canterbury high country lakes water quality monitoring programme

Canterbury high country lakes water quality monitoring programme: Results of the third year monitoring 2007

Report No. U07/50 ISBN: 978-1-86937-678-9

Adrian Meredith

Taryn Wilks

July 2007

Report U07/50 ISBN: 978-1-86937-678-9 58 Kilmore Street PO Box 345 Christchurch Phone (03) 365 3828 Fax (03) 365 3194 75 Church Street PO Box 550 Timaru 7940 Phone (03) 687 7800 Fax (03) 687 7808 Website: www.ecan.govt.nz Customer Services Phone 0800 324 636

Canterbury high country lakes water quality monitoring programme 2007 __________________________________________________________________________________

Environment Canterbury Technical Report U07/50 i

Executive summary High country lake water quality monitoring was undertaken by Environment Canterbury over summer 2006/07 (the third consecutive summer). This programme represents part of the implementation of the MfE Protocols for monitoring trophic levels of New Zealand lakes and reservoirs in Canterbury. The above protocol was condensed to monitoring of a single site on each lake, and monthly sampling over four (previously five) consecutive summer/autumn months by helicopter, so as to maximise the number of lakes able to be monitored within the existing budget. The logistics of helicopter sampling continues to be highly successful. There was a deterioration in a few of the lakes trophic status from summer 2005/06 to summer 2006/07. Lake Emma (mesotrophic) and Lake Georgina (oligotrophic) changed to a eutrophic state, Lakes Pearson, Camp and Alexandrina changed from oligotrophic to a mesotrophic state, while all other lakes were graded as either oligotrophic, or lower trophic status. The increase in trophic status of five out of the twenty one sampled lakes is concerning, particularly Lakes Emma and Georgina. There is no immediate requirement to initiate steps to rehabilitate or manage these lakes of good water quality to reduce their trophic status until we understand the mechanisms driving the changes. The remainder of the lakes sampled remain in good water quality condition, and there is limited potential for obvious visible water quality deterioration (algal blooms, turbid episodes etc.) of these lakes. Lake Emma is currently undergoing changed catchment management and it appeared to be the most degraded out of all the years sampling. However, this may be attributable to increased wind driven mixing, re-suspending bottom sediment and therefore increased nutrient suspension in the water column (a result of past nutrient input) rather than current external nutrient input. The increase in Lake Georgina trophic state from oligotrophic to eutrophic most likely reflects a change in the catchment landuse. Nitrogen concentrations have increased 5 fold, phosphorus concentrations have increased 4 fold and subsequently algal biomass (indicated by Chlorophyll a) concentration has increased 5 fold. Compared to past trophic assessments, many of the lakes have shown increases in mean trophic level scores (90% of lakes). This provides some indication that the water quality of many of the high country lakes has been declining. When data from 2004 to 2007 are pooled, only one lake showed an increased Trophic Lake Index (TLI) category (Lake Coleridge). However, Lake Coleridge appears to naturally fluctuate between an ultra-microtrophic state and a microtrophic state so no action is required. Two lakes were classed “eutrophic” in summer 2007, but on accumulated data (2004-07) Lake Emma remained “mesotrophic” and Lake Georgina remained “oligotrophic”. It is positive that the lakes largely remain in low trophic states, but of concern is that they exhibit trends of increasing trophic levels. Therefore, it is important to maintain this monitoring programme, so as to continue to understand the effects of natural lake cycles, climatic influences (i.e. rainfall, temperature, wind etc) patterns and land use changes on lake ‘state’.


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Table of Contents

Executive summary .................................................................................................... i

1 Introduction ..................................................................................................... 1

2 Methods ........................................................................................................... 1 2.1 Sites ................................................................................................................................ 1 2.2 Sampling methods .......................................................................................................... 1 2.3 Water quality determinands ............................................................................................ 5

3 Results ............................................................................................................. 5 3.1 Trophic Level Index......................................................................................................... 5 3.2 Lake level ........................................................................................................................ 6 3.3 Chlorophyll a ................................................................................................................... 6 3.4 Phosphorus ..................................................................................................................... 8 3.5 Nitrogen .......................................................................................................................... 9 3.6 TN:TP ratios ..................................................................................................................11 3.7 Turbidity ........................................................................................................................11

4 Discussion ..................................................................................................... 13 4.1 Trophic level index ........................................................................................................13 4.2 Shallow lakes ................................................................................................................14 4.3 Lake Emma ...................................................................................................................14 4.4 Lake Georgina ..............................................................................................................15 4.5 Large lakes ...................................................................................................................15 4.6 Nutrient limitation ..........................................................................................................16 4.7 Eutrophication ...............................................................................................................16

5 Conclusion .................................................................................................... 17

6 Acknowledgements ...................................................................................... 17

7 References ..................................................................................................... 17

Appendix 1 Chlorophyll a data from three hydro-electric lakes sampled in summer 2006 and 2007 ...................................................................... 19

Appendix 2 Box and Whisker plots of the raw data for 21 sampled lakes, A) Turbidity, B)Chlorophyll a, C)Total Nitrogen, D) Total Phosphorus ........................................................................................ 20

Appendix 3 Scatterplots of Chlorophyll a data from lakes sampled in summer 2004/05, 2006 and 2007 ....................................................... 21

Appendix 4 Raw data from 2004/05, 2006 and 2007 lakes monitoring for TLI assessment ......................................................................................... 24


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List of tables Table 2.1: High country lakes site list* ............................................................................................ 2Table 3.1: Trophic Level Indices (TLI) and categories for twenty-one Canterbury high country

lakes, as from pre-2004 data, and calculated from summer 2004/05 data, summer 2006, summer 2007 and from 2004-2007 data combined (according to methods of Burns et al., 2000). ......................................................................................................... 7

Table 3.2: TN:TP ratios from medians of data from summer 2004/05, 2006 and 2007 ............... 12

List of figures Figure 2-1: Map of high country lakes sampling location and TLI grading for 2007 (Northern

Canterbury) .................................................................................................................... 3Figure 2-2: High country lakes sampling location and TLI grading for 2007(Southern

Canterbury) .................................................................................................................... 4Figure 3-1: Annual median TP concentrations at 22 high country lake in Canterbury, red

dashed line indicates eutrophic TP concentrations (according to Burns & Bryers 2000) .............................................................................................................................. 8

Figure 3-2: Total phosphorus concentrations; A) Lake Georgina; B) Lake Emma. Red lines are indicative trends in concentration .................................................................................. 9

Figure 3-3: Monthly median total nitrogen concentrations at 22 high country lakes in Canterbury, red dashed line indicates the threshold of eutrophic TN concentrations (according to Burns & Bryers 2000) ............................................................................. 10

Figure 3-4: Total nitrogen concentrations; A) Lake Georgina; B) Lake Emma. Red lines are indicative trends in concentration ................................................................................ 11

Figure 4-1: Lake Pearson: A) April 2006 B) February 2007 ........................................................... 14Figure 4-2: Lake Georgina: A) January 2006 B) February 2007 .................................................... 15


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1 Introduction Environment Canterbury is required to monitor the quality of surface water in representative rivers, streams and lakes throughout the Canterbury region. The Resource Management Act 1991, Regional Policy Statement and the Proposed Natural Resources Regional require Environment Canterbury to monitor the effects of land use and discharges on surface water quality, and to monitor stream health and aquatic ecosystems. The current state of environment (SOE) monitoring framework includes a number of programmes that monitor general physiochemical and microbiological determinands plus specialised programmes that monitor for the effects of land use change and assess water quality for contact recreation purposes. Environment Canterbury currently has two lakes monitoring programmes; coastal lakes (particularly Lakes Ellesmere (Te Waihora) Forsyth (Te Waiwera), Coopers Lagoon and Wainono Lagoon), and the inland lakes of the foothills and high country. A summary of the water quality data from all recent (up to 2003/04) Environment Canterbury inland lake sampling was included in a report to assist in developing a strategy for future lake sampling (Meredith 2004). That report recommended the monitoring strategy from which this current year’s data was collected. Natural and cyclic processes occur in many lakes, sometimes causing variation in trophic level. Therefore it is accepted that a lakes trophic status may change from time to time. However, the rate of change and degree of change is of particular importance to lake managers. Anthropogenic activities can accelerate the eutrophication process by increasing the likelihood of nutrient runoff into lake ecosystems. Conversely, reduction in trophic status of eutrophic lakes is much more difficult. This report is a compilation of the third years sampling (January to April 2007) in the inland lakes monitoring programme. Burns et al. (2000) provides procedures for monitoring lake water quality, assessing trophic state and determining trends. The protocol summarises

water quality information into a categorical trophic level index or TLI. Monitoring of lake water quality is an important aspect of lake management. It not only alerts us to potential problems but also helps us to determine when management intervention is required, or measure the success of management efforts.

2 Methods

2.1 Sites Nineteen lake sites (18 lakes) monitored in 2004/05 (Meredith 2005) and 2006 were again monitored in 2007 (Figures 2-1 and 2-2). An additional three lakes from the Mackenzie Basin were included in 2006 to fill an identified gap, and to allow further consideration for the implementation of the Waitaki Water Allocation Plan (WWAP, 2005), (Table 2.1). The deepest point of each lake was selected and identified for subsequent sampling, where possible or practical. Lakes Pukaki and Ohau were sampled at the southern end of the lakes where the water sampled represented that being entrained into the power scheme network. The site at Lake Benmore was in the northern end approximately 3 km south of the head of the lake, but where all influent waters from the Haldon Arm should have thoroughly mixed.

2.2 Sampling methods Sampling by helicopter (Robinson R44) was again initiated January 2007. Lakes were sampled from north to south. The occasional low morning fog dictated a necessity to sometimes sample as a south to north lake series (one of the four occasions). The helicopter descended until the rotor wash was visible on the surface (approximately 1–3 metres). A weighted aluminium canister containing an uncapped one litre PVC sample bottle was dropped on a rope, so that it rapidly submerged below the lake surface. The bottle was filled within 10 seconds and was retrieved into the helicopter and immediately capped. Samples were stored in a chilli-bin in the back seat of the helicopter and returned to the laboratory for sample preparation on the same day.

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Table 2.1: High country lakes site list*

Site ID Lake Name Site Description Easting Northing Max depth Altitude Area

(m) (m) (km2)CRC300147 Loch Katrine At Mid Lake 2444484 5831828 28 519.88 0.78CRC300079 Lake Sumner Opp Marion Stm Outlet 2446347 5835062 134.5 504.71 13.73CRC300141 Lake Taylor At Mid Lake 2447604 5826123 40.5 578.5 2.07CRC300521 Lake Sarah At Mid Lake 2410306 5794729 6.7 575.37 0.22CRC300525 Lake Grasmere At Mid Lake 2410150 5793263 15 589.18 0.62CRC300497 Lake Pearson-N At North Basin 2410865 5789069 17 603.15 2.02CRC300498 Lake Pearson-S At South Basin 2410624 5787236CRC300486 Lake Hawdon At Mid Lake 2416451 5788620 4 571.06 0.35CRC301043 Lake Lyndon At Mid Lake 2404776 5766555 28 825.96 0.88CRC301047 Lake Georgina At Mid Lake 2393930 5764531 10 536.66 0.17CRC301051 Lake Ida At Mid Lake 2391297 5773629 9 675.65 0.1CRC301065 Lake Selfe At Mid Lake 2389752 5773144 30 568.66 0.65CRC301045 Lake Coleridge At Mid Lake - Near Island 2389200 5765800 200 449.64 36.88CRC301093 Lake Heron At Main Basin 2361901 5745392 37 692.39 6.95CRC302801 Lake Emma At Mid Lake 2357300 5728500 3 639.76 1.67CRC302802 Lake Camp At Mid Lake 2353100 5730700 13 675.94 0.44CRC302804 Lake Clearwater At Mid Lake 2352300 5731900 18 675 1.97CRC301096 Lake Alexandrina At Mid Lake 2304700 5694000 27 711.09 6.46CRC302908 Lake Tekapo At Mid Lake 2310900 5697500 120 685.79 96.59CRC304908 Lake Pukaki Mid Lake at Southern End 2283000 5668000 70 477.64 172.74CRC302909 Lake Ohau Centre - Surface 2258100 5659500 129 455.14 59.27CRC304907 Lake Benmore Centre - Northern Arm 2288000 5644000 120 346.51 75.85

* Information on lakes max depth, altitude and area was provided by MFE 2007.



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Figure 2-1: Map of high country lakes sampling location and TLI grading for 2007 (Northern Canterbury)



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Figure 2-2: High country lakes sampling location and TLI grading for 2007(Southern Canterbury)



2.3 Water quality determinands

Trophic Level Index (TLI) is an indicator of lake water quality compiled from four main determinands; Chlorophyll a (a measure of the amount of algae present), total nitrogen, total phosphorus (total nutrient concentration including soluble compounds available of algal growth and those contained within existing algal biomass) and secchi disc depth (an indicator of water clarity). Due to the difficulty measuring secchi depth from a helicopter generating rotor wash, turbidity was measured as a surrogate measure of water clarity (even though it has been shown to represent variable lake specific secchi:turbidity relationships). Consequently a modified version of the Trophic Level Index described by Burns et al. (2000) has been used, whereby the number of parameters was reduced to three. The omission of a clarity measure from the overall TLI, has both advantages and disadvantages. The main disadvantage is that a three index TLI is not immediately comparable to other assessments in New Zealand. However, in several lakes, secchi is reduced by inorganic sediment and so is not indicative of eutrophication. In this incidence it could be argued to omit any clarity index. A TLI score is calculated for each of the parameters and summarised into a single overall TLI score for the lake. The overall score is categorised into seven trophic states indicating progressively more nutrient enrichment, more algal productivity and reduced water clarity. Of the seven categories only five are represented by our 21 high country lakes (not represented: supertrophic and hypertrophic) (Burns et al. 2000). • Ultra-microtrophic (Pristine) • Microtrophic • Oligotrophic • Mesotrophic (moderately productive) • Eutrophic • Supertrophic • Hypertrophic (extremely degraded, algal

blooms common

3 Results A total of twenty-two sites from twenty-one lakes were successfully sampled for four sequential summer months (January to April inclusive). This also included sampling both basins of Lake Pearson separately. All four measured determinands showed an overall increase in average concentration from summer 2006 to summer 2007 (Appendix 2).

3.1 Trophic Level Index The raw data for sampling over 2004/05, 2006 and 2007, medians and trophic levels based on each determinand, and overall TLI for both time periods are presented sequentially for all lakes in Appendix 4. A summary of the Canterbury high country lakes trophic state is shown in Table 3.1; lake specific information is shown in Appendix 4. The trophic level and site location of the monitored lakes are mapped in Figures 2-1 and 2-2. The mean annual TLI scores increased between 2006 and 2007 at 95% of the twenty two lakes sites (note Lake Pearson is sampled at the northern and southern ends). As a result six of the lake sites have increased trophic state (TLI), one lake site increased up two trophic levels (Lake Georgina; eutrophic) and one lake site’s nutrient status decreased (Lake Coleridge; ultra-microtrophic). Lakes Pukaki, Ohau and Benmore remain in low nutrient status (Appendix 1). When the three years of data are combined to determine the overall average TLI for each lake, nine lakes increased up one trophic level category compared to the first years grading (2004/05). These increased grades are a direct result from increased concentrations in all measured determinands; Chlorophyll a (Chl a), Total Nitrogen (TN) and Total Phosphorus (TP) (Appendix 2 and 4). This change was most prominent from Chlorophyll a graphs, which generally show an increasing trend in the median values between 2004/05 and 2007 (Appendix 3).


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3.2 Lake level In contrast to previous years sampling when the lakes have been relatively low, lake level over summer 2007 appeared to have re-charged slightly (Figures 4-1 and 4-2). This increase in lake level is attributable to Canterbury having “higher than normal” rainfall during winter 2006 (NIWA 2006). MfE (2006) highlight the importance of the relationship between lake trophic status and depth. The relationship with depth corresponds with shallow lakes being both more naturally eutrophic and having less capacity to absorb incoming nutrient loads to their smaller volume. Deep lakes are more commonly nutrient poor because of greater water volume to area ratio and mixing depths and greater capacity to lock up nutrients in their bed sediments.

3.3 Chlorophyll a Chlorophyll a (Chl a) is a green pigment present in all plant life and is necessary for photosynthesis. The concentration of Chl a is generally proportional to the quantity of algae

present in the water column and is therefore used as a common indicator of algal biomass. Nearly all of the twenty two lake sites monitored displayed an increase in Chl a concentrations from summer 2004/05 to 2007 (Appendix 3). The highest monthly Chl a value was observed in summer during January and February. Lake Emma Chl a concentration peaked at 15.1ug/L and Loch Katrine at 10.1 ug/L in January and February respectively. The lowest Chl a value 0.1 ug/L was recorded in lakes Coleridge, Pukaki and Ohau in March 2007. All lake Chl a concentrations decreased in March compared to the other months sampled, despite warm temperatures. Lake Emma had the highest annual median Chl a of 8.1 ug/L, while Lakes Benmore and Ohau had the lowest annual median Chl a value of 0.2 ug/L. Lake Pearson (north and south) has the largest overall increase in Chl a from previous years sampling across all months (Appendix 3).



Table 3.1: Trophic Level Indices (TLI) and categories for twenty-one Canterbury high country lakes, as from pre-2004 data, and calculated from summer 2004/05 data, summer 2006, summer 2007 and from 2004-2007 data combined (according to methods of Burns et al., 2000).

Lake Pre 2004 TLI 04-05 TLI 2006 TLI 2007 TLI 04-07 Loch Katrine 2.75 2.2 1.98 2.6 2.1 Lake Sumner 2 1.3 1.4 1.6 1.4 Lake Taylor 3.0 1.99 2.1 2.3 2.2 Lake Sarah 3.0 2.3 2.7 2.8 2.6 Lake Grasmere 3.5 1.99 2.3 2.8 2.3 Lake Pearson-N 2.5 1.6 2.3 3.0 2.3 Lake Pearson-S 1.7 2.2 3.1 2.3 Lake Hawdon 2.3 2.6 2.9 2.7 Lake Lyndon 1.87 2.6 2.4 2.3 Lake Georgina 2.5 2.3 2.96 4.6 2.9 Lake Ida 3.0 2.2 1.9 2.3 2.1 Lake Selfe 2.75 1.9 2.2 2.3 2.1 Lake Coleridge 0.8 1.1 1.0 1.1 Lake Heron 3.0 1.9 2.2 2.3 2.1 Lake Emma 4.0 3.8 3.8 4.6 4.0 Lake Camp 3.0 2.5 2.7 3.2 2.6 Lake Clearwater 3.25 2.7 3.3 3.6 3.2 Lake Alexandrina 3.25 2.6 2.6 3.2 2.8 Lake Tekapo 1.1 1.4 1.5 1.1 Lake Pukaki n/s 1.4 1.6 1.4 Lake Ohau n/s 1.4 1.9 1.8 Lake Benmore n/s 1.1 1.5 1.4

KEY: TLI Grade Ultra-microtrophic (0.0-1.0) Microtrophic (1.0-2.0) Oligotrophic (2.0-3.0) Mesotrophic (3.0-4.0) Eutrophic (4.0-5.0)

n/s not sampled

SUMMARY 2004-2007 2005* 2006* 2007 2004-07 Ultra-microtrophic (# lakes) 1 0 1 0 Microtrophic (# lakes) 9 5 5 6 Oligotrophic (# lakes) 8 12 9 14 Mesotrophic (# lakes) 1 2 5 2 Eutrophic (# lakes) 0 0 2 0

* not including lakes Pukaki, Ohau and Benmore



3.4 Phosphorus Phosphorus is a key nutrient within biological systems and is often the limiting nutrient in South Island lakes (Table 3.3). Total phosphorus (TP), is considered a better indicator of a lakes nutrient status than soluble reactive phosphorus because it integrates both the soluble P available for stimulating growth and that bound up in existing algal biomass. Meredith & Wilks (2006) showed that the majority of TP is bound up in algal biomass and generally the proportion in soluble form is small. Phosphorus can affect the amount of periphyton, phytoplankton and/or macrophyte growth. However, high phytoplankton biomass generally occurs in lakes as a result of increased nutrients (both N and P). This can have a dramatic affect on the lake ecosystem

and cause a shift from a clear macrophyte dominated system to a turbid phytoplankton dominated state (Schallenberg 2004). Most lakes exhibited increased concentrations of TP in 2007 (Figure 3-1). Lake Emma and Lake Georgina showed very high concentrations of TP and a pattern of increasing annual concentrations (Figure 3-2). According to Burns and Bryers (2000) trophic boundary concentrations, Lake Emma TP mean summer concentrations from 04/05 to 2007 has shifted from mesotrophic to eutrophic and Lake Georgina from microtrophic to oligotrophic to mesotrophic over the three years.

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Figure 3-1: Annual median TP concentrations at 22 high country lake in Canterbury, red

dashed line indicates eutrophic TP concentrations (according to Burns & Bryers 2000)



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Figure 3-2: Total phosphorus concentrations; A) Lake Georgina; B) Lake Emma. Red lines are indicative trends in concentration

3.5 Nitrogen Nitrogen is also an important nutrient for periphyton, macrophyte and phytoplankton growth. Total Nitrogen concentrations have followed a similar increasing pattern to that of TP (Figure 3-3). As observed in Figures 3-3

and 3-4 Lake Georgina had very high TN concentrations over summer 2007. Lake Georgina’s TN concentrations were the highest recorded over the lakes monitoring program. Similarly, Lakes Emma, Hawdon and Clearwater had increased median summer 2007 TN concentrations from previous years sampling.

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Figure 3-3: Monthly median total nitrogen concentrations at 22 high country lakes in

Canterbury, red dashed line indicates the threshold of eutrophic TN concentrations (according to Burns & Bryers 2000)



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Figure 3-4: Total nitrogen concentrations; A) Lake Georgina; B) Lake Emma. Red lines are indicative trends in concentration

3.6 TN:TP ratios The TN:TP ratio can be calculated from the core TLI data. They are based upon only one ‘below detection’ value from the whole dataset, and occasional TP data at the detection level (Appendix 1). Therefore the TN:TP ratios in Table 3.4 are statistically valid, even for the most low nutrient status lakes. The TN:TP ratios indicated that the lakes had similar relative and absolute nutrient ratios between 2006 and 2007 (Table 3.4). Four out of twenty two sites (Lake Lyndon, Lake Alexandrina, Lake Taylor and Loch Katrine) showed an increased ratio between 2006 and 2007, but the increase was minimal and didn’t change the threshold limitation category for those lakes. There were however, seventeen lakes which displayed a decrease in absolute ratios between 2006 and 2007. The decrease changed the limitation category in eight of the seventeen lakes (five became theoretically “Not Limited”, previously “P limited” and three became “N Limited”, previously “Not limited”). Lakes were either indicating potential primarily phosphorus limitation or not limited (with only three indicating potential N-limited). The same four lakes have remained P limited (Hawdon, Georgina, Camp, Clearwater) over the last three years but to a much lesser degree. The hydro-electric lakes first sampled in 2006 were generally in nutrient balance. However, in 2007 both Lake Pukaki and Lake Benmore became N limited. The 2006 and 2007 data indicated Lake Coleridge ceased to be potentially N limited. The combined (2005, 2006 and 2007) data showed a very similar nutrient ratio and limitation for all lakes.

Overall, changes in many lakes trophic state indicate that increased P influx may already be occurring. Therefore, these lakes need to be protected from any additional sources of phosphorous and nitrogen concentrations that could drive increased primary (algal) production.

3.7 Turbidity Turbidity relates to the light scattering properties of the water which is related to how clear the water is, the higher the amount of suspended solids in the water column the higher the turbidity and subsequent reduced water clarity. Turbidity followed a similar increasing pattern as Chl a, TN and TP concentrations. Unlike many situations where reduced water clarity is associated with degradation, glacial lakes are unique with their high turbidity and low water clarity. Lakes Pukaki and to a lesser extent Ohau and Tekapo are turbid all year round as they are fed by active glaciers which continually supply the lakes with very fine ground particles of rock glacial flour. Fluvio-glacial material or glacial flour is brought down from the high snow-covered mountains of the Southern Alps by tributary streams. The fine silt particles reduce light penetration and water clarity, but reflect a brilliant blue water colour. The glacial lakes, Pukaki and Ohau had the highest turbidity values of 8.9 NTU.



Table 3.2: TN:TP ratios from medians of data from summer 2004/05, 2006 and 2007

Medians TN:TP TN:TP TN:TP TN:TP Source lake 2004/05 2006 2007 2004/07 Lake Hawdon 70 144 93 85 Lake Georgina 60 98 98 70 Lake Camp 50 66 46 50 Lake Clearwater 50 68 54 52 Lake Pearson Nth 45 36 25 39 Lake Lyndon 39 33 35 35 Lake Selfe 38 55 39 40 Lake Pearson Sth 36 39 21 30 Lake Sarah 35 33 32 35 Lake Ida 30 53 36 37 Lake Heron 30 39 25 29 Lake Emma 28 30 19 28 Lake Alexandrina 28 32 38 33 Lake Taylor 25 20 22 22 Lake Sumner 25 33 23 25 Loch Katrine 19 31 35 30 Lake Grasmere 18 26 15 20 Lake Tekapo 16 30 16 16 Lake Coleridge 14 20 18 17 Lake Pukaki n/s 24 4 15 Lake Ohau n/s 25 21 24 Lake Benmore n/s 25 9 18

Key: P Limited >30 N Limited <15 Not Limited 15-30 n/s Not Sampled

Canterbury high country lakes water quality monitoring programme 2007


4 Discussion The sampling runs from January to April achieved consistent and reliable sampling from all lakes, as well as illustrating features of the lakes (colour, level etc.) that were not so visible from the ground. As yet no solutions have been found for the inability to determine clarity (secchi depth) as one of the indices. Turbidity measurements continue to be taken as a surrogate for secchi, but they cannot readily be used to determine a clarity index. Therefore the overall lake trophic indices are calculated from 3 rather than 4 sub indices. It is uncertain what the consequence (if any) this necessity may have on reliability, reproducibility, or comparability of the overall trophic level index with other studies around New Zealand. The reduction to four samplings may generate a further degree of uncertainty in comparing results from monthly summer sampling of Canterbury lakes, to monthly (MfE recommended), or quarterly lake monitoring results from lakes in other regions or nationally. However, MfE (2006) suggest the use of this modified version is useful for the sake of national reporting, but suggest some caution when interpreting the results.

4.1 Trophic level index The ranking of lakes according to median concentrations of the key determinands changed quite markedly from the rankings determined from the previous year (Meredith & Wilks 2006). A group of lakes consistently ranked highly in median nutrient concentrations and trophic indicators of all three determinands. These lakes (Emma, Georgina, Clearwater, Alexandrina, Camp, Pearson and to a lesser extent Hawdon, Grasmere and Sarah) were therefore exhibiting a consistent enrichment of trophic determinands such that they may either be sensitive to, or exhibit, the effects of limnetic enrichment. These lakes also all possess either significant lake front resident holiday communities, or intensified farm production on their fringes, that may potentially explain some possible sources for the apparent enrichment. Conversely, the three large lakes (Coleridge, Tekapo, and Sumner), the hydro-electric impounded lake Benmore) and Pukaki, Ohau all exhibited low rankings and low median

values for all determinands, such that they were exhibiting a consistent lack of enrichment. They were therefore very unlikely to currently or in the future exhibit any effects of limnetic enrichment, unless there were some major land use changes, or discharges in the catchments. The remaining 10 lakes yielded more erratic combinations of rankings of the determinands such that lakes were generally not in balanced production states. They are therefore generally limited from exhibiting appreciable primary production by one or more trophic determinands (N or P) being a scarce resource. These lakes therefore also currently appear to be at little risk of degradation of trophic state under current land use patterns but require further monitoring. The overall lake trophic level index calculated from averaging the three indices, gave a similar separation of lakes to those groupings described above. However, of immediate concern is the state of Lake Georgina which increased two trophic levels from oligotrophic to eutrophic. This was primarily due to high total nitrogen concentrations. Lake Emma also increased trophic status from mesotrophic to eutrophic, primarily due to high total phosphorus concentrations and subsequent high Chlorophyll a concentrations. It is very concerning that two lakes were graded as eutrophic in summer 2007 and that all others (with the exception of Coleridge) trophic values increased. The water quality of Canterbury high-country lakes has declined during the period of monitoring. Lakes do not appear to be significantly improving and may require further investigation and management interaction. As hypothesised by Meredith & Wilks (2006), if lakes continue to show an increase in Chlorophyll a concentrations, it could indicate a widespread degradation of the high country lakes. Predicted changes in trophic state categories have occurred, however the process by which this occurs is complex and not immediately clear. In 2006, many of the small lakes were at particularly low lake levels as a result of a sustained period (3-4 years) of low rainfall. Therefore many lakes were in negative water balance and were reduced down to maybe



only half of their full volume. Winter 2006 showed a reversal of these weather patterns with significant early season snowfalls, and a return to average or above average winter month rainfall patterns and resulted in increased lake levels (Figure 4-1). Although the winter of 2006 was relatively wet, there was very little rainfall over the summer of 2007/08 (NIWA 2008).

Figure 4-1: Lake Pearson: A) April 2006

B) February 2007

4.2 Shallow lakes Four shallow lakes (considered <10 m in depth MfE 2006) are included in our monitoring program and have the potential to oscillate between stable states of clear macrophyte dominance and turbid plankton dominance (Scheffer 2001). In shallow lakes there is often a large interface between the epilimnon (surface mixed layer) and lake bed. As a result, substances and processes in sediments can greatly influence the water column, especially when influenced by stochastic events such as strong wind events which re-suspend sediments into the water column. There are a set of theoretical threshold conditions that

delimit the two states and a set of feedbacks that operate to buffer against changes in state (Scheffer 1998). For example, if a clear macrophyte dominated shallow lake receives high nutrient input, enough to stimulate phytoplankton production, light penetration will decrease. As a result macrophyte biomass decreases, decreasing competition for nutrients by lack of ability to assimilate, while adding to internal nutrient concentrations through decomposition. Phytoplankton populations boom and further reduce light penetration until macrophyte communities are no longer present (Schallenberg 2004). This flip flop in lake state may be occurring in some of our shallow high country lakes.

4.3 Lake Emma Lake Emma is a shallow (max depth: 3 m) eutrophic lake with an area of 1.67 km2. In 2004/05, Lake Emma was considered a potential ‘problem’ lake as exhibited by its ‘mesotrophic status’ and presence of potentially toxic or nuisance algal taxa (Anabaena spp.). It was thought that Lake Emma had been improving in 2006, and that it was due to a significant change in management with its catchment reverting to DoC ownership, exclusion of cattle grazing, and removal of exotic vegetation (willows). However, in 2007 Lake Emma appeared to be in an unstable state with increasing nutrient levels and subsequent high Chlorophyll a and turbidity values. Although Lake Emma’s nutrient status has increased, visually it has good clarity but was brown/yellow in colour. It was also noted in 2007 that the lake had obvious dark shadows scattered across its bed, and these are likely to be macrophyte beds establishing in the clearer light climate. In 2005/06 the Chlorophyll a concentrations were relatively stable, however, they were not so in 2007 ranging from 15.1 ug/L to 7 ug/L over two months. It appears that Lake Emma is currently in an unstable state represented by fluctuating turbidity, Chlorophyll a and TP concentrations (Appendix 4). Internal sediment fluxes of nitrogen and particularly phosphorus, in Lake Emma may support a significant fraction of the total nutrient budget. However, we suggest that external nutrient loading (from anthropogenic activities) is now not the issue facing Lake Emma. It is more likely that high nutrient

A

B



loadings (prior to DOC management) have been locked up in bottom sediment. Thus when environmental conditions such as high wind events or anoxic conditions occur, sediments are remobilised and re-suspended back into the water column which are in turn utilised by plankton (Burger et al. 2007). This is most likely the process by which we have observed high Chlorophyll a, total nitrogen, total phosphorus and turbidity values in 2007. It may be necessary in future monitoring programs to quantify nitrogen and phosphorus concentrations in Lake Emma’s sediment and the contribution to the total nutrient load. This will provide important information to lake managers on the nutrient management and lake restoration projects.

4.4 Lake Georgina Lake Georgina is another shallow (max depth: 10 m) eutrophic lake with a small area of 0.17 km2. As seen in Figure 4-2 the water level of Lake Georgina was very low in 2006 but has increased since to that observed in February 2007.

Figure 4-2: Lake Georgina: A) January

2006 B) February 2007

Out of the 21 lakes sampled over the past three years Lake Georgina’s trophic state has declined the fastest. It switched from a stable mesotrophic state to a nutrient enriched eutrophic state over a year, despite increased lake levels. Lake Georgina experienced extremely high total nitrogen concentrations ranging from 1.2-2.1 mg/L and elevated total phosphorus concentrations from 0.017-0.21 mg/L through January to April 2007. Subsequently with high nutrients, Chlorophyll a and turbidity concentrations increased. Along with increased trophic state, Lake Georgina has visually declined from clear to green to brown/yellow in colour over three years. Lake Georgina maybe going through the same process as Lake Emma, in that, due to the shallow nature of these lakes, surface mixing is driving re-suspension of bottom nutrients and thus re-introducing nutrients into the water column. However, we suggest that an increase in external nutrient loading to Lake Georgina could have occurred rather than solely wind driven mixing (green pasture in background Figure 4-2). Patterns of shallow lakes trophic state, whether macrophyte or phytoplankton dominated are complex and largely dependent on climatic forcing (stochastic events), nutrient loading and food web dynamics. It is important to continue monitoring these valuable high country lakes because as described above, important inferences for lake management can be drawn (based on water quality data).

4.5 Large lakes Canterbury’s high country deep lakes tend to be nutrient poor because of their long hydraulic residence times (e.g., 4.9 years for Lake Coleridge); (Schallenberg et al., 1999). The large ratio of volume to inflow in these large lakes means that the water typically stays in the lake for a number of years. This long residence time allows nutrients to be stripped out of the water column by plankton, eventually settling to the bottom sediment, taking nutrients with them (Schallenberg 2004). A downside to long residence times is that these lakes are often slow to respond to nutrient enrichment. This also means that once restoration efforts have been made, such as

A

B



reducing external nutrient input, the water quality is slow to improve. Of the sixteen large lakes (>10 m depth) three lakes changed trophic state. Lakes Alexandrina, Camp and Pearson increased trophic state from oligotrophic to mesotrophic from summer 2006 to summer 2007. This change in trophic state appears to be a natural process for Lake Alexandrina as observed from pre 2004 mesotrophic state. All three lakes showed slight elevations in phosphorus, nitrogen, Chlorophyll a and turbidity concentrations (Appendix 4). It was reassuring that the large lakes (Coleridge, Tekapo, and Sumner), Waitaki hydro-electric impounded lake (Benmore) and Pukaki, Ohau are all of particularly low trophic state (ultra-microtrophic or microtrophic) and so do not signal a requirement for management strategies or intervention, as are occurring on some large lakes in the North Island (Taupo, Rotorua, Rotoiti). However, it should also be noted that monitoring strategies to establish early warnings on these large and deep lakes are often more effectively signalled from sampling depth transects to establish hypolimnetic oxygen deficits and deoxygenation rates. If there are any concerns for the state of the large Canterbury lakes, then additional monitoring along those lines should be considered.

4.6 Nutrient limitation The nutrient data largely confirm that the Canterbury high country lakes continue to largely remain phosphorus limited rather than nitrogen limited. Although 3 lakes appeared to be nitrogen limited in 2007 (Table 3.4). Phosphorus limitation remains a feature contributed to by the relatively low P yield of Canterbury greywacke geology. Lake Coleridge’s apparent N limitation is as much a consequence of its overall low nutrient status. Of more concern was that many lakes were exhibiting an apparent N nutrient surplus, such that they remain sensitive to any increased sources of P nutrients. Increased P yield is most likely to be a result of increasing catchment fertilising with phosphatic fertilisers. In the past this has been limited by low economics returns of hill country farming, However, changes in post management, land tenure and rising commodity prices increase the potential for increased phosphatic (and

nitrogen) fertiliser addition to some lake catchments (potentially happening around Lake Georgina). Others (such as Emma and Heron) may conversely be receiving increased protection via lake shore reservation as a result of land tenure changes. It is therefore important that the pressures on lake catchments are understood and continue to be scrutinised to assist review and explanations of the patterns seen in this programme. Other lake research groups have indicated that TN:TP ratios may be crude or gross estimations of nutrient limitation, and that ratios utilising soluble nutrients may be more useful or realistic. Over 2005/06 we sampled soluble nutrients to enable consideration of this issue. However, the soluble nutrient data was dominated by ‘below detection’ or ‘at laboratory detection’ data, It was decided that it was not necessary to sample for soluble nutrients further unless significant additional discretionary budget becomes available, or there are indications of significantly increased trophic status such that soluble nutrients may become in excess (Meredith and Wilks 2005).

4.7 Eutrophication Since the late 1960’s the problem of nutrient enrichment in freshwater ecosystems has been studied. Lakes are intimately linked to their catchments and thus are highly affected by activities within their catchment. Inputs from landuse activities such as runoff containing contaminants, nutrients and/or sediment can influence the water quality of a lake (often negatively). The typical reaction by which lakes respond to increased nutrients or eutrophication is an increase in phytoplankton biomass and subsequently reduced water clarity (MfE 2006). In Canterbury, the high country is relatively uninhabited. Therefore domestic sewage and industrial waste inputs tend to be minor contributors to eutrophication in Canterbury lakes (opposite to that of Lake Taupo). Recent changes in landuse from sheep to beef have also resulted in the increased intensity of nutrient flux (nitrogen and phosphorus) from land to water (Schallenberg 2004). The main source of nutrient enrichment in Canterbury tends to come from agricultural activities. However, other potential sources such as faecal contamination (bird colonies on and around the lake), septic tanks or enriched



groundwater cannot be ruled out for some of the lakes at this stage.

5 Conclusion It is positive that the majority of Canterbury high country lakes remain in a low trophic state. However since this monitoring program was first instigated a notable decline in lake water quality has occurred in six main lakes. The water quality of lakes Emma and Georgina is degraded and lakes Alexandrina, Camp and Pearson are showing early signs of deterioration. These changes are most likely due to decades of landuse change and intensification of landuse practices in the surrounding catchments, resulting in increased nutrient runoff. Internal loading of lakes due to past nutrient inputs can take decades to recover, especially in shallow lakes. Other regional councils appear to have similar circumstances, where lakes are generally degrading and falling into increasingly ‘eutrophic’ categories (Barnes 2002, Barnes and Burns 2005). Likewise internationally, eutrophication of lakes is a growing problem (Scheffer 2001) and is also attributed to intensified landuse being the primary cause. Through best management practices we should be able hopefully mitigate the affects. The variability between the three years of sampling Canterbury’s high country lakes to date, illustrate that it is important to maintain this monitoring programme, so as to continue to document lake state, and identify any positive or negative trends as early as possible. Climate trends, and current trends and practices in catchment or land use pressures and activities are significant enough to give cause for concern, and warrant ongoing close scrutiny of lake trophic condition and trends. This programme, while generally effective, remains a minimum that is likely to identify and explain any lake responses to these current climate and land use pressures.

6 Acknowledgements We thank staff of Garden City Helicopters, Christchurch, for provision of helicopter services and Paul Champion and Fluer Matheson from NIWA for reviewing the report.

7 References Barnes, G. 2002. Water Quality trends in

selected shallow lakes of the Waikato Region, 1995-2002. Environment Waikato Technical Report 2002/11. Hamilton. 22pp.

Barnes, G., Burns N. 2005. Water Quality of

selected lakes in the Auckland Region. ARC Technical Publication TP268. Auckland Regional Council, Auckland. 51pp.

Burger, D.F., Hamilton, D.P., Pilditch, C.A.,

Gibbs, M.M. 2007. Benthic nutrient fluxes in a eutrophic, polymictic lake. Hydrobiologia. 584:13-25.

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

Protocols for Monitoring Trophic Levels of New Zealand Lakes and Reservoirs. Report prepared by Lakes Consulting for Ministry for the Environment Wellington. 138 pp.

Meredith, A.S. 2004. Monitoring of the Water

Quality of Canterbury High Country Lakes. Environment Canterbury Technical Report: U04/34. Christchurch. 32pp.

Meredith, A.S. 2005. Monitoring of the Water

Quality of Canterbury High Country Lakes: Results of the first year’s monitoring 2004/05. Environment Canterbury Technical Report: U05/42. Christchurch. 20pp.

Meredith, A.S., Wilks, T.C. 2006. Canterbury

high country lakes water quality monitoring programme: Results of the second year’s monitoring 2006 and assessment of nutrient indices. Report No.U06/34.

MfE (Ministry for the Environment) 1994. Water

quality guidelines No. 2 Guidelines for the management of water colour and clarity. Ministry for the Environment, Wellington.



MfE (Ministry for the Environment) (2006): Lake Water Quality in New Zealand. Status in 2006 and recent trends 1990-2006. NIWA Client Report. Wellington. CH2006-145.

NIWA (2006). New Zealand National Climate Study, the year 2006.

NIWA (2008). New Zealand National Climate Study, the year 2007.

Schallenberg, M., James, M., Hawes, I., Howard-Williams, C. 1999. External forcing by wind and turbid inflows on a deep glacial lake and implications for primary production. New Zealand Journal of Marine and Freshwater Research. 33: 311-331.

Schallenberg, M., Burns, C. 2004. Effects of

resuspension on phytoplankton production: teasing apart the influences of light, nutrients and algal entrainment. Freshwater Biology. 49: 143-159.

Schallenberg, M. 2004. Primary production in

the open water. Chapter 22. In Freshwater of New Zealand. Harding, J., Mosley, P., Pearson, C., and Sorrell, B. 2004.

Scheffer, M. 2001. Ecology of shallow lakes.

Kluwer Academic Publishers. London.



Appendix 1 Chlorophyll a data from three hydro-electric lakes sampled in summer 2006 and 2007

Lake Ohau

0

0.2

0.4

0.6

0.8

1

1.2

January Februay March April

Chlo

roph

yll a

(ug/

L)

Summer 2006 Summer 2007

Lake Benmore

0

0.2

0.4

0.6

0.8

1

1.2


Chlo

roph

yll a

(ug/

L)


Lake Pukaki

0

0.2

0.4

0.6

0.8

1

1.2


Chlo

roph

yll a

(ug/

L)




Appendix 2 Box and Whisker plots of the raw data for 21 sampled lakes, A) Turbidity, B)Chlorophyll a, C)Total Nitrogen, D) Total Phosphorus

A)

High Country Lakes Chlorophyll a

Summer 04/05 Summer 2006 Summer 2007-2

0

2

4

6

8

10

12

14

16

CH

La (u

g/L)

B)

High Country Lakes Total Phosphorus

Summer 04/05 Summer 2006 Summer 2007-0.005

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

TP (m

g/L)

C)

High Country Lakes Total Nitrogen

Summer 04/05 Summer 2006 Summer 2007-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

TN (m

g/L)

D

High Country Lakes Turbidity

Summer 04/05 Summer 2006 Summer 2007

0.2

0.4

0.6

0.8

2.0

4.0

6.0

8.0

TUR

B (N

TU)

Key: Median 25%-75% Non-Outlier Range Outliers Extremes



Appendix 3 Scatterplots of Chlorophyll a data from lakes sampled in summer 2004/05, 2006 and 2007

Lake Sumner

R2 = 0.4875

00.20.40.60.8

11.21.41.61.8

2

Aug-04 Feb-05 Sep-05 Mar-06 Oct-06 Apr-07 Nov-07

Date

Chl

orop

hyll

a (u

g/L)

Lake Taylor

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Aug-04 Feb-05 Sep-05 Mar-06 Oct-06 Apr-07 Nov-07Date

Chl

orop

hyll

a (u

g/L)

Lock Katrine

R2 = 0.187

0

2

4

6

8

10

12

1-Aug-04 17-Feb-05 5-Sep-05 24-Mar-06 10-Oct-06 28-Apr-07 14-Nov-07

Date

Chl

orop

hyll

a (u

g/L)

Lake Hawdon

R2 = 0.15

0

0.2

0.4

0.6

0.8

1

1.2

1.4


Date

Chl

orop

hyll

a (u

g/L)

Lake Pearson North

R2 = 0.6232

0

1

2

3

4

5

6


Date

Cho

rolp

hyll

a (u

g/L)

Lake Pearson South

R2 = 0.5182

0

1

2

3

4

5

6

7

8


Date

Chl

orop

hyll

a (u

g/L)

Lake Sarah

R2 = 0.1591

0

0.5

1

1.5

2

2.5

3


Date

Chl

orop

hyll

a (u

g/L)

Lake Grasmere

0

1

2

3

4

5

6

7

8


Date

Chl

orop

hyll

a (u

g/L)



Lake Lyndon

0

0.5

1

1.5

2

2.5

3


Date

Chl

orop

hyll

a (u

g/L)

Lake Coleridge

R2 = 0.2906

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9


Date

Chl

orop

hyll

a (u

g/L)

Lake Georgina

0

1

2

3

4

5

6

7

8

9


Date

Chl

orop

hyll

a (u

g/L)

Lake Ida

R2 = 0.1122

00.5

11.5

22.5

33.5

4

4.55


Date

Chl

orop

hyll

a (u

g/L)

Lake Selfe

R2 = 0.2127

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6


Date

Chl

orop

hyll

a (u

g/L)

Lake Heron

R2 = 0.2791

00.5

11.5

22.5

33.5

44.5

5


Date

Chl

orop

hyll

a (u

g/L)

Lake Alexandrina

R2 = 0.1272

0

0.5

1

1.5

2

2.5

3

3.5

4


Date

Chl

orop

hyll

a (u

g/L)

Lake Emma

R2 = 0.2731

0

2

4

6

8

10

12

14

16


Date

Chl

orop

hyll

a (u

g/L)

Lake Camp

R2 = 0.228

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5


Date

Chl

orop

hyll

a (u

g/L)

Lake Clearwater

R2 = 0.2707

0

1

2

3

4

5

6

7


Date

Chl

orop

hyll

a (u

g/L)



Lake Tekapo

R2 = 0.1041

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


Date

Chl

orop

hyll

a (u

g/L)



Appendix 4 Raw data from 2004/05, 2006 and 2007 lakes monitoring for TLI assessment SHADING TLI: Violet= Ultra-microtrophic; Blue=Microtrophic; Green=Oligotrophic; Yellow=mesotrophic; Red = Eutrophic; Brown = Hypertrophic SHADING RATIOS: Orange =P limited; Orange/Yellow= N limited; Pale yellow= in nutrient balance Source: Loch (Lake) Katrine at mid lake Site No:CRC300147 Site_ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300147 6-Dec-04 1200 0.9 1.6 0.065 0.004 16.3 11-Jan-05 1025 0.8 1.5 0.075 0.003 25 8-Feb-05 900 3.1 0.8 0.13 0.009 14.4 16-Mar-05 1420 0.8 1.1 0.075 0.004 18.8 14-Apr-05 1345 0.9 1.6 0.043 0.002 21.5 CRC300147 24-Jan-06 940 0.4 0.8 0.063 0.003 21 24-Feb-06 803 0.4 3.8 0.093 0.003 31 23-Mar-06 1425 0.4 0.6 0.08 0.002 40 19-Apr-06 835 0.3 1 0.12 0.004 30 CRC300147 30-Jan-07 1538 0.6 10.1 0.15 0.005 30 28-Feb-07 1204 0.5 7.1 0.11 0.003 36.7 27-Mar-07 1701 0.5 1 0.11 0.003 36.7 19-Apr-07 1236 0.3 0.6 0.1 0.003 33.3 Median Summer 05 0.9 1.5 0.075 0.004 18.75 2.2 Median Summer 06 0.4 0.9 0.087 0.003 30.5 3 Median Summer 07 0.5 4.05 0.11 0.003 35 2.6 Median overall 0.5 1.1 0.093 0.003 30 2.1 Source: Lake Sumner at Marion Stream outlet Site No:CRC300079 Site_ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300079 6-Dec-04 1204 0.6 0.3 0.066 0.002 33 11-Jan-05 1020 0.3 0.4 0.039 0.002 19.5 8-Feb-05 905 0.3 0.1 0.053 0.004 13.3 16-Mar-05 1415 0.6 0.4 0.051 0.002 25.5 14-Apr-05 1350 0.5 1 0.025 0.001 25 CRC300079 24-Jan-06 942 1 0.7 0.046 0.002 23 24-Feb-06 805 0.3 1.1 0.07 0.001 70 23-Mar-06 1450 0.2 0.6 0.043 0.001 43 19-Apr-06 840 0.3 1.2 0.051 0.003 17 CRC300079 30-Jan-07 1535 0.6 1.7 0.076 0.003 25.3 28-Feb-07 1206 0.6 1.8 0.034 0.0005 68 27-Mar-07 1658 0.5 0.9 0.04 0.003 13.3 19-Apr-07 1235 0.3 0.7 0.02 0.001 20 Median Summer 05 0.5 0.4 0.051 0.002 25 1.3 Median Summer 06 0.3 0.9 0.049 0.002 33 1.4 Median Summer 07 0.55 1.3 0.037 0.002 22.7 1.6 Median overall 0.5 0.7 0.046 0.002 25 1.4



Source: Lake Taylor at mid lake Site No:CRC300141 Site_ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300141 16-Mar-05 1425 0.3 0.6 0.08 0.002 40 14-Apr-05 1340 0.4 1.6 0.051 0.005 10.2 CRC300141 24-Jan-06 935 0.3 0.5 0.067 0.003 22.3 24-Feb-06 800 0.3 1.2 0.11 0.003 36.7 23-Mar-06 1440 0.2 0.7 0.072 0.004 18 19-Apr-06 830 0.3 1.1 0.11 0.007 15.7 CRC300141 30-Jan-07 1540 0.4 1.2 0.11 0.005 22 28-Feb-07 1200 0.4 1.4 0.17 0.003 56.7 27-Mar-07 1704 0.4 0.3 0.09 0.004 22.5 19-Apr-07 1240 4.7 1.5 0.044 0.004 11 Median Summer 05 0.35 1.1 0.0655 0.0035 25.1 2 Median Summer 06 0.3 0.9 0.091 0.0035 20.2 2.1 Median Summer 07 0.4 1.3 0.1 0.004 22.3 2.3 Median overall 0.35 1.15 0.085 0.004 22.2 2.2 Source: Lake Sarah at mid lake Site No:CRC300521 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300521 6-Dec-04 1232 0.5 0.5 0.11 0.003 36.7 11-Jan-05 1045 0.6 0.8 0.14 0.004 35 8-Feb-05 935 0.5 0.5 0.21 0.017 12.4 16-Mar-05 1325 0.7 0.9 0.14 0.004 35 14-Apr-05 1235 1.1 1.3 0.1 0.004 25 CRC300521 24-Jan-06 958 0.7 0.8 0.16 0.006 26.7 24-Feb-06 825 0.8 2.6 0.19 0.005 38 23-Mar-06 1350 0.5 1.1 0.16 0.003 53.3 19-Apr-06 900 0.4 1.7 0.23 0.008 28.8 CRC300521 30-Jan-07 1510 0.7 2 0.25 0.01 25 28-Feb-07 1229 0.9 2.5 0.17 0.004 42.5 27-Mar-07 1638 0.6 0.1 0.19 0.005 38 19-Apr-07 1211 0.5 1.3 0.17 0.007 24.3 Median Summer 05 0.6 0.8 0.14 0.004 35 2.3 Median Summer 06 0.6 1.4 0.175 0.0055 33.4 2.7 Median Summer 07 0.65 1.65 0.18 0.006 31.5 2.8 Median overall 0.6 1.1 0.17 0.005 35 2.6 Source: Lake Grasmere at mid lake - surface Site No:CRC300525 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300525 6-Dec-04 1235 0.6 1.4 0.082 0.003 27.3 11-Jan-05 1047 1.4 3.6 0.089 0.005 17.8 8-Feb-05 940 0.4 0.3 0.12 0.009 13.3 16-Mar-05 1320 0.4 0.5 0.082 0.003 27.3 14-Apr-05 1230 0.5 1 0.054 0.003 18 CRC300525 24-Jan-06 1000 0.6 1.1 0.091 0.004 22.8 24-Feb-06 830 1.7 4.1 0.12 0.004 30 23-Mar-06 1345 0.6 1.3 0.088 0.003 29.3 19-Apr-06 905 0.5 1.3 0.16 0.008 20 CRC300525 30-Jan-07 1509 1.2 7.4 0.16 0.01 16 28-Feb-07 1233 0.8 2.4 0.078 0.003 26 27-Mar-07 1635 1 0.3 0.12 0.009 13.3 19-Apr-07 1210 0.6 2.2 0.093 0.007 13.3 Median Summer 05 0.5 1 0.082 0.003 18 2 Median Summer 06 0.6 1.3 0.1055 0.004 26.0 2.3 Median Summer 07 0.9 2.3 0.1065 0.008 14.7 2.8 Median overall 0.6 1.3 0.091 0.004 20 2.3



Source: Lake Pearson at north basin Site No:CRC300497 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300497 6-Dec-04 1238 0.5 0.5 0.077 0.002 38.5 11-Jan-05 1050 0.5 1 0.096 0.001 96 8-Feb-05 950 0.5 0.4 0.13 0.006 21.7 16-Mar-05 1310 0.3 0.4 0.09 0.002 45 14-Apr-05 1225 0.6 1.2 0.06 0.001 60 CRC300497 24-Jan-06 1002 0.4 0.8 0.084 0.002 42 24-Feb-06 830 0.4 2.1 0.12 0.004 30 23-Mar-06 1345 0.4 1.6 0.081 0.001 81 19-Apr-06 910 0.3 1.5 0.15 0.005 30 CRC300497 30-Jan-07 1507 0.7 5.1 0.2 0.008 25 28-Feb-07 1236 0.8 5.5 0.12 0.003 40 27-Mar-07 1632 0.8 1.7 0.12 0.005 24 19-Apr-07 1205 0.7 3.6 0.13 0.007 18.6 Median Summer 05 0.5 0.5 0.09 0.002 45 1.6 Median Summer 06 0.4 1.55 0.102 0.003 36 2.3 Median Summer 07 0.75 4.35 0.125 0.006 24.5 3 Median overall 0.5 1.5 0.12 0.003 38.5 2.3 Source: Lake Pearson at south basin Site No:CRC300498 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300498 6-Dec-04 1240 0.6 0.9 0.071 0.002 35.5 11-Jan-05 1052 0.7 0.9 0.091 0.003 30.3 8-Feb-05 955 0.5 0.2 0.12 0.006 20 16-Mar-05 1305 0.4 0.6 0.088 0.002 44 14-Apr-05 1220 0.4 0.7 0.055 0.001 55 CRC300498 24-Jan-06 1004 0.5 1 0.086 0.002 43 24-Feb-06 835 0.4 1.1 0.14 0.004 35 23-Mar-06 1340 0.4 1 0.097 0.001 97 19-Apr-06 915 0.3 1.6 0.14 0.005 28 CRC300498 30-Jan-07 1505 0.7 5.8 0.15 0.007 21.4 28-Feb-07 1237 1.3 7.2 0.12 0.005 24 27-Mar-07 1630 1.4 2.7 0.17 0.008 21.3 19-Apr-07 1205 0.8 2.2 0.12 0.007 17.1 Median Summer 05 0.5 0.7 0.088 0.002 35.5 1.7 Median Summer 06 0.4 1.05 0.1185 0.003 39 2.2 Median Summer 07 1.05 4.25 0.135 0.007 21.3 3.1 Median overall 0.5 1 0.12 0.004 30.3 2.3 Source: Lake Hawdon at mid lake Site No:CRC300486 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC300486 6-Dec-04 1245 0.4 0.2 0.21 0.003 70 11-Jan-05 1100 0.4 0.2 0.26 0.004 65 8-Feb-05 1000 0.5 0.4 0.5 0.008 62.5 16-Mar-05 1330 0.5 0.9 0.29 0.004 72.5 14-Apr-05 1235 0.7 0.8 0.2 0.002 100 CRC300486 24-Jan-06 1008 0.4 1.1 0.34 0.004 85 24-Feb-06 840 0.3 1.1 0.34 0.002 170 23-Mar-06 1355 0.5 0.8 0.33 0.002 165 19-Apr-06 920 0.2 0.4 0.49 0.004 122.5 CRC300486 30-Jan-07 1512 0.5 1.1 0.49 0.006 81.7 28-Feb-07 1243 0.5 1.3 0.42 0.003 140 27-Mar-07 1642 0.5 0.1 0.4 0.005 80 19-Apr-07 1215 0.3 0.9 0.42 0.004 105 Median Summer 05 0.5 0.4 0.26 0.004 70 2.3 Median Summer 06 0.35 0.95 0.34 0.003 143.8 2.6 Median Summer 07 0.5 1 0.42 0.0045 93.3 2.9 Median overall 0.5 0.8 0.34 0.004 85 2.7



Source: Lake Lyndon at mid lake Site No:CRC301043 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301043 6-Dec-04 1332 0.4 0.2 0.077 0.002 38.5 11-Jan-05 1145 0.3 0.1 0.1 0.002 50 8-Feb-05 1050 0.4 0.5 0.15 0.006 25 16-Mar-05 1250 0.4 0.7 0.17 0.003 56.7 14-Apr-05 1210 0.6 0.5 0.076 0.003 25.3 24-Jan-06 1044 0.7 2.7 0.12 0.004 30 24-Feb-06 922 0.7 2.8 0.14 0.004 35 23-Mar-06 1330 0.8 1.7 0.13 0.002 65 19-Apr-06 948 0.7 1.7 0.21 0.008 26.3 CRC301043 30-Jan-07 1438 0.4 1.2 0.19 0.005 38 28-Feb-07 1315 0.4 1.8 0.13 0.003 43.3 27-Mar-07 1615 0.4 0.7 0.13 0.004 32.5 19-Apr-07 1130 0.5 1.7 0.073 0.003 24.3 Median Summer 05 0.4 0.5 0.1 0.003 38.5 1.9 Median Summer 06 0.7 2.2 0.135 0.004 32.5 2.6 Median Summer 07 0.4 1.45 0.13 0.0035 35.3 2.4 Median overall 0.4 1.2 0.13 0.003 35 2.3 Source: Lake Georgina at mid lake Site No:CRC301047 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301047 6-Dec-04 1338 0.7 0.7 0.19 0.003 63.3 11-Jan-05 1151 0.8 0.5 0.24 0.004 60 8-Feb-05 1050 1.2 0.5 0.35 0.008 43.75 16-Mar-05 1245 0.6 0.5 0.28 0.004 70 14-Apr-05 1210 0.6 0.4 0.17 0.004 42.5 CRC301047 24-Jan-06 1047 0.8 0.8 0.42 0.006 70 24-Feb-06 930 1.7 1.2 0.42 0.003 140 23-Mar-06 1330 0.9 1.5 0.5 0.004 125 19-Apr-06 955 0.7 0.7 0.92 0.018 51.1 CRC301047 30-Jan-07 N/R 1.3 8.5 1.2 0.017 70.6 28-Feb-07 1323 1.2 5.2 1.8 0.017 105.9 27-Mar-07 1610 1.6 2.3 1.9 0.02 95 19-Apr-07 1126 0.8 1.4 2.1 0.021 100 Median Summer 05 0.7 0.5 0.24 0.004 60 2.3 Median Summer 06 0.85 1 0.46 0.005 97.5 3 Median Summer 07 1.25 3.75 1.85 0.0185 97.5 4.6 Median overall 0.8 0.8 0.42 0.006 70 2.9 Source: Lake Ida at mid lake Site No:CRC301051 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301051 6-Dec-04 1345 0.3 0.1 0.079 0.002 39.5 11-Jan-05 1158 0.4 0.9 0.11 0.003 36.7 8-Feb-05 1110 0.4 1.2 0.17 0.011 15.5 16-Mar-05 1235 0.4 1.4 0.12 0.004 30 14-Apr-05 1200 0.5 1.6 0.062 0.003 20.7 CRC301051 24-Jan-06 1051 0.4 1 0.091 0.002 45.5 24-Feb-06 934 0.3 1.4 0.12 0.002 60 23-Mar-06 1325 0.3 0.1 0.095 0.001 95 19-Apr-06 958 0.2 0.7 0.14 0.005 28 CRC301051 30-Jan-07 N/R 0.7 2.4 0.14 0.004 35 28-Feb-07 1326 0.5 4.6 0.11 0.001 110 27-Mar-07 1600 0.4 0.5 0.11 0.003 36.7 19-Apr-07 1120 0.2 0.7 0.1 0.003 33.3 Median Summer 05 0.4 1.2 0.11 0.003 30 2.2 Median Summer 06 0.3 0.85 0.1075 0.002 52.8 1.9 Median Summer 07 0.45 1.55 0.11 0.003 35.8 2.3 Median overall 0.4 1 0.11 0.003 36.7 2.1



Source: Lake Selfe at mid lake Site No:CRC301065 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301065 6-Dec-04 1342 0.5 0.4 0.13 0.002 65 11-Jan-05 1155 0.5 0.8 0.15 0.004 37.5 8-Feb-05 1100 0.3 0.5 0.16 0.006 26.7 16-Mar-05 1230 0.3 0.3 0.13 0.003 43.3 14-Apr-05 1205 0.5 0.6 0.08 0.003 26.7 CRC301065 24-Jan-06 N/R 0.3 0.9 0.12 0.003 40 24-Feb-06 938 0.3 0.7 0.14 0.002 70 23-Mar-06 1320 0.4 1.4 0.14 0.002 70 19-Apr-06 1000 0.3 1.5 0.16 0.007 22.9 CRC301065 30-Jan-07 1426 0.5 1.1 0.24 0.005 48 28-Feb-07 1330 0.3 1.1 0.16 0.002 80 27-Mar-07 1605 0.4 0.6 0.12 0.004 30 19-Apr-07 1123 0.2 0.7 0.086 0.003 28.7 Median Summer 05 0.5 0.5 0.13 0.003 37.5 1.9 Median Summer 06 0.3 1.15 0.14 0.0025 55 2.2 Median Summer 07 0.35 0.9 0.14 0.0035 39 2.3 Median overall 0.3 0.7 0.14 0.003 40 2.1 Source: Lake Coleridge at mid lake, near island Site No:CRC301045 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301045 6-Dec-04 1349 0.5 0.1 0.049 0.001 49 11-Jan-05 1202 0.4 0.1 0.057 0.002 28.5 8-Feb-05 1110 0.3 0.1 0.064 0.005 12.8 16-Mar-05 1225 0.4 0.3 0.036 0.003 12 14-Apr-05 1155 0.5 0.2 0.027 0.002 13.5 CRC301045 24-Jan-06 1056 0.5 0.3 0.027 0.002 13.5 24-Feb-06 942 0.4 0.8 0.065 0.0005 130 23-Mar-06 1315 0.3 0.3 0.027 0.001 27 19-Apr-06 1005 0.3 0.5 0.064 0.005 12.8 CRC301045 30-Jan-07 1423 0.7 0.6 0.051 0.003 17 28-Feb-07 1332 0.4 0.5 0.039 0.0005 78 27-Mar-07 1554 0.4 0.1 0.018 0.001 18 19-Apr-07 1116 0.3 0.5 0.0045 0.002 2.25 Median Summer 05 0.4 0.1 0.049 0.002 13.5 0.8 Median Summer 06 0.35 0.4 0.0455 0.0015 20.25 1.1 Median Summer 07 0.4 0.5 0.0285 0.0015 17.5 1.0 Median overall 0.4 0.3 0.039 0.002 17 1.1 Source: Lake Heron at main basin Site No:CRC301093 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301093 6-Dec-04 1408 0.7 0.3 0.093 0.003 31 11-Jan-05 1222 0.4 0.7 0.11 0.003 36.7 8-Feb-05 1130 1 0.5 0.16 0.013 12.3 16-Mar-05 1215 0.3 1 0.081 0.006 13.5 14-Apr-05 1140 0.5 0.8 0.089 0.003 29.7 CRC301093 24-Jan-06 1108 0.3 0.9 0.087 0.003 29 24-Feb-06 954 0.8 1.2 0.14 0.002 70 23-Mar-06 930 0.4 2.7 0.098 0.002 49 19-Apr-06 1020 0.3 1.7 0.11 0.005 22 CRC301093 30-Jan-07 1410 0.4 0.9 0.13 0.006 21.7 28-Feb-07 1350 0.7 1 0.28 0.003 93.3 27-Mar-07 1545 0.3 1.1 0.11 0.004 27.5 19-Apr-07 1105 0.3 4.5 0.077 0.005 15.4 Median Summer 05 0.5 0.7 0.093 0.003 29.7 1.9 Median Summer 06 0.35 1.45 0.104 0.0025 39 2.2 Median Summer 07 0.35 1.05 0.12 0.0045 24.6 2.3 Median overall 0.4 1 0.11 0.003 29 2.1



Source: Lake Emma Centre, surface Site No:CRC302801 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC302801 6-Dec-04 1416 2.2 0.6 0.3 0.008 37.5 11-Jan-05 1230 2.5 3.5 0.32 0.013 24.6 8-Feb-05 1140 3.8 5.4 0.61 0.026 23.5 16-Mar-05 1205 3.1 7.2 0.33 0.012 27.5 14-Apr-05 1130 2.9 10 0.23 0.007 32.9 CRC302801 24-Jan-06 1114 1.6 2.5 0.34 0.012 28.3 24-Feb-06 1004 2.3 5.6 0.32 0.008 40 23-Mar-06 940 3.6 6.6 0.38 0.012 31.7 19-Apr-06 1025 2.8 4.8 0.59 0.024 24.9 CRC302801 30-Jan-07 1400 3.4 8.5 0.55 0.032 17.2 28-Feb-07 1358 4.6 15.1 0.68 0.018 37.8 27-Mar-07 1340 0.3 7.7 0.56 0.026 21.5 19-Apr-07 1100 4.1 7 0.59 0.038 15.5 Median Summer 05 2.9 5.4 0.32 0.012 27.5 3.8 Median Summer 06 2.55 5.2 0.36 0.012 30 3.8 Median Summer 07 3.75 8.1 0.575 0.029 19.7 4.6 Median overall 2.9 6.6 0.38 0.013 27.5 4 Source: Lake Camp Centre, surface Site No:CRC302802 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC302802 6-Dec-04 1420 0.4 0.6 0.21 0.003 70 11-Jan-05 1235 0.4 1.1 0.2 0.004 50 8-Feb-05 1150 0.4 1.3 0.29 0.009 32.2 16-Mar-05 1200 0.5 0.9 0.21 0.004 52.5 14-Apr-05 1125 0.4 0.8 0.15 0.003 50 CRC302802 24-Jan-06 1117 0.4 0.9 0.21 0.004 52.5 24-Feb-06 1008 0.6 2.4 0.23 0.002 115 23-Mar-06 945 0.5 1.9 0.24 0.003 80 19-Apr-06 1032 0.4 1 0.34 0.007 48.6 CRC302802 30-Jan-07 1356 0.7 2.7 0.31 0.007 44.3 28-Feb-07 1400 0.7 3.9 0.45 0.007 64.3 27-Mar-07 1525 0.7 0.4 0.27 0.007 38.6 19-Apr-07 1055 0.4 1.4 0.24 0.005 48 Median Summer 05 0.4 0.9 0.21 0.004 50 2.5 Median Summer 06 0.45 1.45 0.235 0.0035 66.3 2.7 Median Summer 07 0.7 2.05 0.29 0.007 46.1 3.2 Median overall 0.4 1.1 0.24 0.004 50 2.6 Source: Lake Clearwater Centre, surface Site No:CRC302804 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC302804 6-Dec-04 1426 0.6 1 0.21 0.004 52.5 11-Jan-05 1238 0.6 0.9 0.24 0.007 34.3 8-Feb-05 1145 0.7 0.7 0.44 0.015 29.3 16-Mar-05 1155 0.8 1.4 0.25 0.005 50 14-Apr-05 1120 1.5 1.5 0.21 0.003 70 CRC302804 24-Jan-06 1120 0.7 2.7 0.29 0.006 48.3 24-Feb-06 1010 0.7 4.3 0.32 0.002 160 23-Mar-06 950 0.8 6.6 0.32 0.004 80 19-Apr-06 1035 0.5 2.2 0.5 0.009 55.6 CRC302804 30-Jan-07 1357 1 3.4 0.45 0.011 40.9 28-Feb-07 1402 1 3.9 0.56 0.008 70 27-Mar-07 1530 0.9 1.6 0.43 0.007 61.4 19-Apr-07 1050 0.6 3 0.42 0.009 46.7 Median Summer 05 0.7 1 0.24 0.005 50 2.7 Median Summer 06 0.7 3.5 0.32 0.005 67.8 3.3 Median Summer 07 0.95 3.2 0.44 0.0085 54.0 3.6 Median overall 0.7 2.2 0.32 0.007 52.5 3.2



Source: Lake Alexandrina midlake, surface Site No:CRC301096 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC301096 6-Dec-04 1455 0.4 0.8 0.16 0.004 40 11-Jan-05 1312 0.4 0.5 0.17 0.005 34 8-Feb-05 1325 0.2 0.2 0.22 0.008 27.5 16-Mar-05 1045 0.4 1.3 0.19 0.007 27.1 14-Apr-05 1030 0.5 3.8 0.11 0.007 15.7 CRC301096 24-Jan-06 1143 0.3 0.5 0.14 0.004 35 24-Feb-06 1038 0.3 1.6 0.15 0.002 75 23-Mar-06 1015 0.3 2.1 0.14 0.005 28 19-Apr-06 1102 0.3 2.2 0.2 0.01 20 CRC301096 30-Jan-07 1333 0.4 2.7 0.23 0.007 32.9 28-Feb-07 1424 0.3 1.7 0.3 0.005 60 27-Mar-07 1510 0.4 0.8 0.3 0.007 42.9 19-Apr-07 1030 0.4 3.1 0.17 0.012 14.2 Median Summer 05 0.4 0.8 0.17 0.007 27.5 2.6 Median Summer 06 0.3 1.85 0.145 0.0045 31.5 2.6 Median Summer 07 0.4 2.2 0.265 0.007 37.9 3.2 Median overall 0.4 1.6 0.17 0.007 32.9 2.8 Source: LAKE TEKAPO CENTRE, SURFACE Site No:CRC302908 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC302908 6-Dec-04 1448 1 0.3 0.055 0.001 55 11-Jan-05 1305 1.2 0.1 0.062 0.004 15.5 8-Feb-05 1320 1.4 0.2 0.063 0.011 5.7 16-Mar-05 1055 1.4 0.2 0.029 0.002 14.5 14-Apr-05 1020 0.7 0.3 0.034 0.001 34 CRC302908 24-Jan-06 1140 1.4 0.6 0.037 0.003 12.3 24-Feb-06 1032 0.6 0.6 0.093 0.001 93 23-Mar-06 1015 0.5 0.5 0.047 0.001 47 19-Apr-06 1058 0.5 0.3 0.048 0.004 12 CRC302908 30-Jan-07 1336 2.1 0.4 0.09 0.005 18 28-Feb-07 1428 0.8 0.3 0.15 0.005 30 27-Mar-07 1515 0.7 0.2 0.029 0.002 14.5 19-Apr-07 1035 0.5 0.4 0.012 0.002 6 Median Summer 05 1.2 0.2 0.055 0.002 15.5 1.1 Median Summer 06 0.55 0.55 0.0475 0.002 29.7 1.4 Median Summer 07 0.75 0.35 0.0595 0.0035 16.3 1.5 Median overall 0.8 0.3 0.048 0.002 15.5 1.1 Source: Lake Pukaki mid lake at southern end Site No:CRC304908 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC304908 24-Jan-06 1217 7 0.5 0.034 0.003 11.3 24-Feb-06 1130 6.9 0.3 0.069 0.001 69 23-Mar-06 1045 6.2 1 0.028 0.001 28 19-Apr-06 1140 4.4 0.7 0.058 0.003 19.3 CRC304908 30-Jan-07 1258 12 0.4 0.053 0.021 2.5 28-Feb-07 1505 8.7 0.2 0.11 0.005 22 27-Mar-07 1440 8.1 0.1 0.044 0.011 4 19-Apr-07 1000 9.1 0.2 0.013 0.004 3.25 Median Summer 06 6.55 0.6 0.046 0.002 23.7 1.4 Median Summer 07 8.9 0.2 0.0485 0.008 3.6 1.6 Median overall 7.55 0.35 0.0485 0.0035 15.3 1.4



Source: LAKE OHAU CENTRE, SURFACE Site No:CRC302909 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC302909 24-Jan-06 1230 1.4 0.6 0.022 0.002 11 24-Feb-06 1135 0.2 0.3 0.069 0.001 69 23-Mar-06 1050 0.4 1.1 0.025 0.001 25 19-Apr-06 1150 0.3 1.1 0.076 0.003 25.3 CRC302909 30-Jan-07 1249 1 1 0.15 0.004 37.5 28-Feb-07 1515 2.2 0.4 0.1 0.005 20 27-Mar-07 1435 0.8 0.1 0.068 0.003 22.7 19-Apr-07 950 0.4 1.1 0.015 0.001 15 Median Summer 06 0.35 0.85 0.047 0.0015 25.2 1.4 Median Summer 07 0.9 0.7 0.084 0.0035 21.3 1.9 Median overall 0.6 0.8 0.0685 0.0025 23.8 1.8 Source: Lake Benmore Centre- northern arm Site No:CRC304907 Site ID Date Time TURB Chl a TN TP TN:TP Overall TLI CRC304907 24-Jan-06 1235 0.4 0.2 0.024 0.001 24 24-Feb-06 1140 0.5 0.7 0.072 0.001 72 23-Mar-06 1105 0.8 0.7 0.026 0.001 26 19-Apr-06 1200 0.5 1 0.064 0.003 21.3 CRC304907 30-Jan-07 1240 2.6 0.7 0.051 0.006 8.5 28-Feb-07 1525 1.1 0.6 0.074 0.005 14.8 27-Mar-07 1425 1.3 0.2 0.015 0.003 5 19-Apr-07 940 3.9 0.5 0.02 0.002 10 Median Summer 06 0.5 0.7 0.045 0.001 25 1.1 Median Summer 07 1.95 0.55 0.0355 0.004 9.25 1.5 Median overall 0.95 0.65 0.0385 0.0025 18.1 1.4 NTU ug/L mg/L mg/L mg/L

canterbury high country lakes water quality monitoring programme

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