Animal Waste, Water Quality and Human Health

Exposure interventions 307Weather related FIO pollution events have been studied in considerable detail(Crowther et al. 2001 and 2003). SEPA used its extensive national on-linehydrometric network of rain and river monitoring across Scotland, and developed“nowcast” models using preceding rain/river flow to issue “live” site specific bathingwater quality predictions (McPhail & Stidson 2009). The prediction tool (an Excelspreadsheet-based model) derived site-specific trigger limits for rainfall and river flowto predict bathing water quality based on historical correlations between hydrologyand faecal coliform concentrations. Rainfall depth-duration thresholds used previous24, 48 and 72 hours amounts, together with current-day rain forecast to midday (onthe day the message is posted). River flow information was also included in theregression relationships. This was a simple and effective means of predicting bathingwater quality where pollution was predominantly wet weather-driven and elevatedmicrobiological levels occurred during such events. The prediction forecasts werevalidated annually and performance in 2008, as confirmed by water quality testing,was correct on 82% of days. To date, the overall daily signage has been correct orprotective on 98 to 99% of occasions over the last seven years of operation. A publicawareness survey was carried out and beach users, organizations and media continueto provide positive feedback on the signage system (Figure 8.3).Figure 8.3 On-line electronic bathing water quality message sign; Prestwick, Scotland.