The water flowing in a stream or river is fed by numerous smaller streams, which are fed by even smaller streams that collect water from melting snow or ice up in the mountains, from springs, and possibly from human wasterwater sources. The bottoms of rivers are also below the water table in many places, so there will always be water at that level.
Gas density creating our atmosphere
Continental Polar and Maritime Polar ; Polar had a direct connotation with the cold. :)
