Answer: A river's course can be divided into the upper course, middle course, and lower course. Each section has distinct characteristics in terms of flow velocity, erosion and deposition processes, and water quality. Understanding these divisions helps in studying and managing rivers and their associated ecosystems.
Step-by-step explanation:
A river's course can be divided into three main sections:
1) Upper Course: The upper course of a river is the section closest to its source or origin. In this section, the river typically starts as a small stream or a series of small tributaries. The gradient or slope of the land is usually steep, leading to fast-flowing water and the formation of rapids and waterfalls.
The upper course is characterized by erosion processes, where the river cuts into the surrounding landscape, forming a V-shaped valley. The water in this section is often clear and cold, as it is sourced from precipitation, springs, or melting snow.
2) Middle Course: The middle course of a river is located between the upper and lower sections. Here, the river has a larger volume and width compared to the upper course. The gradient of the land becomes gentler, resulting in a slower flow of water.
The middle course is characterized by a meandering pattern, where the river curves and winds its way through the landscape, forming large bends called meanders. In this section, the river undergoes both erosion and deposition processes. Erosion occurs on the outer banks of meanders, while deposition takes place on the inner banks, forming point bars. The water in the middle course is usually murkier due to the presence of sediments and dissolved substances.
3) Lower Course: The lower course of a river is the final section before it reaches its mouth, where it enters a lake, sea, or ocean. This section is characterized by a gentle gradient, resulting in a slow and wide flow of water. The river in the lower course undergoes significant deposition, where sediments carried from upstream are deposited, forming floodplains and deltas.
Floodplains are flat areas adjacent to the river that are periodically flooded during times of high discharge. Deltas are landforms formed at the river's mouth, created by the accumulation of sediments carried by the river. The water in the lower course is often murky and can be influenced by tides and saltwater intrusion in coastal areas.