Community and Public Health is involved with the quality of coastal waters and freshwater waterways which are used for a range of recreational activities such as swimming, sailing, boating, surfing, water skiing, underwater diving and shellfish gathering.
The quality of recreational water is an important environmental health and resource management issue.
Health Risks Associated with Contaminated Water
Water can be contaminated by human or animal excreta (poo) containing disease causing micro-organisms such as viruses, bacteria and protozoa.
Contamination poses a health hazard when the water is used for recreational activities such as swimming and other high contact water sports.
There is a risk that water will be swallowed, inhaled or come into contact with ears, nasal passages, mucous membranes or cuts in the skin, allowing pathogens or algal toxins to enter the body.
The symptoms of exposure to contaminated water are usually minor and short lived, however there is the potential for more serious diseases including hepatitis A, giardiasis and cryptosporidiosis.
Study underway to improve understanding of the health risk of swimming in rivers
Ministry for the Environment media release: 18th December 2019
The Ministry for the Environment is funding research to better understand the relationship between the presence of pathogens in freshwater and people getting sick.
The Quantitative Microbial Risk Assessment (QMRA) pilot study will confirm the best method to establish the link between levels of disease-causing organisms and indicators of them (such as E. coli) in New Zealand rivers to determine the health risks to people in contact with fresh water.
The Ministry for the Environment is working with research institutes (ESR, NIWA and Massey University) and regional councils to determine the best way to provide the data.
Councils will collect around 80 samples for scientists to analyse across 16 freshwater sites throughout New Zealand this summer. The results are expected in June 2020.
The current recreational freshwater public health guidelines are based on a similar study conducted over 20 years ago. The way we use land and manage our waste has changed significantly over that time so it is possible the presence of pathogens and indicators has also changed.
Health Risks associated with Algal Blooms
Algal blooms are appearing more frequently in our waterways. Algal blooms in lakes can be blue/green in colour floating on the surface or colourless globules suspended in the water.
Algal blooms are also found in rivers as blackish benthic mat-forming cyanobacteria clinging to rocks or collecting at the riverbank. Some cyanobacteria species are known to produce toxins.
Symptoms of exposure to toxic algae can range from allergic reactions, asthma, eye irritations, and rashes to rapid onset of nausea and diarrhoea to gastroenteritis to other specific effects such as liver damage and possibly developing cancers.
Health Risks associated with Mahinga kai
Water containing micro-organisms, chemicals, phytoplankton or cyanobacteria can pose a risk to health through recreational contact, drinking and gathering mahinga kai.
Mahinga kai species associated with water are fish (including tuna and inanga), kanakana shellfish (such as mussels, oysters, scallops, tuangi and tuatua) as well as seaweed and watercress.
Responsibility for Monitoring Water Quality
Regional councils like Environment Canterbury coordinate the monitoring of the various sites throughout our region and inform Community and Public Health and the territorial local authority (TLA) if contamination levels present a potential health risk.
The Territorial Local Authority places warning signs to inform the public where a health risk is identified, and takes steps to remove the contamination if possible.
Community and Public Health supports the TLAs in advising the public of the risk and ensuring that they deal with the contamination appropriately.
Contact your local CPH office for further information:
Ph: +64 3 364 1777
Fax: +64 3 379 6125
Ph: +64 3 687 2600
Fax: +64 3 688 6091
Ph: +64 3 768 1160
Fax: +64 3 768 1169
For additional information or to report water pollution, contact:
Environment Canterbury Pollution Hotline
Ph: 03 3664 663 or
0800 765 588
West Coast Pollution Hotline
Ph: 0508 800 118
Toxic algae present in some Canterbury waterways
Updated 27th January 2020
All recreational water users are being reminded to avoid contact with some Canterbury and South Canterbury waterways. Recently added warnings are highlighted in bold.
Potentially toxic algae is currently present in the following locations in the region:
- Lake Ellesmere/Te Waihora
- Lake Pegasus
- Lake Rotorua (Kaikoura) – this is a permanent warning
- Ashley/Rakahuri River at the Rangiora-Loburn Bridge and State Highway 1 bridge
- Opihi River at State Highway 1, Waipopo Huts and Salesyard Bridge
- Selwyn/Waikirikiri River at Glentunnel and downstream of the Whitecliffs Domain
- Waihao River at Bradshaw’s Bridge
- Waihi River at the Wilson’s Street footbridge (Geraldine)
Visit the Environment Canterbury website for more information on water health warnings. Routine monitoring of waterways for summer is underway.