The application of the Overseer model to Lake Rotorua groundwater catchment

The first section of the report summarises publicly available documents describing the Overseer redevelopment work. This included updates to the crop and hydrogeology submodels, assessment of time scale effects, and model evaluation/calibration, and improved sensitivity, uncertainty, and sensibility analysis. Other than updates to S-Map and issues related to podzolised pumice soils, no documents were found that relate specifically to the Lake Rotorua groundwater catchment area. However, it is probable that the findings in this section also apply to the Lake Rotorua groundwater catchment area.

This report also identifies recommendations from the publicly available documents on where Overseer would work best. In summary, the Technical Advisory Group (TAG) report indicate that Overseer performs better for pastoral systems on well-drained soils on flat to rolling land (where overland flow is minimal) and where nitrate N is the primary type of N leaching. The redevelopment work TAG to conclude that the work “gave them more confidence in the tool for modelling nitrate loss on free draining soils”.

Report Number: RE450/2024/045