Monitoring and review
47.—(1) At least every four years the Welsh Ministers must review the effectiveness of the restrictions in nitrate vulnerable zones imposed by these Regulations as a means of reducing or preventing water pollution caused by nitrates from agricultural sources and if necessary revise them.
(2) In order to do this the Welsh Ministers must establish a monitoring programme to assess the effectiveness of the restrictions in these Regulations.
(3) When carrying out this review the Welsh Ministers must take into account—
(a)available scientific and technical data, particularly with reference to respective nitrogen contributions originating from agricultural and other sources; and
(b)regional environmental conditions.