200,000 dairy cows, 70L of effluent each, every day: managing risk to Bay of Plenty’s waterways

Bay of Plenty is home to around 200,000 dairy cows, each producing about 70 litres of effluent per day. While most of this naturally breaks down in the paddocks, around 7 litres of effluent is created per cow during milking in the dairy shed.

Dairy sheds are cleaned daily, and this waste is typically irrigated across paddocks or if conditions are too wet, stored in holding ponds. Properly managed, this effluent can serve as a natural fertiliser. If not, it can saturate the ground and pose a risk to our waterways. Farmers must manage this waste responsibly and the Toi Moana Bay of Plenty Regional Council Compliance Team carries out checks to ensure that that this happens, and consent conditions are being met.

Toi Moana Compliance Team Leader, Fraser Toulmin, emphasises that while many farmers are taking their responsibilities seriously, there are still some areas for improvement.

“It’s important to recognise the efforts by many landowners who are working hard to protect and restore our waterways. The Waihī Estuary is a great example of this. It has long been under threat, due to decades of draining wetlands, changing rivers and land use, as well as contaminated run-off, but a group of motivated landowners have got together to support efforts by iwi, community and council to try and turn this around.

“At the same time, our community expects our waterways to be free from dairy effluent, and we will take action against those not meeting the mark.

Most dairy discharge prosecutions carried out by Toi Moana stem from failed or mismanaged older-style irrigation systems and pipework, which can quickly escalate into serious environmental hazards. Modern set-ups include fail-safe technology which detect failed pipes or spills and instantly turn off, dramatically reducing risk.?

During a routine inspection last year, a Compliance Officer discovered effluent leaking from a 10cm hole in a holding pond which entered the farm's drainage system. The owner and farm manager were instructed to fix the hole, as well as seal a historic outlet pipe, however one month later the historic outlet pipe had not been sealed, the tap was on, and the pipe was discharging effluent from the pond.

Testing in the drain, which was approximately 300m downstream of the pipe, showed elevated levels of E. coli (43,000cfu/100ml) and other contaminants. These can have adverse effects on water quality and negatively impact the receiving environments – in this case, Waihī Estuary.

“We can’t emphasise enough the importance of investing in adequate technology to manage these risks.”

The farm manager was convicted and fined $52,500. Read the full sentencing decision at?www.boprc.govt.nz/environmental-enforcement?

If you suspect dairy effluent is entering a waterway, please call the Pollution Hotline on 0800 884 883.