Pollution model under scrutiny

Horizons Regional Council will await more information before deciding what to do about doubts over the reliability of a tool used to regulate farming pollution.

In a report released this month, Parliamentary Commissioner for the Environment Simon Upton asked if councils could be confident in making regulatory decisions based on Overseer’s modelling.

Overseer is used to model how nitrogen leaches from farms.

Numbers from the model were used when Horizons created the One Plan, which governs how natural resources are used in Horowhenua, Tararua, Rangitı¯kei, Whanganui, Manawatu¯ and Ruapehu.

But changes to Overseer dramatically increased the estimated volume of nitrogen leaching from farms, requiring Horizons to change the One Plan to make it possible for some farmers to get resource consents.

Upton said farmers and regional councils needed to be confident that Overseer’s outputs were reliable.

His recommendations include greater transparency about how the model works, getting an independent review and providing official guidance on how regional councils should use it.

In a meeting this week, Horizons councillor Gordon Mckellar asked what the council was doing in response to the report.

Horizons chief executive Michael Mccartney said it was too early to say where things would head, and staff still had to go through the report in detail.