Why Does Velocity of Water in a Stream Vary at Different Locations?

Why is the velocity of water in a stream slower at the bottom and edges compared to near the surface and in the middle?

Friction and Smoothness Influence Velocity

The velocity of water in a stream is influenced by two main factors: friction along the stream bed and the smoothness of the channel. Friction between the water and the stream bed causes the velocity to decrease, resulting in slower flow at the bottom and edges of the stream where the friction is the greatest.

At the bottom and edges of the stream, the water experiences more resistance due to the friction with the stream bed, which slows down its movement. This is why the velocity of water is the slowest at these locations.

Conversely, near the surface and in the middle of the stream, the velocity of water is faster. This is because there is less friction between the water and the air, allowing the water to flow more freely and at a higher speed.

Additionally, the smoothness of the channel plays a role in determining the velocity of water in a stream. A smoother channel results in faster flow, as there is less resistance to the water's movement. Therefore, the smoother the channel, the faster the flow of water in the stream.