Methodology

 

Habitat Assessment Methodology

The habitat assessment protocol used by the Council is both a qualitative (quality of the habitat) and quantitative (amount of each habitat present) assessment of environmental factors at each site, such as channel stability, periphyton abundance, riparian vegetation, the composition of organic and inorganic substrate in the stream and surrounding land-use (see Appendix 1 – Habitat Assessment Field Data Sheet). The protocol used is based on Pfankuch D. J. (1975), ‘Stream Reach Inventory and Channel Stability Evaluation'.

Sites are assessed every two years. The procedure used involves visiting the same location at each site, to assess the environmental factors (qualitative assessment) in the immediate vicinity of this location. An upstream and downstream transect of the stream channel from this site is then walked, with quantitative assessments made every 10m or where a new feature is observed, for example, a pool.

The qualitative habitat assessment involves assigning scores to the following stream characteristics: aquatic habitat abundance, aquatic habitat diversity, hydrologic heterogeneity, channel alteration, bank stability, channel shade, and riparian vegetation. Scores for each characteristic range from 0 to 20. At the end of the assessment, these scores are summed to give a total score for habitat quality, where 0 – 38 is a poor habitat; 39 - 73 is a marginal habitat; 74 - 108 is a sub-optimal habitat and 109 - 140 is an optimal habitat.

Stability of the streambed and channel at each site is assessed using the Pfankuch stability index (Pfankuch, 1975). This involves assigning scores to 15 environmental variables (such as bank wasting, deposition, stability of stream bed, etc). The variables are split into upper bank, lower bank and stream bottom. The scores are summed and can range from 38 to 152, where a lower total score indicates a more stable stream channel. Scores <38 represent excellent stability; scores 39-76 good stability, 77-114 fair stability and scores >115 poor stability.

Periphyton abundance is recorded in four classes (diatom, mat algae, filamentous algae, and bryophytes) and each of these is classified as either none, rare, common, or abundant. The same scoring system is used to assess the presence of submerged aquatic plants (macrophytes).

Other factors noted at each site include any evidence of livestock access, channel shading, water odour and other observations of interest. A basic measure of water quality at the time of assessment is also taken, including water temperature, dissolved oxygen, conductivity and water clarity.

The quantitative habitat assessment involves walking a transect of the stream channel, both upstream and downstream, with recordings made at a number of stops. Variables recorded include canopy and understorey cover within 0-5m and 5-20m of the stream bank; stability and bank type of each bank; inorganic and organic substrate on the bottom of the stream; wetted width (edge of water on one bank to edge of water on opposite bank); maximum depth of channel and flow type (run/riffle/pool/shute).

Other Sampling Data

In addition to data collected using the habitat assessment methodology, water quality data is recorded for each site on a monthly basis and macro-invertebrate data is collected for each site annually. Although these sampling programmes are run independently of the habitat assessments, data collected through them can be used to help interpret the results from the habitat assessments.

Water quality data recorded monthly for each site includes physical properties, such as temperature, dissolved oxygen, water clarity, turbidity, conductivity and pH, and chemical properties, such as the amount of nutrients (ammonium, total nitrogen, and total phosphorus) present in the water. The amount of bacteria present in the water is also measured at each site.

Macroinvertebrate sampling involves collecting benthic (bottom) samples from each site to record the number and type of macroinvertebrates present. Sites are characterised according to whether they have a hard or soft bottom, with different sampling protocols used for each type.

The number of species present (taxonomic richness) at each site is recorded, along with the percentage Ephemeroptera (Mayfly), Plecoptera (stonefly) and Trichoptera (caddisfly) (% EPT). The more species present, the higher the conservation value of each site.

Each site is also given a Macroinvertebrate Community Index (MCI) and Semi-Quantitative (SQ) MCI score, which reflect the species present and their tolerance to environmental changes and human activity, and the number of individuals belonging to each taxon. The higher the score, the less impacted the environment is by human activity. The lower the score, the more ‘polluted' a site is.

Sampling Sites

The sites assessed by the Council are those included in the Regional River Water Quality Monitoring Network (RWQMN). There are currently 35 sites in this network; 31 of which are monitored by the Council and four by the National Institute of Water and Atmospheric Research (NIWA) (shown in pink in Figure 1).

Map showing the 35 Regional Water Quality Monitoring Network sites.

Figure 1: Map showing the 35 Regional Water Quality Monitoring Network sites (National River Water Quality Network sites in pink).

Sites have been gradually added to the RWQMN since monitoring first began in 1996. In 2005, 19 sites had habitat assessments completed. In 2007, 22 sites were assessed; in 2008, 25 sites were assessed and in 2010, 35 sites were assessed. The sites are listed in Table 1 below.

 

 

Year Assessed

Site Name

Site No.

2005

2007

2008

2010

Awanui at FNDC take

100363

ü

ü

ü

ü

Awanui at Waihue Channel

100370

ü

ü

ü

ü

Hakaru at SH1

109021

 

 

ü

ü

Hatea at Mair Park

101194

 

 

 

ü

Kaeo River at Dip Rd

102674

 

ü

ü

ü

Kaihu at Gorge

102256

ü

ü

ü

ü

Kerikeri at Stone Store

101530

 

 

ü

ü

Mangahahuru at Apotu

100281

ü

ü

ü

ü

Mangahahuru at Main Rd

100237

ü

ü

 

ü

Mangakahia at Titoki

101038

ü

ü

ü

ü

Mangakahia at Twin Bridges

109096

ü

ü

 

ü

Mangamuka at Iwiatua Rd

108978

 

 

ü

ü

Manganui at Mitaitai Rd

102257

ü

 

ü

ü

Mangere at Knight Rd

101625

ü

ü

ü

ü

Ngunguru at Waipoka Rd

109100

 

 

ü

ü

Opouteke at Suspension Bridge

102258

 

ü

 

ü

Oruru at Oruru Rd

108979

 

 

ü

ü

Paparoa at SH12

108977

 

 

ü

ü

Punakitere at Recorder

105231

ü

ü

ü

ü

Ruakaka at Flyger Rd

105008

 

ü

ü

ü

Utakura at Rangihua Rd

109020

 

 

ü

ü

Victoria at Thompson’s Bridge

105532

ü

ü

ü

ü

Waiarohia at 2nd Avenue

105672

 

ü

 

ü

Waiarohia at Whau Valley

107773

ü

ü

 

ü

Waiharakeke at Stringer Rd

100007

 

 

 

ü

Waimamaku at SH12

109098

 

 

ü

ü

Waiotu at SH1

102248

ü

ü

ü

ü

Waipao at Draffin Rd Bridge

108941

 

 

 

ü

Waipapa at Forest Ranger

101751

ü

ü

ü

ü

Waipapa at Waipapa Landing

101524

 

 

ü

ü

Waipoua at SH12

103304

ü

ü

ü

ü

Wairua at Purua

101753

ü

ü

ü

ü

Waitangi at Waimate

103178

ü

ü

 

ü

Waitangi at Watea

101752

ü

ü

 

ü

Whakapara at Cableway

102249

ü

ü

ü

ü

Table 1: RWQMN sites and years sampled

Sampling Period

Comprehensive habitat assessments are carried out at all sites at the same time or as close as possible to the macroinvertebrate sample collection undertaken by the Council. This means that habitat assessment data can be used when interpreting the results from macroinvertebrate sample collection at each site.

In 2008, assessments were undertaken from the end of March to the start of April. In 2010, assessments were undertaken from mid January to mid April.

Data Analysis

The data collected in 2008 and 2010 has been entered into Excel to allow for a comparison of the substrate, vegetation, stability, and over all habitat quality across the sites assessed.

In addition, total Pfankuch stability scores and habitat quality scores for each site from 2005, 2007, 2008 and 2010 have been compared, in order to identify any trends occurring over time.

Hatea River at Mair Park.Hatea River at Mair Park.