How is the tributary different from the river? In fact, this is not such a simple question as it might seem at first glance. In many river systems, there is real confusion about the definition of the main watercourse. Let's try in our article to deal with all the nuances of this geographical problem. In addition, we will tell you what the influx is and what characteristics the main river should have.
The concept of the river system
What is an influx? Before answering this question, you should understand the concept of a river system (or hydrographic network). This is what we will do first.
If we consider the river system in plan, then it is very similar to a tree. Like trees, river systems can be different: symmetric and asymmetric, branched or rare. Their “drawings” depend on a number of factors: the amount and intensity of precipitation, terrain features, the geological structure of the territory, the degree of anthropogenic changes in the landscape, etc.
Any river system consists of a main river (the so-called trunk) and numerous tributaries of several orders. Their number will depend on the degree of branching of the system. The name of the entire river system is usually given by the name of its main river.
What is an influx? And how is it different from a river? This will be discussed later in our article.
What is a tributary of a river? Types of tributaries
What is a tributary of a river? The definition of this concept is extremely simple. This is a natural watercourse that flows into a larger watercourse. However, one should not think that the influx is such a tiny formation. Some of them are capable of reaching several thousand kilometers in length! For example, the Irtysh and Missouri are also tributaries. But at the same time, they are included in the list of the largest rivers of the planet.
All tributaries are divided into right and left (depending on which bank they flow into the main river). In addition, they come in different orders. So, a first-order inflow is a watercourse that flows directly into the main river of the hydrographic network. Second-order tributaries are tributaries of first-order tributaries , and so on. In total, within one river system there can be inflows of up to 20 orders or more.
By and large, the influx from the river is no different. After all, any watercourse can easily be an inflow to another, larger watercourse. One river can absorb the waters of hundreds of tributaries and at the same time be a tributary for another river catchment basin.
So, we have already figured out what a river inflow is. But much more difficult in hydrography is the problem of its definition. What difficulties do scientists face here?
Who falls into whom, or the problem of determining the main river
The most obvious criterion in determining the main river is the constancy of one or another watercourse. For example, if one of the two watercourses dries in the summer, then it will be declared an inflow. However, this variant of determination is suitable only for a few (most often small) rivulets. Further in the table, we list the most important criteria for determining the main watercourse in the river system.
Criterion | Main river | River inflow |
Constancy | Permanent watercourse | Unstable (temporarily drying) watercourse |
Water content (water consumption) | More full flow | Low water flow |
Length | Longer | Less long |
Nature of the current | Calm | Rough, whirlpool |
Geological conditions | The river valley is more ancient | The valley of the watercourse is "young", formed relatively recently |
Branching network | It accepts more streams | It accepts fewer watercourses |
River basin area | The river basin has a large area | Drainage basin takes up less space |
Merge geometry | A watercourse preserves (or approximately preserves) the direction of its course after confluence | The watercourse changes its direction after the confluence point |
Most often, the tributary differs from the main river by a smaller length or water content. But not everything is so simple - there are exceptions. Further, by the example of well-known Russian rivers, we will consider several cases of an incorrect determination of the main watercourse of the river system.
Yenisei and Angara
Having opened any geographical guide, we will read that the Angara River is a tributary of the Yenisei. Two watercourses merge 30 kilometers east of the city of Lesosibirsk (Krasnoyarsk Territory). And if you look at the satellite image of this place, you can be very surprised. The fact is that the Angara looks much wider and more impressive than the Yenisei (see photo below). And this is not just an optical illusion. At the confluence, the Angara carries one and a half times more water in its channel than the Yenisei. And its catchment area is 2.5 times larger. So why is the Yenisei considered the main river?
The Angara is considered a tributary of the Yenisei for the reason that the river valley of the latter has a more ancient geological structure. In addition, Siberia, as you know, mastered from east to west. And the Russian colonialists simply discovered the Yenisei River first. And the Angara and its origins were investigated much later.
Volga and Kama
Even from school, we all know that the Kama River flows into the Volga. However, the total length of the Volga is 1727 km, but the Kama - 2030 km. Maybe the matter is the water content of two streams? But also in terms of water consumption, Kama is in many ways superior to the Volga. In this case, the historical factor turned out to be the decisive criterion for determining the main watercourse. It just so happened that it was with the Volga that the process of the origin and formation of the Russian state is associated. The Kama basin was studied in detail only in the 19th century. The name "Volga" until this time has already been established and entrenched in the minds of Russian people. And, of course, they did not change it.