A tributary is a small part of a river system that flows into a larger part of a river. When looking at it, the order is determined, as well as the left or right arrangement.
Learn to distinguish between first-order and second-order tributaries, etc. In order to determine the order, use a geographic map to find where its mouth is. Recall that the mouth of a river is part of the river system, where the actual tributary flows into the river.
After that, count how many rivers flow into the main one from its very beginning to the place you are considering. Thus, the tributaries of the first order directly flow into the river, the second - first flow into the tributaries of the first, second, and so on.
For example, you need to determine the tributary of what order of the Kama River is the Vyatka River. Find Kamu on the map. Vishera, Chusovaya, Belaya, Vyatka, etc. flow into it. Accordingly, the Vyatka River is a fourth-order tributary of the Kama River.
Often the length and water content of the tributary is less than that of the main river. But there are exceptions, for example, the Oka is considered a more watery river than the Volga, moreover, the area of its basin reaches 250 thousand square kilometers, almost two dozen rivers flow into it, but still it is just a second-order tributary.
Distinguish between right and left tributaries. Find the mouth of the river on a geographical map and imagine that you are facing it. If a tributary flows into a larger river on the right side, then it is on the right, if on the left side - on the left.
For example, it is necessary to determine which tributary of the Volga River is the Oka. After you have imagined that you are standing with your face in front of the mouth, you will understand that the Oka River is on the right hand, therefore, it is the right tributary of the Volga.
In addition, there are small and large tributaries. For example, Kama is big. It helps to determine this knowledge about the length, fullness of the flowing river, its properties, as well as about the features of the watershed. It happens that the rivers flowing into it are of greater length and importance than the main ones, not infrequently the latter are not even suitable for navigation, while their tributaries are actively used.