1. Kakanui Rachel Ozanne, Water Quality Scientist

2. Long-term (SOE) monitoring Water quality ~78 sites Monthly sampling

3. Water clarity and turbidity Clarity – how far you can see underwater Turbidity – how cloudy water is Photo: Mark Gall, NIWA

4. 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)

5. 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

6. Waiareka Creek SOE water quality monitoring - Kakanui Kauru River at Ewings Kakanui at McCones Kakanui River at Clifton

7. PC6A Schedule 15 results (2010 to 2015) Site NameNNNDRPE.coli 0.075 mg/0.01 mg/l260 cfu/100ml Kakanui at Clifton0.0370.042200 Kakanui at McCones0.29 (2.8 x over limit) 0.003130 Kauru at Ewings0.0260.006180 Waiareka Creek0.428 (4.7 x over limit) 0.144 (13.4 x over limit) 488 (0.8 x over limit)

8. High N and P = algae growth Kakanui River - upperKakanui River - lower Kakanui Estuary

9. Nitrogen Significant increase Clifton McCones Waiareka Creek Trends in water quality

10. Bacteria (E.coli) (2004 to 2015) Significant increase Waiareka Creek McCones Trends in water quality

11. Groundwater

13. 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.

14. PC6A and the Kakanui – Overseer N limit 20kg N/ha

15. Continuous nitrate measurements Water quality monitoring - fortnightly 13 x surface water sites 11 x groundwater bores

16. Summer 2015/15 - Swimming – Estuary High flows and rain Date Result Enterococci/100ml Total rainfall (mm) At Clifton Falls Flow (cumecs) At McCones 9/3/155800mm (9 th ), 1mm (8 th ), 2mm (7 th )7.784 17/3/154600mm (17 th ), 0mm (16 th ), 0mm (15 th ), 14.5mm (14 th )1.073 24/3/153200mm (24 th ), 7mm (23rd), 5mm (22nd)1.963 31/3/158000mm (31 st ), 8mm (30 th ), 1mm (29 th )3.862 http://www.orc.govt.nz http://www.lawa.org.nz/ In the Kakanui River flows above 1.29 cumecs indicate substantial rainfall has fallen in the catchment

17. Summer 2014/15 – Swimming - Clifton Falls Date Result E.coli/100ml Total rainfall (mm) At Clifton Falls Flow (cumecs) At Clifton Falls 22/12/14 2600 10.5mm (22 nd ), 0.5mm (21 st ), 0.5mm (20 th )2.696 12/1/14 610 4.5mm (12 th ). 0mm (11 th ), 0mm (10 th )0.483 2/2/15 990 0mm (2 nd ), 3.5mm (1 st ), 0.5mm (31 st )1.613 9/2/15 440 0mm (9 th ), 0mm (8 th ), 0.5mm (7 th )1.246 In the Kakanui River flows above 1.29 cumecs indicate substantial rainfall has fallen in the catchment http://www.orc.govt.nz http://www.lawa.org.nz/

18. Kakanui Estuary Modelling

19. 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

20. 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.

21. Model results – Implications for estuary Algae 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

22. 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.

23. 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

24. River loads OPENSURVEYEDNARROW TARGET DIN at mean summer flow <0.096 mg/l<0.084 mg/l<0.070 mg/l Kakanui RiverWaiareka Creek Current nitrogen0.29 mg/l0.428 mg/l This compares to current dissolved nitrogen concentrations of :

25. Working back up the catchment How 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. OPENSURVEYEDNARROW TARGET dissolved nitrogen (mean summer flow) <0.096 mg/l<0.084 mg/l<0.070 mg/l

26. 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

27. Otago Regional Council 70 Stafford Street Private Bag 1954 Dunedin Phone: 03 474-0827 Free: 0800 474 082 Fax: 03 477-9837