Water consumption and annual flow of rivers. Lakes: classification, water balance, ecology and development

Let us determine the average long-term value (norm) of the annual runoff Kolp River, Upper Dvor point according to the data from 1969 to 1978. (10 years).

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.

Calculate the average multi-year runoff module by the ratio:

l/s km 2

where F - catchment area, km2.

Runoff volume - the volume of water flowing from the catchment for any time interval.

Let us calculate the average long-term runoff volume per year:

W 0 \u003d Q 0 xT \u003d 22.14. 31.54 . 10 6 \u003d 698.3 10 6 m 3

where T is the number of seconds in a year, equal to 31.54. 10 6

The average long-term runoff layer is calculated from the dependence:

220.98 mm/year

Average long-term runoff coefficient

where x 0 is the average long-term precipitation per year

The assessment of the representativeness (sufficiency) of a series of observations is determined by the value of the relative root-mean-square error of the average long-term value (norm) of annual runoff, calculated by the formula:

where C V is the coefficient of variability (variation) of the annual runoff; the length of the series is considered sufficient to determine Q o if ε Q ≤10%. The value of the average long-term runoff is called the runoff rate.

1. Determination of the coefficient of variability Cv of annual runoff

The coefficient of variability C V characterizes the runoff deviations for individual years from the runoff norm; it is equal to:

where σ Q is the root-mean-square deviation of annual discharges from the runoff norm

If the runoff for individual years is expressed in the form of modular coefficients
the coefficient of variation is determined by the formula

Compiling a table for calculating the annual runoff Kolp River, Verkhny Dvor point (Table 1)

Table 1

Data for calculation With v

Let us determine the coefficient of variability C v of the annual runoff:

The relative standard error of the average long-term value of the annual runoff of the Kolp River, Verkhny Dvor point for the period from 1969 to 1978 (10 years) is equal to:

Relative standard error of coefficient of variability With v when it is determined by the method of moments, it is equal to:

1. Determining the runoff rate in case of insufficient observational data by the method of hydrological analogy

Fig.1 Graph of connection of average annual runoff modules

of the studied basin the Kolp River, Verkhny Dvor point and the basin of the analogue of the river. Obnora, p. Sharna.

According to the graph of the connection of the average annual runoff modules, the Kolp River, the Verkhny Dvor point and the basin of the analogue of the river. Obnora, p. Sharna.M 0 \u003d 5.9 l / s km 2 (removed from the graph by the value of M 0a \u003d 7.9 l / s km 2)

Calculate the annual runoff variability coefficient using the formula

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

With V a - in the alignment of the analogous river;

Моа is the mean annual runoff of the analogue river;

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

Finally, to plot the curves, we accept Q o =18.64 m 3 /s, C V =0.336.

1. Construction of an analytical endowment curve and verification of its accuracy using an empirical endowment curve

The coefficient of asymmetry C s characterizes the asymmetry of the hydrological series and is determined by selection, based on the condition of the best correspondence of the analytical curve with the points of actual observations; for rivers located in flat conditions, when calculating the annual runoff, the best results are given by the ratio C s = 2C V. Therefore, we accept for the Kolp River, point Upper Yard C s \u003d 2С V=0.336 followed by 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 \u003d 2C V.

Ordinates of the analytical curve of provision of average annual

water discharge Kolp River, Verkhniy Dvor point

The security of a hydrological quantity is the probability of exceeding the considered value of a hydrological quantity among the totality of all its possible values.

We arrange the modular coefficients of annual costs in descending order (Table 3) and for each of them calculate its actual empirical supply using the formula:

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

n is the number of members of the series.

P m 1 \u003d 1 / (10 + 1) 100 \u003d 9.1 P m 2 \u003d 2 / (10 + 1) 100 \u003d 18.2, etc.

Figure - Analytical endowment curve

Plotting points with coordinates on the graph ( Pm , Q m ) and averaging them by eye, we obtain the curve of availability of the considered hydrological characteristic.

As can be seen, the plotted points lie very close to the analytical curve; from which it follows that the curve is constructed correctly and the relation C S = 2 C V corresponds to reality.

Table 3

Data for constructing an empirical endowment curve

Kolp River, Verkhny Dvor point

	Modular coefficients (K i) descending	Actual security	Years corresponding to K i

Figure - Empirical security

The average annual layers of precipitation in the warm and cold periods of the year / where and They are taken for a given point according to the recommendations of weather stations or according to climate reference books.[ ...]

The average annual river runoff is currently 4,740 km3. The total volume of water in the lakes is 106.4 thousand km3, including 79.2 thousand km3 in the Aral Sea and the Caspian. The water reserve in fresh lakes is 25.2 thousand km3, of which 91% falls on Baikal.[ ...]

4.10

Note, p is the average annual precipitation in mm: P is a coefficient equal to one minus the runoff coefficient; e - annual moisture consumption (total) in mm.[ ...]

The calculation of the annual runoff of Cs into the Tobol River, assuming that its measured concentration at the mouth of the Tura is close to the annual average, gives a value of 3.4-1010 Bq/year (0.93 Ci/year).[ ...]

Yana is the fourth largest river in Yakutia, which has access to the shelf of the Arctic Ocean. It has the largest slope compared to other rivers of Yakutia (15 cm per 1 km), its average annual flow is 32 km3. It is formed at the confluence of Dulgalakh and Sartang, the length of the river is 906 km. The channel is located in the mountainous area of ​​Eastern Verkhoyansk. Yana has 89 tributaries, the largest ones are Adycha, Bytantay, Olde. It flows into the shallow Yansky Bay, which is the southeastern part of the Laptev Sea.[ ...]

The second reason why underground runoff remains a poorly studied component of the water and salt balance of seas and oceans is subjective. For many years and even decades, hydrologists involved in the study of water balance proceeded from the fact that groundwater flow is a small element of the water balance (compared to its other components) and therefore it can be determined using the equation of the average long-term water balance. In other words, in their opinion, underground runoff can be defined as the difference between the average annual precipitation, evaporation and river runoff. The amount of groundwater flow calculated in this way depends entirely on the accuracy of estimating the average values ​​of precipitation, evaporation and river runoff and includes all the errors in their determination, which in total often exceed the value of groundwater runoff directly into the seas.[ ...]

Universal hydrochemical parameters are the average annual and long-term values ​​of the content of individual elements and their compounds and the average annual runoff of chemicals. They are relatively constant for certain periods of time and make it possible to compare the hydrochemical indicators of different years, taking into account short-term natural changes in chemicals. They are relatively constant for certain periods of time and make it possible to compare hydrochemical indicators of different years, taking into account short-term natural changes in the chemical composition of water.[ ...]

The SCM increments are determined mainly by the difference between two large quantities: river runoff and apparent evaporation (precipitation-evaporation difference) from the sea surface. The determining role of river runoff for the interannual variations in the CSL is evidenced by the high correlation coefficient between these values, which is 0.82 for the period 1900-1992. The correlation between apparent evaporation and SCM over the same period is also statistically significant and equals -0.46. It is necessary to note the anthropogenic impact on the river runoff, both on its average annual value and on the annual course. In particular, from the end of the 1940s to the middle of the 1960s, reservoirs in the Volga basin were filled with a total volume of about 200 km². In this paper, we use long-term data for the Volga runoff and precipitation over the Volga catchment area with average monthly resolution obtained from observational data. The flow of the Volga is 82% of the total river flow, and the correlation coefficient between the average annual series of these values ​​is 0.96 (1900-1992).[ ...]

Changes in the level regime in water bodies caused by the reconstruction of runoff in all parts of the river system, low and late floods, fluctuations in the water level during the reproduction of fish with spring-summer breeding periods lead to the suspension of spawning, resorption of germ cells, spawning of a smaller amount of eggs, and sometimes mass death developing eggs, larvae, juvenile fish and spawners on spawning grounds. This sometimes undermines the stocks of fish in the reservoir and adversely affects the size and value of commercial catches. It is quite natural that in reservoirs, along with the development of a species-specific temperature zone of adaptation, at which spawning begins, fish adapted to a certain (average annual, average long-term) level regime of a reservoir, such as when vast ilmen-hollow areas of rivers and lakes with last year's meadow vegetation, which served as a good substrate for the development of spawned eggs. The flood, as a rule, should be long-term with a slow decrease in the level, which enables the hatched juveniles to fully use the food resources of the shallow zone flooded with hollow waters, ensuring its rapid growth and timely migration of juveniles from spawning grounds.[ ...]

Negative values ​​of the balances correspond to the excess of the output runoff of radionuclides over the input as a result of natural drainage from the extensive floodplain system. The corresponding value, equal to the difference between the input and output annual flows, will be carried out during the year from the considered sections of the river floodplains, in particular, 847 GBq 908g and 94 GBq 137C8 from the Ob floodplain between the border with the Tomsk region and Khanty-Mansiysk, and 1145 GBq 908g from floodplain of the Irtysh between n.p. Demyansky and Khanty-Mansiysk. The positive values ​​of the balances in the studied sections of the rivers are associated with the excess of the input runoff of a given radionuclide over the output runoff. A value equal to the difference in flows will be deposited in the corresponding section of the floodplain, in particular, 92 GBq 137Cs in the Irtysh section. Naturally, all the above estimates remain valid provided that the considered average annual runoff dynamics is preserved. More accurate and objective estimates can be obtained on the basis of more detailed radioecological studies.[ ...]

Comparing the hydrological characteristics of the river. Tom in the alignment of the Krapivino whom hydroelectric complex and the river. Ob in the alignment of Novosibirsk, you can see that the flow of the river. Tom (29.6 km3) is almost half the size of the river. Ob (50.2 km3). The useful volume of Kra-Pivinsky is 2, and the full volume is 1.3 times more than Novosibirsk. The increments in the catchment areas of the reservoirs 16 thousand km2 and 13 thousand km2 are close to each other. In years of different water content, the ratio of the useful volume of the Novosibirsk reservoir and the annual runoff of the river. The Ob River varies from 12 to 6% with runoff fluctuations from 36.7 to 73.2 km3. For the Krapivinskoe reservoir, the ratio of these values ​​is much higher. The total volume is 39.5%, and the useful one is 32.8% of the average annual flow of the river in the alignment of the hydroelectric complex and 55.1 and 45.8% of the volume of flow per year of 95% water availability.[ ...]

The natural resources of fresh groundwater in the main aquifers of the Carboniferous deposits, which characterize the average long-term value of their replenishment, are about 100 m3/s with an average annual groundwater runoff module of about 2 l/s km2. The accounted withdrawal of groundwater averages approximately 50 m3/s.[ ...]

Long-term observations were carried out only on one of the watersheds; therefore, the author was unable to verify the constructed regression model on other watersheds. On the other hand, the results of modeling seasonal changes in nitrate runoff are very interesting, data on which were available for all three watersheds and were subjected to regression analysis. The value of the average monthly concentration of nitrate ions in the runoff in the constructed empirical models was influenced by parameters related to the “prehistory” of the watershed: the total amount of precipitation that fell on its territory during the study period and for the previous three months, the total volume of nitrate runoff for eight months (current plus seven previous), average monthly temperature for three months (and not in the simplest combination, but from the 5th to the 3rd, considering the month under study as zero), the total monthly runoff layer, runoff coefficient. But for each of the studied watersheds, which differed significantly not only in size, but also in the average annual rainfall, we had to build our own regression equations. And most importantly: in the resulting equations, the dependence on the same parameters turned out to be logarithmic, then hyperbolic, then quadratic, then linear.[ ...]

Under the natural resources of groundwater is meant the discharge of groundwater provided with food, i.e. that part of them that is continuously renewed in the process of the general water cycle on Earth. Natural resources characterize the amount of groundwater recharge due to infiltration of atmospheric precipitation, absorption of river runoff and overflow from other aquifers, which is cumulatively expressed by the value of the flow rate. Natural groundwater resources are thus an indicator of groundwater replenishment, reflecting their main feature as a renewable mineral resource, and characterize the upper limit of the possible withdrawal of groundwater over a long period without depletion. In the average long-term value, the value of groundwater recharge, minus evaporation, is equal to the value of groundwater runoff. Therefore, in the practice of hydrogeological studies, the natural resources of groundwater are usually expressed by the average annual or minimum values ​​of the groundwater runoff modules (l/s km2) or the size of the water layer (mm/year) entering the aquifer in its recharge area.

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

September

Ma l/s*km 2

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

	river point
	Sura-Kadyshevo

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

		Annual costs m 3 / s

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

Provision, Р%

Curve ordinates

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

Table 3

Data to test the theoretical curve

	Modular coefficients descending K	Actual security	Years corresponding to K

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.

Calculation of the intra-annual distribution of runoff by the layout method (off-season distribution). R. Sura for 1964 - 1973

∑ stock summer-autumn

Average runoff summer-autumn

Spending for the season spring

∑ spring stock

Table 4

Table 4 continued

Calculation of the intra-annual distribution of runoff by the layout method (off-season distribution)

Costs for the limiting summer-autumn season

∑ winter stock

∑ runoff for low-water low water. period winter+summer+autumn

The average value for low water. flow amount period

Descending expenses okay

summer autumn

1 818,40

4 456,70

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 select 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

Total runoff

Average monthly expenses descending

1. For the spring season

Total:

2. For the summer-autumn season

Total:

3. For the winter season

Total:

Estimated monthly expenses

Estimated volumes (million m 3) by months

Note: To get flow volumes in million cubic meters, the costs should be multiplied: a) for a 31-day month by a factor of 2.68, b) for a 30-day month -2.59. c) for a 28-day month -2.42.

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.

28.07.2015

Fluctuations in river runoff and criteria for its assessment. River runoff is the movement of water in the process of its circulation in nature, when it flows down the river channel. River flow is determined by the amount of water flowing through the river channel for a certain period of time.
Numerous factors influence the flow regime: climatic - precipitation, evaporation, humidity and air temperature; topographic - terrain, shape and size of river basins and soil-geological, including vegetation cover.
For any basin, the more precipitation and less evaporation, the greater the flow of the river.
It has been established that with an increase in the catchment area, the duration of the spring flood also increases, while the hydrograph has a more elongated and “calm” shape. In easily permeable soils, there is more filtration and less runoff.
When performing various hydrological calculations related to the design of hydraulic structures, reclamation systems, water supply systems, flood control measures, roads, etc., the following main characteristics of the river flow are determined.
1. Water consumption is the volume of water flowing through the considered section per unit of time. The average water consumption Qcp is calculated as the arithmetic average of the costs for a given period of time T:

2. Flow volume V- this is the volume of water that flows through a given target for the considered period of time T

3. Drain module M is the flow of water per 1 km2 of catchment area F (or flowing from a unit catchment area):

In contrast to the water discharge, the runoff modulus is not associated with a specific section of the river and characterizes the runoff from the basin as a whole. The average multi-year runoff module M0 does not depend on the water content of individual years, but is determined only by the geographical location of the river basin. This made it possible to zonate our country in hydrological terms and to build a map of isolines of average long-term runoff modules. These maps are given in the relevant regulatory literature. Knowing the catchment area of ​​a river and determining the value M0 for it using the isoline map, we can determine the average long-term water flow Q0 of this river using the formula

For closely spaced river sections, the runoff moduli can be taken constant, i.e.

From here, according to the known water discharge in one section Q1 and the known catchment areas in these sections F1 and F2, the water discharge in the other section Q2 can be established by the ratio

4. Drain layer h- this is the height of the water layer, which would be obtained with a uniform distribution over the entire basin area F of the runoff volume V for a certain period of time:

For the average multi-year runoff layer h0 of the spring flood, contour maps were compiled.
5. Modular drain coefficient K is the ratio of any of the above runoff characteristics to its arithmetic mean:

These coefficients can be set for any hydrological characteristics (discharges, levels, precipitation, evaporation, etc.) and for any periods of flow.
6. Runoff coefficient η is the ratio of the runoff layer to the layer of precipitation that fell on the catchment area x:

This coefficient can also be expressed in terms of the ratio of the volume of runoff to the volume of precipitation for the same period of time.
7. Flow rate- the most probable average long-term value of runoff, expressed by any of the above runoff characteristics over a multi-year period. To establish the runoff norm, a series of observations should be at least 40 ... 60 years.
The annual flow rate Q0 is determined by the formula

Since the number of observation years at most water gauges is usually less than 40, it is necessary to check whether this number of years is sufficient to obtain reliable values ​​of the runoff norm Q0. To do this, calculate the root mean square error of the flow rate according to the dependence

The duration of the observation period is sufficient if the value of the root-mean-square error σQ does not exceed 5%.
The change in annual runoff is predominantly influenced by climatic factors: precipitation, evaporation, air temperature, etc. All of them are interconnected and, in turn, depend on a number of reasons that are random in nature. Therefore, the hydrological parameters characterizing the runoff are determined by a set of random variables. When designing measures for timber rafting, it is necessary to know the values ​​of these parameters with the necessary probability of exceeding them. For example, in the hydraulic calculation of timber rafting dams, it is necessary to set the maximum flow rate of the spring flood, which can be exceeded five times in a hundred years. This problem is solved using the methods of mathematical statistics and probability theory. To characterize the values ​​of hydrological parameters - costs, levels, etc., the following concepts are used: frequency(recurrence) and security (duration).
The frequency shows how many cases during the considered period of time the value of the hydrological parameter was in a certain interval. For example, if the average annual water discharge in a given section of the river changed over a number of years of observations from 150 to 350 m3/s, then it is possible to establish how many times the values ​​of this value were in the intervals 150...200, 200...250, 250.. .300 m3/s etc.
security shows in how many cases the value of a hydrological element had values ​​equal to or greater than a certain value. In a broad sense, security is the probability of exceeding a given value. The availability of any hydrological element is equal to the sum of the frequencies of the upstream intervals.
Frequency and availability can be expressed in terms of the number of occurrences, but in hydrological calculations they are most often determined as a percentage of the total number of members of the hydrological series. For example, in the hydrological series there are twenty values ​​of average annual water discharges, six of them had a value equal to or greater than 200 m3/s, which means that this discharge is provided by 30%. Graphically, changes in frequency and availability are depicted by curves of frequency (Fig. 8a) and availability (Fig. 8b).

In hydrological calculations, the probability curve is more often used. It can be seen from this curve that the greater the value of the hydrological parameter, the lower the percentage of availability, and vice versa. Therefore, it is generally accepted that years for which the runoff availability, that is, the average annual water discharge Qg, is less than 50% are high-water, and years with Qg more than 50% are low-water. A year with a runoff security of 50% is considered a year of average water content.
The availability of water in a year is sometimes characterized by its average frequency. For high-water years, the frequency of occurrence shows how often years of a given or greater water content occur on average, for low-water years - of a given or less water content. For example, the average annual discharge of a high-water year with 10% security has an average frequency of 10 times in 100 years or 1 time in 10 years; the average frequency of a dry year of 90% security also has a frequency of 10 times in 100 years, since in 10% of cases the average annual discharge will have lower values.
Years of a certain water content have a corresponding name. In table. 1 for them the availability and repeatability are given.

The relationship between repeatability y and availability p can be written as follows:
for wet years

for dry years

All hydraulic structures for regulating the channel or flow of rivers are calculated according to the water content of the year of a certain supply, which guarantees the reliability and trouble-free operation of the structures.
The estimated percentage of provision of hydrological indicators is regulated by the "Instruction for the design of timber rafting enterprises".
Provision curves and methods of their calculation. In the practice of hydrological calculations, two methods of constructing supply curves are used: empirical and theoretical.
Reasonable calculation empirical endowment curve can only be performed if the number of observations of the river runoff is more than 30...40 years.
When calculating the availability of members of the hydrological series for annual, seasonal and minimum flows, you can use the formula of N.N. Chegodaeva:

To determine the availability of maximum water flow rates, the S.N. dependence is used. Kritsky and M.F. Menkel:

The procedure for constructing an empirical endowment curve:
1) all members of the hydrological series are recorded in decreasing order in absolute value;
2) each member of the series is assigned a serial number, starting from one;
3) the security of each member of the decreasing series is determined by formulas (23) or (24).
Based on the results of the calculation, a security curve is built, similar to the one shown in Fig. 8b.
However, empirical endowment curves have a number of disadvantages. Even with a sufficiently long observation period, it cannot be guaranteed that this interval covers all possible maximum and minimum values ​​of the river flow. Estimated values ​​of runoff security of 1...2% are not reliable, since sufficiently substantiated results can be obtained only with the number of observations for 50...80 years. In this regard, with a limited period of observation of the hydrological regime of the river, when the number of years is less than thirty, or in their complete absence, they build theoretical security curves.
Studies have shown that the distribution of random hydrological variables most well obeys the type III Pearson curve equation, the integral expression of which is the supply curve. Pearson obtained tables for constructing this curve. The security curve can be constructed with sufficient accuracy for practice in three parameters: the arithmetic mean of the terms of the series, the coefficients of variation and asymmetry.
The arithmetic mean of the terms of the series is calculated by formula (19).
If the number of years of observations is less than ten or no observations were made at all, then the average annual water discharge Qgcp is taken equal to the average long-term Q0, that is, Qgcp = Q0. The value of Q0 can be set using the modulus factor K0 or the sink modulus M0 determined from the contour maps, since Q0 = M0*F.
The coefficient of variation Cv characterizes the runoff variability or the degree of its fluctuation relative to the average value in a given series; it is numerically equal to the ratio of the standard error to the arithmetic mean of the series members. The value of the Cv coefficient is significantly affected by climatic conditions, the type of river feeding, and the hydrographic features of its basin.
If there are observational data for at least ten years, the annual runoff variation coefficient is calculated by the formula

The value of Cv varies widely: from 0.05 to 1.50; for timber-rafting rivers Cv = 0.15...0.40.
With a short period of observations of the river runoff or in their complete absence the coefficient of variation can be established by the formula D.L. Sokolovsky:

In hydrological calculations for basins with F > 1000 km2, the isoline map of the Cv coefficient is also used if the total area of ​​lakes does not exceed 3% of the catchment area.
In the normative document SNiP 2.01.14-83, a generalized formula K.P. is recommended for determining the coefficient of variation of unstudied rivers. Resurrection:

Skewness coefficient Cs characterizes the asymmetry of the series of the considered random variable with respect to its average value. The smaller part of the members of the series exceeds the value of the runoff norm, the greater the value of the asymmetry coefficient.
The asymmetry coefficient can be calculated by the formula

However, this dependence gives satisfactory results only for the number of observation years n > 100.
The asymmetry coefficient of unstudied rivers is set according to the Cs/Cv ratio for analogue rivers, and in the absence of sufficiently good analogues, the average Cs/Cv ratios for the rivers of the given region are taken.
If it is impossible to establish the Cs/Cv ratio for a group of analogous rivers, then the values ​​of the Cs coefficient for unstudied rivers are accepted for regulatory reasons: for river basins with a lake coefficient of more than 40%

for zones of excessive and variable moisture - arctic, tundra, forest, forest-steppe, steppe

To build a theoretical endowment curve for the above three parameters - Q0, Cv and Cs - use the method proposed by Foster - Rybkin.
From the above relation for the modular coefficient (17) it follows that the average long-term value of the runoff of a given probability - Qp%, Мр%, Vp%, hp% - can be calculated by the formula

The modulus runoff coefficient of the year of a given probability is determined by the dependence

Having determined a number of any runoff characteristics for a long-term period of different availability, it is possible to construct a supply curve based on these data. In this case, it is advisable to carry out all calculations in tabular form (Tables 3 and 4).

Methods for calculating modular coefficients. To solve many water management problems, it is necessary to know the distribution of runoff by seasons or months of the year. The intra-annual distribution of runoff is expressed in the form of modular coefficients of monthly runoff, representing the ratio of the average monthly flow Qm.av to the average annual Qg.av:

The intra-annual distribution of runoff is different for years of different water content, therefore, in practical calculations, the modular coefficients of monthly runoff are determined for three characteristic years: a high-water year with 10% supply, an average year with 50% supply, and a low-water year with 90% supply.
Monthly runoff modulus coefficients can be established based on actual knowledge of average monthly water discharges in the presence of observational data for at least 30 years, according to an analogue river, or according to standard tables of monthly runoff distribution, which are compiled for different river basins.
The average monthly water consumption is determined based on the formula

(33): Qm.cp = KmQg.sr

Maximum water consumption. When designing dams, bridges, lagoons, measures to strengthen the banks, it is necessary to know the maximum water flow. Depending on the type of river feeding, the maximum flow rate of spring floods or autumn floods can be taken as the calculated maximum discharge. The estimated security of these costs is determined by the class of capital size of hydraulic structures and is regulated by the relevant regulatory documents. For example, timber rafting dams of class Ill of capitality are calculated for the passage of a maximum water flow of 2% security, and class IV - of 5% security, bank protection structures should not collapse at flow rates corresponding to the maximum water flow of 10% security.
The method for determining the value of Qmax depends on the degree of knowledge of the river and on the difference between the maximum discharges of the spring flood and the flood.
If there are observational data for a period of more than 30 ... 40 years, then an empirical security curve Qmax is built, and with a shorter period - a theoretical curve. The calculations take: for spring floods Cs = 2Сv, and for rain floods Cs = (3...4)CV.
Since river regimes are monitored at water-measuring stations, the supply curve is usually plotted for these sites, and the maximum water discharges at the sites where structures are located are calculated by the ratio

For lowland rivers maximum flow of spring flood water given security p% is calculated by the formula

The values ​​of the parameters n and K0 are determined depending on the natural zone and relief category according to Table. 5.

Category I - rivers located within hilly and plateau-like uplands - Central Russian, Strugo-Krasnenskaya, Sudoma uplands, Central Siberian plateau, etc .;
II category - rivers, in the basins of which hilly uplands alternate with depressions between them;
Category III - rivers, most of the basins of which are located within the flat lowlands - Mologo-Sheksninskaya, Meshcherskaya, Belarusian woodlands, Pridnestrovskaya, Vasyuganskaya, etc.
The value of the coefficient μ is set depending on the natural zone and the percentage of security according to Table. 6.

The hp% parameter is calculated from the dependency

The coefficient δ1 is calculated (for h0 > 100 mm) by the formula

The coefficient δ2 is determined by the relation

The calculation of the maximum water discharges during the spring flood is carried out in tabular form (Table 7).

The levels of high waters (HWL) of the calculated supply are established according to the curves of water discharges for the corresponding values ​​of Qmaxp% and calculated sections.
With approximate calculations, the maximum water flow of a rain flood can be set according to the dependence

In responsible calculations, the determination of the maximum water flow should be carried out in accordance with the instructions of regulatory documents.

Water resources are one of the most important resources of the Earth. But they are very limited. Indeed, although ¾ of the planet's surface is occupied by water, most of it is the salty World Ocean. Man needs fresh water.

Its resources are also mostly inaccessible to people, as they are concentrated in the glaciers of the polar and mountain regions, in swamps, underground. Only a small part of the water is suitable for human use. These are fresh lakes and rivers. And if in the first the water lingers for decades, then in the second it is updated about once every two weeks.

River flow: what does this concept mean?

This term has two main meanings. First, it refers to the entire volume of water flowing into the sea or ocean during the year. This is its difference from the other term "river flow", when the calculation is carried out for a day, hours or seconds.

The second value is the amount of water, dissolved and suspended particles carried by all rivers flowing in a given region: mainland, country, region.

Surface and underground river runoff is distinguished. In the first case, we mean the waters flowing into the river along the A underground - these are springs and springs that gush under the bed. They also replenish the water supply in the river, and sometimes (during the summer low water or when the surface is ice-bound) they are its only source of food. Together, these two species make up the total river runoff. When people talk about water resources, they mean it.

Factors affecting river flow

This issue has already been studied enough. Two main factors can be named: the terrain and its climatic conditions. In addition to them, several additional ones stand out, including human activity.

The main reason for the formation of river flow is the climate. It is the ratio of air temperature and precipitation that determines the evaporation rate in a given area. The formation of rivers is possible only with excessive moisture. If evaporation exceeds the amount of precipitation, there will be no surface runoff.

The nutrition of rivers, their water and ice regime depend on the climate. provide moisture replenishment. Low temperatures reduce evaporation, and when the soil freezes, the flow of water from underground sources is reduced.

The relief influences the size of the river catchment area. It depends on the shape of the earth's surface in which direction and at what speed the moisture will flow. If there are closed depressions in the relief, not rivers, but lakes are formed. The slope of the terrain and the permeability of rocks affect the ratio between the parts of precipitation that flow into water bodies and seep into the ground.

The value of rivers for humans

The Nile, the Indus with the Ganges, the Tigris and the Euphrates, the Yellow River and the Yangtze, the Tiber, the Dnieper… These rivers have become the cradle for different civilizations. Since the dawn of mankind, they have served for him not only as a source of water, but also as channels of penetration into new unexplored lands.

Thanks to river flow, irrigated agriculture is possible, which feeds almost half of the world's population. High water consumption also means rich hydropower potential. River resources are used in industrial production. Particularly water-intensive are the production of synthetic fibers and the production of pulp and paper.

River transport is not the fastest, but it is cheap. It is best suited for the transportation of bulk cargo: timber, ores, oil products, etc.

A lot of water is taken for domestic needs. Finally, rivers are of great recreational importance. These are places of rest, restoration of health, a source of inspiration.

The most full-flowing rivers in the world

The largest volume of river flow is in the Amazon. It is almost 7000 km 3 per year. And this is not surprising, because the Amazon is full of water all year round due to the fact that its left and right tributaries overflow at different times. In addition, it collects water from an area almost the size of the entire mainland of Australia (more than 7000 km 2)!

In second place is the African Congo River with a flow of 1445 km 3. Located in the equatorial belt with daily showers, it never becomes shallow.

Following in terms of total river flow resources: the Yangtze is the longest in Asia (1080 km 3), Orinoco (South America, 914 km 3), Mississippi (North America, 599 km 3). All three spill heavily during the rains and pose a considerable threat to the population.

The 6th and 8th places in this list are the great Siberian rivers - the Yenisei and the Lena (624 and 536 km 3, respectively), and between them is the South American Parana (551 km 3). The top ten is closed by another South American river Tocantins (513 km 3) and the African Zambezi (504 km 3).

Water resources of the countries of the world

Water is the source of life. Therefore, it is very important to have its reserves. But they are distributed across the planet extremely unevenly.

The provision of countries with river runoff resources is as follows. The top ten countries richest in water are Brazil (8,233 km 3), Russia (4.5 thousand km 3), USA (more than 3 thousand km 3), Canada, Indonesia, China, Colombia, Peru, India, Congo .

Territories located in a tropical dry climate are poorly provided for: North and South Africa, the countries of the Arabian Peninsula, Australia. There are few rivers in the inland regions of Eurasia, therefore, among the low-income countries are Mongolia, Kazakhstan, and the Central Asian states.

If the number of people using this water is taken into account, the indicators change somewhat.

Availability of river runoff resources

The largest		Least
Countries	security	Countries	security
french guiana	609 thousand	Kuwait	Less than 7
Iceland	540 thousand	United Arab Emirates	33,5
Guyana	316 thousand	Qatar	45,3
Suriname	237 thousand	Bahamas	59,2
Congo	230 thousand	Oman	91,6
Papua New Guinea	122 thousand	Saudi Arabia	95,2
Canada	87 thousand	Libya	95,3
Russia	32 thousand	Algeria	109,1

The densely populated countries of Europe with full-flowing rivers are no longer so rich in fresh water: Germany - 1326, France - 3106, Italy - 3052 m 3 per capita, with an average value for the whole world - 25 thousand m 3.

Transboundary flow and problems associated with it

Many rivers cross the territory of several countries. In this regard, there are difficulties in the joint use of water resources. This problem is especially acute in areas where almost all water is taken to the fields. And the neighbor downstream may not get anything.

For example, belonging in its upper reaches to Tajikistan and Afghanistan, and in the middle and lower reaches to Uzbekistan and Turkmenistan, in recent decades it has not carried its waters to the Aral Sea. Only with good neighborly relations between neighboring states can its resources be used to the benefit of all.

Egypt receives 100% of river water from abroad, and a reduction in the flow of the Nile due to water intake upstream can have an extremely negative impact on the state of the country's agriculture.

In addition, along with water, various pollutants “travel” across the borders of countries: garbage, factory runoff, fertilizers and pesticides washed off the fields. These problems are relevant for the countries lying in the Danube basin.

Rivers of Russia

Our country is rich in large rivers. There are especially many of them in Siberia and the Far East: the Ob, Yenisei, Lena, Amur, Indigirka, Kolyma, etc. And the river flow is the largest in the eastern part of the country. Unfortunately, so far only a small fraction of them have been used. Part goes for domestic needs, for the operation of industrial enterprises.

These rivers have a huge energy potential. Therefore, the largest hydroelectric power plants are built on Siberian rivers. And they are indispensable as transport routes and for timber rafting.

The European part of Russia is also rich in rivers. The largest of them is the Volga, its flow is 243 km 3. But 80% of the country's population and economic potential are concentrated here. Therefore, the lack of water resources is sensitive, especially in the southern part. The flow of the Volga and some of its tributaries is regulated by reservoirs; a cascade of hydroelectric power stations has been built on it. The river with its tributaries is the main part of the Unified Deep Water System of Russia.

In the conditions of the growing water crisis all over the world, Russia is in favorable conditions. The main thing is to prevent pollution of our rivers. Indeed, according to economists, clean water can become a more valuable commodity than oil and other minerals.