Generally, with Australian rural history, I'd recommend contacting the local libraries of the area, as rural librarians are probably quite aware of what local histories of the area might have been published about those specific areas, perhaps on vanity presses.

However, the Blowering Reservoir looks to be part of the Snowy Mountains Scheme, which is an iconic 20th century piece of infrastructure with national significance that's been Heritage listed. As a result, there's a fair amount of information on that scheme, and some of it is likely to deal with the people who were displaced by it. My first port of call if you wanted to know more would be contacting or visiting the Snowy Scheme Museum in Adaminaby, a museum dedicated to the construction of the scheme/the dams. There's also several books on the scheme; mostly the books on the Snowy Scheme focus on the multicultural workforce and how that was the forerunner to a big change in Australian society, but books like Snowy: The Making Of Modern Australia by Brad Collis or The Snowy: The People Behind The Power by Siobhan McHugh might also provide some details on what and who was in the area before the dam was built, at a general level. Hope that helps!