www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 13 4. CHARACTERISATION 4.1. SURFACE WATER SYSTEM The Wharekirauponga is one of four upland stream sub-catchments that flow into the Otahu River. The Otahu River occupies a catchment area of around 70km2 draining to the northeast reaching the sea immediately to the south of the town of Whangamatā (Figure 4-1). The Wharekirauponga sub-catchment is flashy following rainfall, with stream flows supported largely by surface runoff and interflow (unsaturated zone subsurface flow). Figure 4-1:Otahu Catchment (after GWS) Whangamatā Otahu Catchment N
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