Caution needed in nitrate water quality debate

Nitrate levels in Christchurch’s drinking water are not expected to exceed safe drinking levels in the future, Waimakariri Irrigation Limited (WIL) said today.

WIL Chief Executive Brent Walton says that while the debate on the level of nitrates in Canterbury aquifers is an important discussion to be had, and the public must be well informed, it must be focused on science.

An Environment Canterbury investigation* into potential groundwater flows under the Waimakariri River into Christchurch aquifers points to a long-term increase in nitrate levels.

“However there are two key points made in the Environment Canterbury modelling that seem to have been overlooked in recent commentary on the Christchurch water quality issue,” Walton says.

“The first is that any future nitrate increases in the Christchurch water supply are not expected to exceed safe drinking limits – Christchurch water will remain safe to drink.

“Environment Canterbury’s report says that while it is possible, during the next 50 to 100 years, that nitrates in aquifers below the main part of Christchurch might increase, the levels are predicted to remain below the Maximum Acceptable Value,” says Walton.

The Maximum Acceptable Value is based on recommendations from the World Health Organisation, to ensure safe drinking water.

“The second key point is that Environment Canterbury’s modelling is based on the premise of current land use continuing into the future, when we know that land use is already undergoing a change. Extensive environmental mitigation continues to be undertaken by Waimakariri farmers and, with rapidly advancing technology, nitrates and other environmental management can only improve.”

Further, the Ministry of Health has rejected calls for additional research into a 2018 Danish study that reported possible links between the presence of nitrates in drinking water and colorectal cancer. The Ministry stated that the Danish data did not take into account other colorectal cancer risks such as smoking, diet and obesity.

Brent Walton says farmers accept that they have a key role to play in reducing nitrate levels.

“There is not one WIL shareholder or farmer in this catchment who wants to see, or be responsible for, increased nitrate levels,” says Walton.

All WIL farms that irrigate 20 hectares or more (around 108 properties) are required to have a Farm Environment Plan (FEP), which is independently audited each year with results reported to Environment Canterbury.

“Our shareholders have invested heavily in infrastructure, including introducing modern irrigation systems, sophisticated effluent system, fenced-off waterways and riparian plantings to improve water quality and reduce their environmental footprint.”

Flowmeters, weather stations and telemetry monitors are being installed on all WIL properties to ensure efficient water use, by applying precisely the right amount of water, at the right time.  Farmers are provided with daily, weekly and monthly recommendations on whether to irrigate via a mobile app.

“We can now demonstrate that virtually every irrigation event is justified, and nitrogen leaching events caused by irrigation have been significantly reduced.”

Walton says that farmers are part of their community too. “They have children and wider families. They are as concerned for the future wellbeing of their society, culture and environment. They take far more than their own economic wellbeing into account when they’re making decisions about the future operation of their farms.

“The sector has made massive improvements in the past five years, and there is clear motivation to keep that momentum going into the future.

“We are putting forward a solutions package as part of our submission to the Waimakariri Zone Implementation Programme Addendum (ZIPA). WIL shares the same aim as the ZIPA, that is to develop a package of freshwater management solutions which best deliver community outcomes.

“We are very clear that improvements can only be brought about by a combination of both reduction in farming nitrogen losses and wider catchment interventions.

“Our shareholders are here for the long-term. I can assure the public that farmers are not sitting around waiting for the magic wand to appear. Rather than a cause, we want to be seen as part of the solution,” says Walton.