Low-power water level alarm

Hi

I'm planning to build a low-power water level alarm which can last for at least 4 months on continuous usage. I've found a schematic using the 555 timer but it'd use some 30mW. I wonder if it'd be a good idea to use MSP430, put it to sleep and raise an interrupt when a certain pin is short by water's conduction. Is water conductive enough to wake up the MSP430?

Any thought appreciated.

Thanks