The flow of a certain land area is measured by indicators. Determining the flow of a river

The flow of a certain land area is measured by indicators:

• water flow - the volume of water flowing per unit of time through the living section of the river. It is usually expressed in m3/s. The average daily water discharges make it possible to determine the maximum and minimum discharges, as well as the amount of water flow per year from the basin area. Annual flow - 3787 km a - 270 km3;
• drain module. It is called the amount of water in liters, flowing per second from 1 km2 of area. It is calculated by dividing the runoff by the area of ​​the river basin. The tundra and rivers have the largest module;
• runoff coefficient. It shows what proportion of precipitation (in percent) flows into rivers. The highest coefficient has the rivers of the tundra and forest zones (60-80%), in the rivers of the regions it is very low (-4%).

Loose rocks - products are carried by runoff into rivers. In addition, the (destructive) work of rivers also makes them a supplier of loose . In this case, a solid runoff is formed - a mass of suspended, drawn along the bottom and dissolved substances. Their number depends on the energy of moving water and on the resistance of rocks to erosion. Solid runoff is divided into suspended and bottom runoff, but this concept is arbitrary, since when the flow velocity changes, one category can quickly move into another. At high speed, bottom solid runoff can move in a layer up to several tens of centimeters thick. Their movements are very uneven, since the speed at the bottom changes dramatically. Therefore, sandy and rifts can form at the bottom of the river, hindering navigation. The turbidity of the river depends on the value, which, in turn, characterizes the intensity of erosion activity in the river basin. In large river systems, solid runoff is measured in the tens of millions of tons per year. For example, the runoff of elevated sediments of the Amu Darya is 94 million tons per year, the Volga river is 25 million tons per year, - 15 million tons per year, - 6 million tons per year, - 1500 million tons per year, - 450 million tons per year, Nile - 62 million tons per year.

Flow rate depends on a number of factors:

• first of all from . The more precipitation and less evaporation, the more runoff, and vice versa. The amount of runoff depends on the form of precipitation and their distribution over time. The rains of a hot summer period will give less runoff than a cool autumn period, since evaporation is very large. Winter precipitation in the form of snow will not provide surface runoff during the cold months, but is concentrated in the short spring flood period. With a uniform distribution of precipitation throughout the year, the runoff is uniform, and sharp seasonal changes in the amount of precipitation and evaporation rate cause uneven runoff. During prolonged rains, the infiltration of precipitation into the ground is greater than during heavy rains;
• from the area. When the masses rise along the slopes of the mountains, they cool down, as they meet with colder layers, and water vapor, so here the amount of precipitation increases. Already from insignificant hills, the flow is greater than from adjacent ones. So, on the Valdai Upland, the runoff module is 12, and on the neighboring lowlands - only 6. An even greater volume of runoff in the mountains, the runoff module here is from 25 to 75. The water content of mountain rivers, in addition to an increase in precipitation with height, is also affected by a decrease in evaporation in the mountains due to the lowering and steepness of the slopes. From the elevated and mountainous territories, water flows quickly, and from the plains slowly. For these reasons, lowland rivers have a more uniform regime (see Rivers), while mountainous ones react sensitively and violently to;
• from cover. In areas of excessive moisture, soils are saturated with water for most of the year and give it to rivers. In zones of insufficient moisture during the snowmelt season, the soils are able to absorb all the melt water, so the runoff in these zones is weak;
• from vegetation cover. Studies of recent years, carried out in connection with the planting of forest belts in, indicate their positive effect on runoff, since it is more significant in forest zones than in the steppe;
• from influence. It is different in zones of excessive and insufficient moisture. Bogs are regulators of runoff, and in the zone their influence is negative: they suck in surface and water and evaporate them into the atmosphere, thereby disrupting both surface and underground runoff;
• from large flowing lakes. They are a powerful flow regulator, however, their action is local.

From the above brief review of factors affecting runoff, it follows that its magnitude is historically variable.

The zone of the most abundant runoff is, the maximum value of its module here is 1500 mm per year, and the minimum is about 500 mm per year. Here, the runoff is evenly distributed over time. The largest annual flow in .

The zone of minimum runoff is the subpolar latitudes of the Northern Hemisphere, covering. The maximum value of the runoff module here is 200 mm per year or less, with the largest amount occurring in spring and summer.

In the polar regions, the runoff is carried out, the thickness of the layer in terms of water is approximately 80 mm in and 180 mm in.

On each continent there are areas from which the flow is carried out not into the ocean, but into inland water bodies - lakes. Such territories are called areas of internal flow or drainless. The formation of these areas is associated with fallout, as well as with the remoteness of inland territories from the ocean. The largest areas of drainless regions fall on (40% of the total territory of the mainland) and (29% of the total territory).

DEPARTMENT OF HIGHER EDUCATIONAL INSTITUTIONS

Volgograd State Agricultural Academy

Department: _____________________

Discipline: Hydrology

TEST

Performed: third year student,

correspondence department, group __ EMZ, _____

________________________________

Volgograd 2006

OPTION 0 Sura River, p. Kadyshevo, catchment area F=27,900 km 2 , forest cover 30%, no swamps, average long-term precipitation 682 mm.

Average monthly and average annual water discharges and runoff modules

Pool - analogue - r. Sura, Penza.

The average long-term value of the annual runoff (norm) M oa \u003d 3.5 l / s * km 2, C v \u003d 0.27.

Table for determining the parameters when calculating the maximum flow of melt water

1. Determine the average long-term value (norm) of annual runoff in the presence of observational data.

Initial data: average annual water consumption, calculated period of 10 years (from 1964 - 1973).

where Q i is the average annual runoff for the i-th year;

n is the number of years of observations.

Q o \u003d \u003d 99.43 m 3 / s (the value of the average long-term runoff).

The resulting norm in the form of an average long-term water flow must be expressed in terms of other runoff characteristics: modulus, layer, volume, and runoff coefficient.

Runoff module M o = = = 3.56 l / s * km 2, where F is the catchment area, km 2.

Average long-term runoff per year:

W o \u003d Q o * T \u003d 99.43 * 31.54 * 10 6 \u003d 3 136.022 m 3,

where T is the number of seconds in a year, which is approximately 31.54 * 10 6 s.

The average long-term runoff layer h o = = = 112.4 mm / year

Runoff coefficient α= = =0.165,

where x o is the average long-term precipitation per year, mm.

2. Determine the coefficient of variability (variation) Cvannual runoff.

С v =, where is the standard deviation of annual discharges from the runoff norm.

If n<30, то = .

If the runoff for individual years is expressed in the form of modular coefficients k= , then С v = , and for n<30 С v =

Let's make a table for calculating C v of the annual flow of the river.

Table 1

Data for calculation C v

With v = = = = 0.2638783=0.264.

Relative root-mean-square error of the average long-term value of the annual river runoff for the period from 1964 to 1973 (10 years) is equal to:

The relative standard error of the coefficient of variability C v when it is determined by the method of moments is:

The length of the series is considered sufficient to determine Q o and C v if 5-10%, and 10-15%. The value of the average annual runoff under this condition is called the runoff rate. In our case, it is within the permissible, and more than the permissible error. This means that the number of observations is insufficient; it is necessary to lengthen it.

3. Determine the flow rate in case of lack of data using the hydrological analogy method.

The analogue river is selected according to:

– similarity of climatic characteristics;

– synchronism of runoff fluctuations in time;

- homogeneity of the relief, soils, hydrogeological conditions, close degree of coverage of the watershed with forests and swamps;

- the ratio of catchment areas, which should not differ by more than 10 times;

- the absence of factors that distort the runoff (dam construction, withdrawal and discharge of water).

An analogue river must have a long-term period of hydrometric observations to accurately determine the flow rate and at least 6 years of parallel observations with the river under study.

Annual runoff variability coefficient:

where C v is the coefficient of runoff variability in the design section;

C va - in the alignment of the analogue river;

Моа is the mean annual runoff of the analogous river;

A is the tangent of the slope of the communication graph.

In our case:

C v \u003d 1 * 3.5 / 3.8 * 0.27 \u003d 0.25

Finally, we accept M o \u003d 3.8 l / s * km 2, Q O \u003d 106.02 m 3 / s, C v \u003d 0.25.

4. Construct and test the annual runoff supply curve.

In this work, it is required to construct an annual runoff probability curve using a three-parameter gamma distribution curve. To do this, it is necessary to calculate three parameters: Q o - the average long-term value (norm) of the annual runoff, C v and C s of the annual runoff.

Using the results of calculations of the first part of the work for r. Sura, we have Q O \u003d 106.02 m 3 / s, C v \u003d 0.25.

For r. Sura accept C s =2С v =0.50 with subsequent verification.

The ordinates of the curve are determined depending on the coefficient C v according to the tables compiled by S.N. Kritsky and M.F. Menkel for C s =2С v . To improve the accuracy of the curve, it is necessary to take into account the hundredths of C v and interpolate between adjacent columns of numbers.

Ordinates of the theoretical curve for the provision of average annual water discharges of the Sura River c. Kadyshevo.

table 2

Construct a security curve on a probability cell and check its actual observational data.

Table 3

Data to test the theoretical curve

To do this, the modular coefficients of annual costs must be arranged in descending order and for each of them, calculate its actual provision according to the formula Р = , where Р is the provision of a member of the series, located in descending order;

m is the serial number of a member of the series;

n is the number of members of the series.

As can be seen from the last graph, the plotted points average the theoretical curve, which means that the curve is built correctly and the ratio C s =2 С v corresponds to reality.

The calculation is divided into two parts:

a) off-season distribution, which is of the greatest importance;

b) intra-seasonal distribution (by months and decades), established with some schematization.

The calculation is carried out according to hydrological years, i.e. for years beginning with a high-water season. The dates of the seasons begin the same for all years of observations, rounded up to a whole month. The duration of the high-water season is assigned so that the high water is placed within the boundaries of the season both in the years with the earliest onset and with the latest end date.

In the assignment, the duration of the season can be taken as follows: spring-April, May, June; summer-autumn - July, August, September, October, November; winter - December and January, February, March of the next year.

The amount of runoff for individual seasons and periods is determined by the sum of average monthly flows. In the last year, expenses for 3 months (I, II, III) of the first year are added to the expenses for December.

Table 4

Q lo = = 263.83 m 3 / s

Cs=2Cv=0.322

Q inter \u003d \u003d 445.67 m 3 / s

Cs=2Cv=0.363

Q races year \u003d K p * 12 * Q o \u003d 0.78 * 12 * 106.02 \u003d 992.347 m 3 / s

Q races between = K p * Q between = 0.85 * 445.67 \u003d 378.82 m 3 / s

Q ras lo \u003d K p * Q lo \u003d 0.87 * 263.83 \u003d 229.53 m 3 / s

Q races weight \u003d Q races year - Q races between \u003d 992.347-378.82 \u003d 613.53 m 3 / s

Q races winters \u003d Q races between - Q races lo \u003d 378.82-229.53 \u003d 149.29 m 3 / s

Determine the estimated costs using the formulas:

annual runoff Q races year \u003d K, * 12 Q o,

limiting period Q races between \u003d K p, * Q lo,

limiting season Q races lo \u003d K p, * Q races year Q lo,

where K p, K p, K p, are the ordinates of the curves of the three-parameter gamma distribution taken from the table, respectively, for C v annual runoff, C v low-water runoff and C v for summer-autumn.

Note: since the calculations are based on average monthly expenses, the estimated expense for the year must be multiplied by 12.

One of the main conditions of the layout method is the equality Q races year = ∑ Q races. However, this equality is violated if the calculated runoff for non-limiting seasons is also determined from the supply curves (due to the difference in the parameters of the curves). Therefore, the estimated runoff for a non-limiting period (in the task - for the spring) is determined by the difference Q dis weight \u003d Q races year - Q races between, and for a non-limiting season (in the winter task)

Q races winters \u003d Q races between - Q races lo.

Intra-seasonal distribution - is taken averaged over each of the three water content groups (high-water group, including years with runoff per season Р<33%, средняя по водности 33<Р<66%, маловодная Р>66%).

To identify the years included in separate water content groups, it is necessary to arrange the total costs for the season in descending order and calculate their actual supply (an example is Table 4). Since the calculated supply (Р=80%) corresponds to the low-water group, further calculation can be made for the years included in the low-water group (Table 5).

To do this, in the column "Total flow" write out the expenses by season, corresponding to the provision P> 66%, and in the column "Years" - write down the years corresponding to these expenses.

Arrange the average monthly expenses within the season in descending order, indicating the calendar months to which they relate (Table 5). Thus, the first will be the discharge for the most wet month, the last - for the low-water month.

For all years, summarize the costs separately for the season and for each month. Taking the amount of expenses for the season as 100%, determine the percentage of each month A% included in the season, and in the column "Month" write the name of the month that repeats most often. If there are no repetitions, enter any of the occurring ones, but so that each month included in the season has its own percentage of the season.

Then, multiplying the estimated discharge for the season, determined in terms of the inter-seasonal distribution of runoff (Table 4), by the percentage of each month A% (Table 5), calculate the estimated discharge for each month.

Q races IV = = 613.53 * 9.09 / 100% = 55.77 m 3 / s.

According to Table. 5 columns "Estimated costs by months" on graph paper to build an estimated hydrograph R-80% of the studied river (Fig. 3).

6. Determine the estimated maximum flow rate, melt water P = 1% in the absence of hydrometric observation data using the formula:

Q p \u003d M p F \u003d, m 3 / s,

where Q p is the calculated instantaneous maximum flow rate of melt water of a given availability P, m 3 / s;

M p is the module of the maximum design flow rate of a given probability P, m 3 / s * km 2;

h p is the calculated flood layer, cm;

F - catchment area, km 2;

n is the index of the degree of dependence reduction =f(F);

k o - the parameter of the friendliness of the flood;

and – coefficients that take into account the decrease in the maximum discharge of rivers regulated by lakes (reservoirs) and in forested and swampy basins;

– coefficient taking into account the inequality of the statistical parameters of the runoff layer and maximum discharges at Р=1%; =1;

F 1 - additional catchment area, taking into account the decrease in reduction, km 2, taken according to Appendix 3.

HYDROGRAPH

Table 5

Calculation of intra-seasonal flow distribution

The parameter k o is determined according to the data of analogue rivers, in the control work k o is written out from Appendix 3. The parameter n 1 depends on the natural zone, it is determined from Appendix 3.

where K p is the ordinate of the analytical curve of the three-parameter gamma distribution of the specified exceedance probability, determined according to Appendix 2 depending on C v (Appendix 3) at C s =2 C v with an accuracy of hundredths of interpolations between adjacent columns;

h - the middle layer of the flood, is established along the rivers - analogues or interpolation, in the control work - according to Appendix 3.

The coefficient taking into account the decrease in the maximum flow of rivers regulated by flowing lakes should be determined by the formula:

where C is the coefficient taken depending on the value of the average perennial layer of spring runoff h;

foz is the weighted average lake content.

Since there are no flowing lakes in the calculated watersheds, and foz located outside the main channel<2%, принимаем =1. Коэффициент, учитывающий снижение максимальных расходов воды в залесенных водосборах, определяется по формуле:

\u003d / (f l +1) n 2 \u003d 0.654,

where n 2 - the reduction coefficient is taken according to Appendix 3. The coefficient depends on the natural zone, the location of the forest on the catchment area and the total forest cover f l in%; issued according to the application 3.

The coefficient taking into account the reduction in the maximum water flow of wetland basins is determined by the formula:

1-Lg(0,1f+1),

where - coefficient depending on the type of swamps, determined according to Appendix 3;

f is the relative area of ​​marshes and swampy forests and meadows in the basin, %.

According to Appendix 3, we determine F 1 \u003d 2 km 2, h \u003d 80 mm, C v \u003d 0.40, n \u003d 0.25, \u003d 1, K o \u003d 0.02;

according to Appendix 2 K p = 2.16;

h p =k p h=2.16*80=172.8 mm, =1;

\u003d / (f l +1) n 2 \u003d 1.30 (30 + 1) 0.2 \u003d 0.654;

1- Lg(0.1f +1)=1-0.8Lg*(0.1*0+1)=1.

Since not all rivers flowing into the lake are systematically recorded, and the rest of the basin remains unexplored, the calculation is divided into two parts.

a) Calculation of the total runoff from the territory illuminated by observations.

The area of ​​the lake basin is 47800 km², the average surface area of ​​Lake Peipus-Pskov is 3550 km². In 1968, flow monitoring was carried out on the rivers:

The average annual flow of rivers flowing into the lake.

Table 21

Q sv \u003d 105.7 m³ / s

b) Calculation of the average annual runoff from the lake basin.

The total area of ​​the studied rivers:

where М1 …Mn are runoff modules at the points where observations are made, l/s km²; F1 … Fn - catchment areas in these points, km².

Thus, based on all the calculations made:

The total surface inflow of the lake is determined by the formula

2.3.2 Calculation of evaporation from the lake surface

Calculation of evaporation from the surface of Lake Peipus-Pskov for the time intervals of the ice-free period of 1968 is carried out according to the data of reference weather stations Gdov, Pskov and Tiirikoya, evenly spaced along the perimeter of the lake.

Data on water temperature and dates of opening and freezing of the lake were taken from Raskopel, Zalita and Mustvee stations.

The calculation of evaporation begins with the determination of the average length of the acceleration of the air flow over the lake. To do this, two systems of rectangular grids of parallel profiles are applied to the lake plan, oriented in the first case from N to S and from W to E, and in the second - from NW to SE and from NE to SW. The average acceleration length for each profile direction Li is calculated as the arithmetic mean of the lengths of all profiles in this direction:

L cf = 37 km

Then we calculate the wind rose. To do this, according to the meteorological monthly data for the reference year at the reference weather station, we sum up the number of wind events of all eight rhumbs, and then determine the frequency of wind directions in% as the ratio of the number of wind events of the corresponding rhumb for the year to the annual sum of the number of wind events of all eight rhumbs, %.

Repeatability of wind directions, %

Table 11

The average acceleration length for the entire water area of ​​the lake is calculated by the formula:

where Lc-th, etc. is the average length of the air flow acceleration along the profiles of the corresponding directions, km; (Nc+Nyu), etc. is the sum of wind direction repetitions for two mutually opposite points, %.

The values ​​of average monthly wind speeds over the lake at a height of 2 m are determined by the formula:

where K1 is the coefficient taking into account the degree of protection of the meteorological station on land; K2 - coefficient taking into account the nature of the relief; K3 is the coefficient taking into account the average length of the air flow acceleration over the reservoir; U is the wind speed at the height of the weather vane for the estimated time interval.

Calculation of the average wind speed over the water surface at a height of 2 m.

Weather station Gdov. Table 12

Weather station Pskov. Table 13

Tiirikoy weather station. Table 14

Calculation of average monthly values ​​of water vapor elasticity above the lake at a height of 2 m.

Weather station Gdov Table 15

Weather station Pskov Table 16

Tiirikoi weather station Table 17

Calculation of evaporation from the surface of the lake for the time intervals of the ice-free period.

Weather station Gdov Table 18

Weather station Pskov Table 19

Tiirikoi weather station Table 20

The average calculated value for the lake is Е = 587 mm.

Then Wis = 2207 106 m³

In this article, we will consider in detail the question of what is the annual flow of the river. We will also find out what affects this indicator, which determines the fullness of the river. We list the most significant rivers of the planet, leading in annual flow.

river runoff

The most important part of the planetary water cycle - this guarantee of life on Earth - are rivers. The movement of water in their networks occurs under the influence of a gravitational gradient, that is, due to the height difference between two points on the earth's surface. Water moves from a higher area to a lower area.

Fed by melting glaciers, precipitation, and groundwater that has come to the surface, rivers carry their waters at their mouths - usually into one of the seas.

They differ from each other both in the length, density and branching of the river network, and in the flow of water over a certain period of time - in the amount that passes through the section or alignment of the river per unit of time. In this case, the key parameter will be the water flow in the river section at the mouth, since the saturation or full flow changes upward from the source to the mouth.

The annual flow of a river in geography is an indicator, to determine which it is necessary to take into account the amount of water flowing per second per square meter of the territory under consideration, as well as the ratio of water flow to the volume of precipitation.

annual runoff

So, the annual flow of the river is, first of all, the volume of water that the river throws out when it falls into its mouth. You can also say it a little differently. The amount of water that passes for the named period of time through the section of the river at its confluence is the annual flow of the river.

The definition of this parameter helps to characterize the full flow of a particular river. Accordingly, the rivers with the highest rate of annual flow will be the most full-flowing. The unit of measurement of the latter is the volume, expressed in cubic meters or cubic kilometers, per year.

solid stock

When taking into account the magnitude of the annual runoff, it must be taken into account that the river does not carry clean, distilled water. River water, both in dissolved and suspended form, contains a huge amount of solids. Some of them - in the form of insoluble particles - strongly affect the index of its transparency (turbidity).

Solid waste is divided into two types:

• weighted - a suspension of relatively light particles;
• bottom - relatively heavy particles that are drawn along the bottom to the place of confluence.

In addition, solid runoff consists of products of weathering, leaching, erosion, etc. of soils, soils, and rocks. The indicator of solid runoff can reach, depending on the fullness and turbidity of the river, tens, and sometimes hundreds of millions of tons (for example, the Yellow River - 1500, the Indus - 450 million tons).

Climatic factors determining the parameter of annual river runoff

The climatic factors that determine the annual flow of the river are, first of all, the annual amount of precipitation, the catchment area of ​​the river system and the evaporation of water from the surface (mirror) of the river. The latter factor directly depends on the number of sunny days, the average annual temperature, the transparency of river water, as well as on numerous other factors. An important role is also played by the time period in which the greatest amount of precipitation falls. If it is hotter, then this will reduce the annual runoff, and vice versa. Humidity also plays a huge role.

The nature of the relief

Rivers that flow mostly on flat terrain, other things being equal, are less watery than predominantly mountain rivers. In terms of annual runoff, the latter can exceed the flat ones by several times.

There are many reasons for this:

• mountain rivers, which have a much greater slope, flow faster, which means that river water has less time to evaporate;
• in the mountains, the temperature is always much lower, and, therefore, evaporation is weaker;
• in mountainous areas, there is more precipitation and more rivers, which means that the annual flow of the river is higher.

This, running a little ahead, is enhanced by the fact that the nature of soils in mountainous areas has less absorption, respectively, a larger volume of water comes to the mouth.

The nature of soils, soil cover, vegetation

River runoff is largely determined by the nature of the surface over which the river carries its waters. The annual river flow is an indicator that is primarily influenced by the nature of the soil.

Rocks, clay, stony soil, sand greatly differ in their carrying capacity in relation to water. Highly absorbent surfaces (e.g. sand, dry soil) will drastically reduce the volume of the annual flow of the river flowing through them, while almost water-impervious surface types (protruding rocks, dense clays) will have practically no effect on river flow parameters. , passing river waters through its territory without any losses.

Soil water saturation is also an extremely important factor. So, abundantly moistened soils will not only not “take away” melt water during spring snowmelt, but are also able to “share” excess water.

The nature of the vegetation cover of the banks of the river under study is also important. For example, those that flow through wooded areas are more watery, all other things being equal, compared with rivers in the steppe or forest-steppe zone. In particular, this is due to the ability of vegetation to reduce the total evaporation of moisture from the earth's surface.

The largest rivers in the world

Consider the rivers with the most abundant flow. To do this, we bring to your attention a table.

After analyzing this data, one can understand that the annual flow of Russian rivers, such as the Lena or the Yenisei, is quite large, but it still cannot be compared with the annual flow of such powerful full-flowing rivers as the Amazon or the Congo, located in the southern hemisphere.

Water discharge is the volume of water flowing through the cross section of a river per unit time. Water flow is usually measured in cubic meters per second (m3/s). The average long-term water flow of the largest rivers of the republic, for example, the Irtysh, is 960 m/s, and the Syr Darya - 730 m/s.

The flow of water in rivers in a year is called the annual flow. For example, the annual flow of the Irtysh is 28,000 million m3. Water runoff determines surface water resources. The runoff is unevenly distributed throughout the territory of Kazakhstan, the volume of surface runoff is 59 km3. The amount of annual river flow depends primarily on the climate. In the flat regions of Kazakhstan, the annual runoff mainly depends on the nature of the distribution of snow cover and water reserves before the snow melts. Rainwater is almost completely used to moisten the topsoil and evaporate.

The main factor influencing the flow of mountain rivers is the relief. As the absolute height increases, the amount of annual precipitation increases. The moisture coefficient in the north of Kazakhstan is about one, and the annual flow is high, and there is more water in the river. The amount of runoff per square kilometer on the territory of Kazakhstan is on average 20,000 m3. Our republic is ahead of only Turkmenistan in terms of river flow. The flow of rivers varies with the seasons of the year. Plain rivers during the winter months provide 1% of the annual flow.

Reservoirs are built to regulate river flows. Water resources are equally used both in winter and in summer for the needs of the national economy. There are 168 reservoirs in our country, the largest of them are Bukhtarma and Kapchagai.

All solid material carried by the river is called solid runoff. The turbidity of the water depends on its volume. It is measured in grams of a substance contained in 1 m³ of water. The turbidity of lowland rivers is 100 g/m3, while in the middle and lower reaches it is 200 g/m3. The rivers of Western Kazakhstan carry a large amount of loose rocks, turbidity reaches 500-700 g/m3. The turbidity of mountain rivers increases downstream. Turbidity in the river is 650 g/m3, in the lower reaches of the Chu - 900 g/m3, in the Syr Darya 1200 g/m3.

Nutrition and river regime

Kazakhstani rivers have different nutrition: snow, rain, glacial and groundwater. There are no rivers with the same nutrition. The rivers of the flat part of the republic are divided into two types according to the nature of the supply: snow-rain and predominantly snow supply.

Snow-rain fed rivers include rivers located in the forest-steppe and steppe zones. The main ones of this type - Ishim and Tobol - overflow their banks in spring, 50% of the annual runoff falls in April-July. Rivers are first fed by melt water, then rain. Since the low water level is observed in January, at this time they feed on groundwater.

Rivers of the second type have exclusively spring flow (85-95% of the annual flow). This type of food includes rivers located in the desert and semi-desert zones - these are the Nura, Ural, Sagyz, Turgay and Sarysu. The rise of water in these rivers is observed in the first half of spring. The main source of food is snow. The water level rises sharply in the spring when the snow melts. In the CIS countries, such a regime of rivers is called the Kazakhstani type. For example, 98% of its annual flow flows along the Nura River in a short time in spring. The lowest water level occurs in summer. Some rivers dry up completely. After the autumn rains, the water level in the river rises slightly, and in winter it drops again.

In the high-mountainous regions of Kazakhstan, rivers have a mixed type of food, but snow-glacier prevails. These are the Syrdarya, Ili, Karatal and Irtysh rivers. The level in them rises in late spring. The rivers of the Altai Mountains overflow their banks in spring. But the water level in them remains high until mid-summer, due to non-simultaneous snowmelt.

The rivers of the Tien Shan and Zhungarskiy Alatau are full-flowing in the warm season; In spring and summer. This is explained by the fact that in these mountains the melting of snow stretches until autumn. In spring, snowmelt begins from the lower belt, then during the summer, snow of medium height and highland glaciers melt. In the runoff of mountain rivers, the share of rainwater is insignificant (5-15%), and in low mountains it rises to 20-30%.

The flat rivers of Kazakhstan, due to low water and slow flow, quickly freeze with the onset of winter and are covered with ice at the end of November. The ice thickness reaches 70-90 cm. In frosty winters, the ice thickness in the north of the republic reaches 190 cm, and in the southern rivers 110 cm. second half of April.

The glacial regime of high mountain rivers is different. There is no stable ice cover in mountain rivers due to strong currents and groundwater supply. Coastal ice is observed only in some places. Kazakh rivers gradually erode rocks. Rivers flow, deepening their bottom, destroying their banks, rolling small and large stones. In the flat parts of Kazakhstan, the river flow is slow, and it carries solid materials.