What is the line between the zones of aeration and saturation?

In reference to water saturation can mean a few things. It could mean the dew point of the atmosphere at which it can no longer hold any more moisture. It could mean that the water holds the maximum amount of thermal energy before boiling. It could also mean that so much of a solute is dissolved in the water and at its current temperature cannot hold any more solute.Saturation is the point at which a material cannot absorb any more of something else. When a piece of cloth is saturated with water, it can hold no more water. When you are trying to dissolve something in water, such as salt, the water is saturated when no more salt can go into solution.