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Overseer review

A Government-commissioned panel of scientists have reviewed the nitrogen modelling tool Overseer, and have found limitations.

This page will help you find out more information about the review and how it will impact the Tukituki community and our consent process.

Overseer background

It is widely accepted that the water quality of many New Zealand rivers is degraded, and changes need to be made.

One of the main causes of poor water quality is excessive nitrogen.

Discharges of nutrients, including nitrogen, are managed through the use of the tool, Overseer.

Overseer helps estimate nitrogen loss on a farm and in so doing can help with the management of nutrient loss.

We, alongside other regional councils, have used Overseer to gather modelled output data on different farm systems via this online interface.

We are required to use Overseer as a regulatory tool in our operative Tukituki Plan to understand nutrient loss on farms and at a catchment level.

Industry groups have for some time debated the use of Overseer as a tool for regional council’s planning and consent process.

Government review

In late 2018, the Ministry for the Environment and the Ministry for Primary Industries commissioned a review of Overseer by a Science Advisory Panel. Eight independent experts were appointed to the panel.

The panel considered Overseer’s ability to estimate nitrogen loss across a range of conditions found in New Zealand.

The panel concluded that they wouldn’t have confidence in Overseer to estimate the volume of nutrient loss and whether nitrogen was being increased or reduced as a result of on-farm actions

The Government is committed to test, upgrade or supplement Overseer over the next 12 months and will support the use of Overseer over this time to enable regulatory requirements to be met.

You can access the full report here

You can access Government's response here

What this means for the Tukituki community?

In view of the SAP review of Overseer and the Government, the Council is unable to continue with implementation of the Tukituki Catchment plan as it is currently proposed in the Tukituki Catchment Plan (PC6) Procedural Guidelines (version 3, published March 2021).

We have determined that we will be unable to reliably assess whether individual high leachers are exceeding their LUC N allowance, based on Table 5.9.1D, without the use of Overseer. Enforcement of this rule based on Overseer outputs would also be unlikely to succeed. Therefore, we do not believe that we will be able to require applications for individual high leachers that are located outside a DIN exceeding sub-catchment.

We will still require applications for properties located within sub-catchments which are exceeding their DIN target. These farms require consent regardless of their Overseer estimated N loss. However, we will not be able to determine the ‘activity class’, which is based upon the amount of N leaching modelled in an Overseer nutrient budget, as currently required by the rules in the plan. Instead, we propose to apply a single ‘activity class’, of Restricted Discretionary, under Rule TT2 across all the DIN exceeding sub-catchments using other provisions in Rule TT1 (namely Rule TT1(j))4).

Farmers have been implementing good management practices and we expect that to continue.

Consents and farm plans still need to be submitted, and Overseer can still be used to collect farm data.


Overseer key contacts

If you want to talk to our staff about your consent, call Consent Advisor -  027 495 5946.

For general information about Overseer, the Tukituki operative plan call:

Senior Regulatory Advisor - Kate Proctor - 027 201 9698

Team Leader Consents – Paul Barrett – 06 835 9200

What this means for the Tukituki community

For farmers, this doesn’t change things in the short term for the consent process.

Farmers have been implementing good management practices and we expect that to continue.

Consents and farm plans still need to be submitted, and Overseer must still be used to collect farm data.

We are assesing the review to detemine what this means in terms of the ongoing implementation of the operative Tukituki Catchment Plan.

We will be considering evidence as well as Nitrogen loss per hectare when assessing consent applications.

Frequently asked questions

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It is a NZ-developed software tool that estimated nutrient loss from farms using farmer input data and topograhy, soil and climate data.

Farmers and land managers use it to suport efficient financial and environmental decision making.

Overseer has been the best available tool to use to estimate and inform management of nitrogen loss from farms. Overseer was included in the Tukituki Plan when it became legally operative in 2015.

Yes, if your property is located in a dissolved inorganic nitrogen (DIN) exceeding sub catchment.

Yes. We will engage with with landowners in these sub-catchments once we have reviewed our Tukituki Procedural Guidelines.

Yes. It’s a legal requirement in the Tukituki Catchment Plan that FEMPs must be reviewed every three years. The first review was due 31 May 2021.


The Regional Council will be unable to use modelled outputs from Overseer to estimate the amount of individual N leaching from farms in order to set a regulatory outcome. However, the Regional Council still supports Overseer as a useful tool for landowners and will accept Overseer nutrient budgets as part of a consent application or FEMP.

The Regional Council still supports Overseer as a useful tool for landowners and will accept Overseer nutrient budgets as part of a consent application or FEMP.

If you chose not to submit an Overseer nutrient budget, then you will need to provide specific alternative information otherwise included in an Overseer budget. Your FEMP provider will be able to help you with this.

Under the Tukituki Catchment Plan, some landowners who live in the Tukituki catchment need to submit a land use consent (see Tukituki land use consents above).

Overseer is a key part of that consenting process to assess nitrogen loss on farms.

Between February 2021, and February 2022, about 750 consent applications using Overseer are required to be submitted to the council.

We also use Overseer in dairy discharge consents and their monitoring.

Overseer is referenced in the proposed TANK plan, which has been heard and a decision is due.

The Government’s response to the Panel’s findings will be to put in place one or more of the following options:

creation of a new risk index tool, potentially using elements of Overseer (including the user interface); and

redevelopment of Overseer to address the issues raised by the Review Panel and ensure that it is fit for purpose as a tool to use in appropriate regulatory settings; and/or

greater use of controls on practices and inputs to manage nitrogen loss (including through amendment to the NES-F); and/or

a completely new approach to understanding and managing diffuse nutrient loss risk. This might include, for example;

(i)    near real-time monitoring of water quality at the local scale

(ii)   a tool that provides detailed understanding of nutrient loss risk based on the characteristics of land

(iii)  a new nutrient loss model.

The options recognise that Overseer currently plays many roles and a wider suite of tools may be necessary to adequately fill all those future needs.






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