Wetlands can help manage a farm’s environmental footprint and boost biodiversity – and a new NIWA-DairyNZ resource will help farms with wetland design and performance.

Research was undertaken on a farm in the Upper Karapiro catchment, and results have formed some new guidelines for how a wetland on farm can be  of benefit to you and the environment.

From the case study, despite its relatively small size (around one percent of the farm catchment area), good design and extensive planting means the wetland removes around 60 percent of nitrogen, 70 percent of sediment and 20 percent of phosphorus from the water it receives.

The new guidelines highlight that as wetlands increase from one to five percent of a catchment area:

• sediment removal typically increases from 50 to 90 percent
• nitrogen removal increases from 25 to 52 percent in warmer zones of New Zealand
• nitrogen removal increases from 18 to 38 percent in cooler zones of New Zealand
• phosphorus removal increases from 25 to 48 percent.

The guidance is supported by twelve regional councils, Fish & Game NZ and the Waikato River Authority. It can be downloaded via the NIWA website.