A key objective of the second and third River Basin Management Plans will involve the protection and improvement of identified bathing waters and shellfish waters which are at risk of failing WFD objectives due to bacterial contamination. These waters may be at risk from multiple sources of bacterial contamination originating from land use within their respective catchments. Such sources may include septic tanks, grazing livestock, farm steadings, wildlife, marinas, human effluents, etc. Transport pathways to bathing and shellfish waters are also key to the impact of bacterial contamination. Where transport pathways are long and slow then natural die-off will reduce the need for measures compared to catchments with high connectivity. Identifying the major sources of bacterial inputs within a catchment and mapping the zone of influence, will allow relevant measures to be developed and effectively targeted to help achieve WFD objectives.
- Review of literature to provide a state of the art overview of source identification and apportionment, potential measures, and the targeting of measures to reduce bacterial contamination and improve bathing and shellfish water quality.
- Build on the review to scope a method, building on existing models where possible, and taking into account other relevant work, such as faecal typing.
- Develop a methodology allowing SEPA to create FIO risk ‘layers’ based on current science that will provide an input to SEPA’s catchment modelling framework (SIMCAT/SAGIS). The methodology must clearly identify and deliver the scientific mechanics and account for available SEPA datasets as the main drivers of FIO loadings. It must:
- identify the various pollution sources which could potentially contribute to the bacterial load entering a bathing or shellfish water.
- identify where data can be obtained to allow the scale of the above pollution sources to be estimated within a specific catchment
- estimate the bacterial loading from each of these sources on a per unit basis
- Develop a methodology to determine the zone of influence (based on relevant factors such as bacterial die off rates, river typology, etc) around bathing or shellfish waters to allow SEPA to determine the boundary at which point the pollutant source will no longer contribute to the bacterial loading.