Why does velocity increase downstream?

Question

i'm doing a geography project, and i've got my results, but i need to explain them... any help?

Answer 1

In most rivers, the velocity decreases downstream as the river gets closer to the sea.

Answer 2

How did you get your results without an explanation?

Generally speaking, the velocity DECREASES downstream due to dams built along the way.

Answer 3

Velocity downstream increases when there are more streams feeding the main stream. If the total volume of those side streams is bigger than the volume of the main stream, it means that water is "crammed" into the smaller area and has to flow faster.

The same thing happens in our cardiovascular system - blood in the cappilaries flows slower than in arteries, because the total volume of the cappilaries is bigger than the volume of the artery they flow into.

Answer 4

The velocity of a stream depends on the steepness of the stream, the amount of water  that flows through it, and the width and depth of the stream.  If it's steeper downstream the velocity increases.  If either the width or depth decrease, the same amount of water has less space to go through and picks up speed to do so.  However, if the width or depth increase, the velocity decreases!

Answer 5

The effect of gravity underlies all the answers.