A river is a water stream of natural origin that flows along a channel that it has developed. One can measure the length of this stream, the number of its tributaries, the area of the total catchment, and so on. One of the main hydrological indicators is the slope of the river. How to calculate it correctly?
What is the fall of the river?
Any natural watercourse on our planet flows from top to bottom. The reason for this is the law of universal gravitation known to all of us, which was discovered by Isaac Newton in the middle of the 17th century. All rivers, as a rule, start from underground springs or flow from large lakes. Then they carry their waters down (smoothly or swiftly) - to the seas and oceans.
The fall of the river shows us how much this or that watercourse loses in height during its "journey" on the earth's surface. In other words, it is the height difference between the point of the source and the point of the mouth of the river. The fall can be complete or partial (when you need to calculate this indicator for a certain section of the channel).
Calculate the fall of the river is elementary. To do this, you need to know the height of its source and mouth. For example, we are given river A with a total length of 2000 km, which begins its journey at a mark of 250 m, and flows into the lake at a height of 50 m. The differencebetween these two marks will be 200 meters. This will be the fall of the river A.
Knowing the fall, you can calculate the slope of the river. How to do it right - read the next section.
How to calculate the slope of a watercourse?
The slope of a river is the ratio of the magnitude of the fall of a watercourse to its total length. This indicator can be expressed as a percentage, ppm (most often), degrees, or in m / km.
The slopes of lowland and mountain rivers differ significantly. In the first case, this indicator rarely exceeds 0.1 m / km. The slopes of mountain rivers can be tens and even hundreds of times greater.
Calculate this indicator is also easy. Let's return to our river A, the fall of which is 200 meters. To calculate the slope, divide this value by the length of the river: 200 m / 2000 km=0.1 m/km. Based on this, we can say that our river A is flat and has a low speed of its flow.
The fall and slope of a river can be shown graphically. For this, so-called longitudinal profiles are used. The x-axis of such a graph will be the length of the river, and the y-axis will be the height of the terrain. Such a profile looks like this:
The fall and slope of the Volga
Solve similar problems are taught at school, in geography lessons in the 8th grade. Let's take as an example the largest watercourse in Europe - the Volga. Let's try to calculate the fall and slope of the river.
Volga flows in the European part of Russia, within 15 subjects of the federation. She repeatedly changes her direction. This is the most important waterwaycountry, the largest river in the world among those watercourses that do not flow into the sea or ocean.
Volga originates on the Valdai Hills, at an altitude of 228 meters above sea level. Within the Astrakhan region, it flows into the Caspian Sea. In this case, the mouth is located at a height of (–28) meters. Thus, the total fall of the Volga is 256 meters. Now let's calculate the slope of the river.
Volga has a total length of 3530 km. At the same time, it collects its waters from a vast territory of 1.36 million square meters. km. That's four times the size of Germany! To calculate the slope of the Volga, perform the following mathematical operation: 256 meters / 3530 km=0.07 m/km.
The fall and slope of the Amur River
One of the main rivers of the Far East, flowing between the two states (Russia and China), is the Amur. Its source is considered to be the confluence of Shilka and Argun. The height of this point above sea level is 304 meters. Further, the Amur flows mainly to the east and flows into the Sea of Okhotsk. The height of its mouth is 0 meters. Thus, the total fall of the Amur is 304 meters. Calculate the slope of the river.
Amur has a total length of 2824 km. The area of the river basin is 1.85 million square kilometers. km. To calculate the slope of the Amur, you should perform the simplest mathematical operation: 304 meters / 2824 km=0.11 m / km.
This indicator tells us that in a section of the channel one kilometer long, the Amur River "loses" 11 centimeters in height. It is important to note that the gener althe slope of a particular watercourse is not very informative. After all, the geomorphological conditions (relief conditions) in which the riverbed is located can change significantly. Therefore, it is better to calculate this indicator for individual short sections of the river channel.
The fall and slope of the Pechora River
Pechora is a fairly large Russian river flowing within the Komi Republic and the Nenets Autonomous Okrug. It originates in the mountains of the Northern Urals, at an altitude of 630 meters above sea level. The Pechora flows into the eponymous bay of the Barents Sea, forming a vast delta. The height of the mouth is 0 meters. Calculate the fall and slope of the river.
Pechora has a total length of 1809 km. The fall of the river is 630 meters. The area of the river basin of the Pechora in comparison with the Volga and Amur is small - only 330 thousand square meters. km. To calculate the slope of the Pechora River, perform the following mathematical operation: 630 meters / 1809 km=0.35 m/km.
As we can see, among the three rivers considered in this article, the largest slope is characteristic of the Pechora. In general, the definition of this indicator helps hydrologists in studying the valley of a particular river, its water regime and channel processes.
