NSW Facing Water Quality Concerns After Bushfires And Heavy Rains

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NSW's water authority has admitted significant amounts of ash and debris have been washed into Sydney's main catchment area in the wake of devastating bushfires and the state's recent deluge of rain.

Warragamba Dam, in southwest Sydney, received a major dump of water over the past week and as a result, the state's water authority, WaterNSW, now says sediment, ash and debris are clearly visible on the surface of Lake Burragorang — a man-made reservoir forming part of Warragamba in the lower Blue Mountains.

"Our people are the best experts in the area of water quality. We are taking a range of precautionary measures on-site, including the deployment of a third floating boom in the Warragamba Gorge," WaterNSW's CEO David Harris said in a media release.

"Raw water quality at Warragamba is improving, however more inflows may cause further deterioration in water quality at the dam wall."

The authority said it expected this to happen in the wake of the bushfires that burnt more than 320,000 hectares of the Warragamba Catchment but the water was still safe to drink as it was being pooled from deeper within the dam.

"The intrusion is behaving exactly as our expert staff predicted – it is staying in the upper section of the water column," Harris said. "This means that we can safely draw good quality water from much further down in the water column if we need to supply from Warragamba Dam - which we are not doing at the moment."

Poor water quality can mean residents would have to boil water in order to use it for consumption. Tenterfield, near NSW's northern border with Queensland, knows this all too well after residents were advised by NSW Health in early October to boil water after its supplies were contaminated due to heavy rain after the damaging bushfires.

"Recent conditions for fires at the Tenterfield water supply dam have caused problems with water treatment, making drinking water in the Tenterfield Town unsafe," the alert read.

"Water used for drinking or food preparation should be brought to a rolling boil to make it safe."

The boil water restrictions were lifted just before Christmas meaning residents were forced to treat water for nearly two months.

Water levels at Warragamba Dam went from 42.7 to 76.7 per cent within the space of a few days after the region experienced the heaviest rainfall since the 1990s. Despite the 34 per cent increase in dam levels, Sydney is still placed under Level 2 water restrictions for the foreseeable future though they're eventually expected to be lifted.

More rain is expected in the region over the weekend due to a weakened tropical Cyclone Uesi. The Bureau of Meteorology issued a minor flooding alert for areas around the Nepean River, which has been overflowing due to the recent rain, but has since rescinded it as forecasts predict the rainfall will be lower than expected.