120 Figure 29: Summary boxplots of water quality of the Ohinemuri River at four locations, 2010-2021. See Appendix 7 for interpretation of boxplots. 20.4 Treated water discharge and NOF 20.4.1 Ammoniacal Nitrogen 20.4.1.1 NOF limits The NOF sets out ammonia limits for ecosystem health (water quality) for freshwater in New Zealand. These limits relate to ammonia toxicity and are set out in attribute bands for condition of water quality in relation to ecosystem health. The limits for each attribute band are set out for the protection of species in the community (e.g., 99% species protection; no observed effect on any species tested). The NOF attribute bands are set out in Appendix 12. 20.4.1.2 Ammoniacal Nitrogen in the Ohinemuri River We have set out the concentrations of ammoniacal nitrogen recorded from the Ohinemuri River at Waihi as the numeric attribute state limits of the NOF (i.e., annual median and annual maximum) in Table 35. It is evident that the Ohinemuri River meets Attribute A for the annual median at sites upstream at Waihi, but for the most part is within Attribute B in the lower reaches of the river at Waihi (and below the NBL in 2016 and 2018). For the annual maximum of the sample record, the river was in Attribute B (occasionally Attribute A) upstream of the treated water discharge and below the NBL downstream at Waihi (occasionally Attribute B).
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