2023 Quarterly Results
November 2023
Overall, water quality at Mokau River, above the Wairere Dam was good on 13th November 2023.
E. coli was low (190). Nitrate and Ammonia concentrations were well below toxicity levels (Nitrate 0.37 mg/L; Ammonia 0.02 mg/L). Dissolved inorganic nitrogen was low (0.39 mg/L). Dissolved reactive phosphorus was exceptionally low (0.006 mg/L). Water clarity was poor (1.03 m) relative to the national bottom line (1.34 m).
Collection date: 13 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 at Mokau River, above the Wairere Dam was fairly good on 13th September. E. coli and dissolved reactive phosphorus were low, while the concentration of suspended sediment was elevated and Dissolved Inorganic Nitrogen was slightly elevated. E. coli was low (160). Nitrate and ammonia concentrations were well below toxicity levels (Nitrate 0.59 mg/L; Ammonia 0.02 mg/L). Dissolved inorganic nitrogen was 0.61 mg/L, potentially impacting the health of the river. Dissolved reactive phosphorus concentrations was exceptionally low (0.005 mg/L). Water clarity was poor (0.83 m), relative to the national bottom line (1.34 m).
Collection date: 13 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 elevated at both sites (≥ 310). Nitrate and ammonia concentrations were the same for both sites and were below toxicity levels (Nitrate 0.84 mg/L; Ammonia 0.01 mg/L). Both sites had a dissolved inorganic nitrogen concentration exceeding 0.5 mg/L, potentially impacting the health of the river. Dissolved reactive phosphorus concentrations were exceptionally low at both sites (0.006 mg/L). Water clarity was poor at both sites (≤ 0.25 m), relative to the national bottom line (NBL). The NBL is 1.34 m at 7-Mokau River above Wairere Dam; 0.61 m at 8-Paraheka Stream.
Sample date 14 May 2023.
Mokau River – All sites in all sub-catchments (May 2023)
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
Summary 2022
The water quality dial for Lower Mokau combines data collected at 6 monitoring sites between January – December 2022, representing 54 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 and Sediment are the main contaminants of concern in the Lower Mokau.
Site 7-Mokau River above the Wairere dam had the best water quality and the Waikato Regional Council sites had the lowest water quality in 2021.
Attribute bands
A (or blue is the best) through to E (red) which is the worst.
