A river is a constant stream of water of large or medium size. It flows along a natural channel from the source down to the mouth. The rivers are replenished by precipitation, underground sources and glacier melting. Depending on the topography of the area along which the rivers flow, they are subdivided into flat and mountainous.
Features of mountain rivers
There are a number of differences between mountain and lowland rivers.
Mountain rivers, as a rule, are characterized by a steep slope, rapid flow and flow in narrow valleys.
The water temperature in them is quite low - in the upper reaches it varies within the range of only 3-7 degrees, it does not warm up even in shallow water.
The bottom of the mountain rivers is strewn with stones, some of them are mobile. This leads to the inconsistency of the topography of the day.
The speed of water flow in mountain streams is about 10 m / s. This is a significant value. At this speed, the stream is capable of knocking a person down even at shallow depths. By the way, as a rule, mountain rivers are shallow - in the gorges the height of the water increases, and in the gentle sections of the channel again decreases. In areas with a calm flow, the river can bend around obstacles, forming islands of land.
The river bed is often blocked by rocky monoliths of various sizes, which contributes to the emergence of breakers and whirlpools. Sometimes the direction of the original channel changes, as avalanches and rock falls can dam the river.
Sources of food for mountain rivers
The source of mountain rivers can be different. As a rule, this depends on the location of a particular river.
Sources can be snow caps of mountain peaks, underground sources - springs and underground rivers, as well as atmospheric precipitation in those zones where the movement of air masses is stopped by mountains. In this case, the river will originate in an alpine lake.
The last two factors most often give rise to rivers that originate in high mountains. They are stable and give good water flow.
If the mountains are not high, the flow of mountain rivers can vary greatly. In spring they are the most full-flowing, and by autumn they can become shallow and even dry out completely.
If the source of a mountain river is a glacier, its fullness, among other things, will strongly depend on the height of the snow cap. The larger it is, the fuller the river will be.
However, most often rivers have more than one source. As a rule, this is a combination of two factors - glacier melting and underground sources.
In the spring, the melting snow gives small streams that flow down from the mountain ranges. These small streams, when combined, form larger ones. On their way, they meet recharge in the form of underground sources, often invisible to the eye and located in the deep layers of the soil.
But the role of atmospheric precipitation is also great. Rains and warm winds, gathering, are able to form a new river and dramatically increase the water level of an existing one.