Legal Question in Civil Rights Law in California

Re: Neighbor harrassment

False accusations:

The tort that first springs to mind is slander. Particularly if she's accusing you of criminal activity. And quite possibly false imprisonment. If her shenanigans have caused you to be arrested or even detained momentarily (including where you are required to go to the courthouse), this would likely constitute false imprisonment.

Now, the sprinklers:

Trespass to land -- if what she's doing is intentional, and she's basically spraying water onto your land (even if you're a renter), this would be an actionable form of trespass. Trespass need not cause actual damage. You will probably not get a whole lot as a remedy... I'd expect an injunction to ensue (that is, an order to quit sending water onto your land).

the damage caused is more of an annoyance, I assume. To sustain a cause of action for the tort of nuisance, you'd have a much better chance if it was of a more substantial nature, such as with irritating smoke, fumes, excessive noise, or if she decided to start farming hogs. If you're not in your car when it gets rained upon... well, you know, if a tree falls in the woods and nobody's around to hear it...

Now, the specific requirements of each of these torts vary widely from jurisdiction to jurisdiction. To get a firm grasp on what your rights are, contact an attorney, or perhaps consider doing some legal research yourself, if you're prepared for such an undertaking.