Ruahuwai Decision Support Tool
Wairakei Pastoral Limited has invested in the development of the Ruahuwai Decision Support Tool technology for use on Wairakei Estate. This sophisticated catchment calculator comprises a series of coupled models that collectively predict hydrology and water quality outcomes throughout the Ruahuwai Sub-Catchment (see map). This is an area that covers the upper portion of the Waikato River basin.
The RDST is used as part of the adaptive management framework for Wairakei Estate, to model and predict changes in biophysical properties, and the climatic and natural capacity of the landscape to attenuate contaminant losses. The RDST adopts a transient modelling framework, operating on a daily time step.
The RDST can also be used to predict the water quality outcome in different parts of the Ruahuwai Sub-Catchment. For example, the RDST was used to assess relative changes in nitrogen losses into the groundwater within the catchment and across Wairakei Estate.
This exercise identified that, in general, source areas of high groundwater risk are located in the riparian margins adjacent to streams, and the risk progressively reduces with:
- Distance from stream
- Increasing land surface elevation
- In areas with lower permeability sub-soil
Understanding these risks has enabled Wairakei Pastoral Limited to identify and plan for land use changes to avoid nitrogen losses into groundwater and implement targeted mitigation measures, in relation to set back distances, and riparian margins.
The RDST is also used to calculate the current state of water quality across the Estate, in relation to the current land use and mitigations and compares this to future projections to identify our Farm Environmental Plan targets as reduction or improvement from the current state.