Spreading the word, and the water

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Hekeao Hinds Water Enhancement Trust members (from left) Craig Fleming, Rab McDowell, farmer Mark Walls, Brett Painter and Peter Lowe at a new MAR site.

Mid Canterbury’s water assets have been on show to mayors and chief executives from around the South Island.

Mayor Neil Brown and the Ashburton District Council hosted the local government group last Thursday and Friday and put on a tour of the district that included the opening of another managed aquifer recharge (MAR) site.

There were plenty of mayors to choose from for the ribbon-cutting ceremony but Mr Brown had the honour. It was a good opportunity to share the success of the MAR project, which is lowering nitrate levels in shallow groundwater and boosting groundwater storage on the Hinds plains.

The new site is on Timaru Track Road, on the farm of Mark Walls. Part of a canal that once delivered water for border dyke irrigation has been converted into a leaky pit, where water drains downs through the soil and into groundwater, diluting nitrate concentrations and adding more water to aquifers.

Farmers are among those leading the project, that started in June 2016. An initial open basin site at Lagmhor has been expanded to include a network of smaller sites across the Hinds plains, each targeting high nitrate areas.

Mr Brown said while MAR was new to New Zealand, it operated successfully in other countries. The project’s water comes from an unused council stockwater take off the Rangitata Diversion Race.

He said the results had been impressive since the Lagmhor pilot site started operating four years ago.

Near the pilot site, nitrates were 6-7mg/L pre-MAR, but dropped to 1.3-3.5mg/L with MAR. Groundwater levels also rose.

The project’s overall aim is to have median nitrate levels down to less than 6.9mg/L by 2035, the equivalent of a 36 per cent reduction in nutrient leaching. While some areas on the Hinds plains are already there, others are as high as 24mg/L.

MAR spokesman and farmer Peter Lowe said said the recharge system diluted and displaced water and was one tool being used to protect drinking water and improve water quality.

He said high nitrate concentrations were a legacy of previous farming generations but being successfully addressed in Mid Canterbury.

The project has many partners, including Environment Canterbury, the Ashburton District Council, Arowhenua, Fish and Game, MHV Water and the Rangitata Diversion Race company.