Freshwater is formed from rainfall over the continents. The source of that
water is from evaporation of oceanwater, which leaves the salts behind.
This is no problem for the global flood view. There are however, lots of
other problems.
glenn
Adam, Apes, and Anthropology: Finding the Soul of Fossil Man
and
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm