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I don't believe ground water has anything to do with these features. The problem with that is, if I have ground water and it manages to survive for billions of years and manages to come out of a little cliff, today the atmosphere of Mars is so cold and dry, water is gone instantly. It will either freeze or evaporate before it has time to trickle down and carve a little gully.
The idea of water coming from snow gets around all that. The water is in the snow. It's cold, for sure, but the snow acts as a blanket. It insulates to protect the melting water that is inside the snow. The surface is cold but the interior actually warms up and melts and trickles down through the snow possibly eroding the little gullies. You've brought along your own protective blanket to keep the water from just evaporating and freezing.
It's not really surface water, it's underneath a snow blanket. Snow comes and goes: snows on the surface, it melts, snow goes away, comes and goes. It just seems to work better, but it's only a model. Phil Christensen of ASU originally developed this idea for the site described in the attached link:
