2023 Quarterly Results
November 2023
Overall, water quality on fair across Upper Mokau and Mangapehi in November.
E. coli concentrations was low at 14-Mangapehi River (230) and elevated at the other two sites (≥ 310). Nitrate concentrations were well below toxicity levels at all sites, being lowest at 13-Mokau R. HWY 4 (0.16 mg/L) and highest at 18-Mangapehi River (0.46 mg/L). Ammonia concentrations were low at all sites (≤ 0.01 mg/L). Dissolved inorganic nitrogen concentrations were good at all sites (≤ 0.47 mg/L). Dissolved reactive phosphorus concentrations were low at all sites (≤ 0.009 mg/L). Water clarity was fair (1.40 m) to poor at all sites (≤ 1.19 m), relative to the national bottom line (1.34 m).
Collection days: 13 & 14 November 2023
Mokau River – All sites in sub-catchment (November 2023)
Nutrient concentrations (nitrate, ammonia and dissolved reactive phosphorus) were low at most sites. Key contaminants were E. coli and water clarity.
E. coli: 56% of all sites had low concentrations (≤230), 25% had slightly elevated concentrations (between 280 - 530) and 19% had elevated concentrations (> 730). Nitrate and Ammonia: concentrations at 100% of sites were below toxicity levels (Nitrate ≤ 0.62 mg/L; Ammonia ≤ 0.02). Only one site had Dissolved Inorganic Nitrogen (DIN) concentrations above 0.5 mg/L. Ecological impacts, including problematic growth of algae and/or aquatic plants and loss of sensitive aquatic species are likely to occur when DIN regularly exceeds 0.5 mg/L. Dissolved reactive phosphorus: 94% of sites had low concentrations (≤ 0.009 mg/L) and one site (16%) had slightly elevated concentrations (0.011 mg/L).Water clarity: 44% of sites had good water clarity (A or B band), two sites (13%) had reduced water clarity (C band) and 44% of sites had poor water clarity (D band). Bands for each site relate to the national bottom line (NBL) for water clarity and are dependent on landscape characteristics including geology, climate and elevation. The NBL for Mokau River’s monitoring sites are either 1.34 m or 0.61 m, dependant the local landscape characteristics.
September 2023
Overall, water quality on 12th September was fair to good. Suspended sediment was elevated at two out of three sites and E. coli and dissolved inorganic nitrogen were slightly elevated at some sites. E. coli concentrations were low at 2 out of 3 sites (≤ 170) and were elevated at 18-Mangapehi River (320). Nitrate concentrations were below toxicity levels at all sites being lowest at 13-Mokau R. HWY 4 (0.38 mg/L) and highest at 18-Mangapehi River (0.70 mg/L). Ammonia concentrations were low at all sites (≤ 0.02 mg/L). Two sites (14 and 18 on Mangapehi River) had dissolved inorganic nitrogen concentrations exceeding 0.5 mg/L, potentially impacting the health of the river. Dissolved reactive phosphorus concentrations were low at all sites (≤ 0.007 mg/L). Water clarity was very good at 13-Mokau R. HWY 4 and poor at all sites (≤ 1.25 m), relative to the national bottom line (1.34 m).
Collection date: 12 September 2023
Mokau River – All sites in all sub-catchments (September 2023)
Summary of water quality collected at 16 sites located across the Mokau River catchment sampled on 12th or 13th of September. E. coli: 63% of all sites had low concentrations (≤220), 25% had slightly elevated concentrations (between 270 - 380) and 13% of sites had elevated concentrations (> 550). Nitrate and Ammonia: 100% of sites had concentrations below toxicity levels (Nitrate ≤ 0.79 mg/L; Ammonia ≤ 0.09). However, 50% of sites had Dissolved Inorganic Nitrogen (DIN) concentrations over 0.5 mg/L. Ecological impacts, including problematic growth of algae and/or aquatic plants and loss of sensitive aquatic species are likely when the combined concentration of DIN regularly exceed 0.5 mg/L. Dissolved reactive phosphorus: 94% of sites had low concentrations (≤ 0.009 mg/L) and one site (16%) had an elevated concentration (0.011 mg/L). Water clarity: 56% of sites had good water clarity (A or B band) and 44% of sites had poor clarity (D band). Bands for each site relate to the national bottom line for water clarity, which is either 1.34 m or 0.61 m, and is dependent on the local geology, climate and elevation.
May 2023
E. coli concentrations were low at 3 out of 4 sites (≤ 260) and were elevated at 18-Mangapehi River (310). Nitrate concentrations were below toxicity levels at all sites being lowest at 17-Paritikona Stream (0.40 mg/L) and highest at 14-Mangapehi River HWY 4 (0.70 mg/L). Ammonia concentrations were low at 3 sites (≤ 0.02 mg/L) and higher at 14-Mangapehi River HWY 4 (0.04 mg/L). Three out of four sites (all except 17-Paritikona Stream) had dissolved inorganic nitrogen concentrations exceeding 0.5 mg/L, potentially impacting the health of the river. Dissolved reactive phosphorus concentrations were low at all sites (≤ 0.008 mg/L). Water clarity was poor at all sites (≤ 0.71 m), relative to the national bottom line (1.34 m)
Sample date 8 & 14 May 2023.
Mokau River – All sites in all sub-catchments
This summarises the results collected across the Mokau River catchment from 27 sites sampled on either the 8th or 14th of May: E. coli: 58% of all sites had low concentrations (≤260) and 42% had slightly elevated concentrations (between 270 - 360). Nitrate and Ammonia: 100% of sites had concentrations below toxicity levels (Nitrate ≤ 2.39 mg/L; Ammonia ≤ 0.04). However, 67% of sites had Dissolved Inorganic Nitrogen (DIN) concentrations over 0.5 mg/L. Ecological impacts, including problematic growth of algae and/or aquatic plants and loss of sensitive aquatic species are likely when the combined concentration of DIN regularly exceed 0.5 mg/L. Dissolved reactive phosphorus: 83% of sites had low concentrations (≤ 0.009 mg/L) and 17% of sites had elevated concentrations (0.011 – 0.017 mg/L). Water clarity: 8% of sites had good water clarity (A or B band), 8% had moderate clarity (C band) and 83% of sites had poor clarity (D band). Bands for each site relate to the national bottom line for water clarity, which is either 1.34 m or 0.61 m, and is dependent on the local geology, climate and elevation.
February 2023
Water Quality Summary 2022
The water quality dial for Upper Mokau-Mangapehi combines data collected at 5 monitoring sites between January – December 2022, representing 28 individual samples. Nitrates and dissolved reactive phosphorus (DRP) were low. E. coli was elevated, while water clarity was low indicating elevated sediment loading. Arrows indicate an increase or decrease in values compared to the sub-catchment baseline (2015 – 2020). An increase in water clarity is positive for river health while an increase in all other attributes may impair river health.
2021 Summary
E. coli is the main contaminants of concern.
Dissolved Reactive Phosphorus is elevated at Mangaokewa Road – WRC site.
Site 13-Mokau R. HWY 4 had the best water quality and Mangaokewa Rd had the lowest water quality in 2021.
Attribute bands
A (or blue is the best) through to E (red) which is the worst.
