The information in this section of our website is based on a report prepared by AgResearch in September 2015, under the Guidance for Regional Councils in using OVERSEER Project.

The report’s objective is to provide regional council staff with a simple description of the OVERSEER model - including what it can do, its outputs, assumptions and limitations.

The following pages present the report’s information in an accessible web-format:

  1. What OVERSEER is
  2. The OVERSEER farm file
  3. What OVERSEER produces
  4. How the OVERSEER engine works
  5. Uncertainty in model results
  6. OVERSEER Glossary

Any material from these pages must be referenced back to the original report:
Natalie Watkins and Diana Selbie, 2015, Technical Description of OVERSEER for Regional Councils, Report prepared for Bay of Plenty Regional Council, RE500/2015/084. More information on the Guidance in the use of OVERSEER Project can be found here.


OVERSEER models nutrient flows in a farm system, helping users understand how efficiently a farm is using available nutrients. It does this by using information about how the farm is run. OVERSEER then models the complex and dynamic bio-physical processes occurring on a farm to estimate the losses of nutrients through the air, soil and across the land, as shown in the diagram below.

OVERSEER is a product of many years of scientific research, primarily in New Zealand. This Technical Description does not detail the scientific basis of OVERSEER. Scientific and research papers that have been published on the development of OVERSEER can be found here. Details of the science sub-models are described in the Technical Manual Chapters published in the MyOVERSEER users portal. Documentation of the sub-models is a work in progress.