What is the name for the highest section of a river typically found in mountainous regions?

The upper course of a river is characterized as the highest section typically found in mountainous regions. In this stage, the river is often steep and narrow, with a swift flow. The upper course is where the river originates, usually from springs or melted snow, and it has a significant amount of energy for erosion, leading to the formation of features such as V-shaped valleys, waterfalls, and gorges. This area is crucial for the river's overall evolution as it shapes the landscape and influences the other sections of the river downstream. The upper course is distinct from the middle and lower courses, which exhibit different characteristics such as wider channels and slower flow, as well as the delta, which is formed at the mouth of the river where it meets another body of water, often characterized by sediment deposition.