It's not controlled but it is effected by the tides. I'm about 15 miles north of the head of Mobile Bay and when the water is within a couple of feet of normal low summertime levels the tides rise and fall as much as a ft and a half. When the water rises above normal it mostly depends on how much rain we get up state. Pretty much the same as the Achafalia basin. The farther north the less the tide effects it