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Presentation to Lower Opihi Catchment Group 23rd October 2014 Tony McCormick – CEO Opuha Water Ltd 1 River Operations Initiatives for Water Quality Management.

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Presentation on theme: "Presentation to Lower Opihi Catchment Group 23rd October 2014 Tony McCormick – CEO Opuha Water Ltd 1 River Operations Initiatives for Water Quality Management."— Presentation transcript:

1 Presentation to Lower Opihi Catchment Group 23rd October 2014 Tony McCormick – CEO Opuha Water Ltd 1 River Operations Initiatives for Water Quality Management

2 Presentation Overview Opuha – scheme operation Water quality issues – River – Lake Flushing Flows Other Initiatives Conclusion 2

3 Scheme Overview Kakahu Scheme Totara Valley Scheme Lake Opuha Tengawai River Opihi River Opuha River Opihi River Fairlie Pleasant Point Hectares Kakahu 3200 Totara Valley 1766 Levels Plain 3296 Sutherlands 620 Above Dam 2100 Other 5018 Total Max Irrigation Flow 6.6 cumecs Levels Plain Scheme Sutherlands Scheme Saleyards Bridge (min flow measured) Timaru

4 4 Opuha Dam and lake. Power Station is below dam (lower centre of picture)

5 5 Next slide is the view from here, looking downstream

6 6 View downstream from dam showing regulating pond and downstream weir (top right of picture)

7 7 Fusible Embankment 700+ cumecs Fixed Spillway 80 cumecs Radial Gate 32 cumecs View at downstream weir where water release to river is controlled

8 8 Radial Gate Spillway Fusible Embankment View of downstream weir: L to R – Gate (32 cumecs); Spillway (80 cumecs); Fusible Embankment (flood flow ~700+ cumecs)

9 Opuha Dam & Power Station Operation Dam50m high Lake710ha, 72 million m 3, 22m range Power Station 50m head, 7MW, 16 cumecs Annual Generation26 GWh Downstream Weir cumecs Dam Lake Opuha Power Station Opuha River 370m m --- Downstream Weir Regulating Pond level fluctuates with power station operation. River flow is maintained at steady rate through gate at downstream weir 9 Regulating Pond

10 Opuha Dam & Power Station Operation Dam50m high Lake710ha, 72 million m 3, 22m range Power Station 50m head, 7MW, 16 cumecs Annual Generation26 GWh Downstream Weir cumecs Dam Lake Opuha Power Station Opuha River 370m m --- Downstream Weir Regulating Pond level fluctuates with power station operation. River flow is maintained at steady rate through gate at downstream weir 10 Regulating Pond

11 Water Quality Issues 11 River – Periphyton growth Didymo – nuisance Phormidium – toxic Water chemistry Lake – Inflows – nitrate and phosphorous ???? – Top of lake recreation (avian or bovine) ???? – Limnological natural water chemistry when low oxygen conditions exist manganese and iron

12 Flushing Flows – Key Locations Kakahu Scheme Totara Valley Scheme Lake Opuha Tengawai River Opihi River Opuha River Opihi River Fairlie Pleasant Point Levels Plain Scheme Sutherlands Scheme Saleyards Bridge (min flow measured) Timaru Skiptons (13km) (flow measured) Skiptons (13km) (flow measured) Confluence (26 km) Dam site Saleyards Bridge (42km) (flow measured) Saleyards Bridge (42km) (flow measured) SH1 Bridge (52km) (flow measured) SH1 Bridge (52km) (flow measured)

13 2014 v

14 Flow Attenuation 14

15 River Mouth – Opening & Timing 15

16 16 Periphyton Removal

17 17 Periphyton Removal Didymo removal 76%, 85% and 89% Improved on %, 12% and 40%

18 18 River Temperature

19 Other Initiatives 19 River – Operations Adaptive flow regime – Investigations Enhanced monitoring (long term programme) Exposure/Drying Sand feeding Dissolved iron Lake – Operations Aeration enhancement

20 Conclusion 20 No silver bullet Multi faceted issue On going investigations improve understanding and enable … Effective adaptive operations and management


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