This project looked at how modelling can help better understand where E. coli and other faecal indicator organisms (FIOs) in Scotland’s rivers, coastal waters and shellfish areas are coming from. These pollutants can originate from several sources — including livestock, wildlife, septic tanks and wastewater systems — and their behaviour is strongly influenced by rainfall and hydrology. Monitoring alone cannot show which sources are most important, especially during short‑lived events such as storms.
The research examined a wide range of existing models, from simple screening tools to detailed hydrological and water quality models. Each type has strengths and weaknesses. Process based models can represent hydrology well but require large amounts of data. Screening tools are easier to apply and can highlight likely problem areas, but they provide only broad indications of risk. No single model can cover all sources and pathways across a whole catchment in a way that is practical for routine regulatory use.
The review concludes that Scotland would benefit most from a simple national screening tool that can identify likely FIO sources under the conditions that matter most for compliance. This should be supported by targeted, detailed modelling where needed and built on a long term, sustainable framework for data and model maintenance.