Recently it was reported on the fact that Salty Lakes in Broadwater National Park had emptied, leaving behind an almost dry lake bed covered with brown sludge. The sludge was a legacy of the dumping of partially-treated effluent from the Evans Head Sewerage Treatment Plant over many years (POEO Licence #2386) entering the lake.
The Salty Lakes complex consists of a lake to the south, an intermittently closing and opening lake and lagoon (ICOLL) with brackish water, and a saltwater creek to the north connecting to the ocean but opening and closing from time-to-time leading to drainage of the lake.
The contaminated lake had a massive fish and bird kill in 2005 forcing Richmond Valley Council (RVC) to upgrade effluent treatment, and also forcing it to put in place a rehabilitation program to restore lake integrity.
The rehab solution consisted of blocking the connection between the lake and creek so that it could no longer receive saltwater from the ocean via the creek. But it also meant that the lake would not run dry.
No swimming
Unfortunately, this strategy meant the lake was being converted to a freshwater ecological system. The legacy contaminated residue issue was not resolved leaving it to fertilise future algal blooms, perpetuating the compromise of lake health.
A ‘no swimming’ sign is still in place at the lake system some 20 years later raising significant questions not only about the lake but also public health. Visitors often swim in the creek.
Popular mythology has it that the connection between lake and creek was dug by duck hunters but its size suggested that large excavation machinery would have been used and it was most likely local council that did the work to get rid of the contamination created by the dumping of sewage.
Historical information available to us shows that the lake and creek were always connected but with a much smaller naturally-grassed causeway.
A few days ago we reported that the lake had drained and the creek waters were diminished. We continued to monitor the system and noted that the creek had begun to fill two days after we had reported the empty lake, however, it was not until today, three days later, that we discovered that the lake had refilled, the creek bed was covered in water and the entrance of the creek into the ocean had closed.
It was also noted that there had been a significant influx of the ocean during a couple of very high-tide over a couple of days as evidenced by the fact that all the tyre tracks had been washed away and there were very clear signs of water movement into the creek. There had been no rain in the interim which might be used to explain what had happened.
With the filling of the creek the water level had risen to push through the breached connecting barrier between the creek and lake sufficient to refill the lake with salty water.
The discovery that the lake had refilled so quickly came as a surprise because of its size but it is a shallow lake and can refill quite quickly.
We had set out to gather scientific information about the sludge at the bottom of the lake and to take various samples of the water which remained. We were left to look at the properties of the water and the lake and review of the sludge is now pending.
Preliminary analysis of the lake water including comparison with data obtained last year shows that it is salty again, clearly returning to its former status as a brackish ICOLL.
Evans Head Residents for Sustainable Development Incorporated has the view that:
- the rehabilitation strategy for the lake involving blockade of the lake and creek needs to be abandoned and the lake returned to its former status
- the sludge at the bottom of the lake must be removed so that the contamination cycle and algal bloom is stopped
- that the water from the STP be either stopped or put through an artificial wetland, a strategy suggested by the community 20 years ago but rejected by council, or processed for reuse to a potable standard
The burden to do this work should not be borne by National Parks but by the state government which has been cost-shifting to local government and insisting on a growth strategy which is only exacerbating infrastructure costs and problems such as those seen at Salty Lake.
The Salty Lakes complex needs to be returned to its former status reducing long term demand on council resources and reinstating its ecological value.
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