Mangaotama catchment

Mangaotama catchment, Whatawhata, Waikato – win:win for farming and the environment The Mangaotama project is one of the few studies where the effects of land use have been experimentally manipulated and tested on a catchment scale. It’s centred on a 280-hectare model hill farm at the Whatawhata Research Centre near Hamilton, in the Mangaotama catchment (a tributary of the Waipa and Waikato Rivers).

Mangaotama catchment, Whatawhata, Waikato – win:win for farming and the environment

The Mangaotama project is one of the few studies where the effects of land use have been experimentally manipulated and tested on a catchment scale. It’s centred on a 280-hectare model hill farm at the Whatawhata Research Centre near Hamilton, in the Mangaotama catchment (a tributary of the Waipa and Waikato Rivers). Run jointly by NIWA and AgResearch since 1996, the study’s management group included science providers, policy makers, resource managers, and farmers working together to manage the whole catchment, both land and water. This is one of the first practical tests of an integrated catchment management (ICM) approach.

Challenges

The farmland was typical of the farmable North Island hill lands, suffering from low economic return, erosion, high nutrient and sediment loads, and degraded stream ecosystems.

Key actions 

  • Planting radiata pine in the steepest and most erosionprone parts of the catchment, amounting to 50 percent of the catchment.
  • Switching from breeding cows to young bulls.
  • Intensifying beef and sheep farming on the better land.
  • Riparian fencing and planting to exclude stock from most streams.
  • Protecting native forest remnants (including controlling pests).
  • Establishment costs: $600,000 over 10 years (including $260,000 in the first year).

Key outcomes

  • Greatly enhanced per-hectare returns from grazing land: lamb productivity per hectare increased 87 percent and beef productivity 170 percent after five years. 
  • Better long-term financial performance of the farm. 
  • Improvements in water quality - Reduced contaminants added to the Waipa and Waikato Rivers: sediment lost downstream decreased 76 percent, total phosphorus decreased 62 percent, total nitrogen decreased 30 percent, E. coli decreased 90 percent in streams downstream of pine plantings. - Stream temperatures reduced by 1–2 oC. - Invertebrate communities quickly responded, switching from species indicating moderate–severe pollution to mostly clean-water species by 2006–07.
  • However, water flow was 30 percent lower. Overall, this project represents a win:win, enabling high productivity of the farmland and improved water quality and ecosystem health. It has also revealed differences in water quality between forested and pastoral land, and the processes driving land-use effects on stream flow, water quality, and stream organisms.