Investigating the transfer of E. coli through agricultural systems

Here is a quick overview of some work I began at Rothamsted research’s North Wyke farm platform in November:

Intensification of agricultural systems resulting from an increase in demand for food production can lead to unsustainable use of (in)organic fertiliser. For example an increase in on farm livestock numbers will lead to increased volumes of faeces being applied to land either as slurry, manure, or direct deposits from grazing livestock. Following rainfall, mobilisation of pathogens associated with these faeces into the catchment system can impact downstream ecosystem services associated with clean drinking, bathing and shellfish harvesting water.

SCIMAP is a risk based model of diffuse pollution transport which has been optimised for diffuse sediment and nutrient pollution. My trip to the North Wyke farm platform provided an opportunity to test SCIMAP’s consideration of E. coli pollution, an internationally accepted indicator of faecal pollution. SCIMAP uses the critical source area concept whereby sources of pollution are only a problem when they are connected to the stream network. The approach assumes a topographical control on the connection of sources of pollution to the stream network. Therefore we should expect to see increased levels of contamination in the soil of topographical pinch points, points that are disconnected from the stream network but have a large contributing area. Overland flow, and potentially its constituents, will accumulate in these areas. In this study we test this assumption when SCIMAP is applied to E. coli transfer by using SCIMAP to determine the location of topographical pinch points and compare E.coli contamination at these points with non-pinch points.

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This work will contribute to the assessment of SCIMAP as a useful tool for the determination of areas of the landscape that contribute to diffuse faecal pollution providing opportunities for spatial prioritisation of mitigation effort.

Kenneth Porter

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