A geospatial approach to assessing microbiological water quality risks associated with irrigation abstraction

All crops that are eaten raw can present a microbiological risk to consumers. Disease outbreaks in the United Kingdom and United States have illustrated that ready-to-eat crops can be a vehicle for the transmission of gastrointestinal disease. Irrigation water has been implicated as a possible source of microbiological contaminants. Over two-thirds of irrigation water applied to UK salad crops is abstracted from rivers and streams. Many of these are subject to a continuous input of faecal contamination from sewage treatment works as well as intermittent inputs from livestock and sewer overflows. In this paper, we show how geospatial techniques can help to assess the relationships between treated effluent discharges and abstractions and thus provide a new insight into local-scale assessments of irrigation water quality. The extent to which the approach can inform risk assessments and decision-making at the farm scale is demonstrated using a case-study catchment in eastern England.