Organization is important because the structure denotes the function in biology, therefore organization in this case means that it has a high relevance for homeostasis. If something is not organized, it's not in homeostasis, it's as simple as that.
There is much more fresh water underground than on the surface. A rock layer must be porous and permeable to be a good aquifer. An impermeable layer makes up the bottom of an aquifer. The water table rises and falls with additions or subtractions to the groundwater system.