A mountainous region would be a likely source for hydroelectric energy, as mountains often have fast-flowing rivers and streams that can be used to generate electricity through hydropower.
These streams are called Currents. An example would be The Gulf Stream.
I know of no special name for southerly flowing streams. 'Draining in a southerly direction' would perhaps be a description.
In a rainforest, you would see a dense canopy of trees, a variety of plants and flowers, diverse wildlife such as monkeys, birds, and insects, as well as streams and rivers flowing through the forest.
A mountainous region would likely be a good source for hydropower energy due to abundant flowing water that can be harnessed for hydroelectric power generation.
The water usually flows fastest in the middle and top sections of a stream, where the water has the least amount of friction with the streambed and banks. This is because the water in these areas does not experience as much resistance as it would at the bottom of the stream.
Mountain regions can have various bodies of water, such as lakes, rivers, and streams dispersed throughout the area. The exact number of bodies of water in a mountain region would depend on the specific location and geography of that region.
We would usually find the source of a river in upland areas such as mountains or hills because the water in streams and rivers is very fast-flowing, cutting and eroding the land to form valleys, and features such as waterfalls.
The coastal region where seawater and freshwater mix is called an estuary. The mixed water inside the estuary is called brackish.
Free-flowing means that something can flow without hindrance. A example of this is a river that exists without being blocked or impeded by a dam. A dam would resist the flow of a river, causing water to remain in or accumulate in a given region, which would not be a free-flowing scenario.
A V-shaped cross-section would best represent the valley shape where a rapidly flowing stream is cutting into the bedrock in a mountainous area. The steep sides of the V-shape are characteristic of valleys formed by erosion from fast-flowing streams in mountainous terrain.
All rivers are streams but not all streams are rivers. There is a defined method (Link) of sizing flowing water, all these features are streams and are ranked as 1st through 12th order streams. The systems starts with what would be called in non-scientific terms brooks and works up to rivers. Going up in size and strength, streams that are classified as 4th through 6th order are medium streams while anything larger is a river. Examples:The Ohio River in the United States is an 8th order streamThe Mississippi River is a 10th order stream.The Amazon in South America, is a 12th order stream.