Diffuse pollution arises from many sources which, when combined, can have a significant impact. Examples include run-off from agriculture, urban run-off and leakage from septic tanks. Contaminants can include pathogens, hydrocarbons, heavy metals and organic substances. Even when individual inputs are quite small, collectively they can be very damaging.
As more and more point sources of pollution such as sewage discharges are being tackled, diffuse pollution is becoming the major problem in some regions. Areas such as Western Scotland and some beaches in North Devon are thought to be among those that suffer from reduced water quality due to pollution from agricultural run-off.
As, by definition, there is not one single input of pollution, identification of the sources of diffuse pollution can be difficult.
Once the sources of diffuse pollution have been identified, the type of remedial action required can be established. This will have to be done on a case by case basis.
The impacts of agricultural run-off in some areas need to be reduced by the introduction of catchment sensitive farming techniques including practices such as avoiding muck spreading during rainy periods and the building of bunds or vegetation strips to prevent run-off.
Pollution from urban run-off can be tackled by introducing sustainable urban drainage systems (SUDS) such as interception ditches and swales. By providing areas that allow water to permeate, run-off to water courses can be substantially reduced.