River of Diamonds - Drowned Earth, #6

A mechanic who can save the world. A mercenary who should hide from it. Just another day living the dream in post-Rise Australia. Rosa lives in one of the last idyllic settlements since the Rise. Unlike those in other communities, she has grown up with access to ample food, fresh water, and safety-but the community's secretive nature, and the fact they do not offer help to outsiders,  troubles her.
So when Rosa finds a map that could lead to a fortune in fresh water-a scarce commodity-she embarks on a plan to make a real difference to the world. The only problem? There's an apocalyptic wasteland between her and possible salvation. Rosa has a map, a mercenary, and a hope to salvage the future.