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 periods, the tributary gully likely provides an incidental input to the Gladstone wetland downstream. We investigated this tributary gully for any additional water sources and walked most of the length of the reach above Gladstone wetland to ascertain if any wetland features occurred in the headwaters. Seepages were observed at the time of our assessment, and wet ground and pools of water were noted approximately 200 m below the access road at the head of the gully. The headwater gully is not and does not comprise of natural wetland features. The watercourse contains mostly sections of well-defined channel and sections of dry terrace where no channel is evident. Much of the reach was dry at each of our site visits, other than short sections of well-defined channel that contained some pools. These areas occurred below the opening of a former mine adit that seeped water along a short contributing channel. 9.3.1.2 Hydrological Characteristics GWS (2021) considers the hydrogeological aspects of the headwater gully and its relationship with the downstream Gladstone wetland. Catchment rainfall runs off the steep slopes where it goes to soakage mid-slope forming interflow. Interflow only occurs following rainfall and the rate of discharge is governed by the steepness of the topography and the permeability of the soils. Some rainfall infiltration passes though the ash/regolith and enters the shallow groundwater system that forms the permanent water table. The interflow drains down slope under gravity and discharges into the incised headwater gully channel and only occurs after prolonged periods of rainfall (i.e., measured in days) (GWS 2021). The mine adit is not considered to contribute discharge to the headwater gully due to it being above the permanent water table elevation (GWS 2021). We classified the headwater gully as an intermittent watercourse. 9.3.1.3 Vegetation Characteristics All vegetation surrounding the headwater gully is planted. A dense 5 – 10 m wide buffer of manuka and kanuka surrounds the watercourse, while the channel and immediate surrounds contain a simple mix of wetland plants (Carex secta, C. lessoniana, harakeke and cabbage trees). Stands of harakeke and Carex were generally noted as somewhat sparse and unthrifty, probably due to the heavy shade cast by the tall, dense kanuka canopy that covers all but the immediate area above the channel. No naturally established wetland species or “wet tolerant” plants were observed. Soil profiles showed a thin layer of clay over a lower layer of dark, friable soil and an upper layer which may have been imported topsoil. No hydric soil indicators were observed (Figure 9, Figure 10). In the lower reaches where the gully levels out, this has also been revegetated and is comprised of dense swards of Carex virgata interspersed with discrete patches of giant umbrella sedge, a small amount of Machaerina spp., as well as kiokio and other common ground ferns including water fern (Histiopteris incisa) and gully fern (Pneumatopteris pennigera). Also present are some patches of blackberry and exotic herbs. These patches are then surrounded by riparian plantings dominated by flax on the margins and then a dense buffer of kānuka, mānuka and broadleaved shrubs.
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