Please eludicate this quote about communication in a business.downward communication is like water streaming down from a water fall or stream head....

This quote is emphasizing the difficulties of both
downward and upward communication in a business.

It is
saying that downward communication tends to be excessive and that upward communication
tends to be insufficient.  Downward communication is, in one way, easily achieved. 
Superiors can always force subordinates to listen to them.  This happens easily and
often.  However, it can happen too often and be very
unfocused.  The "water" just gushes down and splashes all over everyone in a imprecise
way.

Upward communication is very important, but does not
happen enough.  Subordinates' ideas and input tend to be discounted by those above
them.  This means that their communications do not get
heard.

Both of these are problems that good businesses must
overcome as much as possible so that the right amount of communication each way can
occur.