let us first pump that inland, even if it is less than 100 kilometers inland
Belly,
Great idea ! With so much more run-off now in comparison to before absorbtion into the ground was blocked by infrastructure, that run-off should be irrigated inland via a Bradfield scheme like system. The employment this would create is unfortunately beyond investors' mentality so it has to be a Government project. The voting public would show its appreciation. if only we could have a Government with such foresight.

There are people who don't want food and fibre and fuel productivity in Australia.
Those people have used politics to cause reduction of local production.
Those people then sit back without really working and getting their hands dirty while they import food and fibre and fuel. They put profit from commissions and trade deals into their own pockets. Those in the know with political influence and brown paper bags and foreign tax haven bank accounts just sit back and press a few buttons to make multi millions.

Look at imported fuel and our refineries shut down and gone. Former PM Howard has connections with fuel importers. Former PM Keating got into overseas pork production while world ocean fish depleton was being reported (alternative white meat).

Look at fish. Over 70 percent is now being imported annually because local fishing town economies can no longer supply demand, due to fish depletion linked to river and coast ecosystem devastation being allowed to continue unchecked.

Think about motives.
Why are politicians and government and media not addressing the huge cost to consumers for fresh wild fish that are free without production cost (if they are there to catch) ?

Big producers in other countries don't want productivity in Australia unless they own it. They want all possible control and profit for their, big business. How big?

Fifty million tonnes of aquaculture fish is now being produced worldwide annually from aquaculture.
50 million tonnes x 1,000 kg per tonne x $5 per kilo annually, is beyond capacity of my calculator.

Politics of the motives may already be stopping Aus farmers getting infrastructure to supply water to Australian farmers in general.

There is a way of bringing fresh water to many farmers without costly pumping over the mountains.
See the following link Index F. Fairfax J.C.

Would it be impossible? If so, why?

http://agwhitepaper.agriculture.gov.au/supporting-information/published-submissions-green-paper

There is no economically viable way to pump water over large distances. A cubic metre of water weighs a tonne. However, much of the water that is already inland is used by a few large cotton farmers.

Water can be engineered to flow long distances without pumps.

Food for thought in this food and fibre producing nation of Australia.

http://www.quora.com/How-does-the-California-Aqueduct-transport-water