Figure 4. Soil drainage class across the Waikato (Landcare Research New Zealand Ltd.)
2.6 Effluent Discharges to Land
The location of licensed effluent discharges to land between 1998 and present day (and the volume of discharge per day) were supplied by EW. Three sources of effluent with the potential to contain faecal material were identified: dairy farms, non-dairy agriculture, and utilities (treated sewage waste water). The number of consents per watershed in each of these categories, was determined. Data describing the volume of discharge was incomplete and therefore not used. Figure 5 illustrates all of the consented effluent discharges to land, regardless of category, with their location appearing to broadly correlate with dairying and urban areas.
2.7 Point Source discharges to Water
The location and volume (m3/day) of licensed point source discharges to surface waters were provided by EW. From this, the total volume of point source discharge with a potential to cause faecal contamination was determined for each watershed. Again, the data was divided into three categories – dairy farms, non-dairy agriculture, and utilities, with the latter including stormwater. The bacterial quality of treated sewage waste water was unknown, and it may have varied between sites due to differences in treatment techniques. The pattern of point source discharges across the region (Figure 6) is broadly similar to that of the land discharge of effluent. Since the point source data was from 1997, changes in the type, location and volume of discharge may have occurred during the faecal contamination monitoring program which was initiated in 1998 (section 3.1).
2.8 Ponds
Consent to discharge dairy effluent direct to a watercourse requires that the effluent is first stored within a pond. This practice promotes indicator and pathogen die-off prior to discharge (Sukias et al. 2001). Locations of all consented dairy ponds within the region were provided by EW, and this data was used to determine the number of ponds in each watershed.
2.9 Riparian data
Field survey of 8 selected watersheds (sites 17, 18, 24, 41, 46, 64, 66, and 67) indicated that riparian planting and stock exclusion from streams is highly variable both within and between watersheds. On one farm, for example, livestock were fenced off from the streambank except for a dedicated access point that was regularly visited by cattle. The length of fenced streambank may be irrelevant in determining faecal contamination if the total visitation rate of cattle to the stream is unaffected by the fencing. At site 41 a network of unfenced open drains was observed. These are known to attract cattle, and provide a pathway for the rapid transport of faecal contamination to the stream network during storm events. Such drains are likely to be present at other sites, particularly on flat land.
Riparian survey of all 73 watersheds was beyond the scope of this study and has, therefore, precluded the analysis of riparian planting and/or stock access in explaining faecal contamination across the region. The survey of selected watersheds has, however, highlighted the difficulties associated with the acquisition of riparian data at a regional scale.
Figure 5. Effluent discharge to land throughout the Waikato, sourced from the Waikato State of the Environment report 1988. Copyright Environment Waikato.
Figure 6. Point source discharges to water throughout the region, sourced from the Waikato State of the Environment report 1988. Copyright Environment Waikato.
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