The water knife will sort of inevitably suffer from comparison to Bacigalupi's previous non-YA novel, the award-sweeping Wind up girl. I loved that one, and so did everyone else, apparently. It was thematically related, too - Bacigalupi's futures are environmental dystopias, which is relevant and, of course, more than a little depressing.
Being a Scandinavian whose newsreading is scattered at best, I wouldn't necessarily have been very aware of the California drought if not for SFF writers like Seanan McGuire, who has talked about it in various social media, and wrote a short story about the topic for Lightspeed recently. (And the two Elizabeth Kolbert books I read recently, but my wish to do that was also quite directly inspired by fiction, so...)
But, oh, here we are. The water knife takes us to an American southwest where water is worth more than blood, and borders between us and everyone who isn't us are more rigid than ever. The states aren't all that united, anymore. Texans have become homeless, desperate refugees. A couple of them, along with the rest of the cast, find themselves in Phoenix, Arizona, which is about to go the same way as Texas did.
As always, Bacigalupi builds a world that is real to all my senses; Reading this, I feel like rubbing my eyes as if they're dry from the sandy air, coughing, grimacing at the likely odors of a city without flushing toilets. I'm grateful my imagination doesn't stretch into sharing the resignment of people accustomed to urinating into clearsacs so the fluid can be drunk again.
If I had been able to start connecting with, or caring about, the characters before I'd already worked through half the book, it would be near perfect. That first half felt like a long, long wait for a hook to latch onto, though. With a book like that, it almost makes me feel guilty, like it was a failure on my part to be sufficiently excited by environmental disaster alone.
When I did start to care what was going on with Lucy the reporter and Angel the waterknife, things almost immediately turned very grim for everyone. Very.
As I came to the last page, I certainly didn't regret having spent the time it took to read it - but if I had been the kind of person with the ability to just not finish a book, I can imagine I might have put it away about a hundred pages in. That experience does, obviously, detract from the overall rating of a book, even if it's excellent by the time you get to the end.
So my recommendation goes to readers into environmental SF, obviously, but perhaps only the most patient of them. Who are okay with waiting a certain amount of time and pages for a work of fiction to really get rolling. I imagine you know yourself well enough to judge whether or not you can cope with a few hours of not-immediate-gratification, for now. (Where I am, it's the thundery, moist, hot part of the year, which probably has my own patience at a minimum!)