Farmer-led action makes difference to BOP catchment

AgResearch, working in collaboration with local farmers, is helping improve water quality in a Bay of Plenty lake.

Farmers in the Rerewhakaaitu catchment got together with AgResearch from 2003 onward to reduce the amount of farm nutrients leaching into the catchment’s waterways.

Lake Rerewhakaaitu is the southern most of the twelve lakes in the Rotorua area. Its catchment, bordering Kaingaroa Forest, was the last area around Rotorua to be developed for farming and it is the only lake catchment where the main activity is dairying.

In 2001, Bay of Plenty Regional Council found that the water quality in Lake Rerewhakaaitu was satisfactory but that nutrient levels were increasing in streams flowing into the lake. Farmers within the catchment were concerned about the future condition of the lake and the possible imposition of nutrient constraints on their farming operations.

As a result the farming community has taken the lead by working together for the common goal of maintaining their farming businesses while doing everything possible to reduce nutrient flows into Lake Rerewhakaaitu through minimising effluent and nitrate contamination.

The first two phases of the project focused on reducing nitrogen leaching and phosphorus runoff, respectively, with the mitigations introduced in the second phase reducing phosphorus losses during large runoff events.

By 2009, almost every farmer within the catchment was undertaking Overseer® nutrient budgeting and acting on AgResearch’s recommendations to reduce nutrient losses.

Of the farmers who completed the end-of-project survey, 50% said that the project had created a greater understanding for them of the environmental impact of their farming practices and 29% said they had gained ideas on a lot of ways to minimise nutrient loss.

One hundred percent of respondents said that the projects had achieved the outcome of getting more farmers to consider environmental impacts on water quality when making management decisions.

By reducing nutrient emissions into the catchment through voluntary action, the farmers may have delayed the need for a specific action plan to be developed and implemented by Bay of Plenty Regional Council, or may even made such a plan unnecessary in the future. Results from Overseer® nutrient budgeting has seen catchment on-farm losses from nitrogen leaching reduced from 117 tonnes in 2002/03 to 81 tonnes in 2012/13.  During the same period phosphorus runoff losses reduced from 8.9 to 7.1 tonnes, respectively.

Since the project’s inception, water quality in Lake Rerewhakaaitu, as measured by the trophic level index (TLI), has improved from a TLI peak of 3.9 and has lowered to below the Regional Council’s target TLI benchmark of 3.6. Through on-farm mitigations employed by the catchment’s dairy farmers water quality has improved while sustaining the local economy with an estimated $24 million of revenue earned from dairying each year.