I have a long single strand aluminum wire. I want to use it with a microcontroller to detect water in the tank. I'll be putting one end of the wire inside water tank. Other end of the wire will be connected to a microcontroller to make decision if the first end of wire has come in contact with water. I know two wires can do this job fairly easily (by using one wire as Ground and the other for signalling) but I want to know how can I use a single wire to do the same job. Is it even theoretically possible? I want to detect just a 'zero' or 'one' corresponding to situations: wire 'is' and 'is not' in contact with water! 

Edit: The tank and pipe are made of cement and stand on the ground.