While I was changing the oil today I noticed the bottom of the water pump was wet with antifreeze. Does it need to be replaced? I replaced all the coolant lines and pipes last year.

 

Short answer, yes. The area just south of the big green drop of antifreeze, between the pulley and the pump body, covers the weep hole. When the bearings start to go bad, the weep hole allows some coolant to escape, which helps to avoid destroying the bearings rapidly, as well as lets you know they are compromised.

I would guesstimate within 1-6 months if untreated, you will begin to experience "classic" signs of water pump failure, to include bearing noise, potential belt slippage due to axial play in the pump shaft allowing the pulley to move, and increasingly severe leakage from the weep hole.