A method-centric 'User Manual' for the mitigation of diffuse water pollution from agriculture

We describe the process of how a manual of methods for mitigating diffuse water pollution from agriculture was developed and how it has influenced policy and practice in England and Wales. The objective of the Manual was to provide policy makers and those implementing policies with information about the cost, effectiveness and applicability of potential methods in a form that would be readily understood by non-specialists. The Manual was based on earlier reports synthesising research findings and used the best available research data, and wherever this was not possible expert elicitation, with associated uncertainty. The outcome generated 44 potential methods and for each method described the simultaneous impact of applying the method on baseline losses of nitrate, phosphorus and faecal indicator organisms. Estimates of cost and effectiveness were presented at the whole farm level for seven model farm types. Methods differed widely in their cost-effectiveness and applicability to the different model farms. Advantages and limitations of the approach are discussed and subsequent developments of the original Manual are described, together with the opinions of catchment officers who have used the Manual to implement mitigation methods on farms.