NZ Farmer - Turning farmer's roadside drain into a healthy freshwater ecosystem

New ways to transform water quality and ecology in streams flowing into Canterbury's Te Waihora/Lake Ellesmere are being trialed by Living Water partners Fonterra and the Department of Conservation. Tony Benny reports.

Canterbury's Ararira-LII River is one of five New Zealand catchments included in Fonterra and DOC's $20 million, 10-year, Living Water partnership. Like the Wairua River in Northland, the Peat Lakes in Waikato, Pukorokoro-Miranda in the Firth of Thames and Waituna Lagoon in Southland, the Ararira-LII catchment is environmentally degraded, much of that blamed on dairy farming.

Generally known as the LII (pronounced 'L-two'), the catchment covers 6600ha and includes 12 dairy farms, along with lifestyle blocks, sheep and beef, deer, horticulture and cropping and the towns of Lincoln and Springston

When Europeans arrived much of the area was wetland, with possibly a few standing matai and kahikatea trees, says Living Water site lead Robin Smith from the Department of Conservation.

"Europeans set about draining it because they recognised that those peaty soils that had been formed under that forest environment were pretty rich, good soils, perhaps compared to the stonier soils further up country.

They lowered the water table by digging drains through the wetlands; it dried out and became good farmland and the drains then became the default waterways".

Unlike other drains that only flow when rain creates surface water, these drains are spring-fed. The water in them looks clear and pristine, but in fact carries quite high nitrogen levels, leached into groundwater from farming many kilometres inland. They're also affected by sediment run-off from neighbouring properties.

In summer, plants like watercress and monkey musk regularly choke the streams that don't have enough shade, so every autumn the Selwyn District Council uses diggers to clear them out to reduce the risk of winter flooding.

But mechanical drain clearing is hard on the creatures living in there.

"Even though the LII is probably technically a drain, it's still got a large ecosystem of whitebait, eels, trout and freshwater crayfish and we've found mussels in the drain by our place," says fourth-generation dairy farmer Philip Musson, who's property is bisected by a waterway known as Powells Rd drain.

A keen hunter and fisherman and a member of the council of Fish and Game, Musson is committed to looking after the environment and has changed his farming operation to reduce nitrogen leaching and sediment run-off.

In winter the farm's heavy land is usually wet and is prone to pugging and his 320 cows used to be wintered off-farm on a leased run-off on lighter land. But four years ago Musson built a wintering barn and the herd now stays home year-round.

"The 320 cows just seemed to be doing too much damage to the soils. When we put the barn in we went up 80 cows to 400 and now we're doing less damage and growing 30 per cent more grass."

Musson has also upgraded effluent storage. His 7 million litre pond can hold two years worth of effluent. It's applied to pasture by slurry tanker in summer when the grass can use it for growth, rather than allowing it to leach into the ground.

Wintering the cows off-farm was effectively just shifting the effluent issue to someone else, Musson reckons. He says the nitrogen loss on the runoff was about 80kg/ha compared with 17 on the home farm. Thanks to the wintering barn, that's now down to 4kg/ha annually.

Last year Musson won Fish and Game's Working with Nature environment award for his efforts. He's also working with Living Waters, on-farm as well as helping out with an initiative in a short section of Powells Rd drain next to the farm to find ways to improve water quality as well as reduce the need for drain cleaning by digger.

North Canterbury Fish and Game are partners in the Powells Rd project. Various techniques are being trialled which if successful can be scaled up and adopted by drain managers across the waterway network, says Smith.

"We've started on the Powells Rd waterway alongside Phil Musson's property and we're trying a range of techniques to improve water quality and biodiversity. We're aiming to demonstrate, cost and show other people - 'this is what you could achieve, these are the results you get'."

The drains in the area are mostly steep-sided, deep and prone to erosion. Nutrient-laden sediment that gets into the water column in turn finds its way into Te Waihora-Lake Ellesmere, which has been called New Zealand's most polluted lake.

Because the drains are mostly unshaded, aquatic weeds thrive there in summer and can completely cover the water surface.

Along the stream-side in Powells Rd, carex secta has been planted to create shade. Sandbags filled with river gravel have been placed along the edge to stabilise the bank and some of the bags are filled with top soil in which carex have been planted.

Rocks, stones and logs have been placed in the stream bed to vary the flow and create a variety of habitats.

"The stones provide opportunities for invertebrates to land and lay eggs and create variability in the stream environment as well," says Smith. "You get some narrowed, faster-running water, some pools, otherwise it's all very uniform which may suit some species but not everything."

The aim is to create a stream that no longer needs annual cleaning because aquatic weeds can't thrive in the shady water and sediment runoff has been cut off by improved farming practices and riparian planting.

"We're transforming – and I use that word cautiously because it sounds a bit radical – but transforming the water network into a healthy freshwater ecosystem in a productive agriculture landscape," says Smith.

"Living Water is very much focused on developing and applying solutions that can work at scale. We're using the latest techniques, the latest science and applying some new things to see what results we can get and share that with others. And that's sharing what has worked and also what hasn't."

One of the reasons Powells Rd, which is not far from Lincoln, was chosen is that it is easy for members of the public to stop and have a look at the work there. But there was another reason as well, Smith says.

"It's no fluke we chose that section because Phil Musson owns the land on either side of Powells Rd so what better place to start than with a landowner who's enthusiastic and committed to environmental improvement.

Living Water is working in partnership with the University of Canterbury's School of Biological Sciences, Selwyn District Council, Te Taumutu Runanga and DairyNZ and Fonterra science teams.

The university's Canterbury Waterways Rehabilitation Experiment (Carex) team will provide expertise to monitor the progress of the Powells Rd project.