Simple solutions to clean rivers

By Meg Liptrot

Herald on Sunday·

13 Sep, 2014 09:20 PM5 mins to read

Plants are a cheap, simple way to strengthen riverbanks weakened and cut up by hoofed animals.

Planting is the easy answer to keep effluent out of waterways.

Travelling by bus and train you get a great view of the surrounding countryside, thanks to large picture windows and the fact you're sitting up high. A very "grassy" shade of green is the overwhelming impression of the journey from Auckland to Wellington.

As we travelled, I took pictures. Although the landscapes were verdant, there was something missing. It felt like a blank canvas. The more I looked, the more motivated I became to photograph minor tributaries and drainage ditches in farms with not much in the way of barriers for grazing animals and little biodiversity - cows and sheep grazing right up alongside these channels, with minimal planting to absorb their impact.

Drainage ditches are a distinctive feature of farms in the Waikato and beyond, and appear to be the missing link in the health of our waterways. It is heartening to see that many streams and rivers are being revegetated and fenced off, but if managed incorrectly, drainage ditches will channel animal effluent and topsoil directly into larger streams, undermining this good work.

Hoofed animals cut up the soil, making it easy for rain to wash topsoil straight into tributaries, ending up in rivers, lakes and estuaries, causing sedimentation and spoiling natural habitat for native fish and other stream life. Mechanical clearing of these ditches doesn't help. According to WWF, half the topsoil on our planet has been lost in the past 150 years.

The Waikato was once a giant kahikatea forest and wetland, peat lands that have been extensively drained and cleared for use in dairying. Deep drainage ditches inevitably reduce the ability of the land to recharge its aquifers, in turn making our farms more vulnerable to drought, and increasing the requirement for expensive irrigation and dams.

For the past 30 years, pioneering farmer and racehorse breeder, Peter Andrews, paved the way in natural watershed management on his 2000ha farm, Tarwyn Park in the Upper Hunter Valley, New South Wales. Science now proves that his simple methods work to heal the land and significantly improve water quality. I was lucky to attend several days of terraquaculture training in Taranaki with our own watershed guru, Professor Haikai Tane, who teaches similar techniques. His methods challenged my thinking, even about the species we use for riparian revegetation.

This management style would particularly suit those areas prone to drought, such as Northland and Hawke's Bay. Sadly, Tarwyn Park is now under threat from Korean coal mining interests.

There are plenty of resources to help landowners - planting guides, effective solutions for fencing, and great case studies of healthy farms. I know that operating a farm is a lot of work, and this is just another job to add to the list. My brother-in-law can testify to that. He has 900ha in Hawke's Bay to run. But it is a privilege to care for the land. We have to be kaitiaki for the future. Biting off a little at a time will bring the best results. Electric fencing is cheap and spring is a great time to get planting.

A happy collision: Farming and Permaculture

The outer riparian margin along bigger waterways has potential for growing specialty timber. Poplar, Tasmanian blackwood, macrocarpa, Mexican cypress and several eucalypt species can be successfully grown here.

Sedges and rushes cope with floods, helping filter runoff and stabilise soil. Weeds are a solution, not a problem in riparian zones, as they help uptake pollutants and stabilise the soil. Bullrushes will happily grow in these ditches and help filter the water. This is valuable habitat for native fish, eels and other stream life. Why not turn these zones into burgeoning wildlife corridors?

With a bit of lateral thinking, it is easy to see the potential for food and fibre production here. Taking the idea a step further, riparian land could be opened up to the community to lease, to help improve the value and environmental bottom line of a farm, provide a source of additional income, and benefit the wider community. How about a water chestnut plantation to supply the Chinese greengrocer? Or maybe an eel-fattening farm for vacant drainage ditches? Look at the productivity of Southeast Asia - our landscapes are blank by comparison. Flax fibre was a big industry in Aotearoa in years gone by, and flax gel is used in the natural beauty industry. Riparian zones make the perfect harakeke growing conditions. Up north, bananas and taro also appreciate this rich moist soil. Bee-friendly flowering species could be grown and beehives could pepper these diverse areas, providing income from honey and pollination services in one.

Perhaps we could be a land of milk and honey once again - for everyone - this time.