Mister_e has a nice touch sensor I’m sure you can use to detect water.
You can change its sensitivity both software and hardware.
I used it for some other application and I’m sure it will work for you too.
All you need is a resistor and two parallel pieces of wire (ground and signal) for each sensor and n+1 I/Os for n sensors. You don’t want the wires too close to each other.
Just do a search for “touch sensor” and you’ll find his post.

Regards,

Nick