Research shows sources of pollution in Southland

A study looking at the sources of faecal pollution in Southland’s rivers has been published.

This jointly funded ESR (Institute of Environmental Science and Research) and Environment Southland study tested water samples across Southland, targeting rivers that were known to have high concentrations of E. coli. ESR used molecular and chemical techniques to establish the probable source of the faecal pollution in the rivers, in both dry and wet weather.

The study showed that ruminant pollution (cows, sheep, deer and goats) was present in approximately 50% of samples, with increased prevalence following rainfall. Faecal pollution from ruminants typically contains bacteria such as Campylobacter, Cryptosporidium and Salmonella, which are a concern for human health. Human faecal pollution was also detected at a limited number of locations across Southland.

The dominant faecal pollution in 80% of the rivers sampled was from wildfowl such as geese, swans, gulls and ducks.

Environment Southland science manager and report author Dr Elaine Moriarty said that while the amount of faecal pollution from wildfowl was high, the risk to human health from this source is low.

“The risk of becoming sick after swimming in a river that contains bird pollution is low, while the risk of swimming in a river with even a small amount of pollution from human or ruminant sources is very high as the diseases this pollution carries are more readily transmitted to humans,” she says.

As part of the study, the pathogen Campylobacter was also detected in a number of the sites. This pathogen can be found in the faeces of animals, humans and chickens. New Zealand has one of the highest rate of Campylobacter (approx. 150 cases per 100,000 people) in the developed world. This highlights the potential for people to become unwell after contact with these rivers from activities like swimming and gathering shellfish.

A number of industry bodies including Beef + Lamb NZ, DairyNZ, and Deer Industry NZ, as well as Te Ao Marama Inc, environmental agencies and community catchment groups, Public Health South and staff from the local councils attended a workshop to discuss the report findings and consider how to tackle this issue collectively.

Dr Moriarty acknowledged the workshop as a great step in coming together to look at this complex problem. “We have to work together to see the improvements that we all want for our rivers. We are all in this together from our high country farms to our urban communities – a joined-up approach to this problem is essential.”

The findings from the study will be used to guide the work being done by landcare and catchment groups, and industry bodies across Southland to reduce the health risk from these contaminants. The findings will also be used to inform the work programme of the Regional Forum and in setting nutrient and contaminant limits, which is currently underway through Environment Southland’s People, Water and Land programme.

The study consists of five reports, one for each of the main river catchments (Oreti, Aparima, Mataura and Waiau) and one report looking at faecal contamination in our shellfish gathering areas. Reports are available online:

• Sources of Pollution in the Aparima Freshwater Management Unit
• Sources of Pollution in the Mataura Freshwater Management Unit
• Sources of Pollution in the Oreti Freshwater Management Unit
• Sources of Pollution in the Waiau Freshwater Management Unit
• Environment Southland Recreational Shellfish-Gathering Water Monitoring Results: August 2016-2017