2023 Quarterly Results

November 2023

Overall, water quality was fair across Mapiu-Mapara in November 2023. E. coli was exceptionally low at 21-Waewaepitau Stream (43) and low at 15-Mapara Stream (230), while concentrations were elevated at all other sites (≥730). Nitrate concentrations were below toxicity levels at all sites being lowest at 21-Waewaepitau Stream (0.04 mg/L) and highest at 26-Puputaha Stream (0.35 mg/L). Ammonia concentrations were low at all sites (≤ 0.02 mg/L). Dissolved inorganic nitrogen was low at all sites (≤ 0.35 mg/L). Dissolved reactive phosphorus concentrations were low at all sites (≤ 0.007 mg/L). Water clarity was excellent at 21-Waewaepitau Stream (2.27 m) but scored poorly at all other sites (≤ 1.30 m), relative to the national bottom line (1.34 m).

Collection date: 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 was fair on 12th September. Nutrients were low, however, E. coli and suspended sediment were elevated at many sites. E. coli was exceptionally low at 21-Waewaepitau Stream (64), while concentrations were elevated at all other sites (≥ 270). Nitrate concentrations were below toxicity levels at all sites being lowest at 21-Waewaepitau Stream (0.07 mg/L) and highest at 26-Puputaha Stream (0.52 mg/L). Ammonia concentrations were low at all sites (≤ 0.02 mg/L). 26-Puputaha Stream 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 all sites (≤ 0.006 mg/L). Water clarity was excellent at 21-Waewaepitau Stream (1.98 m) and 20-Mapiu stream (1.86 m) but scored poorly at all sites (≤ 0.94 m), relative to the national bottom line (1.34 m)

Sample date: 12 September 2023

Mokau River - all sites in sub-catchment

All sites in all sub-catchments 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 was exceptionally low at 21-Waewaepitau Stream (15), while concentrations were elevated at all other sites (≥ 300). Nitrate concentrations were below toxicity levels at all sites being lowest at 21-Waewaepitau Stream (0.10 mg/L) and highest at 26-Puputaha Stream (0.51 mg/L). Ammonia concentrations were low at all sites (≤ 0.02 mg/L). 26-Puputaha Stream 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 all sites (≤ 0.006 mg/L). Water clarity was highest at 21-Waewaepitau Stream (1.50 m) but scored poorly at all sites, relative to the national bottom line (1.34 m).

Sample date 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

Summary all Mokau Sites docx

Water Quality Summary 2022

The water quality dial for Mapiu-Mapara combines data collected at 6 monitoring sites between January – December 2022, representing 24 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.

2022 Annual Summary docx

2022 Summary Map pdf