This is the second part in a four-part series that discusses issues about water in our region. Read part 1 here. Part three is a summary report of information shared by Townsville Enterprise Ltd. about the Hell’s Gate Dam feasibility study at our forum that was held on 10 October. Part four asks how climate change will affect our region’s water security.
Guest post written by Vern Veitch. All views expressed are the author’s and not the official opinion of NQCC.
With Townsville in a drought and under Level 3 water restrictions, the public are asking a lot of questions. Water falls out of the sky so why does it cost so much? Why don’t we just build another dam? If the dams are on higher ground, then why does water have to be pumped?
Mainstream media in Townsville certainly muddies the waters by publishing half-truths and not publishing all the really important bits of information. Through a concerted media effort, the public has been led to believe that Hell’s Gate is the answer to endless and cheap water.
SO WHERE IS HELL’S GATE?
Hell’s Gate is about 130 km (in a straight line) north-west of Townsville in the upper reaches of the Burdekin River (see map). The river flows between two hills that are about 90 metres higher than the river bed. Based off levels obtained from Google Earth, a wall that would contain most of the water would need to be about 1 km long, making it both longer and higher than the Burdekin Dam but in a steeper part of the catchment, so volume may be less.
DAMS ARE VERY EXPENSIVE INFRASTRUCTURE.
As a comparison, an estimated costing on the proposed Urannah Dam in 2015[i] which would be a much smaller dam in a more accessible area, was over $250 million. Hells Gate Dam would require much more associated infrastructure such as roads, high voltage power lines for pumping and a very long pipeline if it were to supply Townsville. Obviously this is beyond the capacity of a local council to build and finance and so if built, the dam would likely be run by Sunwater. Council would likely still have to cover the costs of building a pipeline (more than three times longer than the one needed for Burdekin Water) and pumping.
WHY WON’T IT JUST RUN FROM HELL’S GATE TO ROSS DAM?
Simple – Hervey’s Range. The river bed at Hell’s Gate is roughly 325 metres above sea level and Ross Dam is only about 25 metres below the wall. If a straight line were taken from Hell’s Gate, there are some 600-metre-high hills in the way. Even if it followed the lowest possible track – along the old Greenvale Rail Line – it would lose another 20 metres or so to get to a down-river pump station near the rail/river crossing and then need to be pumped up to at least 385 metres over about 80 km before it starts to drop onto the flood plain. It is unfeasible to siphon water over that distance and height in large pipes which means water would need to be pumped. In-pipe generators could be used to recover some of the energy expended on pumping water, but they would be unlikely to cover the initial energy costs. As the dam would be owned by Sunwater, Townsville would still have to buy an allocation to help recover the construction and maintenance costs, as well as pay for the interest and depreciation. The pipeline would also need to be about 20 km longer, funded by ratepayers.
THE ALTERNATE SOLUTION OF A SECOND PIPE TO PUMP FROM THE HAUGHTON BALANCING STORAGE IS STARTING TO LOOK PRETTY CHEAP.
Another alternative put forward in the media was to build a pipeline from the Burdekin Dam to Ross Dam so that the water could gravity flow. I guess it depends on who’s paying for a pipeline 143 km long (in a straight line), cutting through solid granite in places over 100 metres deep for at least 100 km before it reaches the flood plain and can be put at ground level. Again, a Sunwater allocation would be needed along with at least some pumping and probably an upgrade of the water treatment infrastructure.
At present, Townsville has close to the cheapest water in the state, ask any resident in the Great South-east. The cost of an annual supply of 772kl of water in Townsville is $739 compared to $1,109.05 in Brisbane[ii]. If Townsville residents want access to more water with greater reliability, it will not be cheap.
A lot of the justification for the Hell’s Gate Dam has centred around turning the upper Burdekin into a major agricultural supply area to compete with the Murray-Darling agricultural region and overseas sources for both domestic and international consumption.
The economics of such a proposal have to take into consideration the shipping costs of such a relatively remote location. Even to get to the coast would be difficult, given that there is no rail connection. If rail were to be re-established along the old Greenvale line, the cost of building the pipeline to transport water to Townsville would increase significantly. Costs would also need to factor in the use of very high volumes of fertiliser as most of the soils in the upper Burdekin area have heavily leached with very low productivity. It is no oasis, even where water is available from the river.
THEN THERE ARE THE ENVIRONMENTAL FACTORS.
In particular, the challenge of managing increased sediment and nutrient loads entering the river and flowing down to the Great Barrier Reef. Ironically, there is also the issue of long-term sand starvation along the coast as rivers are critical to the supply of sand to coastal beaches. As sea level rises and other impacts of climate change are realised, the effect of sand starvation will compound even further. Dams trap sand better than they trap water but unfortunately allow the fine mud particles that go into suspension or solution to flow straight through. Almost no fine sediments or nutrients are trapped, negatively impacting the Great Barrier Reef. There is also the longer term risk of irrigation salinity, which would likely be an even greater problem in the dry tropics than in the temperate Murray Darling river system.
THERE IS A LOT OF INVESTIGATION TO BE DONE BEFORE HELL’S GATE SHOULD GET A GREEN LIGHT.
Not everywhere is suitable for water storage because of underground substrate formations. Whilst the above ground landscape might seem ripe for development to the untrained eye, there may be fault lines and flow paths that would make it leak like a sieve. In addition, the evaporation rate in that region is well above the 3 metres per annum experienced here on the coast, perhaps as much as double. It is hot and dry for a very long part of the year. The cost of construction also needs to consider that dams further upstream are less reliable than lower in the catchment. For example, this year the Burdekin Dam filled from rainfalls, mostly further west, rather than from the Upper Burdekin itself.
Across Northern Australia, large dams are universally well below their predicted usage. There have been numerous attempts to get more benefit out of the Ord River Dam and even the Burdekin has a significant capacity for expansion. If we truly need more storage in this region, arguably the best bang for buck would be raising Burdekin Falls Dam and improving its downstream distribution infrastructure rather than building another very expensive concrete wall in memory of a politician.
Instead of Hell’s Gate Dam, perhaps it could be called the Crown of Thorns Dam.
[i]An Economic Analysis of the Urannah Dam Project, Mackay Conservation Group pdf here
[ii] Figures based on Rates available For Brisbane: https://www.urbanutilities.com.au/residential/accounts-and-billing/prices-and-charges-2016-17#tab-tab1 and Townsville: https://www.townsville.qld.gov.au/payments-rates-and-permits/rates
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