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. This model has been reviewed by scientific peers and the DEFRA Water Policy Group and is widely expected to become one of the primary methods for rural land management planning through stakeholder participation in the future.
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 land uses such as cereals, maize and grassland.
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—indicative of septic tank numbers
Road and track density
Rainfall and hydrological data combined with information on 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. In addition, the model is 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.
ECM+ in Action
The River Tamar is a key raw water source for South West Water and has been the subject of considerable investment in catchment management interventions through schemes such as Upstream Thinking and Catchment Sensitive Farming.
The Caudworthy Water sub-catchment of the River Ottery in the Tamar catchment is also a satellite study site for the DEFRA Demonstration Test Catchment (DTC) project on the Hampshire Avon.
In light of its importance as a drinking water catchment and for the Water Framework Directive (the Crownhill WTWs catchment is comprised of 45 WFD waterbodies) the ECM+ model has been built for the River Tamar catchment above its tidal limit at Gunnislake through a participatory development process.
Once built, the model has then be used to predict the improvements in water quality that may have been achieved through the delivery of different catchment management scenarios in different locations.