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 7.7.3 Sediment Cover and Grain Size The stream bed of all assessed sites was hard bottom, although the unnamed tributary 2 did comprise areas of mostly silt and sand material in lower gradient reaches. The Mataura Stream contained a diverse mix of different sized particles from silt and sand (<2mm) to boulders (>256 mm). Sediment within the Mataura Stream was generally less than 10%, although there were less exposed areas which had greater sediment cover of between 20 to 50%. Fine sediment cover was within recommended guidelines (Clapcott et al. 2011) for biodiversity and salmonid spawning habitat within the Mataura Stream but was above these limits (>20% fine sediment) in the unnamed tributary 2. Similarly, the measure of deposited fine sediment fell within Atttribute A of the NOF (Table 16, NPS-FM), while tributary 2 fell below the national bottom line. Detail of the stream morphology and substrate is provided in Appendix 4 and sediment particle size in Figure 7. Figure 7: Sediment particle size for Waiharakeke Stream, Mataura Stream and unnamed tributary 2 of the Mataura Stream catchment. 7.7.4 Macroinvertebrate Assemblages The macroinvertebrate assemblage within the Mataura Stream was made up largely of Dobson flies (Archichauliodes), snails (Potamopyrgus), riffle beetles (Elmidae) and caddisflies (Hydropsyche, Aoteapsyche). With the exception of snails, which occur in a large range of water quality and habitat types, the remaining species listed above are largely only found in moderate to good water / habitat quality. The unnamed tributary 2 macroinvertebrate assemblage was made up of oligochaete worms, springtails (Collembola), true flies (Austrosimulium and 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mataura Stream Unnamed tributary 2 Waiharakeke main stem Waiharakeke right branch Percent composition Site Bedrock Boulder Large cobble Small cobble Large gravel Med-large gravel Small-med gravel Small gravel Clay / silt / sand
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