Current conditions in the Bellinger River catchment are similar to those of 2015, when the Bellinger River Snapping Turtles were almost driven to extinction by a virus.
"We're seeing a lot of algal growth, which indicates that there's nutrients and phosphates getting into the water," said OzGREEN's Sue Lennox.
OzGREEN's Riverwatch program has found disturbingly high levels of phosphate in the usually pristine Never Never River.
The Australian standard is for available phosphate levels to be under 0.06mg/L but water testing near Gleniffer Hall on Tuesday revealed current levels are 0.37mg/L, which is six times higher.
Sue said this was likely due to a combination of low rainfall, hot weather and nutrient run-off from fertilizers and animal waste (including humans).
A similar situation prevailed in 2015, when thousands of Snapping Turtles died.
"It was a huge mortality event and it was this time of year and exactly these conditions," Sue said.
Riverwatch was set up in response to that event, as a long-term, community-driven citizen science project whose aim is to monitor and improve the health of the river.
A captive breeding program at Taronga Zoo was also initiated, using 17 turtles retrieved from the last remaining section of the river to which the disease had not spread.
The long-term aim is to raise and release hatchlings back into the Bellinger River.
In the short term, some good rain will help flush the river, but longer term what is required is attention to the health of the vegetation on the banks.
"Part of it is restoring the riparian zones so that nutrient run-off is trapped rather than coming into the rivers. That is something that will help river quality overall," Sue said.
Water quality testing on the Bellinger, Kalang and Never Never Rivers earlier in January found elevated phosphate and low levels of dissolved oxygen at 9 out of 15 sites. Full results and monthly reports can be found at www.ozgreen.org/br_data and on the Facebook page @BellingenRiverwatch