Opponents of Ngai Tahu's controversial Balmoral Forest farm conversion will have this week to convince commissioners not to grant resource consents for the $400 million project.
Ngai Tahu Farming Ltd (NTF) plans to convert 8596 hectares of the Hurunui forest with most - 7000 hectares - turned into irrigated dairy farming.
The proposal has attracted criticism, with one submission only of the 102 received by Environment Canterbury (ECan) supporting the project.
Commissioners Paul Rogers, Emma Christmas and Yvette Couch-Lewis heard expert evidence this month on the effect to the health of the Hurunui River, which borders the farm, and the Waiau River, from which it plans to take up to 5.2 cubic metres per second (cumecs) of water. The case is the first test of ECan's new water rules in the Hurunui and Waiau River Regional Plan.
The plan is five months old but already nutrient levels have been exceeded.
Nitrogen and phosphorus can cause harmful bacteria and algae. Under the plan, 963 tonnes of nitrogen a year is allowed in the State Highway 1 section of the river and 10.7 tonnes of phosphorus.
An ECan report said phosphorus levels were already exceeded, but this has been disputed by experts.
Nitrogen levels were not faring much better, with little room left for development even if NTF's consents were not granted, submitters said.
Other farms in the area waiting for resource consents told the commissioners they were concerned NTF was jumping the queue and no room would be left for them if consents were granted.
Ngai Tahu said it could control nitrogen levels through good farm management.
Environmental consultant Andrew Brough said in his evidence the soil at Balmoral did have "high vulnerability" of leaching nitrogen but was lower in terms of phosphorous.
"Where the vulnerability for leaching may be given as high it does not mean that leaching will occur. This will depend on farm management practices that are employed," he said.
Brough was confident nutrient modelling had overestimated leaching and said the use of Italian ryegrass had been shown to reduce leaching by 24 per cent compared to typical pasture.
The Canterbury District Health Board's concerns about increased levels of bacteria in the water were unlikely because soil had "good filtration", he said.
National Institute of Water and Atmospheric Research scientist Catherine Kilroy told commissioners increased risk of algae blooms was unlikely.
Nitrogen from Balmoral would enter the river downstream of the SH7 bridge which had no public access, she said.
This is not the first forest to farm conversion project NTF has embarked on. It is turning 6700 hectares of Eyrewell Forest into dairy farming.
Last month, NTF won the ECan Water Quality award for its farm near Oxford.
- The Press
Does the continued sale of New Zealand land to overseas interests concern you?Related story: Lochinver Station sale leaves Fed Farmers 'uneasy'