Faecal indicator impacts on recreational waters: budget studies and diffuse source modelling.

ABSTRACT

A series of investigations are underway which have quantified the contribution of faecal indicators delivered to nearshore coastal waters from the sewerage system and riverine inputs. Studies have been completed in Jersey, Staithes, Yorkshire, South Wales and the North-west. The research protocols have involved quantification of high and low flow faecal indicator delivery from the sewerage system and riverine sources as well as construction of nonpoint source models designed to predict faecal indicator delivery from diffuse, catchment sources. These investigations suggest a dynamic, but predictable, balance between inputs from the sewerage system and from 'catchment' sources. The sewerage system dominates during low flow conditions but is often overtaken by riverine inputs during high flow conditions after rainfall. Many bathing beach locations exhibit non-compliance after rainfall when stream inputs, rather than sewerage inputs, commonly dominate. The implications of this input pattern is that routine monitoring data may not provide information relevant to new infrastructure planning designed to achieve bathing beach compliance. This suggests that the present scientific information base is insufficient to underpin the extensive UK infra-structure investment programmes designed to ensure compliance with existing EU Directive 76/160/EEC standards. Furthermore, results to date, suggest that management attention must expand from its historical focus on infra-structure provision to incorporate diffuse sources of faecal indicator loading which present a new set of management and modelling challenges.