the okana river - environment...

The Okana River: assessment of water quality and ecosystem monitoring, July 1992 to May 2002 and water quality implications for Lake Forsyth/Wairewa Report No. U03/20 Prepared by M R Main R M Lavender S Hayward May 2003

Report No. U03/20

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The Okana River: assessment of water quality and ecosystem monitoring, July 1992 to May 2002 and water quality implications for Lake Forsyth/Wairewa

Executive Summary The Little River valley has a long history of land-use modification. In the 1800s, land use in this catchment changed from predominantly forested to predominantly agricultural. This in turn caused significant changes in the Okana River and Lake Forsyth/Wairewa. In particular, there was a loss of fine sediment to the lake. The soils this sediment was derived from contained high concentrations of phosphorus. At the same time, the lake changed from an arm of the sea to an impoundment. Around the turn of the twentieth century, the lake began to suffer from blooms of the toxic cyanobacterium Nodularia. Environment Canterbury began sampling the lake and its catchment in 1992, primarily in an attempt to determine what triggers these blooms, but also as part of a biological health monitoring programme. Stream sites included the Okana River and six of its tributaries. Six of these streams were gauged for four years, and the seventh has a permanent water level recorder. All sites retained a relatively natural channel pattern with limited channelisation and a high diversity of riffles, runs and pools. Undercut banks, wood snags and small areas of submerged macrophytes provided cover for fish and invertebrates. The bed substrates were mainly comprised of loosely packed large and small cobbles and gravel with only a little fine sediment. The invertebrate community in the Okana River was dominated by molluscs, especially the snail Potamopyrgus. This group comprised over 50% of all invertebrates collected from this stream. A mixture of clear water, relatively pollutant sensitive species, such as the mayfly Coloburiscus and Olinga and Helicopsyche caddises, and more tolerant caddis species such as Oxyethira and Aoteapsyche, were also present. All of these species occurred in relatively low abundance, suggesting the Okana River has been affected to some degree by catchment modification and loss of riparian vegetation, but flow and instream habitat were still not degraded sufficiently to cause the extinction of more sensitive species. However, the Hukahuka and Opuahou streams and the Okuti River, which are less modified, supported a greater relative abundance and number of species of mayflies and caddises than the Okana River. Faecal coliform concentrations in all of the streams, except Reynolds Valley stream, were similar to those in other agricultural catchments in Canterbury. Reynolds Valley stream had the lowest concentrations, probably because its catchment is less well developed than that of the others. Mean concentrations of total nitrogen, nitrate and nitrite nitrogen, and ammonia nitrogen were relatively low in all of the streams, although nitrate exhibited a seasonal variation, with relatively high concentrations during the winter. Overall, the concentrations were within guidelines for the control of nuisance periphyton growths. In contrast, all streams had high concentrations of dissolved reactive phosphorus relative to other, similar, streams in Canterbury. There was some seasonality, such that in most streams concentrations were higher during the summer. However, the concentrations were rarely likely to be limiting to plant growth. The highest concentrations were recorded from Reynolds Valley stream, and concentrations in this stream appeared to increase towards the end of the sampling period. Concentrations were negatively related to flow, indicating that most of the dissolved phosphorus was not from runoff. Stream flows at the water quality sampling sites were measured for four years. Flow gauging data were correlated with continuously-recorded data from one of the sites. There was a very close correlation for all of the sites. Mean nutrient loadings were calculated for the period when stream gaugings were made.

Environment Canterbury Technical Report 1


Nutrients, turbidity, pH, conductivity, temperature and chlorophyll a in Lake Forsyth/Wairewa were all very variable, and often quite high. High concentrations of nutrients were often associated with Nodularia blooms, but were not necessarily causative. Controlling phosphorus inputs to the lake will be difficult, because of the highly fertile soils in the catchment. Ultimately though, successful control of Nodularia blooms might require a combination of measures such as attempting to minimise phosphorus inputs to the lake, and dilution, flushing, biological manipulation, and/or antibiosis. All of these have potential limitations, but they will be examined over the coming years to determine their potential for application to this problem.

2 Environment Canterbury Technical Report


Table of Contents

Executive Summary ..................................................................................................1

1 Introduction .....................................................................................................7

2 Methods and sampling sites ..........................................................................9 2.1 Streams...........................................................................................................................9

2.1.1 Water quality ......................................................................................................9 2.1.2 Stream flows ....................................................................................................10 2.1.3 Invertebrate health ...........................................................................................10 2.1.4 Lake sampling..................................................................................................12 2.1.5 Data analyses ..................................................................................................12

2.2 Water quality guidelines................................................................................................12

3 Results ...........................................................................................................15 3.1 The water quality of the Okana River and tributary streams ........................................15

3.1.1 General ............................................................................................................15 3.1.2 Seasonal variation ...........................................................................................18 3.1.3 Variation between sites....................................................................................20

3.2 Stream flows in Okana River and tributaries ................................................................20 3.3 Nutrient loadings...........................................................................................................21 3.4 Invertebrate health monitoring ......................................................................................21 3.5 Lake Forsyth/Wairewa water quality.............................................................................23

3.5.1 Nutrients...........................................................................................................23 3.5.2 Comparison with guidelines .............................................................................23 3.5.3 Specific conductance and salinity ....................................................................27 3.5.4 Temperature.....................................................................................................27 3.5.5 pH.....................................................................................................................27 3.5.6 Turbidity ...........................................................................................................28 3.5.7 Chlorophyll a ....................................................................................................29

4 Discussion.....................................................................................................29

5 Conclusions ..................................................................................................33

6 Glossary.........................................................................................................34

7 Acknowledgements ......................................................................................36

8 References.....................................................................................................36



Appendix I Details of analyses included in the water quality sampling .......41

Appendix II Description of the main determinands included in the water quality sampling.............................................................................43

Appendix III Seasonal variation of determinands in the Okana River and its tributaries........................................................................................47

Appendix IV The continuous flow record for Hukahuka Stream at Lathams Road ................................................................................................55

Appendix V Regression curves for flows in Little River streams compared with Hukahuka Stream at Lathams Road .....................................57

Appendix VI Invertebrate species list for the Okana River and its tributaries (1999-2001)......................................................................................61



List of Figures Figure 1.1 The Forsyth Sawmill at Little River in the 1870s (from Ogilvie, 1990). ............................ 8 Figure 1.2 An accumulation of Nodularia on the shore of Lake Forsyth/Wairewa ................ 8 Figure 2.1 Water quality and stream flow measurement sites in the Okana River-Lake

Forsyth/Wairewa catchment........................................................................................... 10 Figure 2.2 Location of invertebrate health sampling sites (● ) on the Okana River and

its tributaries ................................................................................................................. 11 Figure 2.3 Sampling at Lake Forsyth/Wairewa. The photo shows the recorder tower and

instrument housing holding the water quality probes and water level recorder ............. 14 Figure 3.1 Water quality determinands in the Okana River and tributaries, compared with

those from regional lowland waterways . ....................................................................... 16 Figure 3.2 Dissolved reactive phosphorus concentrations in Reynolds Valley stream

compared with those in the Okana River. ...................................................................... 17 Figure 3.3 Dissolved reactive phosphorus concentrations in Reynolds Valley Stream

compared with stream flow............................................................................................. 18 Figure 3.4 Seasonality in nitrate-plus-nitrite nitrogen concentrations in the Okana River at SH

75.................................................................................................................................... 19 Figure 3.5 Average relative abundance of main taxonomic groups in the Okana River and

tributaries between 1999 and 2001................................................................................ 22 Figure 3.6 Concentrations of dissolved reactive phosphorus in Lake Forsyth/Wairewa

compared with chlorophyll a concentrations (5-point moving averages) ....................... 25 Figure 3.7 Concentrations of nitrate-plus-nitrite nitrogen and ammonia-nitrogen compared with

chlorophyll a in Lake Forsyth/Wairewa (5-point moving averages) ............................... 25 Figure 3.8 Total phosphorus concentrations compared with chlorophyll a concentrations in

Lake Forsyth/Wairewa.................................................................................................... 26 Figure 3.9 Specific conductance and salinity in Lake Forsyth/Wairewa ......................................... 26 Figure 3.10 Water temperatures measured in Lake Forsyth/Wairewa.............................................. 27 Figure 3.11 pH in Lake Forsyth/Wairewa .......................................................................................... 28 Figure 3.12 Turbidity in Lake Forsyth/Wairewa................................................................................. 28 Figure 3.13 Chlorophyll a concentrations in Lake Forsyth/Wairewa ................................................. 29 Figure 4.1 Turbidity in Lakes Ellesmere/Waihora and Forsyth/Wairewa compared (ECan,

unpublished data). ........................................................................................................ 32



List of Tables Table 2.1 Selected guideline values used in the interpretation of data.......................................... 13 Table 3.1 Mean concentrations of nutrients (gm-3), and median concentrations of faecal

coliforms (CFU 100 ml-1) in Okana River tributaries in July 1994-June 2002 ................ 15 Table 3.2 Determinand concentrations between sites compared using the two-tailed

Wilcoxon Signed Rank Test ........................................................................................... 19 Table 3.3 Flow gauging statistics for the Okana River and tributaries. Note: QH equals

the flow in the Hukahuka Stream at Lathams Road............................................... 20 Table 3.4 Mean instantaneous loadings of nutrients in Lake Forsyth/Wairewa

tributaries (gs-1) ............................................................................................................ 21 Table 3.5 Relative invertebrate health scores for Okana River and its tributaries between

1999 and 2001 compared to the average reference condition for Banks Peninsula streams (grading is a five point scale of very poor, poor, fair, good to very good). ....... 22

Table 3.6 QMCI scores for Okana River and tributaries between 1999-2001 ............................... 23 Table 3.7 Mean concentrations of nutrients in Lake Forsyth/Wairewa compared with the

Okana River and tributaries (all concentrations gm-3).................................................... 23 Table 3.8 Values of variables that define the boundaries of lake trophic levels (modified from

Burns et al., 2000) .......................................................................................................... 24 Table 4.1 Similarities and differences between Lakes Forsyth/Wairewa and

Ellesmere/Waihora ......................................................................................................... 32



1 Introduction Lake Forsyth/Wairewa lies in the bottom of the Little River valley on the south-west corner of Banks Peninsula. The lake is fed by the Okana River, which in turn receives flow from the Okuti River, and the Opuahau and Hikuika streams. Reynolds Valley stream flows into the Okuti River. In the 1830s, Lake Forsyth/Wairewa was open to the sea and known as Mowry (probably a misspelling of Maori) Harbour (Anson, 1910, Anderson, 1927). At that time it was navigable by whale boats to its headwaters, and whalers felled trees in the valley, rafted the timber down the lake, and out to their whaling stations in the eastern bays of Banks Peninsula (Anderson, 1927). Sometime in the early nineteenth century, accretion of the gravel barrier along Kaitorete Spit caused the entrance to begin to close over, and by the mid-nineteenth century Henry Sewell recorded that the spit was more-or-less permanently closed (McIntyre, 1980). It began to be opened artificially to the sea to allow drainage in about 1866, when the Little River Roads Board voted a sum of 10 pounds for the purpose (Jacobson, 1940). Jacobson also noted that, at the time of his writing, there were plans to create a permanent outlet, by making a tunnel through the hill to Oashore Bay on the south-east of the peninsula. However, this did not proceed, and currently the lake is opened every year, with the number of openings dependent on the rainfall. The Little River valley was clothed in podocarp forest when the whalers arrived. They began to mill the timber by pit-sawing, and in1863 the first of five sawmills in the area was established at Little River (Figure 1.1; Jacobson, 1940). Other mill sites were at Springvale (Cooptown), and in the Okuti, Western, and Tarawera Valleys (Taylor, 1937). After the trees were milled, the scrub and slash was burned. By 1895 all of the millable trees were gone, and soil erosion had occurred on a large scale (Armstrong, 1962). For example, two men were killed when they were buried by a large slip in 1923 (Ogilvie, 1990). The streams were filled with silt during the latter half of the nineteenth century, and silt accumulated in the lake, so the lake bed had to be dredged to move the timber. By then,

dairy farming had become important in the valley, and the plans were drawn up for a creamery (skimming station) for the Canterbury Central Dairy Co. in1892 (Philpott, 1937). This was the first of several eventually built, and it seems that surplus whey was probably discharged into the streams, as was common done in those times. Lake Forsyth/Wairewa is about 5.6 km2 in maximum extent, although it varies greatly with water level, and it has a catchment of about 110 km2 (Livingston et al., 1986). The average depth varies between about one and two metres, depending on the lake level, with a maximum depth near the outlet of about four metres (Irwin, 1979). The lake has a volume of about 5 to 10 million cubic metres (again depending on lake water level), and a mean turnover time of about 29 to 58 days, assuming a mean inflow of 2 m3 s-1 (see Table 3.3). Rainfall in the catchment is higher than on Canterbury Plains. For example, NZ Meteorological Service (1973) recorded mean annual rainfalls of 1097 mm at Puaha and 1219 mm at a site at 61m elevation in the Okuti Valley, compared with only 689 mm at Lincoln. Some other characteristics of the lake and its catchment are listed in Table 4.1. High concentrations of nutrients occur in Lake Forsyth/Wairewa, and these might be a stimulus to regular toxic cyanobacterial (blue-green algal) blooms, which occur in the lake every year (usually in the period from mid-summer to autumn). The blooms have occurred since at least 1907 (Lyttelton Times, 30/1/1907), and the cyanobacterium accumulates on the lakeshore (Figure 1.2). The Lyttelton Times reported that there was “…scum on the surface of the lake…” and that “The water resembled that product of a child artist made by frequent dipping of brushes in painting a water-colour pastel – it was of a hideous dirty green opaque in thicknesses of one inch.” (Lyttelton Times, 30/1/1907). This is a graphic description of the appearance of a Nodularia bloom. The Times also reported that it was not unusual for the combination of the dirty water and high temperature to kill the fish (referring to a trout kill in the lake associated with the 1907 bloom). However, it went on to say: “The general state of the lake had not been so bad for many years.”



Figure 1.1 The Forsyth Sawmill at Little River in the 1870s (from Ogilvie, 1990).

Figure 1.2 An accumulation of Nodularia on the shore of Lake Forsyth/Wairewa



Nodularia is a cyanobacterium (or blue-green bacterium – previously known as blue-green algae) that produces a hepatotoxin called Nodularin (Mulligan, 1985), and sheep and dogs have died after having drunk water from the lake, or after swimming in it (Connor, 1977). According to Connor (1977), the losses of stock during a large bloom in 1968-69 on one farm alone were reported as: 17 steers, 3 dogs, and a large number of sheep. Lake Forsyth/Wairewa and the lower Okana and Okuti rivers have populations of brown trout, perch and probably tench and rudd. There is also a large population of shortfinned eels, as well as flounder, common smelt, inanga, and common bully. The lake is an exclusive Maori eel fishery. Trout kills sometimes have been associated with heavy Nodularia blooms (Lyttelton Times, 1907; Main and Meredith, 1999). The cause of the fish kills has not been clear, because the toxin is thought not to affect fish directly (Dow and Swoboda, 2000). This is shown by the fact that trout and other species continue to persist in the lake during blooms, although there have been reports from Australia of fish kills of less mobile species during Nodularia blooms that could have been caused by low oxygen concentrations (Potter et al., 1983). One further effect is that odours are produced when the masses of cells (Figure 1.2) die and decompose along the shoreline. These can be very strong and, in January 1907 the Lyttelton Times reported that “Little River itself was, it is said, rendered almost uninhabitable by the odour that came from the lake when a sea-breeze blew.” Water quality in the Okana River and the lake cannot be separated readily, so Environment Canterbury has been undertaking a comprehensive programme of investigations designed to aid our understanding of water quality processes within the lake and its catchment, and this is still on-going. The programme includes sampling water quality for nutrients and faecal coliforms at seven sites on tributary streams of Lake Forsyth/Wairewa and sampling for nutrients and other determinands in Lake Forsyth/Wairewa. There has also been a limited assessment of ecosystem health in the Okana River and some flow gaugings have been made on the tributaries.

There is a permanent water level recorder on Hukahuka Stream. The purpose of this report is to summarise all of the available water quality and invertebrate health data for the Okana River and its tributaries. The intention is not to summarise all of the available data for Lake Forsyth/Wairewa (which will be done later), but only some of those data relating to the influence of the Okana River on water quality in the lake.

2 Methods and sampling sites

2.1 Streams 2.1.1 Water quality Seven sites were sampled on streams in the Lake Forsyth/Wairewa catchment (Figure 2.1). Determinands analysed in these samples were: total nitrogen, ammonia-nitrogen, and nitrate-plus-nitrite nitrogen, total phosphorus, dissolved reactive phosphorus, faecal coliform bacteria, and turbidity. Analytical details are included in Appendix I, and there is a description of the significance of determinands in Appendix II. Samples were collected once a month from July 1992 until May 2002, but turbidity analyses were discontinued in July 1994. Sampling followed the procedures in Environment Canterbury’s Surface Water Quality, Groundwater Quality and Biological and Habitat Assessment Field and Office Procedures Manual (ECan, 1999). Briefly, the sample collection was as follows. No selection of particular flow conditions was made. Samples were collected from the main stream channel using a sample grabber to collect the samples in the flowing channel, avoiding the river margin. Samples were stored in specially prepared bottles provided by the laboratory undertaking the analyses, and kept cooled in insulated bins until delivery to the laboratory. Microbiological samples were analysed within six hours of sampling.



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Reynolds Valley Str eamat B rankins B ridge

Little River

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Lake Forsythat r ecorder

Figure 2.1 Water quality and stream flow measurement sites in the Okana River-Lake Forsyth/Wairewa catchment

2.1.2 Stream flows Between July 1992 and June 1996, six of the stream sites were gauged at monthly intervals, at the same time that water quality samples were collected. These were current meter gaugings, with results calculated by the mean section method, following the ECan Hydrological Field and Office Procedures Manual (ECan, 1997) and ISO (1983). The seventh site, Hukahuka Stream at Lathams Road, has a continuous water level recorder, which is operated by NIWA.

Instantaneous nutrient loadings were estimated by multiplying the nutrient concentrations by the flow at the time of sampling. 2.1.3 Invertebrate health In 1999 four sites were monitored on the Okana River (at Pa Road) and its tributaries (Hukahuka Stream at Lathams Road, Opuahou Stream above Hikuika Stream confluence and the Okuti River at Usshers Road), as part of a region-wide stream biological monitoring and habitat health



Figure 2.2 Location of invertebrate health sampling sites (● ) on the Okana River and

its tributaries



programme (Figure 2.2). The programme was based on Rapid Bioassessment Protocols developed by Plafkin et al. (1989) in the USA. The protocols involve the comparison of streams against relatively pristine reference sites to quantify stream health. In 1999, over 235 wadeable streams throughout Canterbury were sampled in November-December and January-February, to collect baseline data on the habitat and invertebrate health of streams. This was continued each year to assess the effects of low flows in the following summers. Sampling was discontinued on the Okana River and Opuahou Stream after the first two sampling periods, because of a reduction in the scale of the programme. However, data collection continued at Hukahuka Stream and the Okuti River, with the exception of 2002, when an unusually wet weather pattern prevented sampling taking place in January-February. Hukahuka Stream was considered to be a relatively pristine example of a Banks Peninsula stream and was chosen as one of the reference sites at the beginning of the programme. Habitat variables recorded at each site included catchment type, riparian and bank characteristics, instream features and percentage cover and algal type on stones. Invertebrate samples were collected using a kicknet from three transects per site. Samples were preserved in 70% alcohol. In the laboratory, samples were subsampled using a barrel sample splitter, and insects were counted and identified using a Bogorov tray and the "100 fixed count + scan for rare taxa" method (Winterbourn and Gregson, 1989; Stark et al., 2001). 2.1.4 Lake sampling Within the lake, samples were collected for analysis of total nitrogen, nitrate-plus-nitrite nitrogen, and also chlorophyll a, turbidity, conductivity, and pH, from one site on the north-western shore (Figure 2.1). Salinity and temperature were measured in the field at the same time. Between July 1993 and July 1997 these samples were collected monthly, but since then they have been collected weekly. In 1994 water quality probes to measure wind speed, pH, conductivity, and temperature were installed in Lake Forsyth/Wairewa, in association with a water level recorder, to obtain continuous data for this project (Figure

2.3). Later a turbidity probe was added. The focus of this report is on the Okana River, so only a small amount of the data collected by these probes are included in this report. There has also been limited sampling of the invertebrate fauna of Lake Forsyth/Wairewa. The results of that sampling are not included in this report. 2.1.5 Data analyses The Wilcoxon signed rank test procedure of Systat 6.0 (SPSS, 1999) was used to compare the results from those sites which were downstream of one another, and therefore where water quality at the downstream site could be considered to be dependent on water quality at the upstream site. Pairs of sites where this was so, were: Reynolds Valley Stream and Okuti River, Hukahuka Stream at Bachelors Road and at Lathams Road, Hikuika Stream and Okana River, and Opuahou Stream and Okana River. Regressions were performed using the procedure in Excel, between data from the continuously-recorded site and the gauged sites, and on some water quality data from Lake Forsyth/Wairewa. The LOWESS (or LOcally WEighted Scatterplot Smoothing) procedure of Statistica was used to smooth data when dissolved reactive phosphorus concentrations in Reynolds Valley Stream were compared with stream flows. This procedure is useful for removing the effect of a confounding variable (Helsel and Hirsch, 1992). In this case, the confounding variable was high flows.

2.2 Water quality guidelines The use of guidelines can help assess the suitability of the water for various uses including recreational water use, livestock drinking-water or irrigation water etc., and for the protection of the aquatic ecosystem of the river. However, guideline values generally encompass a broad range of river types and may not necessarily represent achievable target values for some types of river systems. A selection of guidelines used in the interpretation of data in this report is listed in Table 2.1.



Table 2.1 Selected guideline values used in the interpretation of data

Determinand Water Use/Value Guideline value Reference

Dissolved Reactive Phosphorus (DRP)

Recreational/Aesthetic (20-day accrual period) (40-day accrual period) Aquatic ecosystems (20-day accrual period) (40-day accrual period)

0.001 gm-3 (mean of monthly data over a 1 year period) 0.001 gm-3 (mean of monthly data over a 1 year period) 0.026 gm-3 (mean of monthly data over a 1 year period) 0.003 gm-3 (mean of monthly data over a 1 year period)

Biggs (2000)

Dissolved Inorganic Nitrogen (DIN)

Recreational/Aesthetic (20-day accrual period) (40-day accrual period) Aquatic ecosystems (20-day accrual period) (40-day accrual period)

0.02 gm-3 (mean of monthly data over a 1 year period) 0.01 gm-3 (mean of monthly data over a 1 year period) 0.295 gm-3 (mean of monthly data over a 1 year period) 0.034 gm-3 (mean of monthly data over a 1 year period)

Biggs (2000)

Ammonia Toxicity (Total ammonia)

Aquatic ecosystems 0.9 gm-3 (at pH 8) ANZECC (2000)

pH Aquatic ecosystems 7.2 – 7.8 ANZECC (2000) Turbidity Aquatic ecosystems 5.6 NTU ANZECC (2000) Temperature Aquatic ecosystems

25 oC 20 °C

RMA (1991) Alabaster and Lloyd (1980)

Faecal coliforms Stock Water Supply Recreational

100 CFU 100mL-1 (median value of several samples). Investigations are recommended when 20 % of samples exceeds 400 cfu/100ml. 1000 CFU 100mL-1 (geometric mean of at least 5 samples per month; no more than 20% to exceed 5000 cfu 100mL-1

200 CFU 100mL-1 (median of at least five samples collected within a 30 day period)

ANZECC (2000) ANZECC (1992) Water & Soil Conservation Act (1967)



Figure 2.3 Sampling at Lake Forsyth/Wairewa. The photo shows the recorder tower and

instrument housing holding the water quality probes and water level recorder



3 Results

3.1 The water quality of the Okana River and tributary streams

3.1.1 General Mean concentrations of nitrogen in all its forms (i.e., total nitrogen, ammonia-nitrogen, and nitrate- plus nitrite-nitrogen) in the lake tributaries (Table 3.1 and Figure 3.1) exceeded Biggs (2000) guidelines for controlling periphyton below nuisance levels for recreation/aesthetic and ecosystem purposes.

However, Mean dissolved inorganic nitrogen (nitrate-plus-nitrite-nitrogen and ammonia-nitrogen) concentrations in Reynolds Valley stream and the Okuti River were within the less conservative MfE (1992) guidelines for control of nuisance periphyton growth in streams (<0.1-0.15 gm-3). In addition, they were low relative to concentrations recorded from Lake Ellesmere/Waihora tributaries. For example, the mean concentrations of nitrate-plus-nitrite nitrogen recorded from the Selwyn River/Waikirikiri (Taylor, 1996) tend to be an order of magnitude higher than those listed in Table 3.1.

Table 3.1 Mean concentrations of nutrients (gm-3), and median concentrations of faecal coliforms (CFU 100 ml-1) in Okana River tributaries in July 1994-June 2002

Total nitrogen

Nitrate + nitrite nitrogen

Ammonia nitrogen

Total phosphorus

Dissolved reactive phosphorus

Faecal coliforms

Site Reynolds Stm At Brankins Bridge

0.19 0.057 0.0013 0.046 0.034 110

Opuahau Stm above Hikuika Stm

0.41 0.20 0.017 0.029 0.024 280

Hikuika Stm above Opuahau Stm

0.48 0.26 0.019 0.058 0.030 250

Hukahuka Stm - Montgomery Rd

0.32 0.16 0.014 0.042 0.018 250

Hukahuka Stm - Lathams Rd

0.30 0.15 0.015 0.037 0.019 290

Okana River at SH 75

0.40 0.21 0.094 0.048 0.021 435

Okuti River at Te Oka Bay Rd

0.31 0.13 0.019 0.048 0.024 465

They were also low compared with concentrations recorded from lowland streams throughout Canterbury (Figure 3.1; Meredith and Hayward, 2002).



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Figure 3.1 Water quality determinands in the Okana River and tributaries, compared with those from regional lowland waterways . Note that Hukahuka 1 is Lathams Road, and Hukahuka 2 is Bachelors Road. Data for regional lowland streams are from Meredith and Hayward (2002)



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001

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/2002D

isso

lved

reac

tive

phos

phor

us c

once

ntra

tion

(gm

-3)

ReynoldsOkana

Figure 3.2 Dissolved reactive phosphorus concentrations in Reynolds Valley stream compared with those in the Okana River.

In contrast, dissolved reactive phosphorus concentrations were high in all of the streams, especially in Reynolds Valley stream, compared with similar streams in Canterbury (Table 3.1, Figure 3.1) and exceeded various guidelines for controlling nuisance periphyton growth (MfE, 1992; Biggs, 2000). For example, Figure 3.2 shows concentrations in this stream compared with those in the Okana River. Reynolds Valley stream is an upper catchment tributary of the Okuti River with a significant proportion (~60%) of the catchment in forest. Hikuika Stream catchment also has quite low agricultural intensity, but it too had quite high phosphorus concentrations (Figure 3.1). However, nuisance periphyton growths are rarely observed in the catchment, probably because dissolved inorganic nitrogen concentrations are relatively low. There was an apparent trend of increasing DRP concentrations in the Okana River (Figure 3.2). Flows towards the latter part of the data record were relatively high, and those higher concentrations might have been flow-related. However, comparing DRP concentrations with stream flows indicated that there was a significant (P<0.005) negative correlation between stream flow and DRP

concentrations, so that the concentrations decreased as the flow increased (Figure 3.3). This suggests not only that those higher concentrations were not flow-related, but also that the increased concentrations of DRP did not come from runoff. Turbidity was similar to most lowland waterways in the region, although it was low in Reynolds Valley stream, and relatively high in Hikuika Stream (Figure 3.1). The low turbidity in Reynolds Valley Stream is understandable, given that it has a large proportion of forest cover and only limited agricultural land use. As well as relatively high turbidity, Hikuika Stream also had the highest mean total phosphorus concentration (Table 3.1). This might indicate that most particulate phosphorus in that stream entered it bound onto soil, because there was a reasonably close correlation between turbidity and total phosphorus concentrations in the streams when the data for all streams were combined (r2=0.26, df=122, P<0.005). However, on the otherhand, the mean total phosphorus concentration in Reynolds Valley stream was relatively high also, even though the turbidity in this stream was low (Table 3.1 and Figure 3.1).



0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

Flow (L/s)

0.00

0.01

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0.04

0.05

0.06D

isso

lved

reac

tive

phos

phor

us c

once

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tion

(gm

-3)

Figure 3.3 Dissolved reactive phosphorus concentrations in Reynolds Valley Stream compared with stream flow. The solid line was fitted by linear regression, while the dashed line is a LOWESS smoothing fit. r2=-0.12; P<0.005.

Median concentrations of faecal coliforms in all of the streams (Table 3.1) were similar to those recorded from other pastoral catchments in Canterbury (Canterbury Regional Council, 1996), except for Reynolds Stream. It consistently had the lowest faecal coliform concentrations (median of 110 CFU 100 mL-1), which is also low for hill streams elsewhere in Canterbury (Figure 3.1). The highest concentrations in streams were generally at the lower catchment sites, which reflects the increasing number of contaminant sources (in this case generally livestock) with increasing distance downstream. Median concentrations of faecal coliforms were higher in 2001-02 than in previous years, probably because of greater runoff over that summer, caused by unseasonably high rainfall. For example, 116 mm was recorded at Taitapu in January 2002, compared with a mean January rainfall of 60mm (ECan, unpublished data). Sampling throughout Canterbury has shown that summer median faecal coliform concentrations

increase when river flows are relatively high (Canterbury Regional Council, 1996). 3.1.2 Seasonal variation There was generally a seasonal pattern of nitrate-and-nitrite concentrations in the streams such that they were highest in the winter and declined to a low point in late summer-early autumn, except in Reynolds Valley stream (Appendix III). This is a commonly-observed phenomenon in hill country streams in Canterbury which is probably related to the growth cycle of aquatic plants, as well as seasonal differences in nitrate leaching from soil and possibly denitrification in riparian margins (Quinn and Stroud, 2002). It is clearly illustrated by data from the Okana River at SH 75 (Figure 3.4). The same seasonal pattern does not occur in spring-fed streams such as the lower reach of the Selwyn River/Waikirikiri, where concentrations are consistently high throughout the year (ECan, unpublished data).



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Nitr

ate-

nitr

ogen

con

cent

ratio

ns (g

m-3

)

Figure 3.4 Seasonality in nitrate-plus-nitrite nitrogen concentrations in the Okana River at SH 75

Table 3.2 Determinand concentrations between sites compared using the two-tailed

Wilcoxon Signed Rank Test

Hukahuka Stream Upstream site Reynolds Stream Bachelors Road Hikuika Stream Opuahou Stream

Downstream site Okuti River Latham Road Okana River Okana RiverTurbidity *** * *** **

↑ ↓ ↑ ↑ Nitrate and nitrite nitrogen *** * ns ***

↑ ↓ ↓ Ammonia nitrogen *** * * ns

↑ ↑ ↑ Dissolved inorganic nitrogen *** ns ns ***

↑ ↓ Total organic nitrogen *** * ns *

↑ ↑ ↓ Total nitrogen *** ns ns ***

↑ ↓ Dissolved reactive phosphorus *** * *** *** ↓ ↑ ↓ ↓

Total phosphorus ** ns ns *** ↑ ↓

Faecal coliforms *** ns *** *** ↑ ↑ ↑

NS = not significant ↑ = increase in determinand concentration at downstream site * = P <0.05 ↓ = decrease in determinand concentration at downstream site ** = P <0.01 *** = P < 0.005



In contrast, concentrations of dissolved reactive phosphorus were usually highest during the summer, although there was little seasonal variability for this, or any other determinand, in the Reynolds Valley stream (Appendix III). The reason for this increased concentration in the summer is unexplained, but it might be caused by spring flow with high concentrations of phosphorus contributing the majority of the stream flow at that time of the year. This concept is elaborated on in the discussion. 3.1.3 Variation between sites The lowest concentrations of all of the forms of nitrogen were generally recorded from Reynolds Valley Stream also, but, in contrast, it had a slightly higher mean concentration of dissolved reactive phosphorus (DRP) than the other sites (Table 3.1 and Figure 3.1). In fact, it was higher than in the Okuti River downstream, against the usual trend of increasing concentrations with increasing distance, although the same was also true of DRP in the Hikuika and Opuahou streams (Table 3.2). In the Opuahou Stream, concentrations of total phosphorus and most forms of nitrogen also decreased with increasing distance downstream (Table 3.2).

3.2 Stream flows in Okana River and tributaries

About three-quarters of the flow into Lake Forsyth/Wairewa between July 1992 and June 1996 was contributed by the Okana River and the remainder by the Okuti (Table 3.3). The stream flows were relatively stable, particularly in the Okuti River. Variation of flow in the Okana River was greater, probably because the catchment area is about twice that of the Okuti, and has a lower proportion in forest. The continuous flow record for Hukahuka Stream at Lathams Road is shown in Appendix IV. The mean and median daily flows there since the site began recording in December 1987 are 212 and 93 L/s, and the FRE3 (that is, three times the daily median flow), is 279 L/s. The highest mean daily flow measured in Hukahuka Stream was 8,466 Ls-1 on 26 July 1994. By extrapolation, using the regression equation in Table 3.3, this equates to a flow of about 34,000 Ls-1 in the Okana River at SH 75. The regressions for flow between Hukahuka Stream at Lathams Road and the other flow measurement sites all had close regression coefficients, which ranged from 0.93-0.97 (Table 3.3: Appendix V).

Table 3.3 Flow gauging statistics for the Okana River and tributaries. Note: QH

equals the flow in the Hukahuka Stream at Lathams Road Mean

flow Ls-1 Median flow Ls-1

Range of flows Ls-1

Regression equation

Regression coefficient

Site Reynolds Stm 73 39 10- 424 y = 0.27QH + 17 0.94 Opuahau Stm 253 124 30-1683 y = 1.1 QH – 11.2 0.96 Hikuika Stm 150 88 16- 948 y = 0.56 QH +

15.6 0.93

Hukahuka Stm – Bachelors Rd

71 40 10- 428 y = 0.29 QH + 1.5 0.96

Hukahuka Stm – Lathams Rd

239 108 33-1427 _ _

Okana River 1600 692 83-6107 y = 4.01 QH – 84.3

0.97

Okuti River 397 233 55-2388 y = 1.68 QH + 43.6

0.95



Table 3.4 Mean instantaneous loadings of nutrients in Lake Forsyth/Wairewa tributaries (gs-1)

Total nitrogen

Ammonia nitrogen

Nitrate + nitrite nitrogen

Total phosphorus


Site Reynolds Stm 0.0057 0.0007 0.014 0.0031 0.0024 Opuahau Stm 0.020 0.0022 0.088 0.012 0.005 Hikuika Stm 0.030 0.0020 0.056 0.010 0.004 Huhahuka Stm – Bachelors Rd

0.0072 0.0005 0.026 0.003 0.0001

Huhahuka Stm – Lathams Rd

0.050 0.0020 0.077 0.009 0.004

Okana River 0.120 0.0125 0.480 0.043 0.016 Okuti River 0.045 0.0049 0.160 0.018 0.009

3.3 Nutrient loadings Of the two main tributaries, the Okana River contributed the highest mean loadings of nutrients (i.e., mean concentrations multiplied by mean flows), which was not surprising considering it had approximately four times the mean flow of the Okuti River (Table 3.4). In an extreme flow event, such as the flood of 26 July 1994, about 140 kg of phosphorus would have entered the lake during a 24-hour period, assuming that the concentration throughout the flood event was similar to the mean in Table 3.1. However, this is unlikely to be true, because sampling in the Selwyn River/Waikirikiri throughout the duration of floods indicates that, unlike DRP, total phosphorus concentrations peak on the rising hydrograph, and begin to decrease before the flow peaks (ECan, unpublished data). This is similar to the “first flush” effect that is often noted with respect to stormwater.

3.4 Invertebrate health monitoring

The Okana River and its tributaries are situated in an agricultural catchment that is extensively modified. Riparian bank vegetation comprises mainly pasture grasses with grazing, interspersed with introduced trees such as willows, and as a result there is only limited shading over the stream. Breaks and scars in riparian bank cover were present,

and bank stability was poor, with areas of active erosion at some sites. All sites retained a relatively natural channel pattern with limited channelisation and a high diversity of riffles, runs and pools. Undercut banks, wood snags and small areas of submerged macrophyte provided cover for fish and invertebrates. The bed substrates mainly comprised loosely packed large and small cobbles and gravel with only a little fine sediment. The invertebrate community in the Okana River was dominated by Mollusca, specifically the small snail Potamopyrgus. This group comprised over 50% of all invertebrates collected from this stream (Figure 3.5). A mixture of clear water, relatively pollutant sensitive species, such as the mayfly Coloburiscus and the caddises Olinga and Helicopsyche, and more tolerant caddis species such as Oxyethira and Aoteapsyche, were present. All of these species occurred in relatively low abundance, suggesting the Okana River has been affected to some degree by catchment modification and loss of riparian vegetation, but flow and instream habitat were still not degraded sufficiently to cause the extinction of more sensitive species. However, this was not the case for the Hukahuka and Opuahou streams and the Okuti River, which supported a greater relative abundance and number of species of mayflies (Ephemeroptera) and caddises (Trichoptera) than the Okana River (Figure 3.5, Appendix VI). The invertebrate communities of the three tributaries were dominated by higher numbers



of sensitive species of caddis including Pycnocentria, Olinga, and Helicopsyche, indicating these streams are less affected by catchment change than the Okana River (Figure 3.5). Invertebrate stream health scores, calculated from a range of indices compared with Banks Peninsula reference sites, ranged from 46.9 or "poor" in November-December 1999 in the Okana River to 101.8 or "very good" in November-December 2000 in the Okuti River. The invertebrate health values for the Okana River are typical of the lower reaches of a modified Banks Peninsula stream situated in

an agricultural catchment with little native riparian vegetation. The values for the Okuti River show a possible trend of decreasing invertebrate health from 1999 to 2001 compared with other streams on Banks Peninsula (Table 3.5), although there was no corresponding trend in QMCI (Table 3.6). Please note here that the relative scores shown in Table 3.5 are not necessarily comparable between years, because of yearly differences in methodology, but the gradings within a year are comparable.

0%

20%

40%

60%

80%

100%

OkutiRiver

OpuahouStm

OkanaRiver

HukahukaTuroaStm

Site

Ave

rage

rela

tive

abun

danc

e %Mollusc

%Chironomidae

%Diptera

%Trichoptera

%Ephemeroptera

Figure 3.5 Average relative abundance of main taxonomic groups in the Okana River and tributaries between 1999 and 2001

Table 3.5 Relative invertebrate health scores for Okana River and its tributaries between

1999 and 2001 compared to the average reference condition for Banks Peninsula streams (grading is a five point scale of very poor, poor, fair, good to very good).

Date Okuti River

Opuahou Stm Okana River Hukahuka

Relative score

Grading Relative score



Grading

ND1999 90.6% very good 56.3% fair 46.9% poor 100.0% very goodJF2000 93.8% very good 84.4% good 50.0% fair 90.6% very goodND2000 101.8% good 98.2% very goodJF2001 87.3% good 98.2% very goodND2001 60.0% fair 78.0% good



Table 3.6 QMCI scores for Okana River and tributaries between 1999-2001

QMCl Okuti River Opuahou Stm Okana River Hukahuka Stm ND1999 6.4 5 3.8 6.2 JF2000 5.6 4.6 3.9 5.6 ND2000 6.3 7.2 JF2001 5.7 6.1 ND2001 6.1 6.3

The effects of possible organic enrichment from sources such as agricultural runoff was quantified using the quantitative QMCI (Stark, 1998). This index allocates invertebrate taxa a score between 1 and 10 depending on their tolerance to organic enrichment. These scores are multiplied by the abundance of the taxon and divided by the total abundance, then combined to give an overall QMCI value. Higher values indicate more pristine water quality. QMCI values in the Okana River ranged from 3.8 to 3.9. These values indicate that water quality in the Okana River falls into the probable severe degradation category as defined by Stark (1998). Values from Opuahou Stream indicate probable mild degradation to possible moderate degradation of water quality. The water quality in the Hukahuka Stream and Okuti River range from clean to mildly degraded on this index (Table 3.6).

3.5 Lake Forsyth/Wairewa water quality

3.5.1 Nutrients Although nutrient concentrations entering the lake were moderate, the concentrations of total nitrogen and total phosphorus within the lake were high (Table 3.7). For example, the mean total phosphorus concentration in Lake Forsyth/Wairewa was about two to three times as high as that in its tributaries (0.11 gm-3,

compared with 0.032 to 0.056 gm-3 in the tributaries). In addition, the mean concentration of total nitrogen within the lake was three to six times higher (1.5 gm-3, compared with 0.25 to 0.45 gm-3). A similar pattern was noted by Taylor (1996) in Lake Ellesmere/Waihora, where the concentrations of total nitrogen and total phosphorus were far higher in the lake than in any of its tributaries. The increased concentrations recorded from the lakes are a result of measuring those nutrients within algal cells. Consequently, very high concentrations tend to coincide with blooms of Nodularia (Main and Meredith, 1999). Recycling of soluble nutrients from lake sediments might provide another source of nutrients additional to nutrients entering the lake, at least during periods of low sediment oxygen concentration, which probably occur during large blooms. In addition, the alga itself is capable of introducing nitrogen into the lake by fixing atmospheric nitrogen gas. 3.5.2 Comparison with guidelines The concentrations listed in Table 3.7 for Lake Forsyth/Wairewa are far in excess of water quality guidelines such as those in ANZECC (1992). These guidelines suggest that, to minimise excessive algal growths, the total phosphorus concentration should be limited to 0.01 to 0.1 gm-3, and total nitrogen to between 0.1 and 0.75 gm-3.

Table 3.7 Mean concentrations of nutrients in Lake Forsyth/Wairewa compared with the

Okana River and tributaries (all concentrations gm-3)

Dissolved inorganic nitrogen


Total nitrogen Total phosphorus

Okana R. and tributaries

0.075-0.26 0.02-0.04 0.19-0.49 0.03-0.053

Lake 0.25 0.02 1.7 0.3



Table 3.8 Values of variables that define the boundaries of lake trophic levels (modified from Burns et al., 2000)

Trophic status Trophic level Chlorophyll a (mgm-3)

Secchi depth (m)

Total phosphorus (gm-3)

Total nitrogen (gm-3)

Ultra-microtrophic

0-1.0 0.13-0.33 33-25.1 <0.004 <0.034

Microtrophic 1.1-2.0 0.34-0.82 25.0-15.1 0.004-0.009 0.034-0.073

Oligotrophic 2.1-3.0 0.83-2.0 15.0-7.1 0.010-015 0.074-0.157

Mesotrophic 3.1-4.0 2.1-5.0 7.0-2.9 0.016-0.025 0.158-0.337

Eutrophic 4.1-5.0 5.1-12 2.8-1.2 0.026-0.050 0.338-0.725

Supertrophic 5.1-6.0 12.1-31 1.1-0.4 0.051-0.096 0.736-1.6

Hypertrophic 6.1-7.0 >31 <0.4 >0.096 >1.6

Another approach to assessing lake nutrient concentrations is to compare them with a trophic index. Burns et al. (2000) produced a trophic index for New Zealand lakes. This has previously been applied in a slightly modified form to lakes in Canterbury (ECan, in prep. and Table 3.8). There are no secchi depth data for Lake Forsyth/Wairewa, but with respect to the other determinands it clearly falls into the hypertrophic category. Concentrations of soluble nutrients were also high sometimes, especially during periods with algal blooms. For example, Figure 3.6 shows dissolved reactive phosphorus concentrations and chlorophyll a concentrations from May 1995 until May 1998, Figure 3.7 shows dissolved inorganic nitrogen concentrations during the same period, while Figure 3.8 shows that there was a strong, positive relationship between total phosphorus and chlorophyll a. There was no clear seasonal pattern of nitrate-plus-nitrite nitrogen concentrations in Lake Forsyth/Wairewa as occurred in the tributary streams; instead this determinand also tended to vary with algal blooms and hence chlorophyll a concentrations (Figure 3.7).



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200

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orop

hyll

a (m

g m

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DRPchl-a

Figure 3.6 Concentrations of dissolved reactive phosphorus in Lake Forsyth/Wairewa compared with chlorophyll a concentrations (5-point moving averages)

igure 3.7 Concentrations of nitrate-plus-nitrite nitrogen and ammonia-nitrogen compared

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Fwith chlorophyll a in Lake Forsyth/Wairewa (5-point moving averages)



log chl-a vs. log TP (3\6\97-)

y = 359.23x1.4068

R2 = 0.6127

1

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10000

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0.1 1

log total phosphorus concentration (gm-3)

log

chlo

roph

yll a

co

ncen

trat

ion

(mg

m-3

)

Figure 3.8 Total phosphorus concentrations compared with chlorophyll a concentrations in Lake Forsyth/Wairewa

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ConductivitySalinity

Spec

ific

cond

ucta

nce

(mSi

emen

s/m

)

Salin

ity (o / oo

)

Figure 3.9 Specific conductance and salinity in Lake Forsyth/Wairewa



3.5.3 Specific conductance and salinity Specific conductance and salinity in Lake Forsyth/Wairewa are always high (Figure 3.9), because the lake is brackish. The salinity reflects the specific conductance (or vise-versa), since the principal ions in the lake are sodium and chloride. Salinity varies between about 1o/oo NaCl (~3% sea water) and 11o/oo NaCl (~30% sea water), with a mean of 6.0o/oo (17% sea water). This wide range of salinities means that only euryhaline plants and animals (i.e., those adapted to a wide salinity range), can live in the lake, and it gives the lake a restricted biota (ECan, unpublished data). 3.5.4 Temperature The water temperatures spot-measured in Lake Forsyth/Wairewa exhibit a fairly typical seasonal pattern, with a minimum in July 2001 of 3.6oC and maximum in December 2000 of 24.8oC (Figure 3.10). These do not necessarily reflect the true extremes of temperature in the lake, because water temperatures exhibit a daily cycle, and the measurements were often not made at the hottest and coldest times of the day. Nevertheless, even 24.8oC is well above the guideline recommended by Alabaster and Lloyd (1980), and is close to the critical

thermal maximum for some fish such as brown trout. 3.5.5 pH pH in Lake Forsyth/Wairewa varies greatly, especially compared with freshwater lakes in the region (ECan, unpublished data). In part, this is because of varying salinity in the lake. For example, the pH of surface sea water normally ranges from 8.0 to 8.2 (USEPA, 1986), and is slightly acid to neutral in freshwater lakes (Stout, 1975). Therefore, we might expect some fluctuations between 7-8, depending upon the salinity of the lake. However, in the summer, very high pH, in the range from 9-10, is often recorded from Lake Forsyth/Wairewa (Figure 3.11), although it does not necessarily coincide with Nodularia blooms. They could be expected to co-occur, because the high rate of photosynthesis by Nodularia removes CO2 from the water, and CO2 has an acid buffering effect (Oliver and Ganf, 2000). On the other hand, there are sometimes blooms of other algae as well, which might account of some of those periods of high pH.

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31/01/1993 15/06/1994 28/10/1995 11/03/1997 24/07/1998 6/12/1999 19/04/2001 1/09/2002 14/01/2004

Tem

pera

ture

(o C)

Figure 3.10 Water temperatures measured in Lake Forsyth/Wairewa



6

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9

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31/01/1993 15/06/1994 28/10/1995 11/03/1997 24/07/1998 6/12/1999 19/04/2001 1/09/2002

pH

Figure 3.11 pH in Lake Forsyth/Wairewa 3.5.6 Turbidity Lake Forsyth/Wairewa is highly turbid (Figure 3.12). This not surprising, considering its shallowness (a maximum depth of 4 metres close to the outlet, with a mean depth of about 1-1.5 metres, depending on the lake level; Irwin, 1979). High turbidity is common in shallow lakes (Scheffer, 1998). Hamilton and Mitchell (1997) found that Lake

Forsyth/Wairewa was the most susceptible of seven shallow South Island lakes to the effects of wind on re-suspension of sediment. There was a poor relationship between turbidity and chlorophyll a concentrations (regression coefficient of only 0.14), which suggests that most of the turbidity in this lake is caused by suspended sediment.

1

10

100

1000

10000

31/01/1993 15/06/1994 28/10/1995 11/03/1997 24/07/1998 6/12/1999 19/04/2001 1/09/2002 14/01/2004

Turb

idity

(NTU

)


Figure 3.12 Turbidity in Lake Forsyth/Wairewa


0.1

1

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100

1000

10000

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15/06/1994 28/10/1995 11/03/1997 24/07/1998 6/12/1999 19/04/2001 1/09/2002 14/01/2004

Chl

orop

hyll

a co

ncen

trat

ion

(mgm

-3)

Figure 3.13 Chlorophyll a concentrations in Lake Forsyth/Wairewa

erosion, with large quantities of soil high in

the catchment probably also added nutrients ame time, the lake

its

control

part of a habitat

presented

QMCI abundance of

streams and the Okuti River support more pristine

unities). The water quality

entrations are high. More etailed sampling in future will be required to

fully assess the invertebrate health of these

3.5.7 Chlorophyll a Chlorophyll a concentrations in the lake fluctuate greatly (Figure 3.13). There tend to be high concentrations during the summer, associated with Nodularia blooms, but relatively low ones during the winter. During the 1997-98 drought, chlorophyll a reached a very high concentration when there was an enormous bloom (20,000 mgm-3; Main and Meredith, 1999).

4 Discussion The catchment of the Okana River and Lake Forsyth/Wairewa underwent dramatic and extensive land use changes during the nineteen century; these were probably the most extensive of any lake catchment in Canterbury. Forest was cleared and the slash

Environment Canterbury has monitored aspects of water quality and invertebrate and habitat health in the Okana River and tributaries, and water quality in Lake Forsyth/Wairewa, since July 1992. This is principally to determine the sources of nutrients into the lake, and factors that Nodularia blooms in the lake, but the invertebrate health aspect was regional biological monitoring and health programme. With respect to the invertebrate monitoring, it should be noted that the results here are effectively only a "snapshot in time" for single localities on the Okana River and its tributaries between 1999 and 2001. The values combined with the high Potamopyrgus, which is typically associated with macrophyte beds, suggest high nutrient levels could be an issue for the Okana River (although the Opuahou and Hukahuka was burnt. This resulted in large-scale soil

phosphorus entering the lake. Dairy factories invertebrate comminto the lake. At the schanged from being an inlet of the sea, to an enclosed water body. Ultimately, these changes probably facilitated the Nodularia blooms that began to occur sometime around the end of the nineteenth century.

sampling shows that it is certainly true that phosphorus concd

streams. The faecal coliform sampling was also beyond the overall aims of the sampling, but the data are included here for completeness. Although



the streams were not sampled strictly in accordance with the former Water and Soil Conservation Act guideline requirement of 5 samples within a 30-day period, faecal coliform concentrations in the Okana River and its tributaries would generally have exceeded that guideline, especially in the summer time. However, that may not be of too much concern, because these streams are not used frequently for contact recreation. Reynolds Valley stream is an exception to the general rule regarding non-compliance, in that it would probably comply with the guideline most of the me. In this respect, Reynolds Valley stream

hey would comply with the ss stringent guideline for stock drinking water

growth is unlikely to be a ubstantial issue in these streams, because a

ast to nitrogen, Reynolds Valley stream ad a higher mean concentration of dissolved

e other streams. The phosphorus

awson and Barry soils

tiwas somewhat unusual compared with most streams in Canterbury (e.g., CRC, 1996). However, its low faecal coliform concentrations are probably due to the fact that about 60% of the catchment is in forest, both native and exotic. Most of the streams would also fail to comply with the very stringent ANZECC (2000) stock drinking water quality guideline for faecal coliforms, although tlein the 1992 version of the ANZECC guidelines. The focus of this sampling programme was on nutrients, and as for faecal coliforms, the lowest concentrations of all forms of nitrogen were generally recorded from Reynolds Valley Stream. Concentrations in the other streams were also relatively low compared with lowland streams and other hill country streams in Canterbury (Meredith and Hayward, 2002). Concentrations of dissolved inorganic nitrogen (i.e., nitrate and nitrite plus ammonia) in all streams were less than the 20 day accrual period guideline for periphyton growth (Biggs, 2000), but they exceeded the 40 day accrual period guideline. This means that excessive periphytonsforty-day accrual period (i.e., 40 days without freshes), occurs infrequently in the continuous flow data record for Hukahuka Stream. The mean annual accrual period for the Hukahuka, calculated from the continuous record for 1988 to 2001 on the basis of a FRE3 of 279 L/s, (i.e., the mean number of days per year between flows exceeding 3 times the median flow; Biggs, 2001), is 35 days. This period is probably quite short for east coast South Island streams, and might be a reflection of the relatively high rainfall in the lake’s catchment

(1000-1200 mm, compared with about 600 mm on the Canterbury Plains; NZ Meterological Service, 1973). Concentrations of ammonia-nitrogen in the Okana River and tributaries were far lower than those that would cause toxicity to aquatic life, and also were well below water quality guidelines (Table 3.1). In contrhreactive phosphorus (DRP) than the other sites. This pattern of higher DRP concentrations in Reynolds Stream is consistent from year to year, and concentrations of total phosphorus in this stream tend also to be higher than in some of thconcentrations recorded in Reynolds Valley stream are also high compared with native forest catchments elsewhere in New Zealand, such as the central North Island (Cooper et al., 1987) and North Westland (O’Loughlin et al., 1980). These were similar to native forest and pasture streams at Whatawhata in the Waikato (means of DRP = 0.011-0.038 gm-3, TP = 0.033-0.067 gm-3; Quinn and Stroud, 2002). There was a limited sampling programme undertaken in Reynolds Valley stream between September 1969 and May 1970 (Ecan, unpublished data). Differences in analytical methods, detection limits and reporting make those results of only limited comparative value. For example, nitrate-nitrogen concentrations were consistently reported as either “nil” or else “trace” (the detection limit appears to have been 1.0 gm-3). However, the results for total phosphorus are potentially useful for comparison with the data collected during this programme. The mean total phosphorus concentration during 1969-70 was 0.11 gm-3 (range 0.05 to 0.38 gm-3, n=8). This is considerably higher than the mean concentration reported in Table 3.1 (0.046 gm-3), which might represent a reduction in the stream concentrations since that time, but is probably just an artifact of the small sample size. In all of the streams, phosphorus concentrations are considerably higher than in most streams elsewhere in the region (Meredith and Hayward, 2002). This is probably because the P



on the lower slopes of the catchment, which

his report does not attempt to address the

ted in this catchment, where natural soil hosphorus concentrations are high.

ing periods of low turbidity (ECan, npublished data). However, the bulk of the

earlier ones.

an e highest concentration recorded by Knox

he largest Nodularia blooms appear to occur

were previously under totara-dominated forest cover, have high phosphorus concentrations (Soil Bureau, 1966), and the soils in turn probably reflect the underlying volcanic geology. Turbidity was low in Reynolds Valley stream, but high in Hikuika Stream, where it often exceeded the ANZECC (2000) guideline. Total phosphorus concentrations in Hikuika Stream were also high, which might imply that the phosphorus in this stream was largely bound to sediment particles. However, sediment is unlikely to be a significant source of the high concentrations of DRP in Reynolds Valley stream, which must leach out of the soil and base rocks. Tquestion of the causes of Nodularia blooms in the lake, as that was not its purpose. Closer examination of the data will be made in an attempt to do that when the sampling programme is wound down, in several years’ time. However, some general observations can be made from the data presented here. The observations regarding nutrient concentrations and loadings in the Okana River and its tributaries have implications for the management of Nodularia blooms in the lake. Nodularia is a nitrogen-fixing plant, which means that it does not require nitrogen in the water for its growth (Nordin and Stein, 1980). Instead, growth is likely to be limited by the availability of phosphorus. The traditional view that agricultural activity increases phosphorus concentrations in waterways (e.g., Cooper et al., 1978), does not appear to be supporp The data analysed to date indicate that increases in chlorophyll a concentrations are usually associated with increases of dissolved reactive phosphorus (Figure 3.6), dissolved nitrogen (Figure 3.7), and total phosphorus (Figure 3.8), usually when these follow a period of relatively calm weather. That is, daily mean wind speeds over the preceding week of less than about 3 metres per second, and often durudissolved nitrogen in the lake at these times is ammonia. At this stage it is unclear whether

the ammonia and DRP actually aid the growth of the algae, or are produced by the decomposition of algal cells through the turnover of a large volume of cells during these bloom periods. In some years there were series of blooms, and it appears that the later blooms sometimes were aided by the availability of soluble nutrients caused by the breakdown of the The lake sediment is also a potential source of phosphorus to the lake water when there are low oxygen (reducing) conditions in the sediment. This probably occurs during heavy Nodularia blooms. Results of limited sampling indicate that the sediment phosphorus concentration is high; up to 1600 mg kg-1 (ECan, unpublished data). This is higher ththand Kilner (1973) from sediment at one site in the Avon-Heathcote Estuary near the oxidation pond outfalls, which was 1235 mg kg-1. The large wildlife population on the lake is an additional, at this stage unquantified, source of nutrients and faecal bacteria. Nodularia is known to require a salinity range of 5-25o/oo (Nordin and Stein, 1980), and this range occurs almost continuously in Lake Forsyth/Wairewa, so salinity will certainly not limit its growth. Tafter periods of drought. Thus, the very large bloom in 1997-98 occurred during a one-in-ten year drought (Horrell et al., 1998). At that time, concentrations of nutrients in the lake were extremely high. They reached 143 gm-3

total nitrogen, 14 gm-3 total phosphorus, 4.2 gm-3 dissolved reactive phosphorus and 2.0 gm-3 ammonia-nitrogen, after the Nodularia bloom peaked at > 20,000 mgm-3 chlorophyll a (Main and Meredith, 1999 and Figure 3.13). This bloom was associated with a trout kill in the Okuti River. The major bloom that occurred in January 1907 was also after a period of drought, and also resulted in a trout kill (Lyttelton Times, 1907). In contrast, the algal bloom in 2001-2002 (a wet summer with relatively high stream flows) was relatively small compared with other years, and concentrations of nutrients in the lake over that period were also relatively low.



Table 4.1 Similarities and differences between Lakes Forsyth/Wairewa and

ean chlocentrat y

Ellesmere/Waihora

Aspect Maximum wind fetch (km)

Macrophytes present?

Mcon

Lake Ellesmere/Waihora

Exposed to winds from all quarters

24 No 89

Lake Forsyth/Wairewa

Exposed to winds from NE and SW

5 Yes 1

Overall, the mean concentrations of nutrients recorded from Lake Forsyth/Wairew

rophyll a ion (gm-3)

Mean total phosphorus concentration (gm-3)

Mean total nitrogen concentration (gm-3)

Mean salinity o/oo

Mean turbiditNTU

0.24 2.35 8.1 90

0.28 1.68 6.0 23

Lake Ellesmere/Waihora is far more turbid than Lake Forsyth/Wairewa; up to four times more so. This is further illustrated in Figure 4.1 by continuously-recorded turbidity data from the two lakes during two periods in 1998 and 1999 (ECan, unpublished data). The highly turbid water in Lake Ellesmere/Waihora appears to be one of the major factors that restricts the re-growth of the macrophytes Ruppia spp. and Potamogeton pectinatus (Gerbeaux 1989). These mac

34

a are imilar to those from Lake Ellesmere/Waihora

oms; it blooms ere only about once every 10 years. It is

4.1.

The main differences between the lakes relate aspect, etch, tur e ofacrophytes, and m ll a

concentrations, all of which are probably d to ten One t of the

to n is possibly because

rophytes were ssentially eliminated from that lake in April

orsyth/Wairewa. Nodularia in Lake Ellesmere/Waihora is

ly ed a contrast, L/W ev clear h

light pene s the rowteither Nodularia or the rophytes

resents a measurement made every half-hour.

sat Taumutu (ECan, unpublished data). However in contrast, Lake Ellesmere/Waihora has infrequent Nodularia blothinstructive to compare these two lakes, and ask the question “why is there a difference in the frequency of blooms between the two lakes”? Some similarities and differences are shown in Table 1968, but remain in Lake F

tom

wind f bidity, thean ch

presence lorophy

probabForsy

relateanswer

some ex the questio

t. par

light-limitairewa is

n doe

s well. In idently not limit

ake that h of

th enougtratio g

mac .

1400

e

Figure 4.1 Turbidity in Lakes Ellesmere/Waunpublished data). Each dot rep

0

200

21/11/1998 11/12/1998 31/12/1998 20/01/1999 9/02/ 1/03/1999 21/03/1999 10/04/1999

L. ForsythL. Ellesmere

ihora and Forsyth/Wairewa compared (ECan,

1999

400

600

800

1000

1200

Turb

idity

(NTU

)



Attempts at managing nutrient dynamics in this catchment, especially of phosphorus, will fail if the high fertility status of the catchment soils is ignored. The consistently higher concentrations of phosphorus in Reynolds Valley stream indicates that anthropogenic sources of phosphorus in the streams are probably swamped by phosphorus from natural sources. Management should therefore focus on attempting to control these natural sources, which probably means minimising sediment inputs into the streams, at least in the Hikuika Stream catchment. However, the value of that in Reynolds Valley, where much of the catchment is forested, and most phosphorus probably enters the stream in a dissolved form, is not so clear. Measurements of phosphorus concentrations in ground and spring water on Banks Peninsula are few, and there are none from

Sanders (198phosphorus concentrations of 0.1 to 0.15 gm-3

in water from four springs at French Farm and Pigeon Bay, although concentrations from most of the springs he sampled were less than 0.1 gm-3. Similarly, concentrations of dissolved reactive phosphorus measured from water in two wells close together in the Kaituna Valley were 0.128 and 0.13 gm-3, while a third had a concentration of 0.4 gm-3, and a fourth was 1.03 gm-3 (ECan, unpublished data). These latter concentrations are very high, especially when compared with concentrations of 0.004 to 0.015 gm-3 measured in five of seven wells in the Christchurch-West Melton groundwater area, with a maximum concentration of 0.11 gm-3 (Hayward, 2002). The also appear to be high in a national context. According to Rosen (2001), the maximum phosphate-P concentration measured from 110 wells throughout New Zealand as part of the National Groundwater Monitoring Network is 0.62 gm-3, but only 18 wells had concentrations greater than 0.1 gm-3. Measurement of phosphorus in springs and groundwater of the Okuti and Okana Valleys, especially in forested areas, would help to resolve how much comes from geological sources compared with soil erosion in runoff, and this in turn would help to focus management efforts. At this stage, the results cited above indicate that much of it could come from groundwater.

Ultimately, successful control of Nodularia blooms in Lake Forsyth/Wairewa might require a combination of management measures such as attempting to minimise phosphorus inputs, and others. These other possible methods include dilution, flushing, biological manipulation, and antibiosis. All of these have potential limitations, but they will be examined in depth over the coming years to determine their potential for application to this problem.

5 Conclusions The Okana River and its tributaries are hill country streams in a catchment where there was large-scale land use change in the nineteenth century, and this has caused impacts that are still on-going. The invertebrate communities and instream

its in

the tributaries, which are less modified than the Okana River mainstem. Faecal coliform concentrations in all of the streams, except Reynolds Valley Stream, were similar to other pastoral streams in Canterbury. Reynolds Valley stream has relatively little pastoral development than the other streams, which is probably the reason for those lower concentrations. Concentrations of nitrogen in these streams are low compared with spring-fed streams in Canterbury. However, concentrations of dissolved reactive phosphorus were high compared with those, as well as other hill country streams. The source of this phosphorus is probably the catchment soils/base rocks, and/or groundwater. Lake Forsyth/Wairewa has regular blooms of the cyanobacterium Nodularia. These blooms are often associated with high concentrations of nutrients, but the high concentrations do not necessarily cause the blooms. Other factors, particularly calm weather and a favourable salinity regime, are also necessary for bloom formation. In the long run, the key to controlling these blooms might lie with measures other than nutrient limitation, which might prove to be impracticable. In the mean time, the sampling

the Lake Forsyth/Wairewa catchment. 6) recorded dissolved reactive

habitat health of the Okana River andtributaries were relatively good, especially



programme in the lake should be maintained to collect further data relating environmental variables to the Nodularia blooms. On the other hand, the stream sampling programme could probably be wound down, except for observations intended to assess the effectiveness of riparian enhancement schemes (should they be initiated) on aquatic ecosystem health. Otherwise, catchment monitoring should focus on identifying the source of phosphorus, including groundwater, to establish the relative importance of soil erosion versus base rocks and natural versus anthropogenic influences. In addition, possible measures for controlling the blooms other than nutrient limitation, such

s dilution, flushing, biological manipulation,

with a groove cut into it, into which the sample is placed.

plants.

of algae-like aquatic bacteria that contain

iforms are bacteria that areassociated with the intestinal

s may be present.

instead of the arithmetic mean when

e in a river or stream.

aand antibiosis, should be assessed.

6 Glossary Some of the terms listed here have meaningsother than those used in the text, but the meanings listed here are as they are used in the text. accrual. Accumulation of algae during flood-

free periods. acid-buffering. An effect whereby the pH of

water tends towards acidity. algae. Simple plants which usually grow in

water. ammonia-nitrogen. See Appendix II. antibiosis. A process whereby plants produce

compounds to prevent the growth of other plants.

anthropogenic. Of or caused by people. barrel sample splitter. A device for sub-

sampling (i.e., sampling a portion of a sample) of aquatic invertebrates

bloom. A very rapid, prolific growth of algae. Bogorov counting tray. A device used to

facilitate counting aquatic invertebrates. It is a piece of perspex

caddis(es). Members of the Trichoptera. A

group of insects with aquatic larvae. Adults are like moths, but are characterised by have hairy wings and long antennae that sweep over the back.

chlorophyll a. A green photosynthetic pigment

found in most algae and other green

conductivity. See Appendix II. critical thermal maximum. The highest

temperature that a group of animals can withstand.

Cyanobacteria(um). A group

chlorophyll. Previously known as the Cyanophyta.

faecal coliform. A group of species of indicator

bacteria. Faecal col

tract (gut) of warm-blooded animals. As such, their presence is an indication of the presence of faecal material, and accordingly indicates that there is a possibility that other pathogenic (disease causing) organism

flow gauging. The measurement of water or

stream flows. gauged. Flow measured. geometric mean. The mean of the logarithms

of a set of values. This measure of central tendency is often used

considering bacterial populations, because bacterial growth rates are logarithmic.

hepatotoxin. A toxin that destroys the liver. hydrograph. A graph showing the flow over

tim Index (plural indices). A methods of reducing

several measurements to one number. invertebrate. An animal without a backbone.



kicknet. A triangular-shaped net for collecting

aquatic invertebrates. In use, one side of the net is held on the bottom of the stream, facing upstream, and the streambed immediately upstream is stirred around by foot.

macrophyte. An aquatic flowering plant. mayfly. A member of the Ephemeroptera.

Flies with an aquatic nymphal stage. The nymph is characterised by having external gills and three tails. Adults are short-lived, and hold the wings

molluscs. Snails.

ee Appendix II.

nes are nitrogen and phosphorus.

nning water. Calculated as the concentration multiplied by the

rganic enrichment. Having large quantities

xidation pond. A sewage treatment system

(oxygen-dependent) biological and chemical

periphy wing on and around the

stream substratum. It includes teria,

and bacterial slimes.

pH. Se

hotosynthesis (verb = photosynthesise). The

presence of carbon dioxide and light.

phosph pool. A

still.

lerance to organic enrichment. These scores are multiplied by the

overall QMCI value. Higher values indicate more pristine water

iable is dependent on the other.

riffle. A

d).

run. A m

salinity.

pecific conductance. See Appendix II.

taxa. Singular taxon. Scientific or taxonomic grouping of plants and animals.

xonomic richness. The diversity (or number)

total nitr transect

ts are made.

ity (ability to grow algae) in a lake.

turbiditylight to transmit through water. The

y

upright above the body when at rest. median. The middle one of a series of

numbers.

nitrate and nitrite nitrogen. S nutrients. Chemicals that plants require in

large quantities to grow. The principal o

nutrient loading. The quantities of nutrients

available in ru

flow.

oof organic matter in water.

owhich relies on aerobic

processes, within a shallow pond.

ton Plants gro

diatoms, other algae, fungi, bac

e Appendix II.

pproduction of sugars by plants in the

orus. See Appendix II.

section of a stream or river that is deep and relatively

QMCI (Quantitative Macrocommunity Index).

A method of measuring the invertbrate health of streams and rivers. This index allocates invertebrate taxa a score between 1 and 10 depending on their to

abundance of the taxon and divided by the total abundance, then combined to give an

quality. regression. A statistical technical that

compares two variables, where the size of one var

shallow, fast-flowing stretch of water,

where the surface of the water is broken (ripple

riparian. Stream or river margin or bank.

edium-depth, slowly flowing section of water, with an unbroken surface.

A measure of the amount of salt in water. Pure seawater has about 35 parts per thousand (ppt or o/oo) of salt, and freshwater has less than 1ppt.

s

ta

of species in an area

ogen. See Appendix II.

. A line across a stream or river, along which samples are collected or measuremen

Trichoptera. Caddisflies. trophic index. An index that measures the

trophic state, or productiv

. An arbitrary measure of the ability of

measurement is made against turbidit



standards by a meter, and is

Water l

vel. This information is later used with a flow

expressed in NTU (nephelometric turbidity units).

evel recorder. A station fixed by a river or stream that periodically records the water

legauging to calculate water flows.

7 AJulie ELocking ,

hile Ross and Trish carried out the stream

were from the NIWA water level recorder at athams Road. Ken Taylor (ECan) and John

de useful suggestions for proving the manuscript.

8 RAlabast ter

Quality Criteria for Freshwater Fish.

Anderso

sula: A Topographical History. N.Z.

gton. 238 pp plus map.

Anson,

on. 171pp.

ANZEC

Quality Guidelines for Fresh and Australian and New

Zealand Environment and

ANZEC

Environment and Conservation tralian Water

Quality Guidelines for Fresh and

Zealand Environment and

APHA

Armstrong, I.D. 1962. The Valley of Little

hy, University of Canterbury. 98pp.

Biggs, B

enrichment of streams. Ministry for the Environment,

Burns, N., Bryers, G., and Bowman, E. 2000.

Protocol for monitoring trophic levels voirs.

Ministry for the Environment,

anterbury Regional Council. 1996. Regional

Chapma lity

Assessments. Chapman and Hall Ltd,

99. Government Printer, Wellington.

ooper, A.B., Hewitt, J.E., and Cooke, J.G.

impacts of streamwater nitrogen and phosphorus.

ow, C.S. and Swoboda, U.K. 2000.

Pp 613-632, In: Whitton, B.A. and Potts, M. (eds).

Can (Environment Canterbury). 1997. Rivers

cknowledgements dwards, Ross Everest, and Trish ton collected most of the samples

wgaugings. Flow data for Hukahuka Stream

LQuinn (NIWA) maim

eferences er, J.S. and Lloyd, R. 1980. Wa

Butterworth Scientific.

n, J.C. 1927. Place Names of Banks Penin

Board of Science and Art Manual No. 6. Government printer, Wellin

F.A. 1911. The Piraki Log or Diary of Captain Hempleman. Henry Frowde, Oxford University Press, Lond

C (Australian and New Zealand Environment and Conservation Council). 1992. Australian Water

Marine Water.

Conservation Council, Melbourne.

C (Australian and New Zealand

Council), 2000: Aus

Marine Water. Australian and New

Conservation Council, Melbourne.

(American Public Health Association). 1998. Standard methods for the examination of water and wastewater. 20th edition. American Public Health Association, Washington.

River: Its Development and Present Geographical Character. MA Thesis in Geograp

.J.F. 2000. New Zealand periphyton guideline: Detecting, monitoring and managing

Wellington. 122pp.

of New Zealand lakes and reser

Wellington. 138pp.

CEnvironment Report, 1995/96. Report97(10). 129pp.

n, D., 1992: Water Qua

London. Connor, H.E. 1977. The Poisonous Plants in

New Zealand. DSIR Bulletin

247pp.

C1987. Land use

N.Z. Journal of Forestry Science 17: 179-192.

DCyanotoxins.

The Ecology of Cyanobacteria. Kluwer Academic Publishers.

Eand Hazards Section, Surface Water Hydrological Field and Office Procedures manual.



ECan

Quality, Groundwater Quality, Biological and Habitat

ury draft technical report.

ECan prep. River and lake water quality. Regional Environment Report 1996-2001.

lorophyll in seven shallow lakes. Freshwater Biology 38: 159-168.

hristchurch-West

2002. Environment Canterbury Technical

Helsel, and Hirsch, R.M. 1992.

Science Publishers, Amsterdam. 522pp.

Horrell,

anterbury Region. Canterbury Regional Council Technical Report

Irwin, J

ISO. 1 16:

Measurement of liquid flow in open

Jacobso

Peninsula 1840-1940: Story of French

of Canterbury. Akaroa mail Co. Akaroa.

Knox,

port to the Christchurch Drainage Board, by the

Livingst

Inventory of New Zealand Lakes. Part II: South Island. National

Lyttelton ry 1907, page 8.

Lake Forsyth: The regatta question.

Main, M

ury. Environment Canterbury, Technical Report U99/61.

McIntyre, W.D. (ed). 1980. The Journal of

Henry Sewell, 1853-7. Edited with an

ury region. Environment Canterbury Report No. R02/25. 30pp.

MfE (M

e biological growths in water. N.Z. Ministry for the

MfE (M

ent of water colour and clarity. N.Z. Ministry

(Environment Canterbury). 1999. Surface Water

Assessment Field and Office Procedures Manual. Environment Canterb

(Environment Canterbury). In

Gerbeaux, P.J. 1989. Aquatic plant decline in Lake Ellesmere: A case for macrophyte management in a shallow New Zealand lake. PhD. Thesis, University of Canterbury. 276pp plus appendices.

Hamilton, D.P. and Mitchell, S.F. 1996.

Wind-induced shear stresses, plant nutrients and ch

Hayward, S.A. 2002. C

Melton Groundwater Quality: A Review of Groundwater Monitoring Data from January 1986 to March

Report No. U02/47. 141pp.

D.R.Statistical Methods in Water Resources. Studies in Environmental Science 49. Elsevier

G.A., Dicker, MJ.I., Pilbrow, R.D. and McFall, K.B. 1998. 1997/98 drought in the C

U98(31). 40pp.

. 1979. Lake Forsyth bathymetry, 1:10,000. NZ Oceanogrphic Institute, DSIR, Lake Series.

983. Standards Handbook

channels. International Organisation for Standardisation, Switzerland. 518pp.

n, W.E.M. 1940. Akaroa and Banks

Colonising Venture and Early Whaling Activities: The First Settlement

396pp.

G.A. and Kilner, A.R. 1973. The Ecology of the Avon-Heathcote Estuary. Unpublished re

Estuarine Research Unit, University of Canterbury. 358pp.

on, M. E., Biggs, B.J. and Gifford, J.S. 1986.

Water and Soil Conservation Authority, Water and Soil Miscellaneous Publication No. 81. 193pp.

Times. 30 Janua

.R. and Meredith, A.S. 1999. Fishery, water quality, recreational, and wildlife impacts of the 1997-98 and 1998-99 droughts in Canterb

22pp.

Introduction. Vol II; May 1854-May 1857. Whitcoulls, Christchurch. 371pp.

Meredith, A.S. and Hayward, S. 2002. An

overview of the surface water quality of the rivers and streams of the Canterb

inistry for the Environment). 1992. Water quality guidelines No. 1: Guidelines for the control of undesirabl

Environment, Wellington. 57pp.

inistry for the Environment). 1994. Water quality guidelines No. .2: Guidelines for the managem

for the Environment, Wellington. 74pp.



Mulligan, P.E. 1985. Isolation and

New Ze 973.

Rainfall normals for New Zealand.

ordin, R.N. and Stein, J.R. 1980. Taxonomic

Ogilvie,

.P. Books. 283pp.

Publishers.

drological Regime with special Reference to

hilpott, H.G. 1937. A History of the New

Plafkin, M.T., Porter, K.D.,

Gross, S.K. and Hughes, R.M. 1989.

and fish. EPA/444/4-89-001. Office of Water,

ant

green algae and fish population

Quinn,

from New Zealand hill-land catchments of contrasting land use.

Rinehar

stin, and the configuration of adda. Journal of the

Rosen,

.A. (eds). Groundwaters of New Zealand. New

MA. 1991. Resource Management Act,

Sanders

.

Soil Bureau. 1966. General soil survey of

South Island, New Zealand. Soil

SPSS, 1

tark, J.D. 1998. SQMCI: a biotic index for

Stark, J J.S.,

Maxted, J.R. and Scarsbrook, M.R.

y for the Environment. Sustainable management Fund Project No. 5103. 57p.

characterisation of the Nodularia spumigena toxin. Unpublished MSc thesis in Chemistry, University of Canterbury.

aland Meteorological Service. 1

N.Z. Meteorological Service, Miscellaneous Publication 145.

Nrevision of Nodularia (Cyanophyceae/ Cyanobacteria). Canadian Journal of Botany 58: 1211-1224.

G. 1990. Banks Peninsula: Cradle of Canterbury. G

Oliver, R.L. and Ganf, G.G. 2000. Freshwater

blooms. Pp 149-194, In: Whitton, B.A. and Potts, M. (eds). The Ecology of Cyanobacteria. Kluwer Academic

O’Loughlin, C.L., Rowe, L.K., and Pearce, A.J.

1980. Sediment yield and water quality responses to clearfelling of evergreen mixed forests in western New Zealand. Pp 285-292, In: The Influence of Man on the Hy

Representative and Experimental Basins. Proceedings of the Helsinki Symposium. IASH-AISH Publication no. 130.

PZealand Dairy Industry, 1840-1935. Government Printer, Wellington. 413pp.

J.L., Barbour,

Rapid bioassessment protocols for use in streams and rivers: benthic macroinvertebrates

U.S. Environmental Protection Agency, Washington D.C.

Potter, I.C., Loneragan, N.R., Len on, R.C.J., and Chrystal, P.J. 1983. Blue-

changes in a eutrophic estuary. Marine Pollution Bulletin 14: 228-233.

J.M. and Stroud, M.J. 2002. Water quality and sediment and nutrient export

N.Z. Journal of Marina and Freshwater Research 36: 409-429.

d, K.L., Harada, K. H., Namikoshi, M., Chen, C. and Harvis, C.A. 1988. Nodularin, microcy

American Chemical Society 110: 8557-8558.

M.R. 2001. Hydrochemistry of New Zealand’s aquifers. Pp 77-110, In: Rosen, M.R. and White, P

Zealand Hydrological Society.

R1991.

, R. A. 1986. Hydrogeological studies of springs in Akaroa County, Banks Peninsula. MSc thesis in Engineering Geology

Scheffer, M. 1998. Ecology of Shallow Lakes.

Kluwer Academic Publishers, Dordrect. 357pp.

Bureau Bulletin 27. DSIR, Wellington. 404pp.

999: Systat Inc., Illinois.

Sfreshwater macroinvertebrate coded-abundance data. New Zealand Journal of Marine and Freshwater Research 32:55-66

.D., Boothroyd, I.K.G., Harding,

2001. Protocols for sampling macroinvertebrates in wadeable streams. New Zealand Macroinvertebrate Working Group Report No. 1. Prepared for the Ministr



.M. 1975. Canterbury, Nelson, and Westland lakes. P

Stout, Vp 110-122, In: Jolly,

rsity Press, Auckland.

Taylor,

eport 96(7). 322pp.

USEPA ater. EPA 440/5-86-001.

Winterb

9, 96pp.

V.H., and Brown, J.M.A. New Zealand Lakes. Auckland Unive

A.W. 1937. Banks Peninsula:

Picturesque and Historic. Bascands Print, Christchurch.

Taylor, K.J.W. (ed.) 1996. The natural

resources of Lake Ellesmere (Te Waihora) and catchment. Canterbury Regional Council R

. 1986. Quality Criteria for W

ourn, M.J and Gregson, K.L.D. 1989. Guide to the "Aquatic Insects of New Zealand. Bulletin of the Entomological Society of New Zealand


The Okana R

iver: assessment of w

ater quality and ecosystem m

onitoring, July 1992 to M

ay 2002 and water quality im

plications for Lake Forsyth/Wairew

a

Environment C

anterbury Technical Report

41

Appendix I

Determinand

Temperature (TEMP)

pH ConductivityTurbidity (TURB) Nitrate/nitrite nitrogen (NNN)

Total ammonia-nitrogen (NH3N)

Dissolved inorganic nitrogen (DIN) Total Kjeldahl nitrogen (TKN)

Total nitrogen (TN) Dissolved reactive phosphorus (DRP)

Total phosphorus (TP)

Faecal coliforms (FC)

Specific conductance

Salinity ECan – EnvironmentCIN – Caw

Details of analyses included in the water quality sampling Type of Measurement Method Time Period Detection

Limit Units

Field measurement YSI 58 DO/TEMP meter or YSI Model 30 Salinity/conductivity/temperature meter

°C

Laboratory analysis (ECan) Hach One pH/ISE meter (COND) Laboratory analysis (ECan) Radiometer CDM 2e meter 2 mS/m

Laboratory analysis (ECan) Hach 2100A meter NTU Laboratory analysis (ECan) APHA 4500 NO3-E (18th Ed) Cadmium reduction method July 1992 – August 1995 0.010 mg/L Laboratory analysis (ECan) APHA 4500 NO3-E (20th ED)

Automated cadmium reduction method September 1995 – 0.010 mg/L

Laboratory analysis (ECan) Water and Soil 38 Indophenol blue colorimetry July 1992 – August 1995 0.005

mg/L

Laboratory analysis (ECan) APHA 4500 NH3-F – modified Automated method September 1995 – April 1996 0.005 mg/L

Laboratory analysis (ECan) APHA 4500 NH3-F – modified (20th ED) Automated gas diffusion method

May 1996 – 0.005 mg/L

Calculation (NNN +NH3N) Laboratory analysis (ECan) In house method H2SO4/K2SO4/CuSO4 Digestion July 1992 – August 1996 0.05 mg/L Laboratory analysis (CIN) Kjeldahl digestion 1996 0.01 mg/L Calculation (TKN+NNN) July 1992 – May 1996 mg/L Laboratory analysis (ECan) APHA 4500 N D (19TH Ed) SFA persulphate digestion September 1996 – 0.05 mg/L

Laboratory analysis (ECan) Water and Soil 38 Ascorbic acid Mo-Sb reagent July 1992 – December 1995 0.003 mg/L

Laboratory analysis (ECan) APHA 4500-P F (19th Ed) Automated ascorbic acid reduction method

January 1996 – 0.003 mg/L

Laboratory analysis (CIN) Water and Soil 38 H2SO4/K2S2O8 Digestion Ascorbic acid Mo-Sb reagent

July 1992 – June 1995 0.001 mg/L

Laboratory analysis (ECan) Water and Soil 38 H2SO4/K2S2O8 Digestion Ascorbic acid Mo-Sb reagent

July 1995 – December 1995 0.008 mg/L

Laboratory analysis (ECan) APHA –P B Persulfate digestion method January 1996 – 0.008 mg/L Laboratory analysis (ECan) APHA 9222 D – modified 4hrs resuscitation, membrane

filtration 1991 – July 1997 1 cfu/100mL

Laboratory analysis (ECan) APHA 9222 D 5hrs resuscitation, membrane filtration

August 1997 –

1 cfu/100mL

Laboratory analysis (ECan) Radiometer CDM230 mSiemens/m

Field measurement YSI Model 30 Salinity/conductivity/temperature meter ppt

Canterbury Laboratory thron Institute Laboratory



micro- and macro- organisms in nuisance quantities. Phosphates also occur in bottom sediments and

Appendix II Description of the main determinands included in the water quality sampling

Temperature Water temperature has a substantial effect on the functioning of aquatic ecosystems and the physiology of the biota. Physiological processes have thermal optima, and alterations to ambient temperatures may affect the species exposed in a variety of ways. Growth and metabolism, timing and success of reproduction, mobility and migration patterns and reproduction may all be altered by changes in ambient temperature regimes. Effects may be direct, through changes to the metabolism, or indirect, through influence on the solubility of oxygen in water and changes to the toxicity of ammonia (ANZECC, 1992). Water temperature of rivers is a function of air temperatures, insolation, flow and water depth. Air temperatures vary seasonally, diurnally, and as a result of localised variation in shading and air circulation. Discharges to rivers from heated effluents, and cooling waters or groundwater seepage and underflow in gravel-bedded rivers can also influence water temperatures. Although cool waters can affect some physiological processes, increases in water temperatures pose greater risks to the healthy functioning of the aquatic ecosystem. pH pH is the measure of the hydrogen ion concentration (activity). It is reported at the negative logarithm to the base 10 of the hydrogen ion concentration (activity), and therefore, higher pH values have lower hydrogen ion activities, i.e., less acidic. The effects of changes in pH on aquatic ecosystems include direct effects on spawning and hatching at low pH values (less than 6.0), as well as indirect effects such as increasing toxicity of pollutants like ammonia and cyanide (ANZECC, 1992). Turbidity Visual clarity of water is important for aesthetic and safety aspects of recreational use of water bodies. Reduction in clarity can affect the behavioural patterns of fish and macro-invertebrates, especially of the migratory and predatory species. Clarity of the water will also affect primary production such as algal growth. Turbidity is a relative measurement of light scattering by suspended particles in water. Informally, turbidity measurement is considered synonymous with ‘cloudiness’ (loss of visual clarity) (MfE, 1994). Turbidity is also crucial for fishability of the river as an angling resource. There is a window of optimal clarity for spin fishing as rivers clear that optimises angler effectiveness and fish catchability, although fly anglers generally prefer the greatest possible clarity. Phosphorus Phosphorus occurs in natural waters almost solely as phosphates. These are classified as orthophosphates, condensed phosphates and organically bound phosphates. They occur in solution, in particles or detritus, or in the bodies of aquatic organisms. Phosphorus is essential to the growth of organisms and can be the nutrient that limits the primary productivity of a body of water. In instances where phosphate is a growth-limiting nutrient, the discharge of raw or treated wastewater, agricultural drainage, or certain industrial wastes to that water may stimulate the growth of photosynthetic aquatic


in biological sludges, both as precipitated inorganic forms and incorporated into organic c(APHA, 1998).

is a form of dissolved phosphate (orthophosphate) that is avagrowth.

of the concentration of orthophosphates, condensed phosphates a

ompounds

Dissolved reactive phosphorus ilable immediately for plant and algal Total phosphorus is a measure nd

rganically bound phosphates in the water. This includes both dissolved and suspended phosphates.

te (NO2-) by denitrification processes, usually under anaerobic conditions.

rising from the breakdown of nitrogenous organic and anic matter in soil and water, excretion by biota, reduction of the nitrogen gas in water by micro-nisms and from gas exchange with the atmosphere. It is also discharged into water bodies by

3

3 city effects also the ammonium ion (ANZECC, 2000). There is about a 1000-fold difference. Measurement ia concentrations usually measures total ammonia (NH3+ NH4

+). Guideline values for the

nitrogen is the sum of organic nitrogen and ammonia nitrogen.

l quality of river water is important to recreational water users, and for drinking-water

o

itrogen N In waters the forms of nitrogen of greatest interest are, in order of decreasing oxidation state, nitrate, nitrite, ammonia, and organic nitrogen. All these forms of nitrogen, as well as nitrogen gas (N2) and dinitrogen oxide (N2O), are biologically interconvertible and are components of the nitrogen cycle (APHA, 1998). The nitrate ion (NO3

-) is the common form of combined nitrogen found in natural waters. It may be iochemically reduced to nitrib

The nitrite ion is rapidly oxidised to nitrate (Chapman, 1992). Nitrate and nitrite-nitrogen (NNN, also called total oxidised nitrogen) is the sum two oxidised forms of inorganic nitrogen. It is reported in terms of the sum of concentration of nitrogen that was in the forms of nitrate and nitrite.

mmonia occurs naturally in water bodies aAinorg

rgaosome industrial processes and also as a component of municipal or community waste (Chapman, 1992). Compared to nitrate, ammonia is usually a very minor component of plant available nitrogen. The main concern with ammonia concentrations in water bodies is toxicity effects on aquatic ecosystems. Ammonia occurs as two forms in water depending on the pH. The ammonium ion (NH4

+) dominates in waters with pH values below 9.3; above this pH value ammonia (NH ) is the ominant form. The un-ionised form of ammonia (NH ) is the most toxic, although toxid

occur withf ammono

protection of aquatic ecosystems are either based on unionised or else total ammonia concentrations for a given pH value and temperature. Dissolved inorganic nitrogen is a measure of the nitrogen available to plants, and is the sum of the concentrations of nitrate and nitrite-nitrogen and ammonia nitrogen.

otal KjeldahlT Total nitrogen is a measure of all nitrogen in the water; both inorganic and organic nitrogen forms.

aecal coliforms F

he microbiaTsupplies for humans and livestock. Faecal coliforms are a group of bacteria that usually originate in the gut of warm-blooded animals and are present in animal (including bird) faeces (although there are species that can be free-living). The presence of faecal coliforms in water indicates recent contamination of the water with faecal material, and therefore, also potentially with pathogenic (disease-causing) organisms.



Specific conductance and conductivity Specific conductance and conductivity and are measures of the ability of water to conduct an electric

is that specific conductance is the conductivity corrected to 5oC.

current. For a given water body, they are related to the concentrations of total dissolved solids and major ions. The difference between them2




Appendix III Seasonal variation of determinands in the Okana River and its tributaries

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

5

10

15

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.05

0.10

0.15

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.4

0.8

1.2

1.6

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.01

0.02

0.03

0.04

0.05

DRP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.05

0.10

0.15

0.20

0.25

TP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

10

20

30

40

50

N_P

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

FC

Opuahou Stream



W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

5

10

15

20

25

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

DRP

W INTER

SPRING

SUMMER

AUTUMN0.0

0.1

0.2

0.3

0.4

0.5

0.6

TP

W INTER

SPRING

SUMMER

AUTUMN0

10

20

30

40

50

60

70

N_P

W INTER

SPRING

SUMMER

AUTUMN0

1000

2000

3000

4000

5000

FC

Hukahuka Stream at Bachelors Rd ford

SEASON SEASON SEASON


W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

10

20

30

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.01

0.02

0.03

0.04

0.05

0.06

DRP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.05

0.10

0.15

TP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

10

20

30

40

N_P

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

1000

2000

3000

4000

5000

6000

7000

FC

Hikuika Stream



W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

5

10

15

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.02

0.04

0.06

0.08

0.10

0.12

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

2.0

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

DRP

TER INGMER

UMN0.00

0.05

0.10

0.15

0.20

TP

TER INGMER

UMN0

10

20

30

40

50

60

70

80

90

N_P

TER INGMER

UMN0

5000

10000

15000

20000

FC

Okana River

SUMAUT

SEASONSPR

W INSUM

AUT

SEASONSPR

W INSUM

AUT

SEASONSPR

W IN



Reynolds Stream

W INTER

SPRING

SUMMER

AUTUMN

SEASON

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.2

0.4

0.6

0.8

1.0

1.2

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

2.0

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.5

1.0

1.5

2.0

2.5

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

DRP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.05

0.10

0.15

TP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

10

20

30

40

50

N_P

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

1000

2000

3000

4000

5000

FC



W INTER

SPRING

SUMMER

AUTUMN

SEASON

1

2

3

4

5

6

7

8

9

10

11

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.2

0.4

0.6

0.8

1.0

1.2

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

DRP

W INTER

SPRING

SUMMER

AUTUMN0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

TP

W INTER

SPRING

SUMMER

AUTUMN0

10

20

30

40

50

60

N_P

W INTER

SPRING

SUMMER

AUTUMN0

1000

2000

3000

4000

5000

6000

7000

FC

Hukahuka Stream at Lathams Rd

SEASON SEASON SEASON



W INTER

SPRING

SUMMER

AUTUMN

SEASON

1

2

3

4

5

6

7

8

9

TURB

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

NNN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

NH3N

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

TON

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

TN

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.01

0.02

0.03

0.04

0.05

0.06

DRP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0.00

0.05

0.10

0.15

TP

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

10

20

30

N_P

W INTER

SPRING

SUMMER

AUTUMN

SEASON

0

5000

10000

15000

20000

25000

FC

Okuti River




Appendix IV The continuous flow record for Hukahuka Stream at

26/05/1992 12/12/1992 30/06/1993 16/01/1994 4/08/1994 20/02/1995 8/09/1995 26/03/1996

Lathams Road

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Flow

(L/s

)



Appendix V Regression curves for flows in Little River streams compared with Hukahuka Stream at Lathams Road

Reynolds Valley Stream at Brankins Bridge

0

50

100

150

200

250

300

0 200 400 600 800 1000 1200 1400 1600

Hukahuka flow at Lathams Rd (L/s)

Rey

nold

s flo

w (L

/s)

y = 0.2662x + 16.986R2 = 0.9336

350

400

450


Hukahuka Stream at Bachelors Road


Okuti River at Kinloch Road

0

50

100

150

200

250

300

350

0 200 400 600 800 1000 1200 1400 1600


Huk

ahuk

a flo

w a

t Bac

helo

rs R

d (L

y = 0.292x + 1.5044R2 = 0.9593

450

400/s)

y = 1.6774x + 43.63R2 = 0.9546

0

500

1000

1500

2000

2500

3000

0 200 400 600 800 1000 1200 1400 1600


Oku

ti flo

w (L

/s)


y = 0.5595x + 15.585R2 = 0.9306

0

100

200

300

400

500

600

700

800

900

1000

0 200 400 600 800 1000 1200 1400 1600


Hik

uika

flow

(L/s

)

Hikuika Stream above Opuahou Stream

puahou Stream above Hikuika Stream

y = 1.1023x - 11.191R2 = 0.9572

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800 1000 1200 1400 1600


Opu

ahou

flow

(L/s

)

1800

O



y = 4.0101x - 84.306R2 = 0.9747

0

1000

2000

3000

4000

5000

6000

7000

0 200 400 600 800 1000 1200 1400 1600


OK

ana

flow

at S

H 7

5 (L

/s)


A. Okana River at SH 75



Appendix VI Invertebrate species list for the Okana River and its

tributaries (1999-2001).

Okuti River Opuahou Stm Okana River Hukahuka StmEPHEMEROPTERADeleatidium * * * *Coloburiscus * * *Neozephlebia *Austroclima *TRICHOPTERAAoteapsyche * * * *Hydrobiosis * * * *Neurochorema *Psilochorema * * * *Pycnocentria * * * *Costachorema *Helicopsyche * * * *Polyplectropis *Pycnocentrodes * * * *

* * * *Oxyethira * *

dsonema * * * *Triplectides * *DIPTERAAphrophila * * *Austrosimulium * * * *Neocurupira * * *Muscidae * *Mischoderus *Zelandotipula *Paradixa *Peritheates *Tanyderidae *CHIRONOMIDAEOrthocladiinae * * * *Chironominae * *Tanypodinae * * * *Diamesinae * * *Podonominae *COLEOPTERAElmidae larvae * *Hydraenidae * *MOLLUSCAPotamopyrgus * * * *Pisidium/Sphaerium * *Physa *Gyraulus *OLIGOCHAETA * * * *CRUSTACEAParacalliope * * * *Ostracoda * *NEMATODA *PLATYHELMINTHES *MEGALOPTERA

Olinga Hu

Archichauliodes * *Acarina *

the okana river - environment...

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