"The Onyx River is a meltwater stream which flows westward through the Wright Valley from Wright Lower Glacier to Lake Vanda, during a few months of the Antarctic summer."
http://en.wikipedia.org/wiki/Onyx_River
Picture here:
http://seattlepi.nwsource.com/antarctica/photos/photo.asp?SubID=23&PhotoID=409
Water from melting snow has to go somewhere. Even if it goes underground, it can resurface.