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 13.3 Water quality and ecology of the Ohinemuri River catchment 13.3.1 Background There have been several programmes and reports detailing the water quality and ecology of the Ohinemuri River. The commencement of silver and gold mining within the catchment in the 1980s after a period of relative inactivity in mining in the area resulted in a number of baseline assessments of potential impacts reports on the water quality and ecological condition of the river (e.g., Bioreseaches 1997) and many reports on the annual biological and water quality compliance monitoring (e.g., Golder 2016, 2017, 2018, Ryder 2019a, 2020, 2021). This information provides useful historical baseline information. The most relevant, recent, and long-term water and ecological monitoring programmes are held and reported by OGNZL (annual compliance monitoring since 1987), NIWA (National Rivers programme), and the WRC State of the Environment monitoring. These programmes have been established to achieve different purposes, and each is described briefly below. All of the programmes include sampling water quality and ecological attributes of the river. It is not our intention to summarise and repeat all of the data from these monitoring programmes; such data is well reported and will be referenced accordingly. However, we draw on the data available, particularly the OGNZL compliance monitoring data, to inform our discussion on the water quality and ecology of the Ohinemuri River. 13.3.2 NIWA National River Water Quality Network (NRWQN) NIWA undertakes a national water quality and ecological sampling programme of some 77 sites on 35 rivers around the country. Sites were selected so that a national perspective of state and trends of water quality could be developed. On most rivers there are two or more sites representing an upstream ‘Baseline’ site (lightly impacted) and a downstream ‘Impact’ site (reflecting the impacts of humans on water quality). A single site on the Ohinemuri River is sampled at the Karangahake Gorge. The NIWA programme measures the following water quality parameters: • Physico - chemical variables: dissolved oxygen, temperature, pH, conductivity • Optical variables: Visual clarity, turbidity, coloured dissolved organic matter • Nutrients: Total and dissolved forms of nitrogen and phosphorus • Microbial Indicator: E. coli (since 2005). 13.3.3 WRC State of the Environment Water Quality Monitoring WRC undertakes monthly State of the Environment (SoE) monitoring of river and stream sites throughout the region14. Four sites are listed for the Ohinemuri River: • Ohinemuri River at the SH 25 Bridge (upstream of OGNZL site) • Ohinemuri River at Queen’s Head (downstream of the OGNZL site) 14 https://www.waikatoregion.govt.nz/environment/natural-resources/water/rivers/healthyrivers/
RkJQdWJsaXNoZXIy MjE2NDg3