A group of farmers in the Rotorua area have started an experiment to see if they can reduce pollution in the lake by holding back flood water on their land.
The aim is to reduce the amount of phosphorus washed off farms into Lake Rotorua and other waterways during storms.
About 12 tonnes of phosphorus, mainly from fertiliser, gets carried into the lake each year during storms.
It and nitrogen are the two main nutrients polluting the lake.
The farmers are testing the theory that building bunds, or low-level earth dams around paddocks, will help to contain the phosphorous and keep it on the pasture where it belongs.
Bay of Plenty Regional Council's sustainable farming adviser, John Paterson, who is also a deer farmer, is leading the "P Project" as it's called.
Mr Paterson says 1.5 metre high bunds have been built on five farms so far, with more under construction, and the results will be monitored this year to see if it is worthwhile continuing with the project.
A field day will be held on Thursday 19 July at Jamie and Chris Paterson's Stewart Road dairy farm, where one of the experimental bunds has been built, so farmers can see how the bunds work and find out more about the process.