Animal Waste, Water Quality and Human Health

176Animal Waste, Water Quality and Human Healthin a study of on-farm remedial measures (BMPs) implemented in California.Similarly, Haydon and Deletic (2006) modelled land use impacts on surface andsub-surface FIO flux using wash-off and loss equations linked to a hydrologicalmodel (SimHyd). The model required water quality data for each catchment tocalculate the FIO coefficients to predict microbial flux for a range of rural, periurbanand urban catchments within Australia.Tong and Chen (2002) report an application of the USEPA BASINS modelcalibrated against 11 water quality parameters including faecal coliforms in Ohio.FIO monitoring data will commonly have runs of low flow and low concentrationinterspersed with occasional high values caused by agricultural diffuse pollutionand intermittent discharges from sewers. The authors report (Page 379) that: “Inthe data set for [………] and faecal coliform, there are a few outliers (in theform of extremely high values). These outliers as well as missing data and“zero” values were deleted from the data set”. Information on the proportion ofdata deleted is not given, but modelling the episodic nature of FIO flux wouldneed to address the high values which are the periods of peak contamination andhealth risk.In one of the rare longitudinal (before and after) catchment-scale studiesdesigned to quantify the effect of a BMP (in this case cattle exclusion fromcatchment streams) on FIO flux from a 56.7 ha drainage basin, Line (2003)reported data derived from a 7.5 years sampling period which suggested 65.9%and 57.0% reductions in faecal coliform and enterococci export, respectively. Itis also reported that the provision of an alternate water supply without fencingwas not effective in producing FIO reduction (see also Shreeram & Mostaghimi2002). In a two year longitudinal investigation in the United Kingdom of FIOexport through a period of de-stocking due to an outbreak of foot-and-mouthdisease Chalmers et al. (2005) and Sanders et al. (2005) report a surprisinglyslow improvement in water quality following the most drastic BMP of >95%stock removal from the 254.6 ha Caldew catchment in Cumbria. A longitudinalstudy at Brighouse Bay in Scotland examined the effects of BMPs on waterquality in catchment streams and at an adjacent bathing water beach. Theprincipal BMP was stream bank fencing to create a RBS with associatedprovision of drinking troughs. Containment of dirty water from farms was alsoimplemented. The stream water quality data suggested extreme seasonality withthe summer period having markedly higher FIO concentrations in catchmentstreams. However, comparison with an unmodified adjacent control catchmentsuggested a 66% reduction in E. coli summer high-flow export coefficient (incfu · m −2 ·hr −1 ) with a parallel 81% reduction in intestinal enterococci export.Detailed monitoring through a rainfall event in the post-remediation periodsuggested that even this improvement would be insufficient to guarantee bathing