The Water Framework Directive explicitly mobilizes economic theory for reducing excessive pollution in the aquatic environment: incentive based on EU penalty and tariff, cost-benefit analysis and cost-efficiency analysis. Tools proposed by the WFD aiming to encourage Member States to correct this under-optimality will impact the State Regulator's function. At this stage, Member States will consider sharing out pollution control efforts upstream and downstream, thus modifying the incentive instruments acting at the source.