Article posted on 20/01/2015
Reliable irrigation water for landowners in the Manuherikia catchment and a healthier river in the valley are the aims of the Manuherikia Catchment Water Strategy Group.
Formed in 2011, the group of 40 people, in either executive or advisory roles, comprises representatives of the existing irrigation companies in the catchment, local farmers, both large and small, the district and regional councils, Kai Tahu ki Otago, the Central Otago Environmental Society, Forest and Bird, the Department of Conservation and Fish and Game. The group is chaired by Upper Clutha high country merino sheep farmer, Allan Kane, who has a long history of spearheading agricultural and conservation initiatives.
The group, and its hydrological, ecological and geotechnical consultants, are investigating ways to increase water storage in the catchment, improve the distribution system to reduce water loss and the risk of seepage and runoff into waterways, and to increase flows in the Manuherikia River to provide a healthier habitat for aquatic life and recreational pursuits.
It is very important to the group that any infrastructure upgrade benefits the entire community and satisfies both agricultural and environmental needs.
An infrastructure upgrade is required as the Government has instructed regional councils to improve water quality and set minimum flows for rivers. Put simply, this means there will be less water for irrigation. Therefore, a change to spray irrigation, rather than the current flooding methods, is necessary as it uses substantially less water. Quite rightly, the rules have also tightened up on seepage and runoff from farms into waterways. Again, spray irrigation has a major advantage over flood irrigation, as it puts considerably less water onto the land. In addition, the “mining privilege” water rights which enable landowners to use flood irrigation will expire in 2021 and resource consents will be required instead.
At present, 10,000 hectares on the Manuherikia Valley floor have a reliable irrigation supply, depending on flows in the Manuherikia River and the amount of water stored in Falls Dam. The group is aiming to ensure these landowners have a more reliable water supply throughout the irrigation season. It is also hoping increasing the height of Falls Dam would mean up to another 15,000 hectares on the valley floor could be irrigated.
To enable this, the group is investigating the feasibility of raising Falls Dam and building two dams in the Ida Valley. These highly detailed feasibility studies are nearing completion and cost estimates for the upgrade are being developed. The initial estimates, made before the Canterbury earthquakes, put the cost at $70 million. New seismic strength standards have been introduced since the earthquakes, which have raised the estimate to $194 million. Engineers, who have a great deal of local and international expertise and experience in this field, are currently reviewing the plans on which the differing cost estimates are based and the group is confident the final cost estimate will be viable for landowners to commit to.