Irrigation Leader
Aerial photo of Sheffield Reservoir. A square body of water surrounded by green grass.
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Sheffield Reservoir Another Milestone for the Central Plains Water Enhancement Scheme

With the recent completion of the Sheffield Reservoir, Central Plains Water Limited (CPWL) is realizing the next stage of its water enhancement plan for a section of underserved lands in New Zealand’s Canterbury Plains. The newly constructed reservoir is a lynchpin of the Sheffield Scheme, which will introduce surface water irrigation to farmers in the area for the first time. As part of the larger Central Plains Water Enhancement Scheme, the Sheffield Scheme is part of the greater effort to provide surface water irrigation to the surrounding 148,263 acres of land within the Canterbury Plains.

Beginning in December 2016, CPWL began working on bringing water to the region’s high-quality soils that have unreliable rainfall while avoiding significant costs associated with traditional water pumping. Prior to the introduction of surface water, farmers who wished to irrigate their crops had to drill up to 492 feet deep to tap into groundwater at great expense.

CPWL contractors designed two sources for the Sheffield Reservoir. Using the existing stock water network system operated by the Selwyn District Council, CPWL is directing water from the Kowai River into the new reservoir. In addition, CPWL constructed a river intake and single large pump station on the bank of the Waimakariri River to transfer 2 cubic meters of water a second into the reservoir.

In a mere 10 months from the start of construction, CPWL contractors constructed the river intake, a reservoir, and a 30-kilometer pipe distribution network. The closed system does not lose water to evaporation or ground infiltration during transport, making the Sheffield Scheme efficient and reliable.

Today, the new, fully lined reservoir covers an area close to 74 acres and is approximately 28 feet deep. All in all, the reservoir will hold 2 weeks of storage for the 10,625 acres it supports. Once the water is collected, a network of high-density polyethylene pipes will distribute 4 millimeters of the stored water a day to farmers. The scheme will also provide water for stock water, rural fire, and supplemental domestic village water supplies.

While not as large as the other elements of the Central Plains Water Enhancement Scheme, the reservoir is enhancing agriculture in the area. Farmers in the area have traditionally grown ryegrass, peas, corn, carrots, potatoes, radish seed, barley, and wheat; however, yields had been variable. The new water is expected to stabilize the area’s grain production. Some winter grazing and dairy farms also operate in the area. Additionally, farmers who have typically raised sheep now have an opportunity to convert their farms to dairy farms due to the water the scheme provides.

Overall, the water supply stability provided by the new surface water irrigation system is fostering new agricultural opportunities; and local stakeholders and CPWL continue to look for new efficiencies for the Sheffield system and opportunities to further expand irrigation within the Central Plains.