Damming the Adelaide

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Matt Flynn
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Damming the Adelaide

Post by Matt Flynn » Wed May 08, 2019 8:43 pm

Smells like an election ...
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Re: Damming the Adelaide

Post by NT Wombat » Thu May 09, 2019 9:20 am

Off stream water storage isn't damming the river....


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Re: Damming the Adelaide

Post by NT Wombat » Thu May 09, 2019 11:01 am

I'm pretty sure they are looking at the gully between the hills between Manton dam and the river. A mate out that way had geo survey blokes going thru his place apparently surveying "the off river storage site" a couple of years back. The other thing with off river storage is that a lot of them are filled with pumped water from the river as most don't have large enough catchments. Still better than putting a fish proof barrier across the river, and if they are only pumping water out of the river in times of high flows shouldn't be that big an issue.

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Re: Damming the Adelaide

Post by Matt Flynn » Thu May 09, 2019 7:37 pm

Interesting. After reading the Daly cherabin study a few years back, with millions of cherabin migrating each night, I shudder to think what a dam could do to a major Top End river. That mass of migrating crustaceans would be a life support system, one can only imagine how they are tied into the ecosystem.

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Re: Damming the Adelaide

Post by ronje » Fri May 10, 2019 6:13 pm

Cubby station in Qld uses that sort of overland flow (flooding) harvest system. No pumping from river supposedly.
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Re: Damming the Adelaide

Post by NinjaFish » Fri May 17, 2019 5:54 pm

Here's the the full CSIRO report. There's 228 interesting pages and over 20M potential sites in the 'Darwin region'!

The Adelaide works out the most efficient 'cost wise' to produce.

https://publications.csiro.au/rpr/downl ... 9&dsid=DS4

There is an opinion piece somewhere online referencing the biological effects on Barra re the effects of 'off river' storage. I'll post it when I find it :roll: .

It was an adverse effect.

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Re: Damming the Adelaide

Post by Matt Flynn » Fri Jun 14, 2019 9:29 pm

Article I wrote for the paper.
****
A private water company wants to alter the catchment of one of the Top End's wild barramundi rivers.
An "Off Stream Water Storage" to store 310,000 megalitres is being discussed, to be located on the east side of the Adelaide River at the same latitude as the existing Manton Dam.
The "Off Stream Water Storage" (AROWS) label smacks of spin.
Let's call it damming of the catchment, with a significant annual extraction of water.
Interestingly, the ABC said the company plans to capture wet season flows about 40km upstream and channel it into the storage area.
This is an important point with regards to the potential impact upon the river on seasonally mobile species such as cherabin.
To provide perspective on size, Darwin River Dam carries 320,000 megalitres, of which Power and Water extracts about 37,000 megalitres a year for Darwin and surrounds.
Power Water also extracts about 6000 megalitres annually from dolomite borefields near Darwin.
Manton Dam is small by comparison, carrying just 14,000 megalitres, which is not used other than for fishing and water-skiing.
Nonetheless, Manton Dam is an existing obstruction on part of the Adelaide River's catchment as Manton Creek doesn't flow when the dam wall doesn't breach.
The Adelaide River, until now, has escaped large-scale development.
Aside from Manton Dam, there were earthen dams built on the catchment in the 1950s in an attempt to establish rice farms.
The farms didn't work out, but the local waterfowl loved the product and the impounded water.
The Harrison and Fogg dam walls are still there today, more or less, still holding enough water to attract swarms of waterfowl.
The Adelaide River catchment became infested with the woody weed mimosa in the 1950s, which changed the nature of its floodplains.
An aquaculture operation, the crocodile cruises and Goat Island Lodge are the only commercial establishments on the tidal river.
It is one of the most naturally turbid rivers in the world, but we can assume it is relatively free of fire-fighting chemicals, free of uranium ore and mine tailings, unlike some Territory rivers.
The Adelaide catchment has been of continuing interest to water managers.
There is a separate proposal to create a "Marrakai Dam", which covers a catchment as large as Manton and Darwin River Dam catchments combined.
A CSIRO report concluded that the AROWS proposal currently under discussion could extract more than 50,000 megalitres of water a year.
It said that losing 50,000 megalitres a year during high-flow events in the wet season "would have a negligible impact on the flow habitats of estuarine and coastal species".
Unfortunately, not every wet season produces high flow, but irrigators will still be screaming for their water.
Having just experienced the terrible 2018/19 wet season, Top Enders know too well that substantial wet season rainfall is not guaranteed each year.
Top End rivers needed every drop they could get this year, and the effect on barramundi was plainly obvious in the Barra Classic and Barra Nationals catches on the Daly River.
Secondly, the Adelaide River already has a dam on one of its major creeks.
What is most concerning though is the annnual movement of cherabin.
Cherabin, or giant freshwater prawns, are hugely important in northern rivers.
Charles Darwin University PhD candidate Peter Novak studied Daly River cherabin from September 2011 to April 2014.
He monitored a 400km stretch of the Daly, and the Edith and Ferguson tributaries, surveying more than 4500 adult cherabin and thousands of juveniles and larvae.
He discovered that the larvae needed to migrate from freshwater to saltwater within seven days of hatching to survive.
“We were very surprised to see females breeding throughout the river, up to 400km from the river mouth, because the larvae need to reach the saltwater within seven days to survive. We found that a larva hatched in the Katherine River more than 400km upstream can reach the estuary in time, but only during larger wet season floods,” he said.
The annual journey of cherabin begins when waterflow increases with the onset of the monsoon, from December to March.
At the end of the wet season, during the run-off months, juvenile cherabin the size of a person’s thumb migrate back upstream.
For about 30 days in April and May, Peter observed about a million juveniles every night moving back up the Daly River.
The results from his study suggested that large wet season flows are critical for the survival of larvae that hatch well upstream, and that bigger flows probably increase cherabin populations.
Because cherabin are a critical food item for fish and other wildlife, reducing river flows would have negative consequences for the entire ecosystem.
Keep in mind the mentioned observation of a million cherabin moving each night.
That biomass is part of the marine cycle as well, as the cherabin move up and down the river.
Perhaps the greatest concerns with the AROWS project come from the planned thousands of hectares of irrigated crops.
These will no doubt be treated with chemicals.
Some agricultural chemicals are incredibly harmful to aquatic life.
I am well familiar with the Adelaide River from Goat Island upstream as it was my favourite inland fishing place for many years.
The water near the top of the tidal reach is clear enough to fish for much of the year after a decent wet season.
It is a special place, with rockbars, snags, river bend eddies and undercut banks, and the green water holds plenty of mostly small but legal-sized barra.
I believe the AROWS project carries great potential risk for this stretch of river, if not the whole river.
It may affect the fishability of the upper tidal section, and may impact on cherabin migration during poor wet seasons.
The addition of potentially a 10,000 hectare intensive agricultural precinct to the catchment could adversely affect barramundi and other fish.
With the Gunner Government being hounded to bolster the NT economy and create jobs, it is a tough situation, much like the situation the world economy finds itself in, with global CO2 skyrocketing.
The last thing the world needs now is growth, but people desperately need jobs.
A perfect storm?

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