Water quality in earthquake-affected rivers and estuaries returns to normal
Water quality in earthquake affected rivers and estuaries have returned to pre-earthquake levels, Environment Canterbury scientist Michele Stevenson said today.
Environment Canterbury has been monitoring a range of sites each week for the last nine weeks to track levels of bacterial contamination. “The results from this week’s monitoring show that bacterial concentrations at all sites are back down to the range we have seen at these sites in the past.
“This is really good news for all recreational water users, and is directly related to the speed at which the Christchurch City Council and Waimakariri District Council have repaired sewers and pumping stations damaged in the earthquake.”
Earlier this week both Christchurch City and Waimakariri District announced sewage discharges into all waterways had halted as a result of the rapid repairs which had been undertaken.
However, Canterbury Medical Officer of Health Alistair Humphrey warned that the risk to water quality and public health is still higher following significant rainfall and people should avoid contact with all waterways for 48 hours after heavy rainfall.
“This caution should be taken very seriously as sewer and stormwater pipes are still under repair and rainfall can result in sewage overflows and leakage from these damaged sewers.
“It will be up to two years before all sewers are reinstated to their pre-earthquake state and so people should bear this longer period in mind regarding rainfall events.”
Ms Stevenson said that water testing sites along the Avon/Otakaro, Styx, Kaiapoi and Waimakariri rivers, and at the northern part of the Avon-Heathcote Estuary/Ihutai had shown significantly elevated levels of indicator bacteria in the weeks following the earthquake, but testing showed these had now returned to normal levels.
“Next week Environment Canterbury starts its normal summertime water quality testing of swimming sites. Popular recreational sites are graded based on past data and a risk assessment so check out these grades to see whether a site is safe for swimming. If you’re interested in seeing what water quality is like at your favourite swimming place at any time during the summer months, have a look at the information on our website.”
Ms Stevenson said Environment Canterbury’s water quality monitoring relies on community volunteers who collect weekly samples from the Avon-Heathcote Estuary/Ihutai, Lyttelton Harbour/Whakaraupō, Akaroa Harbour and Okains Bay. “It is great to have this community support so we can provide this service.”