Opuha Dam Partnership

May 2010

The outcome of the Opuha Dam community water storage scheme

The Opuha Dam community water storage, irrigation, electricity and amenity scheme built in 1998 for $27 million is estimated to have increased farm output by $124 million annually and created 500 jobs in South Canterbury. Large water users include organic dairy farmer Tom Lambie and large-scale arable and vegetable farmer Tony Howey, both excellent examples of the production benefits of irrigation water in a district (Pleasant Point) which has no other river or groundwater sources and which was prior to 1998 regularly in drought.

Farmers in the Opuha, Totara Valley, Pleasant Point and Levels districts of South Canterbury formed a company and gained resource consent to build a dam on the Opuha River above Fairlie (Ashwick Flat location) to form a 710ha lake, store water from annual rainfall events, generate electricity with a water turbine, provide reticulated water for irrigation over 16,000ha of South Canterbury plains and foothills, provide potable water for Timaru (domestic and industrial supply)and to enhance the in-stream flows of the Opihi River, which was prone to running dry during the summer. Both Lake Opuha and the Opihi are now excellent recreational facilities, including boating, swimming and fishing.

The actual project itself consists of a 50 metre high earth dam, with a single Kavenar turbine and a lake storing over 100 million cubic metres of water.

Annual recharge of the dam requires two significant rainfall events a year of perhaps 75mm over three or four days in the catchment area. Failure to get that rain is forecast as a one in 20 years event. A proposal to augment the rainfall recharge with snowmelt water from Lake Tekapo, via pipeline through Burke Pass, is under consideration.

Former Federated Farmers national president Tom Lambie has organically dairy farmed in the Totara Valley near Pleasant Point since 1982, when the family had 89ha, of which 60ha was irrigated from the Opihi. Interruptions to water supply were common, because of lack of rainfall and drought.

Spencerfield organic dairy farm in the Totara Valley (owned by the Lambie family) is 410ha, of which 380ha is irrigated from the Opuha Dam, on the Totara Valley scheme under the South Canterbury Farmers Irrigation Society. The main irrigation network is 300 sprinklers connected to long laterals, supplemented with a new centre-pivot. It takes two people two hours to move all of the sprinklers every day. Tom has introduced GPS positioning of the sprinklers, to ensure even water coverage. He will provide details of the water coverage each season under each irrigation type and the milk production per cow and per hectare.

Alpine Fresh arable farming company was formed in 1996 by the managing director, Tony Howey. Shareholders include the immediate Howey family. The company employs 13 staff, and farms 900 ha in several blocks, mainly in the irrigated Levels area on alluvial silt loams. Crops grown this year are onions (70ha), potatoes (110ha), peas (82ha), wheat (313ha), carrots (103ha), and seed crops of prairie grass (20ha), hakari (27ha), browntop (33ha) and ryegrass (69ha). Smaller areas are used for growing carrot seed and brassica seed. Tony also has 46ha of blackcurrants. As a comparison for showing the value of irrigation water, dryland wheat yields are around 4T/ha in an unfavourable year, whereas Tonys irrigated wheat averages 10T/ha. Water is delivered to property boundaries via the Levels Plain Irrigation Co (LPIC) canal system. This water is gravity feed from the Opihi river which in turn is linked to the Opuha Dam. The land the Howeys farm has been abstracting water from the Opihi since the 1940s. With minimum flow restrictions being imposed with the Opihi River Management Plan the ability to irrigate with any reliability was going to become a major obstacle in the 1990s. The LPIC was therefore a very strong supporter of the Opuha project and contributed proportionally more initially than other farmers to show that level of support. As all the infrastructure was all in place for the LPIC area the water from the Opuha Dam was used immediately. When Tony bought the first land on the Levels Plain all the irrigation was done with big guns, and a lot of the water was reticulated with hand shift aluminum pipe. All the areas that could be developed with lateral or pivot systems have been developed and now account for approx 80% of the area with the balance using hard hose big guns. Monitoring of water use employs a combination of neutron probes, telemetered gypsum blocks and a spade. A spade is often the best as get to see and feel the soil. At present only four paddocks are telemetered next year Tony plans to have all paddocks telemetered. He also plans to check the irrigation efficiencies of pivots and laterals as discrepancies between rain gauges and programmed application rates are apparent.

What is the value of the Opuha water to the farmers and to the regional economy? Tony Howey says the very light free draining soils on the Levels Plain without irrigation would only be good for extensive livestock production. A valid comparison is therefore approx $13000/ha gross farm revenue for vegetable crops compared to around $500/ha for dryland livestock on light soils. As the input costs for vegetable growing are very high, the majority of the gross farm revenue is spent in the community producing the crop. On this basis the increase that vegetable production under irrigation over dryland livestock is in the order of 26 times and if the multiplier effect is applied to this of 8X (Harris Report) then the economic benefit of the water from the Opuha to the wider community from vegetable production is more like a factor of 200 over landuse options without water. Water and delivery charges on LPIC total $180/ha. With all the fixed and variable costs the total is around $1200 per hectare or $4 to $6 per mm/ha of water applied. The Harris report (2005) showed irrigated land with gross revenue $2073/ha, versus dryland of $862, being a ratio in favour of irrigation of 2.4 times. Cash farm surplus was $208/ha for dryland and $570 for irrigated. For the entire economy of the region each 1000ha of irrigation adds $7.7 million in output, 30 full-time equivalent jobs, $2.5 million in value added and $1.2 million in household income. Multiply these figures by 16 for the total irrigated area and the economic impact (2005 figures) is $123 million additional gross output and 480 jobs. Opuha Dam is now cited as an example of how a community funded water project can add a considerable multiplier to the primary production of a district or region. Tom Lambie said the original cost of the dam is kept by Opuha Water Co on interest-only loan as the infrastructure has inter-generational benefits.

Alpine Fresh has been involved in growing onions since 1997, and built the packhouse at Washdyke to handle the first crop of onions to be cured with the UK shed method. Alpine Fresh is now a one-third shareholder in Southern Packers Ltd, formed in 1999 by local growers and exporters, which grades, packs and exports onion to the UK, Europe and Asia and supplies the local market. Alpine Fresh operates a 3000 mt capacity bulk store at Washdyke, located behind Southern Packers. The current shareholders in Southern Packers are Murray Turley, Dean Pye, and Tony Howey. The main reason for forming the company was to provide a means to prepare the crop for export. Colin Tarrant is the current manager. Southern Packers Ltd is a significant local employer and owes its existence to the Opuha water.