Rather than going for expensive man-made methods of channelling water west, advantage should be taken of natural water courses. Extremely careful selecting of engineers is vital for a positive outcome with a project like this. Consulting engineers companies must be put on stage by stage contracts not just given the job no questions asked. Once the water runs downhill west the the game is won. Ideally, a mono rail should be built alongside at the same time. It'd help with the delivery of equioment to the sites & once finished it'll provide flood-proof all year round transport.

Natural Australian outback river beds are mostly too sandy to drain water long term without considerable loss due to seepage. The natural beds cope well for sudden brief flood water flows.
Depression in those river beds, waterholes, do hold water long term but they are too few and far between to avoid loss of water due to seepage.

There is also evaporation to consider especially in shallow channel country rivers where bkack soil does help prevent too much seepage.

Steel aqueduct will generate business for mining and steel and food and fibre local and export industries,& while generating drought proofing for many farmers at the same time.

JF Aus,
Yes, Natural sandy riverbeds will absort a massive amount of water in the beginning. The secret is to saturate them as the work progresses. There'll need to be weirs & reservoirs along the way, in fact the more water is absorbed in the beginning the more will then flow on. The groundwater has been so depleted that it'll need several monsoons to replenish but again, once that is achieved, it'll become easier as it goes along. It will very likely result in a new, wetter weather pattern which will add to the permanency of usable water in the long run. The key words are political will & patience. Nature will be enhanced a great deal. The good part is that this project would not require as much effort as many people believe it would.

individual,

I doubt there is enough water at the source to soak and saturate vast distances of bone dry sandy river beds.
Better for available water supply to be used on stock and crops and wetlands.

I wonder if the new PM will give water infrastructure and farmers a fair go. A fair hearing of ideas until proven feasible or impossible.
Australia is a food producing nation isn't it?

I doubt there is enough water at the source to soak and saturate vast distances of bone dry sandy river beds.
JF Aus,
That's where the pragmatists will come into the picture. Use existing watercourses & wherever required, modify them to reduce water seepage. From a technical & economical point this is hardly worth of considering as an obstacle. Where the riverbeds are too wide, narrow them !
Where they're too narrow, widen them ! where there is too much seepage, seal it or divert.
The two most important factors are; 1 get water beyong the Great Dividing range & 2 curb the ever increasing run-off into the GBR.
This project could be an economic stimulus beyond the grasp of those who aren't interested in anything outside suburbia. As I stated before, combine the channelling of fresh water with a progressive construction of a rail line. For least maintenance expense & least environmental impact this should be a mono rail. Whereever necessary, the rail structure could incorporate irrigation piping.