Methods
Physicochemical and microbiological water quality
Where practical, individual RWQE monitoring sites are sampled at the same time of the month (and usually at the same time of the day) and all sites on a river or stream are sampled on the same day. Field meters are calibrated on the morning of the day of sampling and on the return. Water samples are collected in mid-stream (where possible), typically in run-type habitat from a representative reach of stream. Samples requiring laboratory analysis are placed in chilly bins with ice and couriered overnight to RJ Hill Laboratories in Hamilton. Water samples for heavy metal and dissolved nutrient analysis were all laboratory filtered.
| Variable | Method | Detection limit |
|---|---|---|
| Water temperature | Field meter – generally YSI ProDSS | 0.01 ºC |
| Dissolved oxygen | Field meter – generally YSI ProDSS | 0.01 mg/L |
| Visual clarity | Black disc (20 mm disc or clarity tube if clarity <0.5 m, 60 mm disc for clarity between 0.5 m and 1.5 m, 200 mm disc for clarity >1.5 m) | 0.01 m |
| Deposited sediment | In-stream visual estimate of proportion of habitat covered by deposited sediment using the SAM2 method (Clapcott et al. 2011) | 5% |
| pH | Lab pH meter | 0.01 units |
| Conductivity | Field meter – generally YSI ProDSS | 0.1 µS/cm |
| Turbidity | Analysis using a Hach 2100N, Turbidity meter. APHA 2130 B 22nd Ed. 2012 | 0.05 NTU |
| Total suspended solids | Filtration using Whatman 934 AH, Advantec GC-50 or 1-2 equivalent filters (nominal pore size 1.2–1.5µm), gravimetric determination. APHA 2540 D 22nd Ed. 2012 | 2 mg/L |
| Suspended sediment concentration | Filtration using Advantec GC-50 or equivalent 125mm diameter filters (nominal pore size 1.2 - 1.5µm), gravimetric determination. Entire sample filtered. No correction for density. Note: g/m3 units are equivalent to mg/L. ASTM D3977-97 (Modified). | 10 mg/L |
| Ammoniacal nitrogen | Filtered sample. Phenol/hyperclorite colorimetry. Discrete Analyser. (NH4-N = NH4+-N + NH3-N) APHA 4500-NH3 F (modified from manual analysis) 22nd Ed. 2012 | 0.005 mg/L |
| Nitrite nitrogen | Automated Azo dye colorimetry, Flow injection analyser. APHA 4500-NO3- I (Modified) 22nd Ed. 2012 | 0.001 mg/L |
| Nitrate nitrogen | Calculation: (Nitrate-N + Nitrite-N) – Nitrite-N | 0.001 mg/L |
| Nitrate + nitrite nitrogen | Total oxidised nitrogen. Automated cadmium reduction, Flow injection analyser. APHA 4500-NO3- I (Modified) 22nd Ed. 2012 | 0.001 mg/L |
| Total Kjeldahl nitrogen | Kjeldahl digestion, phenol/hyperclorite colorimetry (Discrete Analysis). APHA 4500-N Org C. (modified) 4500-NH3 F (modified) 22nd Ed. 2012 | 0.1 mg/L |
| Total nitrogen | Calculation: TKN + Nitrate-N + Nitrite-N | 0.11 mg/L1 |
| Total phosphorus | Total Phosphorus digestion, ascorbic acid colorimetry. Discrete Analyser. APHA 4500-P E (modified from manual analysis) 22nd Ed. 2012 | 0.004 mg/L |
| Dissolved reactive phosphorus | Filtered sample. Molybdenum blue colorimetry. Discrete Analyser. APHA 4500-P E (modified from manual analysis) 22nd Ed. 2012 | 0.001 mg/L |
| Faecal coliforms | APHA 9222D 22nd Ed. 2012 | 1 cfu/100mL |
| E. coli | APHA 9222G 22nd Ed. 2012 | 1 cfu/100mL |
| Total recoverable copper | Nitric/Hydrochloric acid extraction, 85°C, 2.75 hr, ICP-MS, trace level. APHA 3125 B 22nd ed. 2012. | 0.0005 mg/L |
| Total recoverable zinc | Nitric/Hydrochloric acid extraction, 85°C, 2.75 hr, ICP-MS, trace level. APHA 3125 B 22nd ed. 2012. | 0.001 mg/L |
| Dissolved copper | Filtered sample, ICP-MS, trace level. APHA 3125 B 22nd Ed. 2012 | 0.0005 mg/L |
| Dissolved zinc | Filtered sample, ICP-MS, trace level. APHA 3125 B 22nd Ed. 2012 | 0.0010 mg/L |
| Dissolved Calcium | Filtered sample, ICP-MS, trace level. APHA 3125 B 22nd Ed. 2013 | 0.05 mg/L |
| Dissolved Magnesium | Filtered sample, ICP-MS, trace level. APHA 3125 B 22nd Ed. 2014 | 0.02 mg/L |
| Dissolved Organic Carbon | Filtered sample, Supercritical persulphate oxidation. APHA 5310 C (modified) 22nd ed. 2012. | 0.5 mg/L |
| Total hardness | Calculation from Calcium and Magnesium. APHA 2340 B 22nd ed. 2012. | 1.0 mg/L as CaCO3 |
Periphyton
Formal periphyton assessments are limited to the 38 RWQE sites with hard substrates.
Monthly assessment of visible streambed cover
Periphyton cover is determined by estimating the percentage of mat (>1 mm thick) cyanobacterial mat (>1 mm thick) and filamentous (>2 cm long) periphyton present on the stream or river bed. Note that cover of mat and cyanobacterial mat-periphyton are mutually exclusive (ie, cyanobacterial mat cover >1 mm thick will be counted as separate from mat-periphyton). A total of 20 observations are taken at each site from two transects of ten observations, or, if the stream or river is not wide enough or too swift to wade across more than half of the river’s width, four transects of five observations. Each observation is typically made with an underwater viewer and covers an approximate area of a 30 cm diameter circle. Visible streambed periphyton cover assessments are carried out equally in both run and riffle-type habitats if these are present at a sampling site/reach.
Monthly assessment of biomass
Periphyton samples for quantitative biomass assessments (chlorophyll a) are collected on a monthly basis. During 2017/18, chlorophyll a samples were collected from 15 of the 44 RWQE sites with hard substrates. Sampling protocols involved collecting samples from a run habitat and following modified versions of quantitative methods 1b (QM-1b) and 3 (QM-3) as outlined by Biggs and Kilroy (2000). This involves pooling periphyton samples from 10 rocks into a single composite sample for analysis (See Greenfield (2016) for further details).
Macroinvertebrates
A single macroinvertebrate sample is collected at RWQE water sampling sites during summer/early autumn. The timing of sampling is determined at random, although macroinvertebrate sampling is, where practicable, avoided within two weeks of any flood event (flood events are defined as flows greater than three times the median river flow). Samples are collected with the use of a kick-net (0.5 mm mesh size) following Protocol C1 of the national macroinvertebrate sampling protocols (Stark et al. 2001) for the 38 sites with hard substrate (in riffle habitat) and Protocol C2 for the seven sites with a soft substrate. All samples are processed in accordance with Protocol P2 (Stark et al. 2001).
Habitat quality
Habitat assessments are undertaken annually at RWQE sites where macroinvertebrate during summer/early autumn when invertebrates samples are collected following the updated methods outlined in Clapcott (2015). This assessment provides an indication of the condition of the physical habitat and its ability to support stream biota, and incorporates the following variables: deposited sediment cover, invertebrate habitat abundance and diversity, fish habitat abundance and diversity, hydraulic heterogeneity, bank erosion and vegetation, and riparian width and shade. Each category is scored between 1 (‘poor’) and 10 (‘excellent’). Summation of individual scores provides an overall total habitat quality score for each site (lowest and highest possible scores are 10 and 100, respectively). This methodology was developed with a focus on wadeable hard-bottomed streams (Clapcott 2015) and hence its applicability to other stream/river types has not been explored.
