An innovative project carried out by WSP Opus for Owl Farm has created a greater understanding of how wetlands can be used as a tool for the management of farm nutrient runoff.

Sharing expertise

Owl Farm on the site of St Peter’s School in Cambridge, is a joint venture demonstration dairy farm between St Peter’s School and Lincoln University. As a result of extensive research carried out here, Waikato farmers have access to world class resources, information and on-farm practices.

Stephen McNally, Head of Primary Industries, says WSP Opus has had a long and positive association with the school, sharing broad expertise in planning, ecological science and farm infrastructure engineering.

“It’s been our immense pleasure to share this knowledge with programme participants and see the positive and significant benefits this work has, particularly as it contributes to future food security for our communities.”

Harnessing nature

Environmental pollutants generated from agricultural fertilisers and livestock are carried in the water leaving farms and make their way into waterways, impacting water quality. It’s an issue that industry is working hard to address.

WSP Opus designed and established a wetland on Owl Farm to investigate the use of wetlands in a farming context as a way of removing nitrogen from the water.

The project involved the assessment of the extent of surface flows and ground water seepage, selection of a suitable site, hydraulic design, planting plans and construction supervision – including dealing with geotechnical solutions.

McNally says the project has offered up insights on the design of wetlands.

“We’re aware of overly simplistic wetland designs that don’t fully consider the biological and hydraulic processes to be truly effective. While biodiversity is an outcome, a good wetland needs to be much more than an aesthetic feature or duck pond.”

He says that effective and sustainable land and nutrient management is fundamental to rural business success and long term operational viability.

While well designed and established wetlands that consider hydraulic, bioremediation and phytoremediation processes become largely self-sustaining, they do still need monitoring like any other business asset. Analysis of early data is extremely positive, suggesting that 60-90% of nitrate has been removed from water before entering the Waikato River. McNally says the project is now an integral part of the Owl Farm environment and its teaching function.

“For WSP Opus it’s been a great pleasure to see the opportunity the wetland has presented as an example for other farmers and as a learning experience for students in the sciences and agriculture programmes.”

Effective and sustainable land and nutrient management is fundamental to rural business success and long term operational viability.

Restoring kūkūwa

Over 150 years ago, when European settlement of New Zealand began, we had around 670,000 hectares of freshwater kūkūwa wetlands. Today more than 90% of these no longer exist.

Wetlands are of great cultural and spiritual significance to Māori. They provided Māori with food – wildfowl, tuna (eels) and other freshwater fish. They were also places to grow taro and harvest harakeke (flax) and other materials for medicinal, food, building and crafts.

During the pioneering era, wetlands were considered wastelands that needed to be drained in order to become ‘productive’ and this trend continued as land was reclaimed for agriculture. In recent years however there has been a considerable change in this approach, particularly as the vast benefits of wetlands have been better understood.

Peter Matthewson, Global Director – Water, says most New Zealanders want to do the right thing when it comes to improving water quality and is pleased to see change happening.

“With the greater intensification of farming we have a lot of nitrates running off land and into rivers which has changed the natural biology of waterways and the nitrification of lakes. A lot of farmers are taking really positive steps in terms of retiring land close to waterways and planting natives, and work in the area of these wetlands is adding to that knowledge.”

McNally says there has been a massive commitment of time, energy and cost from rural families and enterprises in managing their catchment.

“Some of the decisions in the past were probably based on the demands for a new nation finding its role. With a better-informed decision process and understanding of the sensitivity in balance it’s fallen to the current generation of land owners to redress past decisions.”

McNally says WSP Opus’ approach is to help clients seek solutions that have a much greater weighting on intergenerational outcomes armed with the latest technology, data and analysis to achieve security of safe affordable nutritional food while minimising the impact on the environment.