Finding out when your great-grandfather owned his land and working forward may reveal when it might have been taken from him.
Australian land records
The FamilySearch Research Wiki's article Australia Land and Property outlines events in the history and development of Australia. According to their timeline, land records for South Australia begin in 1836. Another important waypoint is 1858:
1858: Torrens system of land conveyance and registration in South
Australia provides title registration for first time; other states
Wikipedia's article Torrens Title says:
Torrens title is a system of land title in which a register of land
holdings maintained by the state guarantees an indefeasible title to
those included in the register. Land ownership is transferred through
registration of title instead of using deeds. Its main purpose is to
simplify land transactions and to certify to the ownership of an
absolute title to realty. It has become pervasive around the countries
strongly influenced by Britain, especially those in the Commonwealth
of Nations and has spread to many countries in that group.
The FamilySearch Wiki also says:
Many land records are held in the states’ Land Title Offices. Land
Title Offices also have parish maps that can be used as plat maps to
identify your ancestor’s land holdings, as well as to identify the
land owned by other individuals in the surrounding areas. Parish maps
are divided into areas that provide names of the original grantees and
For holdings in the Family History Library catalog, do a place search for AUSTRALIA, SOUTH AUSTRALIA. There may not be any records for the time period you're looking for, but these categories may be of interest, and could be searched for in other archives:
- Archives and Libraries and its subcategories (for lists of holdings, and books on how to use the archives and libraries)
- Business Records and Commerce
- Directories (to find directory years that you may not have seen yet)
- Land and Property (the FHL holdings are mostly from 1830s-1840s)
- Law and Legislation (the FHL holdings are too early) for the eminent domain bill
- Newspapers and other Periodicals
- Public Records (one entry has business licenses, but too early for your inquiry)
Now that we have the groundwork of how land ownership is recorded in Australia, let's turn to the subject of how land can be taken away.
Compulsory acquisition (Australia) / Eminent domain (United States) / compulsory purchase (UK)
Eminent domain is the term used in the US for "the power of a state or a national government to take private property for public use"; Wikipedia lists the terms from many countries and says Australia uses the term compulsory acquisition (as in your question), and resumption.
The subsection Australia gives the history of compulsory acquisition in Australia and notes:
The term resumption is a reflection of the fact that, as a matter of
Australian law, all land was originally owned by the Crown before it
was sold, leased or granted and that, through the act of
compulsory acquisition, the Crown is "resuming" possession.
For Australian legal words and phrases, see Guide to Online Legal Research Publications at Southern Cross University. If you cannot access the online versions of the printed law dictionaries, search Google Books for the same title -- sometimes older editions are available for download.
Local histories and political writings may also be of interest. If the government was executing its power of resumption on a wide scale, you might find contemporary reports in newspapers, plus later discussion and analysis in local histories, and academic papers and dissertations.