GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 78 . Figure 4.6 NRS 2020 groundwater and TB1a stream levels and rainfall (CLIFLO Athenree 2 station 18638). Monitoring locations presented in Figure 4.1. 4.3.3 Surface water-groundwater interactions The Ohinemuri River flows roughly north to south past the proposed NRS site (Figure 4.1). Flow in the Ohinemuri River during baseflow conditions is typically recorded to be less than 0.3 m3/sec (23,200 m3/day) at the Frendrups flow gauge southwest of the NRS site (Figure 2.1). No significant gaining conditions have been recorded between flow gauging stations located up and down stream of the NRS site, indicating that groundwater discharge is likely to be small relative to river flow. Ohinemuri tributary TB1 flows from southeast to northwest, from the existing northern storage area across the proposed NRS site, before discharging into the Ohinemuri River (Figure 4.1). The surface water catchment area of TB1 is approximately 112 hectares, with the upper reaches being spring fed (WRS TB) as discussed in Section 4.3.2. The northern storage area is inferred to be situated over historical flow path(s) of the tributary, moving the current alignment further to the east (TB1b) (Figure 4.1). Flow gauging along tributary TB1 (Appendix F) indicates that although groundwater spring discharges form the headwaters of the tributary, the stream is typically recorded as neutral under base flow conditions. This indicates a close hydraulic connection with groundwater across the site, with gaining and losing sections likely to occur along its length. Gaining conditions were recorded following a high rainfall period in September 2019, which is likely to be due to increasing runoff and interflow between gauging locations as well as greater groundwater discharge. Typical groundwater flow at TB1a (Figure 4.1) is approximately 3 L/s (Appendix F).
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