GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 87 Table I.4 Calibrated stream baseflow Stream baseflow (RU07) Modelled value Measured (Feb-Mar 2018): Stream length(1) 350 m Baseflow (per meter stream length) 0.002 m3/d -0.4 to 0.2 m3/d (2) Baseflow along 350 m stream length 0.01 L/s -1.5 to 0.7 L/s Regime Neutral (3) Neutral to losing 1 Between RU07 and upstream gauging location RU12. 2 Measured values from baseflow monitoring between RU12 and RU07 in February 2019. The range of values provided represents the range of error. 3 The results indicate only very slightly gaining, but are considered within the magnitude of the model and error to be neutral. Table I.5 Calibrated groundwater levels and well pair vertical gradients Wells (screen depth) Groundwater Level (mRL unless otherwise noted) Modelled value Measured (Feb-Mar 2018) Northern Ridge Deep 1,115.88 - ΔH Downward gradient down n/a AP11 well pair AP11 (3-5 m) Water table - in m bgl* 3.9 4.9 AP11a (17-20 m) Deep well 1,114.33 1,114.89 ΔH Downward gradient down n/a AP08 / DH12 well pair AP08 (2.5 - 5.5 m) Shallow well 1,113.90 1,114.11 DH12 (20-21 m) Deep well 1,113.24 1,113.20 ΔH Downward gradient -0.7 -0.9 AP06 well pair AP06 (3-5 m) Shallow well GWL 1,112.94 1,113.05 AP06a (21 - 24 m) Deep well GWL 1,112.40 1,112.67 ΔH Downward gradient -0.5 -0.4 AP02 well pair AP02 (3-5 m) Shallow well GWL 1,110.35 1,111.47 AP02a (27-30 m) Deep well GWL 1,111.21 1,112.17 ΔH Upward gradient +0.9 +0.7 AP1a well pair AP01 (3-5 m) Shallow well GWL 1,109.20 1,110.23 AP01a (37-40 m) Deep well GWL 1,109.91 1,110.45 ΔH Upward gradient +0.7 +0.2 AP04 well pair AP04 (4-6 m) Shallow well GWL 1,108.56 1,109.40 AP04a (27-30 m) Deep well GWL 1,108.62 1,109.47 ΔH Upward gradient +0.1 +0.1 Groundwater levels R2 = 0.98 (refer to Figure I.3) Vertical ΔH R2 = 0.88 (refer to Figure I.3) * The cross section does not fully align with the AP11 well pair, which is elevated in comparison to the cross section at this location. The AP11 well water levels are perched at this location, with the base of the shallow well located above the measured deeper wells water level. Further, the corresponding water level elevations at the shallow well exceed the model ground surface at this location. Calibration at this location focused on the primary aquifer (deeper well AP11a), and a water table within 5 mbgl (as measured).
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