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 Sample period 2014-2018 20082021 20082021 20082021 20082021 # Outlier discharge temperatures ranging from 40.6°C - 43.4°C occurred for 12 days during June 2018 and we have removed this data from our summary Table 41: Number of records from four OGNZL monitoring sites within the Ohinemuri River over the critical summer period where temperatures have exceeded recommended temperature thresholds 20°C to 25°C (AC 2012). Site locations shown in Figure 14. Sample site Temperature exceedance OC2 OH3 OH5 OH6 > 25°C 0 0 1 2 > 24°C 3 2 7 10 > 23°C 5 4 20 26 > 22°C 17 13 39 49 > 21°C 28 22 55 68 > 20°C 50 41 89 89 n 628 889 801 782 Sample period 2006-2021 2008-2021 2003-2021 2004-2021 Table 42:. Number of recorded temperature differences between upstream and downstream monitoring sites over the critical summer period (January – March inclusive) in the Ohinemuri River at Waihi. Site locations shown in Figure 14. Temperature change OC2 and OH5 OC2 and OH6 > 3°C 4 6 > 2°C 16 21 > 1°C 16 21 n 124 122 20.5.4 Continuous temperature records 2019-2020 20.5.4.1 Background Water temperature varies diurnally and seasonally and while both minimum and maximum temperatures can affect river health, maximum temperatures most often limit biota. Many published temperature limits for aquatic organisms are derived from laboratory-based experiments that expose organisms to constant temperature. Cox & Rutherford (2000) concluded that temperature limits should be applied to a temperature midway between the daily average and the daily maximum of a diurnal profile. From this, the Cox-Rutherford Index (CRI) has been developed as the average of daily maximum and daily mean temperatures and provides a measure that permits application of (constant)
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