Flooding pasture may be good for lake water quality

Farmers in the Rotorua catchment are experimenting to see if controlled flooding of some of their best pasture land can capture phosphorus during storms and stop it polluting Lake Rotorua.

About 12 tonnes of phosphorus (P), gets carried into Lake Rotorua each year during storms, contributing nutrients which lead to poor water quality and algal blooms.

Bay of Plenty Regional Council staff are leading the "P Project", with support from DairyNZ. The project aims to find out if flood water detained on farms for a controlled time will prevent phosphorous run-off reaching the lake.

Five large detainment bunds have been built on Rotorua farms and will be tested until the end of the year. The project is part of the Rotorua Te Arawa Lakes Protection and Restoration Action Programme. It is a collaborative effort, partly funded by the Regional Council, with the farmers pitching in with their own machinery to help build the bunds.

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.

"We hope the phosphorus will settle out onto the pasture and be retained on the farm, rather than end up in the lake where it helps nuisance algae grow instead," Mr Paterson said.

If the trial is successful, building of more bunds on farms is scheduled for a four to five year programme.

Rotorua dairy farmer Robbie Moore already has two detention dams on his property that have successfully eliminated flood water for the past 15 years. He is a strong advocate for the new type of detainment bund.

"It's great to see this project providing evidence of the amount of phosphorus we can capture during and after storms. It will also help keep Tauranga Direct Road open during big floods, which have caused massive damage on several occasions," Mr Moore said.

The field day is open to any interested landowners and will be held at the Paterson's farm on Stewart Road off Tauranga Direct Road - SH 36, starting at 10am.

For more information contact John Paterson on 027 249 6114 or Sharon Morrell on 0274 922 907.