Animal Waste, Water Quality and Human Health

246Animal Waste, Water Quality and Human Healthavoidance of lagoon overflow, elimination of steading runoff, prevention of cattleaccess to streams, prevention of soil compaction in cattle congregation areas –each of which was shown to reduce the output load of EC from the catchment.6.8 SYNTHESIS AND CONCLUSIONSIdeally, agencies responsible for the design and implementation of POMs toattenuate the transport of livestock-derived pathogens and FIOs withincatchments require accurate empirical data characterising the rates of attenuationassociated with each BMP. Unfortunately, the effectiveness of certain measuresis overwhelmingly site-dependent. For example, the reductions in microbialfluxes resulting from the containment of steading or feedlot runoff that waspreviously transmitted to a watercourse, or from streambank fencing/bridging,are both critically dependent upon levels and patterns of usage by livestock,which will vary from farm-to-farm and field-to-field. In other cases, discreteinfluent and effluent waters associated with a particular BMP cannot readily beidentified and monitored (e.g. practices relating to the location and timing ofgrazing and manure applications to avoid areas and times of high pollution risk).The situation is further complicated by the fact that a BMP may eliminate onesource of faecal contamination, yet create a potential secondary source(s), forexample, containment of steading runoff creates a need for treatment of thecontaminated water, with resultant effluent fluxes, or disposal to land withattendant risks of microbes being transported to watercourses via surface runoffand/or bypass flow through soils.In the present chapter, datasets presented for six BMPs have shown each to beeffective in attenuating microbial fluxes within catchments. As would beanticipated from the nature of the data reported, all six measures exhibit verymarked variability (Figure 2). The median values also differ quite markedly,with values ranging from 0.67 (VBSs)–1.59 log 10 (ISPs). Interestingly,somewhat higher median rates of attenuation (≥1.12 log 10 ) are recorded for thethree BMPs that include ponding of water and/or wetlands. A median reductionof 1.08 log 10 is recorded for WCs, though this is based on just two data values.By comparison, a lower median log 10 attenuation is recorded for the twosystems based on dry-land vegetative systems for attenuating microbial fluxes insurface flows: VTAs (0.67) and VBSs (1.00). In addition, a range of othermeasures identified in the chapter needs to be considered in the design ofPOMs. Some, such as streambank fencing/bridging and the containment ofsteading and feedlot runoff that would otherwise discharge to streams, willclearly have a direct and immediate impact, whereas the effectiveness of othersis less easily quantified.