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 3.3 Overview of catchment water quality We discuss specific water quality in the vicinity of the OceanaGold operations in later sections of our report. However, WRC (2019) recently summarised the overall water quality of the Ohinemuri River and concluded that, for most water quality variables, the Ohinemuri River system can regulate contaminants to a satisfactory or excellent rating for human and ecological health (assessed against WRC water quality guidelines and standards). The two notable exceptions where catchment pressures are regarded as exceeding the regulatory capacity of the main stem of the Ohinemuri catchment are concentrations of total nitrogen which are at unsatisfactory levels (out of the three monitoring sites along the main stem of the river), along with temperature requirements for fish spawning. With regard to heavy metals, WRC (2019) draw on the monitoring undertaken by OGNZL (summarised in BML 2018) that heavy metal concentrations are below resource consent compliance limits that are based on USEPA (1986) criteria. The Ohinemuri River has improved considerably since the 1950s when it was essentially a 'dead' river with a heavy load of gold mining tailings dumped in the river. Indeed, the river downstream of the current operations was declared a sludge channel in the early 20th century by the government of the day. 3.4 Recreational Fishing (trout) The Ohinemuri River, its tributary the Waitawheta River and to a lesser extent the Waitekauri River tributary, are popular rivers for fishing. The Ohinemuri River is regarded as having excellent access and a good population of both rainbow and brown trout and the section through the Karangahake Gorge is the most popular and productive section of the river for trout fishing. Access to much of the Ohinemuri is relatively easy as State Highway (SH) 2 follows the river for much of its length. In the 2014/15 National Angling Survey, angler days totalled 1030 for the Ohinemuri River system (comprising the combined results for the mainstem (700 +/- 240), Waitawheta Stream (320 +/- 80) and Waitekauri River (10 +/- 10) (Unwin 2016). However, angling days in the Ohinemuri River has declined by some 50% from the initial survey in 1994/95 (NIWA 1998). WRC (2019) suggest that this decline is most likely influenced by increasing water temperatures and for 7-8 months of the year this thermal barrier limits trout occupancy in the lower section of the river. Earlier studies (Bioresearches 1982) suggested that the highest quality native fish habitat was present in the northern tributaries and headwaters of the Ohinemuri River. Of these tributaries the Mataura Stream and Waitekauri River were considered to provide the widest range and best quality habitat for all life stages of trout and probably played a major role in sustaining the mainstem of the Ohinemuri River trout fishery. In addition, the Ratarua, lower Walmsley and Waitete Streams all had suitable trout habitat. The Ohinemuri River provided extensive area of trout habitat and juvenile trout were numerous in the middle and upper sections of the river. The tributaries of the Ohinemuri River are considered important trout spawning and nursery grounds. In previous expert evidence, Daniel (2017) stated that the ‘Ohinemuri trout population crashes frequently and Sport Fly Fishing NZ stopped using the river for fly fishing competitions in 2013 due to a lack of fish. Fish and Game attempted to stock the Ohinemuri river with 500 tagged yearling trout in 2015 but despite extensive fishing no tagged fish were ever recovered indicating very low survival compared to normal recovery rate of 6.5%. After the exceptionally
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