The main river of the Far Eastern District is Amur. According to its hydrological parameters, it is in 4th place among the 10 largest Russian rivers. Ahead of it are only the Ob, Yenisei and Lena, carrying their waters from southern Siberia to the seas of the Arctic Ocean. In contrast, Cupid chose another basin - the Pacific, and flows from west to east. A watercourse begins in the mountain plain of Transbaikalia from the confluence of Shilka and Argun. Having covered 2824 km, the Amur river waters flow into the Pacific Ocean near the city of Nikolaevsk-on-Amur, which stretches along the coast of the Tatar Strait. The catchment area of the river basin is 1855 sq. Km. The fall and slope of the Amur River depends on the terrain: in the upper reaches it is mountainous, in the lower reaches - plain.
Hydrological terms
The property of water flowing over an inclined surface is reflected in terms such as a river fall and a longitudinal slope. To determine these parameters, you need to know the elevations of the water surface (edges) at the defined points and the distance between them, measured by the watercourse. Water level marks are determined during the period of the lowest standing water - at low water.
Fall of the river - excess of the mark at the point downstream over the point located upstream. Measured in linear units of length - in meters or centimeters.
The river slope is a calculated numerical value determined by the quotient of dividing the fall of the river by its length between the defined points. It is expressed in ‰ - ppm (thousandth of a number) or in% (hundredths of a percent).
The slope of the river is expressed by the formula I = h1 - h2 / L, where:
I - the longitudinal slope of the channel,% or ‰;
h1 - river level mark at the top of the determined segment, m;
h2 - the same, at the lower point, m;
L is the length of the river between the defined points, in m or in km.
The complete fall of the river is the difference in elevations at the source and mouth. It does not matter what the marks will be - relative or absolute.
The averaged slope of the river is the result of dividing the total fall by its total length.
By the value of the slope of the river, you can determine what type it belongs to. Mountain rivers are characterized by large slopes, measured from tens of cm to the first tens of meters. For lowland slopes, slight slopes are measured in centimeters. The slope characterizes the flow velocity of river waters.
Amur river
The fall from its beginning to the mouth is 304 m. This number is the difference between the elevations at the mouth (0 m is sea level) and at the source of the river.
The beginning of the Amur is the merger of Shilka with Argun. The surface mark at this point with coordinates of 53 degrees 21.5 minutes is 304 m. Therefore, the total fall of the Amur River will be: 304 - 0 = 304 m.
Knowing the length of the river and the fall, we find the averaged longitudinal slope of the watercourse, it is equal to:
I = 304/2824 = 0.107 ‰ or rounded 0.11 ‰.
This means that depending on the direction in which to move (on the terrain or on the map), for every kilometer of the river’s length, the water surface level in it changes by 11 cm. If the movement is downstream, then the fall of the Amur River decreases with every kilometer 11 cm. But this value is approximate, as if the watercourse flowed on the surface at the same angle.
In fact, there are no such conditions for the rivers of the globe anywhere. Their channels are laid in various geomorphological conditions. They affect the variability of the parameters of fall and slope even over the course of one river.
The Amur River is divided into 3 parts (conditionally), depending on the terrain and the nature of the course. The fall and slopes on the Upper, Middle and Lower Amur are different.
Upper Cupid
Its source begins from the merger of Argun and Shilka. The place is defined by the point on the eastern shore of the island of Mad with a mark of the cutoff of 304 m. The mouth of the Zeya River, a left tributary that flows 1936 km from the mouth of the Amur, is taken as the end. Consequently, the length of the Lower Amur is 888 km. The elevation is leveled off with a value of 125 m. The fall and slope of the Amur River in this section will be 179 m and 0.2 ‰, respectively. The nature of the current is close to the mountain stream - the current velocity here is an average of 1.5 m / s. The width of the channel at low water is from 420 m to 1 km.
Middle Cupid
The site is limited by points: upstream - the mouth of the Zeya river (Blagoveshchensk) with a height mark of 125 m, lower - the mouth of the Ussuri river (near the village of Kazakevichevo) - the height of the ridge is 41 m. The length of the site is 970 km. The fall of the Amur River here is 84 m, and the slope (84/970) is 0.086 ‰. This means a decrease in the elevation of the ridge of 8.6 cm per 1 km of the river. The flow velocity is 5.5 km / h or 1, 47 m / s. The width of the channel is from 530 to 1170 m.
Lower Amur
The distance between the points of determination along the river is 966 km (from the mouth of the Amur River to the inflow of the Ussuri tributary into it). Marks of heights: the upper point is 41 m, the lower is sea level, 0 m. Therefore, the fall of the Amur River in this section is 41 m. The slope is 0.042 ‰. The flow velocity in the low-water period is 0.9 m / s, in the flood up to 1.2 m / s. The width of the channel is from 2 km (in places) to 11 km, and at the mouth - up to 16 km.
Hydrological regime of the river
Amur is characterized by high water mobility indicators: annual average annual flow 403 cubic km, average annual discharge at the mouth of 12800 cubic meters per second.
The main source of food (up to 80% of runoff) is summer and autumn rain showers. The remaining 20% is accounted for by melt and groundwater, approximately equal in percentage terms.
Melt water feeds the river from April to May, so the flood is stretched and a small amount of runoff does not raise high levels. The flood period is usually from July to August from year to year. At this time, sometimes 75% of the annual flow occurs.
Regarding the marks of low levels (low-water), it should be noted that floods exceed them by 10-15 m in the upper and middle reaches, and in the lower reaches up to 6-8 m. Heavy rains cause spills of the Middle and Lower Amur to 25 km and high levels are maintained on the flooded area up to 70 days.
The multi-day monsoon rains of August 2013 caused a catastrophic flood in the Amur basin, which flooded settlements and agricultural land.
Summer low water after the departure of "root" water (melting snow in the mountains) - at the end of June. Autumn - in late September-early October. Freeze-up occurs in late October - early November. Opening of ice - after the first decade of April and until May.