32 7.7.2 Mataura Stream Water Quality A summary of the water quality results collected at the two sampling sites (Mataura Stream and unnamed tributary 2) is provided in Table 11. We have compared the water quality of these two sites to WRC water quality guidelines and the NOF attributes where applicable. Spot measurements from both sampling sites showed good dissolved oxygen concentrations. Water temperature and pH are likely to fluctuate daily and with seasons. Heavy metal concentrations from the sediment quality analysis did not exceed applicable guidelines. Nutrient concentrations were generally low, with higher concentrations of nitrogen and phosphorus found in the unnamed tributary compared to Mataura Stream. This is to be expected with stock access excluded from the Mataura Stream as well as native forest (low nutrient source) comprising part of the upper catchment. Water quality results for Mataura Stream were mostly within the WRC guidelines (Appendix 6) except for some nutrient parameters (total ammoniacal nitrogen, total phosphorus). Table 11: Water and sediment quality results from the Mataura Stream. Analytes Units Mataura Stream (2020)a Mataura Stream 2015-2018 (n=3)b Unnamed tributary 2a WRC guideline NOF Temperature ⁰C 12.6 15.4 - 18.9 14.7 <12 & <20 Dissolved oxygen mg/l 11.44 - 10.01 - Band Ac % 108.0 - 107.5 >80 Conductivity µs/cm 55.4 - 49.6 - pH pH units 6.72 6.5 - 7.5 6.05 6.5 - 9 Copper g/m3 - 0.0005 - - Lead g/m3 - 0.0001 - - Zinc g/m3 - 0.001 - 0.0023 - - Nitrate g/m3 - 0.1 - 0.5 - - Band A Nitrite + Nitrate g/m3 - 0.1 - 0.5 - - Total ammoniacal N g/m3 - 0.01 - 0.058 - 0.88 Band A-B Total Phosphorus g/m3 - 0.005 - 0.049 - 0.04 Dissolved reactive phosphorus g/m3 - 0.004 - 0.022 - - Total suspended solids g/m3 - 3 - 7 - - Sediment quality Total copper mg/kg 10.0 - 13.0 - Total lead mg/kg 6.0 - 12.3 - Total zinc mg/kg 43 - 46.0 - Total phosphorus mg/kg 210 - 730.0 - Total nitrogen g/100g <0.05 - 0.32 - a Data collected by Boffa Miskell, July 2020. b Data collected by OGNZL, 2015-2018. c NOF states dissolved oxygen for use below point source discharges only.
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