Kakanui Rachel Ozanne, Water Quality Scientist

Long-term (SOE) monitoring

• Water quality• ~78 sites• Monthly sampling

Water clarity and turbidity

• Clarity – how far you can see underwater

• Turbidity – how cloudy water is

Photo: Mark Gall, NIWA

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)

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

Waiareka Creek

SOE water quality monitoring - Kakanui

Kauru River at Ewings

Kakanui at McCones

Kakanui River at Clifton

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)

High N and P = algae growth

Kakanui River - upper Kakanui River - lower

Kakanui Estuary

Nitrogen

Significant increase• Clifton• McCones• Waiareka Creek

Trends in water quality

Bacteria (E.coli) (2004 to 2015)

Significant increase• Waiareka Creek• McCones

Trends in water quality

Groundwater

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.

PC6A and the Kakanui –Overseer N limit

20kg N/ha

Continuous nitrate measurements

Water quality monitoring - fortnightly13 x surface water sites11 x groundwater bores

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

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/

Kakanui Estuary Modelling

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

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.

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

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.

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

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 :

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

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

Otago Regional Council70 Stafford StreetPrivate Bag 1954Dunedin

Phone:  03 474-0827

Free: 0800 474 082

Fax:       03  477-9837