Which 1.6 do you have 75 or 101PS?
I know from experience that the O-rings between head / motor block / water pump and their flanges like to start leaking with age. Sometimes also flanges themselves are cracked. Quite often that's a slow progress and not immediately visible, in particular water pump flange or then it may be the water pump itself.
If you have a 101PS engine that's not a big deal, cos the pump is driven by the alternator belt, on 75PS ones it's driven off your cam belt, so more tricky / expensive to change.
If you have a blue lid I wouldn't suspect that so much anymore, one from scrappy won't be better than yours cos it could be 10+ years old.