Meridian Energy would pay for a raft of measures to reduce the impact of a power scheme it wants to build on the lower Waitaki River.
That would lead to more human intervention, including clearing vegetation and using heavy machinery.
However, the Lower Waitaki River Management Society is opposing the scheme in the Environment Court, questioning the extent of effects and whether Meridian's proposed mitigation will achieve the desired results.
Meridian proposes to reduce the flow of the river between the Waitaki dam and Stonewall by up to 260cumecs, leaving monthly variable flows of between 110 and 150cumecs, for its north bank tunnel concept power scheme.
That will cause a wide range of effects, which it will mitigate by management plans, some of which will be adapted if unforeseen effects emerge during operation of the scheme.
Yesterday, extensive evidence was presented to the court about the effect of the scheme on the river and how that will impact on such things as river birds, erosion, wetlands, build-up of materials and braids.
The management plans, part of resource consent conditions, involve human intervention.
Some of these include clearing willow, broom and gorse to improve access to the river for anglers, reduce flooding and build-up of stones, shingle and gravel, reduce erosion and improve habitat for river birds.
This would benefit river birds by halting and substantially reversing the decline in their habitat.
Nesting birds would benefit from fewer fluctuations in river flows, but losses to predators would still be a problem.
Tributary outlets into the main river would be monitored and opened by machinery if they became blocked.
Flushing and flood flows would be released to mitigate effects such as a build-up of water plants, algae, sediment and shingle.
Lower flows could lead to more vegetation, and Meridian would finance greater clearance work not only in the stretch of the river affected by the scheme but to the river mouth.
That includes river margins as well as islands.
The number of braids between the dam and Stonewall could decrease from the current eight or nine to six or seven.
Ecologist Di Robertson estimated up to 60% of riparian wetlands and up to 15% of riparian braids could be lost if there was no mitigation.
That would affect up to 135ha of riparian wetlands and 10ha of riparian braids.
Meridian proposes a wetlands management plan to ensure terrace and riparian wetlands achieve no net losses and maintain ecological values, access to waterfowl hunting and traditional Maori food-gathering sites.
The plan was to retain and improve existing wetlands and create new wetlands.
Some existing wetlands were on private land and it was not known whether Meridian would get access.
However, Meridian owned "plenty of land" - about 3000ha in the lower Waitaki Valley - to achieve no net loss by creating new wetlands, she said.
The plan would be adaptive, setting base lines before the scheme was built and then ensuring its aims and objectives were met if unforeseen effects emerged during operation of the scheme.
Day 4
• The Meridian Energy Ltd north bank tunnel concept power scheme, costing up to $993 million, is to take up to 260cumecs of water from Lake Waitaki into a 34km tunnel between the Waitaki dam and Stonewall, with one powerhouse generating between 1100 and 1400GWh a year.
• Environment Canterbury (Ecan) granted four water-only resource consents in December for the power scheme.
• Five appeals were filed with the Environment Court by the Waitaki Protection Trust, Waitaki River Management Society, Ngai Tahu, Ngati-Mamoe Fishers People and Black Point farmer Garth Dovey.
• Ngai Tahu and its runanga, Mr Dovey and Ngai Tahu-Mamoe Fishers People have withdrawn appeals. Waitaki Protection Trust is now not opposing scheme.
• Interested parties: Central South Island Fish and Game Council, Waitaki First, Lower Waitaki Irrigation Company, North Otago Irrigation Company, Maerewhenua District Water Resources Company, Kokoamo Farm Ltd, K and D Farms Ltd, Wainui Station, Dugald MacTavish.
• Environment Court hearing June 22 to July 3, Oamaru; July 6 to 10, Christchurch. Hearing before Judge Jon Jackson, commissioners Dr Alex Sutherland and Helen Beaumont and deputy commissioner Ken Fletcher.
• Evidence yesterday: Effects on the geomorphology of the river and coast, wetlands.
