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Kakanui Rachel Ozanne, Water Quality Scientist
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Long-term (SOE) monitoring
• Water quality• ~78 sites• Monthly sampling
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Water clarity and turbidity
• Clarity – how far you can see underwater
• Turbidity – how cloudy water is
Photo: Mark Gall, NIWA
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Nutrients – Nitrogen and Phosphorus
Sources – livestock, fertiliser, effluent
•Reduces recreational values•Smothers gravel for fish spawning & invertebrates•Causes oxygen and pH fluctuations•Traps sediment• Clogs water intake screens• Growth of algae (+ toxic algae)
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Bacteria (E.coli)Sources in freshwater:• Livestock (and effluent)• Untreated sewage discharges • Septic tanks• Surface run-off• Bird colonies• Dogs & waterfowl
Risks to human health:• Contaminated groundwater
and drinking wells• Recreational activities
impacted• Mauri values impacted
Giardia
Cryptosporidium
Campylobacter
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Waiareka Creek
SOE water quality monitoring - Kakanui
Kauru River at Ewings
Kakanui at McCones
Kakanui River at Clifton
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PC6A Schedule 15 results (2010 to 2015)
Site Name NNN DRP E.coli
0.075 mg/ 0.01 mg/l 260 cfu/100mlKakanui at Clifton 0.037 0.042 200
Kakanui at McCones 0.29(2.8 x over limit)
0.003 130
Kauru at Ewings 0.026 0.006 180
Waiareka Creek 0.428(4.7 x over limit)
0.144(13.4 x over limit)
488(0.8 x over limit)
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High N and P = algae growth
Kakanui River - upper Kakanui River - lower
Kakanui Estuary
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Nitrogen
Significant increase• Clifton• McCones• Waiareka Creek
Trends in water quality
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Bacteria (E.coli) (2004 to 2015)
Significant increase• Waiareka Creek• McCones
Trends in water quality
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Groundwater
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Water (quality) entering aquifer from river
Water (quality) entering river from aquifer
•Due to the highly permeable stony soils, what is put on the
ground goes straight into groundwater.
•What goes into the groundwater eventually makes
it into the River.
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PC6A and the Kakanui –Overseer N limit
20kg N/ha
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Continuous nitrate measurements
Water quality monitoring - fortnightly13 x surface water sites11 x groundwater bores
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Summer 2015/15 - Swimming – Estuary
1/12
/201
4
8/12
/201
4
15/1
2/20
14
22/1
2/20
14
29/1
2/20
14
5/01
/201
5
12/0
1/20
15
19/0
1/20
15
26/0
1/20
15
2/02
/201
5
9/02
/201
5
16/0
2/20
15
23/0
2/20
15
2/03
/201
5
9/03
/201
3
17/0
3/20
15
24/0
3/20
15
31/0
3/20
15 *0
200
400
600
800
1000
Result Action/Red Level Alert/Amber Level
En
tero
cocc
i/10
0ml
High flows and rainDate Result
Enterococci/100mlTotal rainfall (mm)At Clifton Falls
Flow (cumecs)At McCones
9/3/15 580 0mm (9th), 1mm (8th), 2mm (7th) 7.78417/3/15 460 0mm (17th), 0mm (16th), 0mm (15th), 14.5mm (14th) 1.07324/3/15 320 0mm (24th), 7mm (23rd), 5mm (22nd) 1.96331/3/15 800 0mm (31st), 8mm (30th), 1mm (29th) 3.862
http://www.orc.govt.nzhttp://www.lawa.org.nz/
In the Kakanui River flows above 1.29 cumecs indicate substantial rainfall has fallen in the catchment
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Summer 2014/15 – Swimming - Clifton Falls
1/12
/201
4
8/12
/201
4
15/1
2/20
14
22/1
2/20
14
29/1
2/20
14
5/01
/201
5
12/0
1/20
15
19/0
1/20
15
26/0
1/20
15
2/02
/201
5
9/02
/201
5
16/0
2/20
15
23/0
2/20
15
2/03
/201
5
9/03
/201
5
17/0
3/20
15
24/0
3/20
15
31/0
3/20
15 *0
500
1000
1500
2000
2500
3000
Result Action/Red Level Alert/Amber Level
E.c
oli
/100
ml
Date
ResultE.coli/100ml Total rainfall (mm)
At Clifton FallsFlow (cumecs)At Clifton Falls
22/12/14 2600 10.5mm (22nd), 0.5mm (21st), 0.5mm (20th) 2.696
12/1/14 610 4.5mm (12th). 0mm (11th), 0mm (10th) 0.483
2/2/15 990 0mm (2nd), 3.5mm (1st), 0.5mm (31st) 1.613
9/2/15 440 0mm (9th), 0mm (8th), 0.5mm (7th) 1.246
In the Kakanui River flows above 1.29 cumecs indicate substantial rainfall has fallen in the catchment
http://www.orc.govt.nzhttp://www.lawa.org.nz/
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Kakanui Estuary Modelling
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Estuary model
NIWA Model to predict• What nutrient loads will deliver
acceptable algal growth?• What flows affect estuary health? • Bathymetry survey• Continuous water levels at
three locations• Weekly water quality
monitoring
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Model results – Nutrient concentrations
Nutrient concentrations
• Closed mouth – near uniform
• Open mouth - nutrient concentrations are highest in the upper reaches of the estuary, and decrease towards the mouth
• High concentrations of nitrogen in Waiareka Creek is apparent.
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Model results –
Implications for estuaryAlgae samples collected from the Kakanui Estuary indicated moderate - high levels of nitrogen availability, but light and temperature also affect growth of algae
Draft target ranges therefore suggested for• Algae nitrogen content• Water nitrogen concentrations
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Estuary mouth
Estuary mouth
• Closed mouth increased nitrogen in estuary by 25-40% (compared to the open mouth scenario)
• Nitrogen concentrations predicted for an open mouth would result in moderate to high growth rates of algae.
• Opening the mouth is not likely to cause significant reduction in algae growth without reductions in nutrient inputs from the Kakanui River and Waiareka Creek.
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River loads
• At low flows Waiareka Creek contributes a large proportion (>50% ) of the nitrogen loading to the estuary.
• As Kakanui River flow increased, nitrogen concentrations in the estuary reflected that of the river.
• Nitrogen concentrations in the estuary would have to reduce to <0.07 mg/l to reduce algae growth
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River loads
OPEN SURVEYED NARROW
TARGET DIN at mean summer flow
<0.096 mg/l <0.084 mg/l <0.070 mg/l
Kakanui River Waiareka Creek
Current nitrogen 0.29 mg/l 0.428 mg/l
This compares to current dissolved nitrogen concentrations of :
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Working back up the catchmentHow does this estuary target fit with the PC6A river limit of 0.075mg/l
• ORC had set a limit of 0.075 mg/l in the Kakanui River in order to prevent algae growth.
• It looks like this was correct.
OPEN SURVEYED NARROW
TARGET dissolved nitrogen (mean summer flow)
<0.096 mg/l <0.084 mg/l <0.070 mg/l
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SUMMARY
ORC monitoring shows :• increasing nitrogen concentrations• increasing bacteria concentrations• high nutrient loads from Waiareka Creek• Swimming usually OK in estuary
NIWA model shows:• Uniform mixing when mouth closed• Target of <0.070mg/l N for low algae growth
ORC limit is 0.075mg/l N in Kakanui River
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Otago Regional Council70 Stafford StreetPrivate Bag 1954Dunedin
Phone: 03 474-0827
Free: 0800 474 082
Fax: 03 477-9837