A working prototype of the Risk Index Tool for nitrogen loss has been tested with industry groups, farmers, councils, iwi groups, irrigation schemes, and farm advisors. The first version of the tool is now online. We are now working to implement the tool using a staged approach.
The Risk Index Tool (RIT) is a decision-making tool for farmers, growers and/or their farm advisors. It enables users to:
The RIT could help inform Freshwater farm plans (FWFPs) or council resource consent processing, but its use is not required under legislation.
Councils and users will need to interpret the risk scores alongside other information to determine what they mean for each catchment.
The tool was developed following the review of the Overseer nutrient management model and the Government response to the findings of the Overseer peer review report.
See Government response to the findings of the Overseer peer review report.
The risk is based on a range of factors, including farm system type, farm management practices and biophysical factors (soil, slope and climate).
The tool currently models the risk of nitrogen loss. The framework is built on publicly available data, scientific knowledge and Agricultural Production Systems sIMulator (APSIM) modelling of robust climate, landform and land use combinations.
Phase one of the RIT provides:
N.B.: The RIT does not provide a figure for kg of nitrogen.
This will enable land managers to determine how land and practice management decisions impact nitrogen-loss risk. Areas of higher nitrogen-loss risk may need more work to improve freshwater outcomes.
Documentation has been produced to support the Risk Index Tool. These documents should be read to inform any use of the RIT.
Anyone can create an account and use the tool.
One of the key principles of the Risk Index Tool (RIT) is transparency. We therefore have aimed to highlight any areas where the RIT is not functioning as intended and that require improvement in future updates of the RIT.
While we have written an assumption and limitations section into the Phase 1 Implementation Guidance and included comments in the Technical Document, there are four known issues that are considered important for users to be aware of when using and interpreting the tool’s results.
The table below describes these four important technical issues of the RIT.
| No. | Date added | Issue | Description | Proposed solution | Date fixed |
|---|---|---|---|---|---|
| 001 | 01/09/2025 | Some polygons with a low Curve Number and low rainfall are producing zero values for runoff risk. | Some areas that are flat (and so a low Curve Number) and with low rainfall (eg, in parts of central Otago) are returning runoff risk values of zero for some months. | The Technical Working Group have already identified a fix and provided the ministry with a new geospatial dataset. This issue will be resolved once the latest RIT transport factor database has been incorporated into the tool. This will be implemented in a future release. | |
| 002 | 01/09/2025 | Catch crop modifier | The tool does not allow users to enter catch crop planting and harvest months. Nor could they select a planting area. This impacts the modifiers efficacy. A short-term solution has been implemented with modifiers 17a and 17b which allows users to select one of two modifiers representing an early or late season planting date. | The long-term solution identified is to enable users to enter catch crop details for each block, including planting and harvest date for catch crop and the area planted. The tool would then automatically apply modifier factors to the appropriate months and proportion of the block. | |
| 003 | 01/09/2025 | Shallow-rooted crops | The RIT’s transport factors are based on a moderate rooting depth- based on pasture. Many vegetable crops are shallow rooted. While developing the model there was very little data available on shallow rooted crops in New Zealand. |
The ministry has two options to ensure the tool works better for shallow rooting crops. Option 1) When appropriate data on shallow rooted crops becomes publicly available, further work could be undertaken to improve the transport factors for shallow rooted crops. |
|
| 004 | 01/09/2025 | Unproductive land should be treated as native forestry | The tool currently treats unproductive/ineffective areas as exotic forestry. This should be treated as native forestry. | In a future update to the tool the intention is to change the current calculation from exotic to native forestry values to align with the Technical Working Groups intention and documentation. |
While the tool is now publicly available, the Ministry is currently identifying groups of people to work with (key stakeholders) to roll out the implementation of the tool. We will:
If you wish to be involved, you can express your interest in being involved at riskindextool@mfe.govt.nz
A Technical Working Group of scientists and modellers provided technical and scientific oversight, guidance, advice, and leadership in the development of the Risk Index Tool. The Group consists of:
The Group developed technical documentation on the design and function of the RIT. These documents have undergone an independent peer-review.
Science and modelling experts from the Ministry for the Environment and the Ministry for Primary Industries have supported the group throughout the process.
Read the contaminant loss risk index tool technical document.
A nominated group of regional councils were involved in the RIT development. This group consisted of representatives from:
The Reference Group ensured that the RIT was developed to meet council needs, with some members also involved in the RIT’s user acceptance testing.
If you have any queries or want to ensure you receive future news and updates on the RIT, please email: riskindextool@mfe.govt.nz