular evaluations of groundwater management. As part of the EU Water Framework Directive, EU member countries are required to provide reports on the state of implementation and the qualitative and quantitative status of groundwater management bodies.