Aorere Catchment - Whats happening on the Land?
The Aorere catchment lies to the north of Takaka in Golden Bay. The largest settlement is Collingwood on the shores of the Ruataniwha Estuary. The estuary covers 1610ha and is listed as nationally significant. The catchment is dominated by native vegetation (3% of the catchment is scrub, 1% exotic forestry, and 16% is in agriculture). Dairying is the most common farming type with approximately 11,000-13,500 cows within the catchment.
Water quality within the catchment is generally good, although high rainfalls (3.5-4.5m/yr) do result in contaminant runoff from pastures. Nutrient concentrations are not generally of high concern within the Aorere mainstream. However, the receiving environment is particularly sensitive to faecal bacterial runoff and this is a problem, given the importance of aquaculture within the bay.
The Aorere catchment project is facilitated by the NZ Landcare Trust and was initiated by local dairy farmers to reduce their adverse impacts to waterways. The project differs from most other BMP projects around New Zealand in that it's focus was on reducing faecal bacteria contamination rather than nutrient loss.
As faecal bacteria concentrations are generally highest after rainfall (resulting in runoff from pastures), aquaculturists must cease harvesting when coastal salinity levels drop. Initially the industry could harvest 70% of the time. As high E. coli results have occurred during lower salinity conditions, aquaculturists now harvest only 30% of the time. Closure of the $15M Aorere aquaculture industry is a real threat. Aquaculturists can cope with high E. coli and closures during high river flow conditions but want local dairy farmers to eliminate point source discharges to waterways in low flow conditions. Domestic sewage may also be a problem.
This project seeks to design and implement a set of catchment principles for reducing the adverse impacts of dairy farming to both waterways and the coastal environment.
Over the next 3 months, interviews will be conducted on all willing dairy farms in the catchment and about half the farmers are willing to be involved at this stage. The survey will allow the project team to understand the issues, perceptions, information gaps, and aims of Aorere farmers.
Gretchen Roberston is a spokesperson for the Aorere Catchment Management Group that has been formed to ensure the waterways remain healthy and sustain a healthy community.
"The Aorere is a beautiful river with generally very high water quality that meets guidelines for nutrients and contact recreation and it sustains a healthy and increasing trout fishery. Sustainable land management through community involvement" is the mission statement of the NZ Landcare Trust. The Trust believes in community led resource management and has offered its support.
There is a lot of pride in the area as a lot of the community are intergenerational farmers who have lived and worked with the landscape for many years.
Unlike many other waterway enhancement projects around the country, the Aorere project does not face an excess nutrient issue. Water quality monitoring undertaken by the Tasman District Council shows that generally nutrient (nitrogen and phosphorus) concentrations are well within guideline limits for healthy waterways. Water quality issues in the Aorere focus mainly on pathogen/faecal bacteria/bad bug concentrations. Marine farms rely on levels of nutrient run off from the land to help stimulate the growth of shellfish. However as filter feeders of small particles (including bacteria and viruses) the shellfish are very sensitive to faecal pathogen levels. Shellfish harvesting has been cut back from 70% to 30% of the year in the Aorere to avoid the contamination of shellfish flesh by pathogens. The high rainfall in the Aorere means runoff from the surrounding landscape to the waterways is an ongoing issue. Avoiding adverse effects will require a strong commitment to implementation of best management practices that work in trying conditions. What works in other areas may not work here.
Dairying in the Aorere produces a payout of around $18M/year and marine farms produce $11.5M/year. Both are important industries for the Aorere catchment.
Sustaining the health of the waterways is recognised as an important goal for the Aorere dairy farmers because:
* They are proud of the landscape and attached to the river
* The industry wants to be seen as a responsible guardian of the landscape
* They want to see the community prospering together and that means ensuring other industries are also able to thrive in the area
Sue Brown & John Nalder are farmers in the Aorere catchment. In 2004 there were serious problems with E. coli in the bay. The Tasman District Council did a survey in 2005 and reported to a community meeting in November 2005. Initial reaction from the farming community to the news that they were the main source of bacteria affecting marine farming was one of disbelief and then shock. They didn't know what to do, but Landcare Trust offered to help with an application to the Sustainable Farming Fund to help study the issues and start the process of change. The Tasman District Council's initial work was on seven of the most coastal farms, but in fact the issue is a matter for the whole catchment.
There are 33 dairy farms in the valley, and about 90% of the land use is dairying. Sue and some other key farmers worked on an application to the Sustainable Farming Fund and sent that away in February 2006. Funding was granted later in the year, and work is now getting under way.
There is some controversy over who is causing what. Most farmers will acknowledge that their effluent runoff is a potential source of pathogens, but question the role of other potential sources, such as sewage from the township and septic tanks in other nearby coastal settlements, large numbers of black swans in the estuary, and runoff from other catchments brought into the Bay by winds and currents.
Sue says that she felt farmers were being asked to patch up something that may not have been all their problem. She understands that cow numbers have remained the same over the years and contamination levels have not increased, and there are no data to show that E. coli levels have increased, but what has changed are the trigger levels for stopping the harvest of shellfish.
It is hoped that the project will clarify where the problems are and provide sound technical information that farmers can use where necessary to improve their effluent treatment systems and farm management practices. Sue also believes that the collaborative approach will bring all parties on board.
Farmers are working to ensure that they meet the Clean Streams Accord, and manage their waste disposal so that there is no direct discharge of effluent into the waterways, particularly in low flow conditions. That generally means keeping cattle out of streams by fencing them off and providing crossings, reticulating water in troughs, managing the runoff from races, preventing overflow from ponds and not irrigating onto saturated soils. The last-mentioned means increasing storage capacity for shed effluent.
There is a wide variety of soil types and rainfall levels, so management measures will need to be tailored to each situation, and generally farmers want to be in charge and decide for themselves what is the best course of action rather than have it imposed on them arbitrarily.