NSW Health documents obtained by the ABC reveal areas where deadly pathogens are regularly detected at dangerous levels in unfiltered drinking water pumped from rivers, lakes and dams.
The water safety reports, obtained after a lengthy freedom-of-information battle, also show more than 100,000 NSW residents were issued protective boil-water alerts in the last five years.
Around Grafton, a population of 40,000 are at risk from cryptosporidium, a parasite that causes gastrointestinal illness.
Residents have faced 10 boil-water alerts since 2006, issued “in response to the inability of the water supply system to manage risks”.
The documents say faecal contamination from cattle, and even swimmers along the Clarence River, is the parasite’s source.
Deadly bugs originate in “onsite sewerage system discharges”, “failures and presence of septic systems” and from dairy farms upstream.
The documents say “chlorine-resistant pathogens” — not killed by chemical treatments — are a threat to more than 40,000 people.
Around Kempsey, the risk identified is cyanobacteria — a toxic blue-green algae that can shut supply for 15,000 residents.
Grazing dairy cattle and raw sewage discharges near the Steuart McIntyre Dam trigger algae outbreaks here.
Alarmingly, the documents say “all pathogen groups” including e. coli are present in Kempsey water, and that a further “vulnerability assessment” should be undertaken.
In the Upper Hunter, more than 6,000 residents in Scone, Murrurundi and Aberdeen are rated at “very high risk” from dangerous pathogens flowing from an abattoir and septic tanks in the catchment.
The alpine towns of Jindabyne and Barry Way also face a “moderate risk from the presence of cryptosporidium” as well as toxic “blue-green algae” in their catchment.
Livestock faeces, and sewage, including from the Perisher ski resort are blamed.
The documents also identify other communities with one-off water concerns.
Last year boil-water alerts were issued in Dubbo, as well as villages including Toomelah, Gravesend, and Jubullum.
Billion-dollar filtration would improve rural water
The documents say the use of filtration systems would lift rural water supplies up to a standard enjoyed by large cities.
Many country councils supply unfiltered surface water, taken from watercourses, lakes or dams and treated with chlorine or UV disinfection.
But the documents reveal this simple approach is increasingly ineffective against resistant parasites, such as cryptosporidium.
The cost of introducing filtration across rural NSW is estimated to be in the order of $1.5 billion to $2 billion.
The documents also reveal a letter from Kerry Chant, the state’s chief health officer, to Gavin Hanlon, an executive in the Department of Primary Industries, warning that many unfiltered supplies would not meet Australian drinking water guidelines.
Dr Chant warned that in overseas incidents major waterborne outbreaks of cryptosporidiosis showed “the majority of consumers in a supply system became ill”, and urged a whole-of-government approach to devising and funding local solutions.
NSW Health Minister Brad Hazzard was approached for comment, but was unavailable due to heavy commitments.