Death of a Lake by Arthur Upfield. It's out of print, but you can still find copies at AbeBooks.
Raymond Gillen goes swimming in Lake Otway one night and is never seen again. Also missing is the £12,000 he won in a lottery. Now, thanks to an intense drought, the lake is drying up and the inhabitants of the sheep station are on edge.
The book's hero is Inspector Napoleon Bonaparte, a half-European, half-Aborigine who's working undercover as a horsebreaker and watching events unfold. The cast of characters includes the cook and her nubile young daughter who have been playing one man against another since before Gillem's disappearance. Death of a Lake offers a convincing portrayal of life in the outback where seven people who don't really like each other are forced by circumstances and their isolation to work, live and eat together.
But the book's most compelling character is the landscape: The lush 17-foot lake has attracted waterfowl and wild animals in great numbers. And rabbits. The depiction of the lake's last days is as thrilling and disturbing as any murder scene. And those rabbits ...