Appendix 12: NOF Environmental Limits for Attributes for Freshwater Boffa Miskell Ltd | Waihi North Project: Freshwater Ecological Assessment | [Subject] Table 12-3: Environmental limits for periphyton for ecosystem health values in freshwater in New Zealand (from NPS-FM 2020). Value (and component) Ecosystem health (Aquatic Life) Freshwater body type Rivers Attribute unit mg chl-a/m2 (milligrams chlorophyll-a per square metre) Attribute band and description Numeric attribute state (default class) Numeric attribute state (productive class) Exceeded no more than 8% of samples Exceeded no more than 17% of samples A Rare blooms reflecting negligible nutrient enrichment and/or alteration of the natural flow regime or habitat. ≤50 ≤50 B Occasional blooms reflecting low nutrient enrichment and/or alteration of the natural flow regime or habitat. >50 and ≤120 >50 and ≤120 C Periodic short-duration nuisance blooms reflecting moderate nutrient enrichment and/or moderate alteration of the natural flow regime or habitat. >120 and ≤200 >120 and ≤200 National bottom line 200 200 D Regular and/or extended-duration nuisance blooms reflecting high nutrient enrichment and/or significant alteration of the natural flow regime or habitat. >200 >200 At low risk sites monitoring may be conducted using visual estimates of periphyton cover. Should monitoring based on visual cover estimates indicate that a site is approaching the relevant periphyton abundance threshold, monitoring should then be upgraded to include measurement of chlorophyll-a. Classes are streams and rivers defined according to types in the River Environment Classification (REC). The Productive periphyton class is defined by the combination of REC “Dry” Climate categories (that is, Warm-Dry (WD) and Cool-Dry (CD)) and REC Geology categories that have naturally high levels of nutrient enrichment due to their catchment geology (that is, Soft-Sedimentary (SS), Volcanic Acidic (VA) and Volcanic Basic (VB)). Therefore the productive category is defined by the following REC defined types: WD/SS, WD/VB, WD/VA, CD/SS, CD/VB, CD/VA. The Default class includes all REC types not in the Productive class. Based on a monthly monitoring regime. The minimum record length for grading a site based on periphyton (chlorophyll-a) is 3 years.
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