Water is diverted from the Waitaki River into Bortons Pond, south of Duntroon. Canals deliver the water to two primary pump stations, each with four huge pumps that lift water to a head pond 145 m above the Waitaki Valley. From the head pond, gravity pipelines takes water into the Waiareka and Kakanui Valleys, with the scheme extending as far south as Herbert. Across the 65,000 ha command area, water is distributed to farmers via 220km of pipelines and is pressure boosted where necessary via 14 booster pump stations.
16
Pump stations
220
KM + of pressurised pipeline
~$165
Million estimated infrastructure value
Bortons pond was built in the 1970s as the intake area for the Lower Waitaki Irrigation Scheme. The intake gates are capable of allowing up to 27 cumecs (27,000 litres per second) of water from the Waitaki River into the pond. Of this, 19 cumecs are for the Lower Waitaki Irrigation Company and 8 cumecs are for NOIC. This allocation is sufficient for NOIC to issue a total of 20,000 shares, which in turn allows irrigation of up to approximately 26,000 hectares (based on an average use of 1.3 hectares per share).
Canals & Pressure Mains
A 550 m long ‘Still Arm’ canal, crossing under State Highway 83, carries the water from Bortons pond to a large pump station at Black Point (PS1). A 600 m long, 1.8 m diameter epoxy coated steel pipe carries the water from PS1 up to a second 1.9 km long canal, a vertical lift of 84 m. The canal is split by a road crossing which is also the regional boundary between Canterbury and Otago. The two canal sections are referred to as the Canterbury and Otago canals respectively. The Otago canal delivers water to a second large pump station at Camp Hill (PS2). From here, a 2.8 km long pressure main, with a vertical lift of 61 m, delivers the water to an operational storage pond (the Head Pond) beside the Ngapara Georgetown Road.
Head pond
The Head Pond holds 90,000 cubic meters of water (90 million litres) and has a surface area of 3 ha. The pond is lined with high density polyethylene (HDPE) liner. Sensors in the canals and at the head pond enable PS1 and PS2 to respond to irrigation demand, automatically starting when water levels drop.
PS1 houses four large axial split case irrigation pumps and a smaller stock water pump system. The pumps are powered by 2.5 - 2.8 MW (3350 HP) water-cooled electric motors, with an average electricity use equivalent to around 2,000 households per pump. Each pump can deliver 2000 litres (2 tonnes) of water per second, approximately 70 Olympic swimming pools per pump per day, through a vertical lift of 84 m. These pumps were reputedly the largest in the Southern hemisphere at the time of construction. PS2 contains four similar axial split case irrigation pumps, each 2.2 MW.
Water is distributed to farmers via an underground pressurised pipe network. The distributary works include over 220 km of pipeline and associated valves and structures. Pipelines traverse privately owned land and Waitaki District Council road boundaries. The distribution network comprises 20 area-based pipelines and 14 booster pump stations, with the scheme extending from Duntroon to as far south as Herbert.
There are two large pressure reducing valves (PRVs) located on the scheme designed to lower the pressure for safety, leak reduction and capital cost savings (through reduced pipe pressure rating). The PRV stations have a safety relief valve that discharges water in the event of a pressure surge, protecting the downstream network.
Water is delivered to the farmer’s property via an offtake box, which contains an isolating valve, a pressure reducing valve and a flow meter. The offtake regulates the pressure and the amount of water able to be delivered to individual properties in accordance with their share ownership and on-farm system requirements. There are currently over 200 offtakes on the scheme. The total volumetric flow taken by each offtake is measured continuously by a mechanical meter and is reported and checked each month.
In addition to the piped system, water is also augmented to the Waiareka Creek for abstraction by shareholders further down the catchment, and to provide a minimum environmental enhancement flow of 100 L/s. The environmental enhancement flow is required by the resource consents held by NOIC and is intended to improve the in-stream environmental values of the creek.
NOIC has a permit to discharge up to 1 cumec of water to the creek. Water is currently discharged from the Waiareka line at a discharge structure located near Pig Island Rd. Creek shareholders are required to order water through an established protocol to ensure that NOIC can manage flows within the creek. A flow monitoring device is located at Rocklands Rd and is linked to the Otago Regional Council (ORC) via telemetry to ensure that a minimum flow of 100 L/s is maintained during the irrigation season.
All water taken from the creek is separately metered and telemetered directly to the ORC.
Disclaimer: This GIS mapping is illustrative and indicative only and you must independently verify its accuracy before taking any action in reliance upon it, i.e. the actual locations of any pipes must be physically verified on site by a qualified surveyor prior to any design, construction or other works taking place.