This case study addresses water quality concerns within the Avon River, Christchurch New Zealand, the study focuses on the presence of faecal indicators; specifically Escherichia coli (E. coli) which has links to the faeces of humans, animals and birds.
This indicator provides possible links to other more harmful micro-organisms which can cause disease in humans. This study aims to find links to sources so the potential impacts from this contamination can be managed or remedied.
With measured levels of E. coli in the Avon River regularly exceeding Ministry for the Environment and Ministry of Health standards it was necessary from a management point of view to determine the source of the faecal material so that some form of remediation could occur to return water quality levels to a level which is acceptable to human health as set out in policy.
Sample analysis for E. coli was undertaken by the Christchurch City Council (CCC) according to APHA 9213 D and expressed as units per 100ml. From those samples it was then required to use faecal source tracking tools including Molecular markers, Fluorescent Whitening Agents and Faecal Sterols. A more in depth methodology has been outlined in the 2009 report.
This case study was able to link the samples tested, both at low flow and high flows, to predominantly water fowl and canine sources, the proportion of which varied with a higher input of canine contamination after rainfall events. There was an occasional exception of human waste at one test site after high rain fall events which had potential to be linked to older deposits. The links to what species were providing E. coli sources was based predominantly on DNA based molecular Markers. These findings could then be used to direct better management strategies and planning for the area to reduce water way contamination, such a high input from canine species suggested that better management along river banks for dog waste was necessary with possible treatment of storm water sources from further afield also being a possible option.
Levels of cultured E. coli (CFU.100ml) and PCR based markers (copy number) detected at Antigua Boatsheds under low flow conditions.
This case study highlighted that it was possible to trace sources of water contaminants right back to the source animal that was producing the waste. In doing so possible management solutions could be developed to reduce the introduction of harmful waste, micro-organisms and pathogens into waterways and specifically waterways which hold strong cultural and recreational value.
The framework of tools has been developed and used by the Institute of Environmental Science and Research New Zealand (ESR).
Elaine Moriarty and Brent Gilpin (2009): Faecal source tracking in the Avon River, Christchurch. Report No. R09/67. Prepared for Environment Canterbury by Institute of Environmental Science and Research Ltd, Christchurch