The Manning River near Taree has stopped flowing

Killabakh resident and president of Garden Clubs of Australia, George Hoad crossed the Manning River at several points returning home from Tamworth and was distressed at seeing the Manning not flowing. Photo courtesy George Hoad
Killabakh resident and president of Garden Clubs of Australia, George Hoad crossed the Manning River at several points returning home from Tamworth and was distressed at seeing the Manning not flowing. Photo courtesy George Hoad

Aquatic ecologist, Dr Keith Bishop knows the Manning River and its catchment like the back of his hand.

He has been doing regular surveys of the river, on the Mid-North Coast of NSW, for 12 years. And what he has seen this year has shocked him deeply.

Dr Bishop usually surveys at night, but this October, wanting to save travel time, he decided to camp out and look around.

"The upper valley and river are in such a stressed condition, very depressing," he said. "I am surprised how ignorant I was."

While people are well aware of the plight of farmers due to what is one of the the worst drought in the region's recorded history, what is currently occurring in our river system is only now beginning to appear on peoples' radars.

"I think it is important the broader community realise what is going on, so close to home," Dr Bishop said.

I think it is important the broader community realise what is going on, so close to home.

Dr Keith Bishop, aquatic ecologist

The Manning River is famous for being the only river in the southern hemisphere to have a 'double delta' - there are two entrances to the river, one at Old Bar and one at Harrington. It is one of only two rivers in the world to have permanent multiple entrances, the other being the Nile in Egypt.

Its headwaters are in the Barrington Tops National Park on the north eastern slopes of the Great Dividing Range. It descends 1500m and runs for 261kms to the coast. It is joined by 11 tributaries along the way, including the Barnard, Nowendoc and Gloucester rivers.

The Manning is one of the few major rivers in NSW not to be dammed for water supply.

The Manning River is the primary source of water supply for residents from Harrington, north of Taree, down to Pacific Palms, south of Forster and services 90 per cent of MidCoast Council's customers. Water is pumped from the Manning River and stored in Bootawa Dam, near Wingham. This dam supplies water for the entire Manning scheme.

The river is home to the endangered Manning River helmeted turtle, which is endemic to the upper and middle catchment of the Manning River.

Gravel pit: the Barnard River, a tributary of the Manning River, at Bretti Reserve. Photo: Darren Ray

Gravel pit: the Barnard River, a tributary of the Manning River, at Bretti Reserve. Photo: Darren Ray

Valley sides along the Manning River upstream of Mount George are covered by dead and dying trees. Landholders are indicating trees more than 100 years old are dying.

The river has stopped flowing at its main measuring point at Killawarra, just upriver of the tidal limit near Wingham.

Other rivers in the catchment that are tributaries for the Manning have also dried up. The Little Manning and the Barrington rivers were reportedly still flowing, but that was some months ago.

"With no trickle flows, the river in shallower areas is now reduced to algae-smothered ponds lined with decaying organic material and developing layers of sludge, instead of clean cobbles and gravel underlying sparkling waters.

"There is a feeling of a strong of cesspools rather than a river. The smells are also powerful, from the decaying organic sludge, rotten-egg gas being released when you wade in and, of course, the omnipresent stench of cattle which have died and are now decaying in the heat."

Dr Bishop reports that native fish species, such as Australian bass, have now stopped breeding, with no young sighted since early 2018. Other species have stopped migrating. The decline of breeding and movement of native fish species has allowed alien species to spread upstream very quickly when small flows allow.

Dr Bishop asked landholders if they have seen conditions like this before and their answers depended on where in the catchment they came from.

Bodies of cattle are decaying on the river's edge. Photo Dr Keith Bishop.

Bodies of cattle are decaying on the river's edge. Photo Dr Keith Bishop.

"In the upper Manning, upstream from the influence of the Gloucester River which still collects water from southern rainfall events, long-time landholders say they have never seen such a climatic event before.

"In the lower Manning, which gets that water from the Gloucester River, and receives occasional showers from coastal-fringe rainfall events, long-time landholders say they have had droughts like this before, for example in the 1960s and 1980s," Dr Bishop said.

Data from the WaterNSW website extrapolated from 229 days up to December 12, 2019 shows that the Manning River has endured 167 days of very low flow (less than 100 megalitres a day) in 2019 to that date. A graph of this data shows this is dramatically more than any other period since data was available from World War II.

The river is measured at Killawarra for level, flow, and turbidity. As at December 12, the river height was 0.11 metres and falling and the discharge (or river flow) was 0.5ML/day. A very low for the Manning River is considered to be less than 100ML/day.

Dr Bishop has not seen the river not flowing in the 12 years he has been surveying river.

"This is the very first time ever," he said.

Map showing zero flow on Manning River at Killawarra. Source WaterNSW

Map showing zero flow on Manning River at Killawarra. Source WaterNSW

"It's turning into another system. If you see something of that size, there's a system change going on. Something very drastic is going on," Dr Bishop said.

"I'm not a climate modeller but it looks like a very extreme shift, potentially, if you go along with what the climate modellers are saying.

"Also very weird things are happening in the upper estuary with saltwater pouring upstream with the low flows - school prawns, garfish and silver batfish turning up at the tidal limit." The tidal limit of the Manning River is just past Wingham at Abbotts Falls. "I expect bottle-nose dolphins to appear soon and let's hope there will be no more mortalities as has happened before," he said.

Water flow at Killawarra for November 2019. Very low flow for the Manning is considered to be 100ML/d. Now, the flow is below the bottom level in this graph at 0.5ML/d. Data source WaterNSW.

Water flow at Killawarra for November 2019. Very low flow for the Manning is considered to be 100ML/d. Now, the flow is below the bottom level in this graph at 0.5ML/d. Data source WaterNSW.

When I was interviewing Dr Bishop for this story originally in October, he indicated that morning there was 100ML coming out of the Gloucester River, but only 60ML further downstream in Killawarra.

"So there's a 40ML loss along that system, possibly due to irrigation," he said.

Irrigators are required to cease pumping from the Manning River at 98ML/day

Only months of water supply estimated left in Bootawa Dam

At the time of publishing the original story on November 8, level three water restrictions were about to be introduced. At that time, MidCoast Council estimated that if water restrictions were to remain at level three, there would be approximately 80-90 days of supply in Bootawa Dam.

However since then level four restrictions were introduced on November 25, and the bushfires that have roared through the MidCoast Region have taken a big toll on water supplies, with water being taken from water supplies to fight the fires - a necessity.

According to Rob Scott, council's director of Infrastructure and Engineering Services, council stopped pumping from the Manning River to fill the dam on October 11.

Bootawa Dam's capacity has been falling since that date and is currently at approximately 60 per cent, Mr Scott said.

Council had started to draw from the Nabiac acquifier, and has started drilling new bores at the Nabiac site and establishing a mobile desalination plant adjacent to the treatment plant. The Nabiac aquifier is currently producting 8-10 ML/day and with the new bores should be producting 12-15ML/day.

Mr Scott said the work council is currently doing at Nabiac will extend supply by 30 to 40 days, with more work continuously extending the supply

Once the desalination plant is drawing water from the Wallamba River, Mr Scott expects the acquifer to be producing an additional 5ML/day.

Mr Scott said council is hoping to have the desalination plant on site in March 2020.

At the time of writing the original story MidCoast Council was in the process of renegotiating its water access licence conditions with the National Resource Access Regulator to allow it to pump from the river to "maximise their yield".

This story The river runs dry: Manning River at zero flow first appeared on Wingham Chronicle.