Final answer:
The gradient of a river dictates its slope, which impacts the flow rate and velocity of water. A steeper gradient leads to a faster flow and clearer water, whereas a gentle gradient results in slower waters and higher sedimentation, influencing river ecosystems and the water's clarity.
Step-by-step explanation:
The gradient of a river significantly affects its flow. As a river moves downstream from its source, several changes occur that influence the flow rate and the velocity of the water. The gradient typically becomes less steep further down the river which contributes to a slower flow.
At the same time, rivers generally widen and increase in volume as they accumulate water from tributaries, which can lead to more sedimentation due to the reduced speed of the water flow. A higher gradient means that the river's slope is steeper, typically resulting in faster-moving water, less sediment deposition, and clearer water. However, as the gradient decreases, the water moves more slowly, leading to greater sediment deposition and murkier water.
Ecosystems within the river also change in relation to the flow and sedimentation rates. Near the river's source where the water is clear and moves quickly due to a steeper gradient, organisms such as trout can rely on vision to find food. Downstream, in slower-moving and silt-laden waters with a gentle gradient, other vertebrates such as frogs and fish are likely to rely on other senses like taste or chemical cues due to reduced visibility.