James is correct, unlike the US or Europe, the interior is quite sparsely populated - remember it is a country the size of the US with the population of NY. We all cling to the coast.
Royal Adelaide of course could be argued to be an in land links, but it is only a couple of miles inland.
The courses along the murray river were originanlly built from gambling - the Murray River is the border between NSW (where gambling was allowed) and Vic (where it was not) so a lot of courses were built on the NSW side in the 80's to atract the gambling and golfing set from Melbourne. The law difference no longer exists, and so these places now struggle, but there are still one or two decent ones, however they were still products of the 80's and so a little silly.
Kooralbyn Valley was built some distance in from Brisbane in the 70's and was a fine bush course in the days, but has fallen on hard times in the last 10 years.
Lack of water is ultimatley the issue, but possibly the best by reputation was Horsham in Vic, M Clayton seems to speak its praises - however i have never played it and it was wiped out by the recent bushfires, no idea if it has come back.