MCWSG media release, May 22 2014:
Manuherikia Valley landowners will be asked to decide in February how the catchment’s irrigation water should be used in the future.
The Manuherikia Catchment Water Strategy Group was formed in 2011 to help all parties reach an agreement. Since last year it has been investigating the following storage and distribution opportunities:
- Raising the existing Falls Dam, at the head of the Manuherikia Valley, by five, 15 or 27 metres.
- Building a dam at the head of the Ida Valley, which would be called the Mt Ida Dam.
- Upgrading the existing Manuherikia water race network, at the lower end of the Manuherikia Valley.
- Another option, to pipe water from Lake Dunstan, is considered unfeasible and has been disregarded.
Why is change necessary?
At present flood irrigation is most common in the valley, which involves damming the water races until they spill over the surrounding land. This system uses more water than is necessary and can lead to runoff and seepage of nutrients into waterways.
Strategy group chairperson, Allan Kane, said irrigation systems need to change for several reasons:
- The Government has instructed regional councils to improve water quality in waterways, and to set minimum flows on rivers – many of which are over-allocated to irrigators – to ensure healthy aquatic life and recreational opportunities.
- The Otago Regional Council’s Plan Change 6A, which came into effect on May 1, states landowners need to prevent runoff and seepage into waterways to ensure water quality. Other ORC plan changes are being developed to set minimum flows for rivers, including the Manuherikia River.
- The mining privilege water permits, which were given to gold miners and transferred to farmers when gold mining ceased, expire in 2021 and landowners will then need resource consent to take water.
Mr Kane said, in effect, the amount of water allocated to landowners is going to drop and the existing flood irrigation systems use significantly more water per hectare than spray systems.
“So, people who want to irrigate their land are going to have to invest in spray systems and, to make that worthwhile, we’re going to need storage dams in the Manuherikia Valley, so they have a reliable supply of water throughout the irrigation season. Our research shows there’s definitely no shortage of water in the valley, just a lack of storage.”
How much land would be irrigated?
Currently 25,000 hectares are irrigated in the Manuherikia Valley. Fifteen-thousand are irrigated throughout the irrigation season of spring, summer and autumn and 10,000 are only irrigated in spring and autumn as the supply reduces in summer.
Mr Kane said raising the Falls Dam by five metres would provide existing irrigators with water throughout the irrigation season. Raising it by 15 metres, building the Mt Ida Dam and upgrading the water race network would enable another 5000 hectares to be irrigated. Raising it by 27 metres, plus the other infrastructure, would mean another 11,000 hectares could be irrigated, taking the total amount of irrigated land in the Manuherikia Valley to 35,000 hectares. Only the valley floor would be irrigated.
Mr Kane said there would be significant economic benefits for Central Otago, both short term during construction of the infrastructure and long term as a result of more productive land.
The move from flood irrigation to spray systems, which use significantly less water, would reduce the risk of runoff and seepage into the Manuherikia River and the storage dams would mean sufficient river levels year-round, he said.
Fish and Game Otago chief executive, Niall Watson, who is a member of the strategy group, said consistently adequate river levels help maintain – or improve – water quality and provide a healthier environment for aquatic life and recreational pursuits. An ecological assessment to identify any species that may be affected by the project is underway.
The prefeasibility study indicated raising the Falls Dam by 27 metres would carry off-farm costs of about $5500 per hectare of land to be irrigated, for landowners in the upper Manuherikia Valley who did not currently irrigate. The cost for existing irrigators would be around $2500 per hectare of land to be irrigated. The on-farm costs would be about $4500 per hectare of land to be irrigated, depending on what type of irrigation system the landowner chose.
Mr Kane said the great advantage of the proposed Manuherikia Catchment scheme was that it would be gravity fed from the dams to the farm boundaries, meaning there would not be any ongoing off-farm pumping costs. While landowners on schemes in some other parts of the country paid between $600 and $1000 per hectare per annum in operating costs, the ongoing costs for Manuherikia Catchment landowners would be “very low.”
The work to date has been funded by the valley’s six irrigation companies, the ORC and the Government’s Irrigation Acceleration Fund. The infrastructure costs would be funded by landowners who wished to irrigate.
Mr Kane said the minimal operating costs meant sheep farming and cropping, including valuable seed crops, would be profitable, whereas in some other parts of the country farmers have been forced to convert to dairying or dairy support operations to cover the cost of irrigation.
Mr Kane said the ORC’s Plan Change 6A set nutrient limits which farmers must operate within, and it was likely the companies which held the consents to store and distribute water in the Manuherikia Valley would employ an environmental officer and require landowners to submit and abide by best-practice environmental plans, for example fencing waterways.
In addition to the ORC’s environmental monitoring, the companies would have the ability to “turn off the tap” to landowners who breached the rules, he said.
Mr Watson said Fish and Game believed the strategy group’s “group approach” is the best way to integrate water storage plans with good environmental outcomes for the Manuherikia River.
“Changes in land use pose a number of significant environmental challenges, but getting stakeholders together is the best way to manage those challenges effectively. It’s pleasing to see the commitment of landowners and irrigators to healthy rivers and streams,” he said.
A prefeasibility study of the options was carried out last year and released publicly. More detailed analysis is now underway. Information is being released as it becomes available and a full information package – including costs, anticipated financial returns, environmental limitations, and environmental impacts and how these would be mitigated – will be publicly released by Christmas. Potential investors will then have until the end of February to decide whether or not to proceed.
The interests represented on the strategy group include local landowners, irrigation companies, iwi, Forest and Bird, Fish and Game, Central Otago Environmental Society, Central Otago District Council, ORC, tourism organisations and power generation companies.
The strategy group is led by Mr Kane, a Merino farmer and keen fly-fisherman from Upper Clutha, who has a proven ability to bring people with varying viewpoints together to reach a satisfactory agreement. While not an irrigator himself, Mr Kane said he accepted the practice was becoming common throughout the country and that it brought great economic benefits. He wants the Manuherikia Valley to be on the “front foot” to receive these benefits, while ensuring any adverse impact on the environment is mitigated.