Media Statement
3 April 2016 – for immediate release
IrrigationNZ and Feds ask for scientific integrity
IrrigationNZ and Federated Farmers say greater scrutiny of claims irrigation causes increased ‘rumbly-gut’ is needed, as
recent assertions by Alison Dewes are not scientifically sound.
The industry bodies have joined forces to ask for improved scientific integrity when making claims in the media as “the
validity of the argument around increased pathogen losses resulting from irrigation or water storage are not sound,”
says IrrigationNZ CEO Andrew Curtis.
“Our understanding is pathogen contamination of a water supply generally occurs through a direct pathway – a point
source contamination. Neither irrigation nor water storage create pathogen issues, except through natural means, the
increased birdlife around a water storage lake for example. The main causes of pathogen contamination are poor water
treatment from domestic discharges or inadequately protected well-heads. ” says Mr Curtis.
Federated Farmers also takes exception with the focus on dairy farming.
“Dairy farmers are too often used as an easy target when the reality is that this in an industry that takes
environmental performance very seriously. Dairy farmers have invested $1 billion in the past five years on environmental
initiatives such as stock exclusion, riparian planting land and developing wetlands. Farmers are custodians of the
environment and they will continue to invest in actions that make a difference to managing their farms’ environmental
impact,” says Federated Farmers Water Spokesperson Chris Allen.
Lincoln University has established a series of monitoring wells at three locations across the Lincoln University Dairy
Farm. These wells enable monitoring of the shallow aquifer (6-12 metres below ground) as the groundwater moves
underneath the farm. While there are as yet no published results available, Ron Pellow, Executive Director - South
Island Dairying Development Centre says initial comparisons of changes from the upper to lower wells confirm the soil in
an irrigated, well managed dairy farm is an effective filter of material that may have been deposited on the surface
from grazing animals or transient bird life.
Issues from pathogens generally arise through the following pathways.
1. Septic tanks that have failed that are located up gradient of a domestic water supply.
Septic tanks need to be regularly maintained. When they fail domestic waste water can directly leak into groundwater.
For older properties it is common for a shallow well to provide the domestic water supply. If a failing septic tank is
located up gradient of this well there is an increased chance of contamination.
2. Livestock effluent that is injected into an irrigation system without backflow prevention.
If the water supply used for effluent irrigation (from a well or surface water take) is not protected through a backflow
prevention system (a backflow prevention system stops any water taken returning to the aquifer or surface water body and
is standard for all new irrigation systems) it is possible for contaminated water to ‘backflow’ into the source.
3. Poor well-head protection.
It is possible for water to move down the side of a well case, or if left open directly into it. This provides a direct
pathway for contaminants to enter into an aquifer. Sealing the well-head (both the bore itself and around it) solve this
issue. Concreting (sealing) around the top of wells is now a requirement in Canterbury. Keeping livestock away from
well-heads is also advisable.
“A good example of this issue is the Dunsandel domestic water supply” says IrrigationNZ’s Andrew Curtis. “For a number
of years high levels of e.coli were frequently detected in the drinking water and irrigation was blamed for this.
However, post the district council concreting around the water supply well and alterations being made to other nearby
wells to ensure they were suitably protected, the issue seems to have largely disappeared. This points to a point-source
discharge being the issue, not irrigation.”