U:\2021\BM210482_IBo_Waihi_North_Project\Documents\WNP_Freshwater_Report_May_2022\FINAL_Freshwater_Report_FOR DELIVERY_June 2022\FINAL DELIVERED 17 JUNE 2022\WAI-985-000-REP-LC-0007_Rev0_Freshwater_20220621_FINAL.docx Table 24: Results of biological indices from recent in-river biological monitoring of the Ohinemuri River in the vicinity of Oceana Gold Waihi (Data from Golder 2015-2017, and Ryder 2018-2021). Categories for MCI are: <80 = poor; 80-99 = Fair; 100-119 = Good; >119 = Excellent (Stark 1985). MCI QMCI Nov 2014 Fair Poor March 2015 Poor-Fair Poor-Fair Nov 2015 Poor-Fair Poor May 2016 Poor-Fair Poor Nov 2016 Poor-Fair Poor-Fair May 2017 Poor-Fair Poor-Fair Nov 2017 Fair Poor March 2018 Poor-Fair Poor-Fair Dec 2018 Poor-Fair Poor-Fair March 2019 Poor-Fair Poor-Fair Dec 2019 Poor-Fair Poor-Fair March 2020 Poor-Fair Poor-Fair Dec 2020 Poor-Fair Poor-Fair March 2021 Poor-Fair Poor-Fair Ordinations of the macroinvertebrate communities 2009-2021, are shown in Figure 17. The ordinations reveal patterns in the overall data. The smaller the cluster for each site (shown in different colours in Figure 17), means a higher degree of similarity (that is, the communities of macroinvertebrates over the years have not changed greatly). The broader the spread of each site cluster the more dissimilarity is exhibited within the site data. More importantly, the position of each site cluster relative to the others reveals how similar, or different, the patterns of macroinvertebrate community have been over the 2009-2021 period. The closer each cluster is to each other, the more similar the macroinvertebrate communities, and the further apart they indicate how different or dissimilar they are. For the most part, the clusters of macroinvertebrate communities, are actually on top of each other, in a pancake pattern. This indicates a very high degree of similarity between the sites, both in autumn and spring. In part, this is expected, given the sample sites occur over a relatively short stretch of river with generally consistent habitat conditions. More importantly, it shows that the macroinvertebrate communities at sites downstream of the treated wastewater discharge are very similar to the macroinvertebrate communities above the discharge (or put another way, do not deviate from the control standard upstream of the discharges). Above all it shows that the ecological values as assessed by macroinvertebrates have essentially remained consistent throughout the monitoring period. The NOF sets out limits for macroinvertebrates for ecosystem health (aquatic life) for freshwaters in New Zealand. These limits relate to MCI, QMCI and ASPM23 metrics and are set out in attribute bands for condition of water quality for ecosystem health. The limits for each attribute band are set out to reflect organic pollution/nutrient enrichment. The NOF attribute bands are set out in Appendix 12. For the most part, the MCI levels within the Ohinemuri River were in Attribute band C or below the NBL in Attribute D. In summary, the condition of the Ohinemuri River, as measured by macroinvertebrate indicators, is poor to fair. This condition occurs throughout the reach of the river in the vicinity of 23 APSM = Macroinvertebrate Average Score Per Metric.
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