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Summary 22We describe the development of a manual of methods for mitigating diffuse water pollution 23 from agriculture and its important influence on policy and practice in England and Wales. The 24 objective of the 'User Manual' was to provide policy makers and those implementing policies 25 with information about the cost, effectiveness and applicability of potential methods in a form 26 that would be readily understood by non-specialists. The 'User Manual' was based on earlier 27 reports synthesising available research data and, where data were unavailable, used expert 28 elicitation. The outcome generated 44 potential methods (under the broad categories of land 29 use, soil management, livestock management, fertiliser management, manure management 30 and farm infrastructure) and described the simultaneous impact of applying each method on 31 losses of nitrate, phosphorus and faecal indicator organisms relative to baseline losses. 32Estimates of cost and effectiveness were presented at the whole-farm level for seven model 33 farm types. Methods differed widely in their cost-effectiveness and applicability to the 34 different model farms. Advantages and limitations of the approach are discussed and 35 subsequent developments of the original 'User Manual' are described, together with the 36 opinions of catchment officers who have used the 'User Manual' to implement mitigation 37 methods on farms. 38

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