Why are rivers rich?

Question

There are four river in such a way that they are like following -

River Temple River Temple River Temple River 

All the rivers are magical, moment a worshiper crosses a river with any number of flowers, it becomes double. (For eg 1 flower becomes 2 flowers, 2 become 4 and so on).

How many minimum number of flowers a worshiper needs to carry from beginning such that he offers equal number of flowers in all the three temples, and he is left with zero flowers at the end of fourth river.

Answer 1

Because rivers have banks :)

Answer 2

A river is rich when it has many substantial tributaries