While hiking in the North you have enough possibilities to refill potable water, because you will pass often houses, farms, villages
and gas stations with stores.
In the South there simply is no water, unless there has been rainfall. You will need to carry more water or cache water. There are a lot of threads about that caching or carrying water.
I hiked the trail without caching water and had to carry sometimes for 2 days of water and on those days I didn't see any water.