Extended Nutrient Export Coefficient Model (ECM+)

The Extended Nutrient Export Coefficient Model (ECM+) has been developed by the University of East Anglia under the Rural Economy and Land Use (RELU) Programme and part-funded by the Westcountry Rivers Trust.

ECM+ has been developed to predict the effects implementation of Best Management Practices (BMP’s) (Cuttle et al. 2007) will have on sediment, faecal indicator organisms (FIOs), phosphorus and nitrogen inputs into watercourses.

Put simply, the model uses export coefficients for different land-use types to calculate exports of these pollutants based on the following input data:

• Landuse distribution—including urban and various agricultural landuses.
• Livestock numbers—including numbers of cattle, sheep, pigs and poultry.
• Population served, treatment levels and locations of Sewage Treatment Works (STWs).
• Population not served by STWs: i.e. septic tanks.
• Road and track density.
• Rainfall and hydrological data combined with in-stream processing of pollutants.
• Location and area of lakes and reservoirs with modelled impact on pollutant load at outflow.
• Farming practices: current uptake of Best Management Practices and effectiveness in reducing pollutant export.

What makes the ECM+ model such a powerful tool is that it is constructed with the participation of farmers, water company representatives and other stakeholders in the catchment and this allows all of the input data to be ‘ground-truthed’ before it is added into the model. The model is also calibrated at the sub-catchment level with real-world, in-stream measurements of pollutant load derived from Environment Agency monitoring data.

Another important component of the ECM+ model is that, once it has been built, it is then possible to develop and run a number of scenarios with the stakeholders (which can include different blends of both Best Management Practices on farms and improved sewage treatment measures) and observe their effects on the export of pollutants to the watercourse.