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Summer water quality readings in Southland are "unfortunately" similar to last summer and the sources of some high E. coli levels are being investigated, Environment Southland ecosystem response team leader Nick Ward says.
All 10 ocean sites in Southland that have summer sampling for E. coli have "green" or "safe for swimming" gradings at present, but all 10 river or estuary sites have "amber" (caution advised) or "red" (unsuitable for swimming) gradings.
The Aparima River, at Thornbury, Mataura River (Gore) Waiau River (Tuatapere), Jacobs River Estuary (Railway Bridge East) and New River Estuary (Water Ski Club) all have red gradings.
Based on the last three years of data, the Aparima and Mataura Rivers also have overall "red" gradings, and Waiau, New River and Jacobs have amber gradings.
The Mataura River, at the Riversdale Bridge, Oreti River (Wallacetown), Oreti River (Winton Bridge), Waikaia River (Waikaia) and New River Estuary (Omaui) all have amber gradings. All five have red three-yearly gradings.
Mr Ward said the Southland lowland rivers and streams "do show poorer water quality than those higher up in the region".
"Unfortunately, it looks like the results we’re seeing this year are similar to last year; however, we’d need to do more analysis at the end of the summer monitoring season to confirm this."
Environment Southland was investigating the sources of the high E. coli readings in the Omaui area and working with the Invercargill City Council.
The city council operates a wastewater treatment plant at Omaui.
A spokesman for the regional council said a request for "source tracking" would normally come from Environment Southland itself, "but in theory anyone with the right knowledge can take their own samples and request the same tests". For Omaui, normal regional council samples would be taken this week.
If another high E. coli reading was recorded, source tracking analysis, i.e. DNA testing, could be done.
"If it’s identified as human sources, then we can do some work with the Invercargill City Council and community to try and find out why that’s the case. "If it’s other animals, then we can work with others to figure out the most likely source and see what can be done about tidying that up."
The "inherent complexity" made it almost impossible to attribute a high result to a particular cause or party, so enforcement action had not been taken as a result of any summer monitoring results.
In the past, Environment Southland had worked with the community and local councils to identify and remedy the problem in certain areas where there was a particular health risk.
Mr Ward also encouraged people living "more rurally" to have their septic tanks checked, and to continue to plant and fence along river and stream banks.
• Environment Southland rules stipulate dairy farms must have discharge permits for their farms. Effluent was not allowed to reach waterways. District councils also had to have discharge consents for wastewater and stormwater, Mr Ward said.
• E. coli bacteria come from the intestines of people and animals and are introduced to the environment through faeces.
• They can cause diarrhoea, nausea and occasionally vomiting, fatigue and fever.
• The presence of faecal indicator bacteria indicates other harmful pathogens may also be present.