Final answer:
River capture can have significant physical impacts on the captured stream, such as changes in water flow, temperature, chemistry, and sediment loads. It can also obstruct fish migration and lead to flooding and population relocations.
Step-by-step explanation:
When a river is captured by another river, the physical impact on the captured stream can be significant. The capture can lead to changes in water flow, water chemistry, water temperature, and sediment loads, which in turn can have effects on the ecology and physical characteristics of the river both upstream and downstream. For example, the damming of a river can obstruct fish migration and block access to spawning areas, and the creation of reservoirs can flood natural areas and force populations to relocate.