12552081 4 Table 1 Current and Recommended Continuous flow Measurement Locations – Wharekirauponga Catchment Location Status Latitude Longitude Recorded Flow (L/sec)# Purpose WKP1 Current 68.2 – 254.7* WKP2 Current 48.6 – 426.2 WKP3 Current 36.9 – 424.5 T-Stream East Current 26.3 – 244.5 T-Stream West Current 23.6 – 252.9 #A (North Trib) Proposed S37.29673 S37.29677 E175.81467 E175.81522 11.0 – 22.5 Monitoring Headwaters in North Tributary #B (South Trib) Proposed S37.297960 E175.81541 26.5 – 27.9 Monitoring Headwaters in T Stream West #C (Edmonds) Proposed S37.297752 E175.819334 25.7 – 30.2 Monitoring Edwards Stream before discharge to Wharekirauponga Stream #D (Trib R) Proposed S37.293385 E175.824654 3.2 – 4.7 Monitoring unnamed tributary stream before discharge to Wharekirauponga Stream #E (Thompson) Proposed S37.288942 E175.833283 16.1 Monitoring Thompson Stream before discharge to Wharekirauponga Stream #Manual gauging’s 2019 - 2021 *Manual gauging’s not inclusive of higher flow events at WKP01 In addition to these recommended continuous monitoring locations, manual measurements of the Hot spring discharge and Adams Stream should be undertaken in conjunction with manual measurements at the other locations. 2.2 Draft Conditions - Water Balance Model Development In order to ascertain the likely range in stream flow rates, a water balance model (WBM) to represent the catchments hydrological response to antecedent climate conditions is recommended to be developed. This can then provide a probabilistic estimation of stream flow behaviour based on pre-development conditions at the locations outlined in Table 1. The model can then be utilised to provide the expected range of flows based on measured climatic data at a point in time at each modelled location and could be utilised as a key tool in compliance monitoring during mining in regards to the effects of mining on surface water flows. This likely range of flows could be utilised within the consent conditions as a basis for compliance and trigger levels. The model would be developed with the following principals in mind: – Probabilistic rainfall / runoff relationship for the surface water monitoring locations outlined in Table 1 based on the available baseline surface flow and rainfall data will be developed. These would be incorporated in the WBM utilising an Australian Water Balance Model (AWBM) approach similar to that applied in the existing operational Goldsim Waihi WBM for modelling the Ohinemuri River. Available rainfall records from Golden Cross, Wharekirauponga and Waihi will be utilised for this purpose. – The known seepage rates (and their range) will be incorporated into the WBM to support model calibration. – Flow / rainfall responses within the model will be checked / updated following each manual gauging event to ensure statistical predictions are up to date. – The calibration will focus on flow regimes below typical mean flows with the intent to capture basal flow regimes that are more likely affected by changes in ground water conditions. This record should enable long term compliance evaluation with real time data.
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