The scheme takes water from the Waitaki River, pumps it from Borton’s Pond (at the intake of the Lower Waitaki Irrigation Scheme) into a canal, and then a second pump station lifts the water to the Head Pond. Three pumped side lines take water from the canal to the Duntroon Line, Glen Settlement and Tilverstowe Lines, and to the Head Pond. From the Head pond a gravity line takes approximately two thirds of the 4 cumecs available down into the Waiareka Valley. A major attraction of this scheme is that the water is delivered under pressure to most farms and in almost every case there is no further pumping needed on the farms.
Up to one cumec of water is consented to be delivered into the Waiareka Creek and this water is used by irrigators further down the Creek. A condition of the resource consent was that NOIC puts an additional 100 litres per second into the Waiareka Creek to improve the habitat of the Creek; this is a major environmental benefit for the district.
Delivery to Farmers Properties
A share provides 0.4 litres per second per hectare which is equivalent of 25mm per week – or almost an inch per week. Water is delivered to the farmers property via an offtake box which is part of the scheme infrastructure. This offtake contains an isolating valve and a pressure reducing valve and flow meter which regulates the pressure and the amount of water able to be delivered to individual properties.
Water Take from Waiareka Creek
Secondary pumping of water is undertaken from the Waiareka Creek to properties serviced from the Waiareka Creek distribution channel provided by the Waiareka Creek to adjacent properties.
Borton’s pond was created as the intake area for the Lower Waitaki Irrigation Scheme when it was built in the 1970’s. The intake gates are capable of allowing up to 27 cumecs ( 27,000 litres per second) into the pond. Of this 19 cumecs are for the Lower Waitaki Irrigation Company and 8 cumecs are for the North Otago Irrigation Company (NOIC). This is enough water for NOIC to irrigate 20,000 hectares.
Pump Station 1 Adjacent to State Highway 83
The pump station is currently set up for stage one with two main motors and pumps and a smaller stock water supply. The water cooled electric motors are 2.5megawatts each 3350 horse power. Each pump is capable of delivering 2 cumecs (2 tonnes) of water per second. This pump is reputedly the biggest in the Southern hemisphere.
Substation at Pump Station 1 Site
The substation is fed with electricity from the national grid on the north side of the Waitaki River and converts the 110kv supply to 11kv to operate the pumps at the Pump Station 1 (PS1). Transmission lines distribute this electricity to pump station 2 and to pump stations on the Duntroon line. The substation is a partnership between Network Waitaki Ltd and NOIC.
Water Transfer to the Head Pond
A 1.8metre diameter epoxy covered steel pipe takes the water from PS1 up the hill to a 2 kilometre long canal to Pump Station 2 (PS2). From PS2 the water is pumped through a 2.8 kilometre long pipe line to the Head Pond.
The first Duntroon pump station is at the edge of the canal beside Smillies Road. This pump station pumps water to two further pump stations spread over 13 kilometres of pipeline on the Duntroon line. These three pump station are interconnected by fibre optic cables and telemetry to ensure that they operate with each other when water is required by farmers.
The Head Pond holds 30,000 cubic meters of water (30 million litres). The pond is lined with high density polyethylene (HDPE) liner. Sensors at the pond enable pump stations 1 and 2 to automatically fill when the level drops.
Glenn Settlement Tilverstowe Pump Station
Glen Settlement Tilverstowe pump stations draw water from Head Pond and this pressurised water flows through pipes along the Glenn Settlement line and the Tilverstowe line.
From the Head Pond water flows under gravity down the Waiareka line as far as Pig Island Road. Water is distributed to farmers via the Five Forks line, Burnside line and the Windsor Park line. There is 75kms of pipe line to provide water to the farmer’s boundaries.
Discharge Structure to Waiareka Creek
Up to 1000 litres per second (1 cumec) can be fed into the Waiareka Creek. The discharge structure below Pig Island Road allows for up to 700 litres per second to be discharged into the creek. Water in the Waiareka line at this point is under very high pressure and the discharge dissipates this pressure before it is released into the Waiareka Creek. NOIC's consent requires the company to maintain the flow in the Waiareka Creek at a minimum of 100 litres per second.