"A fantasy, uneconomic, impractical if not impossible" is a typical response when the Bradfield Scheme is mentioned, and I hadn't thought much about it until I talked to a couple of proponents of the new schemes. One was Leon Ashby, irrigator, water-spreading designer, 1999 runner-up for the Queensland Landcare research award, and centenary medal recipient for conservation and the environment. The other was Sir Leo Hielscher, 19 years chairman of the Queensland Treasury Corporation and a key figure in the development of Queensland's economy.
Both are schemes for conveying water inland by gravitation from the headwaters of coastal rivers. Gravitational flow enables a meager marginal cost for water delivery. Both are capable of delivering a massive increase in irrigated land in Australia while addressing many environmental problems: access to quality water for towns and mining, mitigation of coastal flooding and reef degradation, and meeting renewable energy targets, to name a few.
Over-hyped the Bradfield Scheme as initially proposed may have been, pumping water over the Great Divide and running down existing watercourses to Lake Eyre. However, there appears to be a route for a fully gravitational aqueduct with an ideal gradient of 1:5000. The route starts near Niall at 420m Australian Height Datum (AHD) within a potential Hell's Gate Dam extent at the headwaters of the Burdekin River. It crosses the Flinders Highway between Homestead and Pentland at 375m AHD, and on to Lake Buchanan at 320m AHD, a salt lake perched on the Great Dividing Range. Then it's downhill to the entire Mitchell Grass Downs, including the towns of Barcaldine at 267m AHD, Aramac, Muttaburra, Longreach, Ilfracombe, Winton and Richmond to Julia Creek at 150m AHD. The dams and route do not overlap with any protected areas or endangered ecosystems.
Tunnels from the Hell's Gate mega-dam are also an option. They should be cheaper to construct now than at the time of the construction of the Snowy Mountains Scheme. Sir Leo's scheme with tunnels and a mega-dam at Hell's Gate has been developed by engineers, so it should work.
The Snowy Mountains Scheme on average diverts 2,100 gigalitres (GL) of water per annum into the Murray-Darling Basin through pipelines, tunnels, and aqueducts, and has a total installed capacity of almost 4 gigawatts of power. More than 2000 GL per annum could also be expected from the Hell's Gate dam alone, based on the long term average stream flow data recorded at Mount Fullstop monitoring station. Leon Ashby estimates that his larger scheme from the headwaters of the Gulf Rivers, and Tully, Herbert and Burdekin Rivers could turn inland more than 20,000 GL, 10% of the average annual runoff. I have not seen hydropower estimates, but the potential is there to generate more than Wivenhoe Dam pumped hydro with 0.5 gigawatts installed capacity, the largest hydropower station in Queensland.
Ashby's scheme could irrigate 2 million hectares of land. By comparison, the Murray-Darling irrigation scheme distributes around 10,000 GL of water over 1 million hectares of irrigated land to generate $22 billion in revenue per annum, almost half the gross value of the nation's agricultural production. A scheme with the agrarian potential twice the size of the Murray-Darling Basin should not be dismissed lightly.
Suitable soils for irrigated farming lie throughout the Mitchell Grass Downs country. Richmond has recently conducted a successful pilot for crop types and market niches and is planning to expand the area under irrigation with a new local dam. Towns in the region are well serviced with road, rail and air transport, have a stable population, and a higher than average proportion of younger workers in the 25 – 44 years age bracket. There is clearly much more demand for water from these townships and industries, and suitable land available for irrigated cropping, than there is water currently available even if irrigation is restricted to the highest quality land.
Future population and industrial growth will lead to a significant increase in the township water demand not accommodated by current dams. Potable water from the Artesian Basin is of low quality. Before the recent rains, many storages were below 10% full. Ilfracombe hired a temporary desalination plant. The costs of developing new town storage should be offset against the cost of a Bradfield Scheme.
Offering a new option for long-term water supply will aid the growth of industry, due to the multiplier effects of a significant irrigation industry. Much is to be gained to the nation by fully engaging the outback communities with opportunities, building business capacity, engaging the indigenous population through procurement, training, and employment, attracting and retaining a workforce for construction and operation, and integrating project planning with policies at the national, state and local levels.
For example, the progress of the Adani Coal Mine between Clermont and Charters Towers has been held up by their water plan. The hitch seems to be that unlimited access to groundwater may risk desert oases at Doongmabulla Springs and also the high use of surface waters from the Suttor River. A pipeline from Lake Buchanan could provide Adani Mine with reliable supply and mitigate environmental effects of taking ground and surface waters. Other coal mines in the Bowen and Galilee Basins could help finance the scheme. At the end of the mines' life, they would have helped to build a permanent water infrastructure based around a renewable resource, water, in exchange for the extraction of the limited resource, coal.
Flood flows carry debris, sediments, nutrients, and other pollutants into the ocean adding stress to the Great Barrier Reef. A recent study supports better control over flood flows, as improving local water quality may help some reefs better withstand bleaching events. Currently, 95% of flood flows are uncontrolled, cascading over spillways of already full dams. Flooding also causes considerable damage to coastal assets. Capturing flood water high in the catchment and directing it inland in large capacity aqueducts would reduce the flow downstream and may eliminate the need for costly retrofits like increasing the spillway capacity of the Burdekin Falls Dam. Besides, relocating agricultural development to the west of the Great Divide would reduce the pressure on coastal water systems further.
Getting water into the Murray-Darling Basin would enable Queensland to sell water into a mature water trading market, or to participate directly in the Federal buyback scheme. But is this possible? Leon Ashby thinks it may be via a 1000 GL dam about 60 km north west of Blackall at an elevation of 250m AHD, and then gravitationally via a tunnel or by pumping water into the Bulloo River.