Nitrates - Lower Waihao

Nitrate exists naturally in soil from the breakdown of organic matter and is also added through animal urine and fertilizer that has dissolved and has not been absorbed by the plants. If nitrate transfers into a water supply and is above 50 mg/L nitrate (NO3), the water will not meet drinking water standards for health.

Nitrate is a water soluble molecule made of nitrogen and oxygen. It is formed when nitrogen from ammonia or another source combines with oxygenated water. Nitrate is naturally found in plants and many foods, and is tasteless and odourless. Consequently it is naturally occurring in the environment, but also can enter the environment by other pathways including, but not limited to, chemical fertilisers and various land uses.

Nitrate values are commonly reported as either:

• Nitrate-N = nitrate nitrogen (NO3-N), used by the Laboratories

• Nitrate-NO3 = nitrate (NO3) is used in the New Zealand Drinking Water Standards

1 mg/L of Nitrate-N (nitrate nitrogen [NO3-N]) = 4.43 mg/L of Nitrate-NO3 (nitrate [NO3])

Council continue to undertake regular sampling at the water source, with these samples independently tested by an accredited laboratory. Council also has an online nitrate probe to monitor the nitrate levels in real-time, so simply put, we are keeping very close tabs on the situation.

There is no enforceable drinking water standard for livestock in New Zealand, however it is recommended that animals do not drink water with more than 443 mg/l Nitrate-NO3, according to the Colorado State University (CSU). This is especially true of young animals, as they are affected by nitrates the same way as human babies. Older animals may tolerate higher levels.

Ruminant animals (cattle, sheep) are susceptible to nitrate poisoning because bacteria present in the rumen convert nitrate to nitrite. Non-ruminant animals (swine, chickens) rapidly eliminate nitrate in their urine. Horses are monogastric, but their large cecum acts much like a rumen. This makes them more susceptible to nitrate poisoning than other monogastric animals.

If the nitrate level was, for example, 42 mg/L of Nitrate-NO3. This is would only be 9.5% of the recommendation, and therefore the risk to livestock is virtually nil. So an alternate source of water is unlikely to be required.

In New Zealand there has been no recorded cases of methaemoglobinaemia in stock associated with drinking water.

As for smaller animals such as cats and dogs (pets), we recommend household pets be given potable drinking water. While cats and dogs can handle a higher level of nitrates than most people, it’s advisable to err on the side of caution when providing their water intake.

We also advise those with any fish tanks that they monitor the water quality. Nitrate levels in fish tanks should be less than 20 mg/L to keep fish healthy, however nitrate toxicity to fish varies depending on species, age and overall health.

We recommend that you keep quick test strips or a test kit that uses chemical reagents on hand to monitor nitrate levels in your fish tank closely.

To assure water quality is safe for fish, either source water without high nitrate levels, or use fish water tank conditioner to detoxify nitrates. Please follow supplier directions on use (not for human consumption). For further advice talk to your pet store or vet.

If you have questions about the advice on this page, or concerns not covered, please contact your local veterinarian.

Ryan Luckman BVSc (Dist)
MANZCVS (Epidemiology)
VETERINARIAN

Can I shower and bathe in the water?
Yes, nitrates in water only affect you if digested, do not use the water for food preparation or drinking, but you can bathe, wash your clothes and flush your toilet with the water.

Where does the water for the water tank stations come from, and is it safe?
The water in the potable water tank stations is compliant with the New Zealand Drinking Water Standards and is safe. It is chlorinated, and staff monitor the free available chlorine levels weekly along with bacterial monitoring (E.coli & Total coliforms), to assure the drinking water is safe and compliant. The tanks are also topped with fresh water fortnightly.

The drinking water supplied to the tanks is delivered by a registered drinking water carrier that comes from Temuka Transport. This means the water supplied so far has currently come from Temuka township, which is also a compliant registered drinking water supply in the Timaru District. Both the source and transport of water meet the current New Zealand Drinking Water Standards requirements.

Why is there a water station on Studholme Street in Waimate?
Council have this water station available for the convenience of the Lower Waihao (including Waikakahi East) scheme users who are regularly in Waimate. This water comes directly from the Waimate township water supply.

What if I have difficulty getting to, or collecting the potable water from the council water station tanks?
If you or someone you know has difficulty accessing these locations, please contact Council on 03 689 0000.

Will those on the scheme be required to replace their point of supply storage tanks?
No, you will not need to replace your point of supply storage tanks. We are still working through how best to deal with the water at point of supply storage tanks once the denitrification processes are in place. We would look at options such as cycling the water i.e normal draw off and replenishment with compliant drinking water over a period of time. This is yet to be determined.

What about my pets?
During this nitrate advisory, we recommend household pets be given the potable drinking water. While dogs and cats can handle a higher level of nitrates than most people, it’s advisable to err on the side of caution when providing their water intake.

If you have any further queries or issues relating to animals, please speak with your local vet.

Should I be testing my private bore?
Yes, Environment Canterbury and Council recommend anyone who takes their drinking water from a private bore undergoes regular water quality testing to ensure the safety of their drinking water. There is also raised concern as we know of our own nitrate issue. Nitrate is tasteless so your water may be affected even if you haven’t found any noticeable change in taste.

Understanding nitrate exceedance
Environment Canterbury (ECan) is supporting Waimate District Council to help resolve the nitrate exceedance at its Lower Waihao Rural Water Supply in the Glenavy and Morven area with technical advice and additional monitoring of land use activities in the area. To learn more about ECan's involvement, click below.

Nitrate in waterways - what's the story? | Environment Canterbury

Protecting your private drinking water source
Testing private wells is the owner’s responsibility. It should be undertaken at least four times per year for E. coli, as well as annually for nitrate.

ECan has produced a brochure with practical information about how to protect your well head.
Click HERE to download a copy.