Imapct of raw Sewerage Discharges on the Water Quality of the Avon River Christchurch, Post Earthquakes

Prior to the 2010 and 2011 Christchurch earthquakes, microbial water quality measurements of the Avon River intermittently exceeded recreational water quality guidelines. The 2011 earthquakes resulted in direct sewage discharges to the Avon River of more than 5,000 cubic meters a day over six months. A study was commissioned to test water and sediment samples from the Avon River tested for the presence of E. coli and Campylobacter, and sediment samples tested for Giardia and Cryptosporidium. Selected samples were also tested using faecal source tracking markers. The levels of E. coli at the Boatshed and Kerrs Reach were similar throughout the study with human and wildfowl sources identified. During the 2013 sampling the E. coli levels at Owles Terrace were <550 E. coli per 100ml. Campylobacter was detected in water from all three sites.

Concentrations of E. coli in 2013 were lower in sediments from the Boatsheds and Owles Terrace than observed in 2011-2102, while at Kerrs Reach, E. coli levels were higher than the average concentration previously The Kerrs Reach samples were also the only sediment samples in which Campylobacter was detected. There was a marked decrease in concentration of protozoa in sediments at all sites in 2013.