Chapter 4:Impacts of Agriculture on Water-borne Pathogens

Microbial indicators of water quality are used to quantify the risk derived from faecally contaminated surface and drinking waters. The historical focus in this area has centred on human-derived sewage contamination of bathing, shellfish and drinking waters. However, emerging catchment-scale water legislation in North America and Europe, in particular, is driving a more holistic approach in which quantification of microbial pollution from all sources is undertaken, to inform and prioritise appropriate remedial action designed to ensure health risk is minimised. This involves integrated management of agricultural livestock-derived pollution alongside sewage effluents to ensure compliance of impacted sites with appropriate regulatory standards. The evidence-base for the design of best management practices by farmers which will remove and/or attenuate microbial flux from catchment systems is very limited when compared to the chemical parameters associated with ecological impairments, such as phosphorus and nitrogen. However, early empirical investigations do suggest the potential to realise very significant water quality benefits from simple interventions, such as stock exclusion fencing of stream banks and well-designed constructed wetland systems. Further process-based investigation of these areas is underway and this research effort is becoming imperative as emerging experience of catchment-scale legislation strongly suggests the importance of microbial pollution as the principal reason for non-compliance with water quality standards in North America.