Parts of the river…
“Flow” refers to the water running in a river or stream. There are two important aspects to a river’s natural flow. First, there is the amount of water that flows in the river. Some rivers get enough water from their headwaters, tributaries, and rain to flow all year round. Others go from cold, raging rivers to small, warm streams as the snowpack runs out, or even stop flowing completely. A river’s natural ups and downs are called “pulses.” Like a human being’s pulse, a river’s natural flow of water is life support for animals, plants, and fish, delivering what they need to survive at the right times. When we divert water away from a river, we change the river’s natural flow.
The second component of natural flow is how water moves through a river’s channel. In a natural, wild river, the water runs freely. But in more developed or degraded rivers, dams and other structures can slow or stop a river’s flow. When a river’s flow is blocked, migratory fish like salmon can suffer, unable to move up or downstream.
– From Americanrivers.org