Water level sensor question

Tested it with my DMM and yeah a NPN.

I am having a little trouble wrapping my head around R1 and trace.

Trace is effectively an open until exposed to water. Why is the signal wire getting more voltage with more water?

Vout= (Vs*R2)/(R1+R2)

I am see Base=Signal wire voltage with my DMM.

Base is starting at a low voltage and going up with more water exposed.