The arid locations mentioned in the article are lacking one of the feedstocks for this reaction -- water. I am not an Aussie, so what I know may be wrong, but doesn't Australia already have a water shortage inland?
You probably need relatively little water compared to other processes that evaporate/drain it (agriculture) or use it for run-through cooling (power plants). Even an ocean tanker full of water wouldn't make much of a dent into the flow rates of a river.
Other articles talking about this technology mention the possibility of using clean energy (solar/wind) to desalinate water to facilitate the production of ammonia.