This Action Programme is based on the Nitrates Directive. Article 5 of the Directive provides that Member States should review the action programs drawn up under this Directive, including any additional measures taken pursuant to paragraph 5, at least every four years and revise them as necessary. To comply with the Nitrates Directive and the Water Framework Directive, where contamination is caused nitrogen and phosphorus from current agriculture, there will be taken in addition to the existing policy such as described in Chapter 3, the measures described in Chapter 5. The measures in the sixth Action Program build on the measures deployed in the previous action programs.