INTRODUCTION

Tasks of hydrological calculations and their role in the development of the country's economy. Connection of hydrological calculations with other sciences. History of the development of hydrological calculations: the first works of foreign scientists in the 17th-19th centuries; works of Russian scientists of the late 19th - early 20th centuries; the first textbook of hydrology in Russia; Soviet period of development of hydrological calculations; All-Union hydrological congresses and their role in the development of methods for calculating river runoff; post-Soviet period of development of hydrological calculations. The main characteristics of river flow. Three cases of determining hydrological characteristics.

METHODS FOR ANALYSIS OF RIVER FLOW CHARACTERISTICS.

Genetic analysis of hydrological data: geographic and hydrological method and its special cases - methods hydrological analogy, geographic interpolation and hydrological-hydrogeological. Probabilistic-statistical analysis: method of moments, maximum likelihood method, quantifier method, correlation and regression analysis, factor analysis, principal component method, discriminant analysis method. Computational Mathematics Analysis Methods: Systems algebraic equations, differentiation and integration of functions, partial differential equations, Monte Carlo method. Mathematical modeling hydrological phenomena and processes, classes and types of models. System analysis.

METHODS FOR GENERALIZING HYDROLOGICAL CHARACTERISTICS.

Runoff contour maps: construction principles, runoff determination reliability. Hydrological zoning of the territory: concept, boundaries of application, principles of zoning and approaches to zoning, methods for determining the boundaries of regions, homogeneity of regions. Graphic processing of hydrological data: rectilinear, exponential and exponential graphic dependences.

FACTORS OF RIVER FLOW FORMATION.

The importance of understanding the mechanism and degree of influence of physical and geographical factors on the regime and magnitude of river runoff. The equation water balance river basin. Classification of river runoff formation factors. Climatic and meteorological factors of river flow: precipitation, evaporation, air temperature. Influence of factors of the river basin and its underlying surface on the runoff: geographical position, dimensions, shape of the river basin, relief, vegetation, soils and rocks, permafrost, lakes, swampiness, glaciers and icing within the basin. Influence economic activity on river runoff: creation of reservoirs and ponds, redistribution of runoff between river basins, irrigation of agricultural fields, drainage of marshes and wetlands, agroforestry activities in river catchment areas, water consumption for industrial and domestic needs, urbanization, mining.

STATISTICAL PARAMETERS OF RIVER FLOW.

RELIABILITY OF INITIAL HYDROLOGICAL INFORMATION.

The flow rate and the principles of its calculation. River runoff variability, its relative (coefficient of variation) and absolute (average standard deviation) expression, connection with meteorological factors. Variability of intra-annual distribution of runoff, maximum runoff of spring floods and rain floods, minimum winter and summer runoff. Asymmetry coefficient. The degree of reliability of the hydrological background information. Causes of errors in regime hydrological information.

FORMATION CONDITIONS AND CALCULATIONS OF ANNUAL FLOW RATE.

Annual runoff of rivers as the main hydrological characteristic. Formation conditions annual runoff: precipitation, evaporation, air temperature. Influence of lakes, swamps, glaciers, ice floes, basin area, watershed height, forest and its clearing, creation of reservoirs, irrigation, industrial and municipal water consumption, drainage of swamps and wetlands, agroforestry measures on the formation of annual river flow. The concept of the representativeness of a series of hydrological data. Elements of cyclic fluctuations in runoff. Synchronicity, asynchrony, in-phase, out-of-phase fluctuations of the drain. Calculations of the annual flow rate in the presence, insufficiency and absence of observational data. Distribution of annual runoff across the territory of Russia.

FORMATION FACTORS AND CALCULATION

INTRA-ANNUAL DISTRIBUTION OF RIVER FLOW.

Practical significance knowledge about the intra-annual distribution of runoff. The role of climate in the distribution of runoff during the year. Underlying surface factors that correct intra-annual distribution runoff: lakes, swamps, river floodplain, glaciers, permafrost, icing, forest, karst, river basin size, catchment shape. Influence of the creation of reservoirs and ponds, irrigation, agroforestry activities and drainage on the intra-annual distribution of river flow. Calculation of the intra-annual distribution of runoff in the presence, insufficiency and absence of observational data. Calculation of the daily distribution of runoff. Curves of duration of daily expenses. Coefficient of natural runoff regulation. Coefficient of intra-annual runoff unevenness.

FEATURES OF FORMATION AND CALCULATION OF THE MAXIMUM

RIVER FLOW DURING THE SPRING FLOOD PERIOD.

The concept of "catastrophic flood (flood)". Practical and scientific significance reliable assessment of the statistical parameters of floods. Causes catastrophic floods. Genetic groups of maximum water flow rates. Estimated sufficiency of maximum water flow rates depending on capital class hydraulic structure. Quality of initial information on maximum water discharges. Conditions for the formation of flood runoff: snow reserves in the river basin and water reserves in the snow cover, evaporation losses from snow, intensity and duration of snowmelt, losses melt water. Underlying surface factors: relief, slope exposure, dimensions, configuration, dissection of the basin, lakes and swamps, soils and soils. Anthropogenic factors formation of the maximum flow of floods. Genetic theory of formation of maximum runoff. Reduction of the maximum flow. Calculations of the maximum spring runoff in the presence, insufficiency and absence of observational data. Mathematical and physico-mathematical models of the processes of formation of melt water runoff.

MAXIMUM RIVER FLOW DURING RAIN FLOOD PERIOD.

Areas of distribution of high rain maxima. Difficulties in researching and generalizing the characteristics of rain runoff. Types of rain and their components. Features of the formation of rain floods: the intensity and duration of rain, the intensity of infiltration, the speed and time of rainwater runoff. The role of underlying surface factors and types of economic activity in the formation of rain runoff. Calculations of the maximum water discharges of rain floods in the presence, insufficiency and absence of observational data. Simulation of the runoff of rain floods.

FORMATION CONDITIONS AND CALCULATIONS OF THE MINIMUM SUMMER
AND WINTER DRAIN OF RIVERS.

The concept of low-water period and low-water runoff. The practical significance of knowledge about the minimum flow of rivers. The main design characteristics of the minimum and low flow of rivers. The duration of the winter and summer or summer-autumn low-water periods on the rivers of Russia. Types of low water and low water periods of Russian rivers. Factors of formation of the minimum runoff: precipitation, temperature, evaporation, connection of the waters of the aeration zone, groundwater, karst and artesian waters with the river, geological and hydrogeological conditions in the basin, lakes, swamps, forest, dissection and height of the terrain, river floodplain, depth of the erosion cut river beds, areas of surface and underground watersheds, slope and orientation of the watershed, irrigation of agricultural lands, industrial and domestic consumption of river water, drainage, use groundwater, creation of reservoirs, urbanization. Calculations of the minimum low-water runoff for different volumes of initial hydrological information.

4. PRACTICAL WORKS.

PRACTICAL WORK No. 1.

CALCULATIONS OF ANNUAL RUNOFF OF RIVERS
WITH INSUFFICIENCY AND ABSENCE OF OBSERVATION DATA.

TASK 1: Select a river basin with a catchment area of ​​at least 2000 km² and not more than 50000km ² within the Tyumen region and extract from the publications of the WRC for this basin a number of observations of average annual discharges.

TASK 2: Determine the statistical parameters of the curve for the average annual flow of the selected river using the methods of moments, maximum likelihood, graph-analytical.

TASK 3: Determine the annual flow of the river with a security of 1%, 50% and 95%.

TASK 4: Calculate the average annual runoff of the same river using the isoline map of the module and runoff layer and evaluate the accuracy of the calculation.

THEORY: In the presence or insufficiency of observational data, the main statistical parameters of river runoff are determined by three methods: the method of moments, the maximum likelihood method, and the graph-analytical method.

METHOD OF MOMENTS.

To determine the parameters of the distribution curveQo, Cv and Cs by the method of moments, the following formulas are used:

1) average long-term value of water consumption

Qо = ΣQi /n, where

Qi – annual values ​​of water consumption, m³/s;

n is the number of years of observations; for observation series of less than 30 years, instead of n, take (n - 1).

2) coefficient of variation

Cv \u003d ((Σ (Ki -1)²) / n)½, where

Ki - modular coefficient calculated by the formula

Ki \u003d Qi / Qo.

3) coefficient of asymmetry

Cs \u003d Σ (Ki - 1)³ / (n Cv³).

Based on the Cv and Cs values, the Cs / Cv ratio and the calculation errors of Qo, Cv and Cs are calculated:

1) Qo error

σ = (Cv /n½) 100%;

2) Cv error should be no more than 10-15%

Έ = ((1+Cv²) / 2n)½ 100%,

3) Cs error

έ = ((6/n)½ (1+6Cv²+5Cv ( ½ / Cs) 100%.

Maximum likelihood method .

The essence of the method is that the most probable is the value of the unknown parameter at which the likelihood function reaches the highest possible value. In this case, the members of the series, which correspond to greater value functions. This method is based on the use of statistics λ 1 , λ 2 , λ 3. Statistics λ 2 and λ 3 are connected with each other and their ratio changes from the change in Cv and the ratio of Cs / Cv. Statistics are calculated using the formulas:

1) statistics λ 1 there is an average arithmetic series observations

λ 1 = ΣQi / n;

2) statistics λ 2

λ 2 \u003d Σ IgKi / (n - 1);

3) statistics λ 3

λ 3 = Σ Ki· IgКi /(n – 1).

The determination of the coefficient of variability Cv and the ratio Cs / Cv is carried out according to nomograms (see in the textbook. Practical hydrology. L .: Gidrometeoizdat, 1976, p. 137) in accordance with the calculated statistics λ 2 and λ 3 . On the nomograms, we find the point of intersection of the values ​​of the statistics λ 2 and λ 3 . The Cv value is determined from the vertical curve closest to it, and the Cs / Cv ratio is determined from the horizontal curve, from which we proceed to the Cs value. The error Cv is determined by the formula:

Έ = (3 / (2n(3+ Cv²)))½ 100%.

GRAPH-ANALYTICAL METHOD .

With this method, the statistical parameters of the analytical endowment curve are calculated by three characteristic ordinates of the smoothed empirical endowment curve. These ordinates are Q

On the semi-logarithmic fiber of probabilities, the dependence Q = f (P) is built. To construct a smoothed empirical supply curve, it is necessary to build a series of observations in descending sequence and for each ranked value of water consumption Q ub . assign the value of security P, calculated by the formula:

P \u003d (m / n + 1) 100%, where

m- serial number row member;

n is the number of members of the series.

Provision values ​​are plotted along the horizontal axis, the corresponding Q kill The intersection points are indicated by circles with a diameter of 1.5-2 mm and fixed with ink. A smoothed empirical security curve is drawn over the points with a pencil. Three characteristic ordinates Q are taken from this curve 5% ,Q 50% and Q 95% availability, thanks to which the value of the coefficient of skewness S of the supply curve is calculated according to the following formula:

S = (Q 5% + Q 95% - 2 Q 50% ) / (Q 5% - Q 95% ).

The skew factor is a function of the skewness factor. Therefore, according to the calculated value of S, the value of Cs is determined (see Appendix 3 in the textbook. Practical Hydrology. L .: Gidrometeoizdat, 1976, p. 431). According to the same application, depending on the obtained value of Cs, the difference of normalized deviations (Ф 5% - F 95% ) and normalized deviation Ф 50% . Next, calculate the standard deviation σ, the average perennial runoff Qо´and the coefficient of variation Сv according to the following formulas:

σ \u003d (Q 5% - Q 95% ) / (F 5% - F 95% ),

Qo ´ \u003d Q 50% - σ F 50%,

Сv = σ / Q´.

The analytical endowment curve is considered to be sufficiently consistent with the empirical distribution if the following inequality is satisfied:

IQo - Qo´I< 0,02·Qо.

Medium quadratic error Qо´ is calculated by the formula:

σ Qo´ = (Сv / n½) 100%.

Coefficient of variation error

Έ = ((1+ Сv²) / 2n)½ 100%.

CALCULATION OF THE EXPENSES OF THE GIVEN SECURITY .

The consumption of a given security is calculated by the formula:

Qр = Кр·Qо, where

Кр - modular coefficient of the given security p%, calculated by the formula

Kp \u003d Fr Cv + 1, where

Fr - normalized deviations of a given security from the average value of the ordinates of the binomial distribution curve, determined according to Appendix 3 of the training manual. Practical hydrology. L .: Gidrometeoizdat, 1976, p. 431.

Recommended for further hydrological calculations and design work statistical parameters for the river basin and its secured costs are obtained by calculating the arithmetic mean of those obtained by the above three methods Qo, Cv, Cs, Q 5% ,Q 50% and Q 95% security.

DETERMINATION OF THE VALUES OF AVERAGE ANNUAL RIVER FLOW

CARDS.

In the absence of observational data on the runoff, one of the ways to determine it is the maps of the isolines of the modules and the runoff layer (see Fig. tutorial. Practical hydrology. L.: Gidrometeoizdat, 1976, pp. 169-170). The value of the modulus or runoff layer is determined for the center of the catchment area of ​​the river. If the center of the watershed lies on the isoline, then the average value of the runoff of this watershed is taken from the value of this isoline. If the watershed lies between two isolines, then the runoff value for its center is determined by linear interpolation. If the watershed is crossed by several isolines, then the value of the runoff module (or runoff layer) for the center of the watershed is determined by the weighted average method according to the formula:

Мср = (М 1 f 1 + М 2 f 2 +…М n f n ) / (f 1 + f 2 +…f n ), where

M 1, M 2 ... - average runoff values ​​between adjacent isolines crossing the watershed;

f1, f2… - catchment areas between contour lines within the catchment area (in km² or in scale divisions).

For determining water flow in the river still to be determined average speed river currents. This can be done in various ways:

To determine the flow of the river depending on the area of ​​the basin, the height of the sediment layer, etc. in hydrology, the following quantities are used:

• river runoff,
• drain module
• runoff factor.

River runoff called water consumption over a long period of time, for example, per day, decade, month, year.

Drain module called the amount of water, expressed in liters, flowing on average in 1 second from the area of ​​​​the river basin of 1 km2:

Runoff coefficient call the ratio of water flow in the river to the amount of precipitation (M) on the area of ​​the river basin for the same time, expressed as a percentage:

where a is the runoff coefficient in percent, Qr is the annual runoff in cubic meters, M is the annual amount of precipitation in millimeters.

To determine the annual water flow of the river under study, it is necessary to multiply the water flow by the number of seconds in a year, i.e. by 31.5-106 sec.

For sink module definitions it is necessary to know the water discharge and the area of ​​the basin above the target, according to which the water discharge of this river was determined.

River basin area can be measured on a map. For this, the following methods are used:

1. planning,
2. breakdown into elementary figures and calculation of their areas;
3. area measurement using a palette;
4. calculation of areas using geodetic tables.

We believe that it will be easiest for students to use the third method and measure the area using a palette, that is, transparent paper (tracing paper) with squares printed on it (if there is no tracing paper, then you can oil the paper).

Having a map of the area under study in a certain scale, you need to make a palette with squares corresponding to the scale of the map. First, you should outline the basin of this river above a certain alignment, and then put a palette on the map, on which to transfer the contour of the basin. To determine the area, you first need to count the number of full squares located inside the contour, and then add up these squares, partially covering the basin of the given river. Adding the squares and multiplying the resulting number by the area of ​​one square, we find out the area of ​​the river basin above this alignment.

where Q is the water flow. For translate cubic meters in liters we multiply the consumption by 1000, S is the area of ​​​​the pool.

For determining river runoff coefficient you need to know the annual flow of the river and the volume of water that has fallen on the area of ​​a given river basin. The volume of water that fell on the area of ​​a given pool is easy to determine. To do this, you need the area of ​​​​the pool, expressed in square kilometers, multiply by the thickness of the precipitation layer (also in kilometers).

For example, if precipitation in a given area was 600 mm per year, then the thickness will be equal to 0.0006 km and the runoff coefficient will be equal to

where Qp is the annual flow of the river, and M is the area of ​​the basin; multiply the fraction by 100 to determine the runoff coefficient as a percentage.

Determining the nutrition of the river.

It is necessary to find out the types of feeding of the river: soil, rain, from melting snow, lake or swamp. For example, r. Klyazma is fed by ground, snow and rain, of which ground feeding is 19%, snow - 55% and rain - 26%.

The student himself will not be able to calculate these percentage data, they will have to be taken from literary sources.

Determination of the river flow regime

To characterize the flow regime of the river, you need to establish:

a) what seasonal changes the water level undergoes (a river with a constant level, very shallow in summer, drying up, losing water in ponors and disappearing from the surface);

b) the time of the flood, if it happens;

c) the height of the water during the flood (if there are no independent observations, then according to polling data);

d) the duration of the freezing of the river, if it happens (according to their personal observations or according to information obtained through a survey).

Determination of water quality.

To determine the quality of water, you need to find out whether it is cloudy or transparent, drinkable or not. The transparency of the water is determined by a white disk (Secchi disk) with a diameter of approximately 30 cm, summed up on a marked line or attached to a marked pole. If the disk is lowered on the line, then a weight is attached below, under the disk, so that the disk is not carried away by the current. The depth at which this disk becomes invisible is an indication of the transparency of the water. You can make a disc out of plywood and paint it in White color, but then the load must be hung heavy enough so that it falls vertically into the water, and the disk itself maintains a horizontal position; or plywood sheet can be replaced with a plate.

Determination of water temperature in the river

The temperature of the water in the river is determined by a spring thermometer, both on the surface of the water and at different depths. Keep the thermometer in water for 5 minutes. A spring thermometer can be replaced with a conventional wooden-framed bath thermometer, but in order for it to sink into the water at different depths, a weight must be tied to it.

You can determine the temperature of the water in the river with the help of bathometers: a bathometer-tachymeter and a bottle bathometer. The bathometer-tachymeter consists of a flexible rubber balloon with a volume of about 900 cm3; a tube with a diameter of 6 mm is inserted into it. The bathometer-tachymeter is fixed on a rod and lowered to different depths to take water. The resulting water is poured into a glass and its temperature is determined.

It is not difficult to make a bathometer-tachymeter for the student himself. To do this, you need to buy a small rubber chamber, put on it and tie a rubber tube with a diameter of 6 mm. The bar can be replaced with a wooden pole, dividing it into centimeters. The rod with the tachometer-botometer must be lowered vertically into the water to a certain depth, so that the hole of the tachometer-tachometer is directed downstream. Having lowered to a certain depth, the rod must be rotated 180 ° and held for about 100 seconds in order to collect water, after which the rod must be rotated 180 ° again. It should be removed so that water does not spill out of the bottle. After pouring water into a glass, determine the temperature of the water at a given depth with a thermometer.

As a result of the turbulence of water movement in the river, the temperature of the bottom and surface layers is almost the same. For example, the bottom water temperature is 20.5°, and on the surface it is 21.5°.

It is useful to simultaneously measure the air temperature with a sling thermometer and compare it with the temperature of the river water, making sure to record the time of observation. Sometimes the temperature difference reaches several degrees. For example, at 13 o'clock the air temperature is 20°, the temperature of the water in the river is 18°.

Research in certain areas of the nature of the riverbed

When studying in certain areas of the nature of the riverbed, it is necessary:

a) mark the main reaches and rifts, determine their depths;

b) when detecting rapids and waterfalls, determine the height of the fall;

c) sketch and, if possible, measure islands, shoals, middles, side channels;

d) collect information in which places the river erodes the banks, and in places that are especially strongly eroded, determine the nature of the eroded rocks;

e) to study the nature of the delta, if the estuarine section of the river is being investigated, and plot it on the visual plan; see if the individual arms correspond to those shown on the map.

Acquaintance with the appearance of the riverbed

When studying appearance the riverbed should give a description of it and make sketches of different sections of the channel, best of all elevated places.

General characteristics of the river and its use

With a general description of the river, you need to find out:

a) in which part of the river is mainly eroding and in which accumulating;

b) degree of meandering.

To determine the degree of meandering, you need to know the tortuosity coefficient, i.e. the ratio of the length of the river in the study area to the shortest distance between certain points in the study part of the river; for example, river A has a length of 502 km, and shortest distance between the source and the mouth is only 233 km, therefore, the tortuosity coefficient

where K is the sinuosity coefficient, L is the length of the river, l is the shortest distance between the source and the mouth, and therefore

Characteristics of the annual runoff

Runoff is the movement of water over the surface, as well as in the thickness of the soil and rocks during its cycle in nature. In calculations, runoff is understood as the amount of water flowing from the catchment for any period of time. This amount of water can be expressed as a flow rate Q, a volume W, a modulus M, or a runoff layer h.

Runoff volume W - the amount of water flowing from the catchment for any period of time (day, month, year, etc.) - is determined by the formula

W \u003d QT [m 3], (19)

where Q is the average water consumption for the calculated time period, m 3 /s, T is the number of seconds in the calculated time period.

Since the average water discharge was calculated earlier as the annual flow rate, the flow volume of the r. Kegets per year W \u003d 2.39 365.25 24 3600 \u003d 31764096 m 3.

Runoff module M - the amount of water flowing from a unit catchment area per unit time - is determined by the formula

М=103Q/F [l/(sqm2)], (20)

where F is the catchment area, km 2.

Drain module Kegets М=10 3 2.39/178 = 13.42 l/(sqm 2).

Runoff layer h mm - the amount of water flowing from the catchment for any period of time, equal to the thickness of the layer, evenly distributed over the area of ​​this catchment, is determined by the formula

h=W/(F 10 3)=QT/(F 10 3). (21)

The runoff layer for the river basin. Kegets h = 31764096/ (178 10 3) = 178.44 mm.

The dimensionless characteristics include the modulus factor and the runoff factor.

The modular coefficient K is the ratio of the runoff for any particular year to the runoff rate:

K \u003d Q i /Q 0 \u003d W i / W 0 \u003d h i / h 0, (22)

and for r. Kegets for the period under consideration K varies from K = 1.58 / 2.39 = 0.66 for a year with a minimum flow to K = 3.26 / 2.39 = 1.36 for a maximum flow.

Runoff coefficient - the ratio of the volume or layer of runoff to the amount of precipitation x that fell on the catchment area, which caused the occurrence of runoff:

The runoff coefficient shows how much of the precipitation goes to the formation of runoff.

AT term paper it is necessary to determine the characteristics of the annual runoff for the considered basin, taking the runoff rate from the section

Intra-annual runoff distribution

The intra-annual distribution of river runoff takes important place in the issue of studying and calculating runoff, both in practical and scientific terms, being at the same time the most challenging task hydrological research /2,4,13/.

The main factors determining the intra-annual distribution of runoff and its overall value, - climatic. They define general character(background) distribution of runoff in the year of a particular geographical area; territorial changes runoff distributions follow climate change.

The factors influencing the distribution of runoff throughout the year include lakes, forest cover, swampiness, the size of watersheds, the nature of soils and soils, the depth of groundwater, etc., which to a certain extent should be taken into account in the calculations both in the absence and in the presence of observational materials.

Depending on the availability of hydrometric data, the following methods calculation of intra-annual runoff distribution:

in the presence of observations for a period of at least 10 years: a) distribution by analogy with the distribution of a real year; b) the method of arranging the seasons;

in the absence or insufficiency (less than 10 years) of observational data: a) by analogy with the distribution of the runoff of the studied analogue river; b) according to regional schemes and regional dependences of the parameters of the intra-annual distribution of runoff on physical and geographical factors.

The intra-annual flow distribution is usually calculated not by calendar years, but by water management years, starting from the high-water season. The boundaries of the seasons are assigned the same for all years, rounded to the nearest month.

The estimated probability of flow exceeding for a year, limiting the period and season, is assigned in accordance with the tasks of the water management use of the river flow.

In the course work, it is necessary to perform calculations in the presence of hydrometric observations.

Calculations of the intra-annual distribution of runoff by the layout method

The initial data for the calculation are the average monthly water consumption and, depending on the purpose of using the calculation, the given percentage of supply P and division into periods and seasons.

The calculation is divided into two parts:

inter-seasonal distribution, which is of the greatest importance;

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

Interseasonal distribution. Depending on the type of intra-annual distribution of runoff, the year is divided into two periods: high water and low water (low water). Depending on the purpose of use, one of them is assigned limiting.

The limiting period (season) is the most stressful in terms of water use. For drainage purposes, the limiting period is high water; for irrigation, energy-shallow water.

The period includes one or two seasons. On rivers with spring floods for irrigation purposes, the following are distinguished: a high-water period (aka season) - spring and a low-water (limiting) period, which includes seasons; summer-autumn and winter, and the limiting season for irrigation is summer-autumn (winter for energy use).

The calculation is carried out according to hydrological years, i.e. for years beginning with a high-water season. The dates of the seasons are assigned the same for all years of observations, rounded up to the nearest 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 task, the duration of the seasons can be taken as follows: spring - April, May, June; summer-autumn - July, August, September, October, November; winter - December and January, February, March next year.

The amount of runoff for individual seasons and periods is determined by the sum of average monthly discharges (Table 10). AT last year the costs for December are added to the costs for three months (I, II, III) of the first year.

When calculating according to the layout method, the intra-annual distribution of runoff is taken from the condition of equality of the probability of exceeding the runoff for the year, the runoff for the limiting period, and within it for the limiting season. Therefore, it is necessary to determine the costs of the security specified by the project (in the task P = 80%) for the year, the limiting period and season. Therefore, it is required to calculate the parameters of the supply curves (О 0 , С v and С s) for the limiting period and season (for the annual runoff, the parameters are calculated above). Calculations are made by the method of moments in Table. 10 according to the scheme outlined above for the annual flow.

You can determine the estimated costs using the formulas:

annual runoff

Orasgod \u003d Kr "12Q 0, (26)

limiting period

Orasinter = KрQ0inter, (27)

limiting season

Oraslo \u003d Kr "Qlo (27)

where Kp", Kp, Kp" 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 flow 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

Orasgod = Orasses. However, this equality will be 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

Orasves = Orasgod - Orasmezh, (28)

and for a non-limiting season (in the task-winter)

Oraszim = Orasmezh. - Qlo (29)

The calculation is more convenient to perform in the form of a table. ten.

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 seasons in descending order and calculate their actual supply. Since the calculated availability (Р=80%) corresponds to the low-water group, further calculation can be made for the years included in the low-water group (Table 11).

For this in in the column "Total flow" write down the expenses by seasons, 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 11). 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, write out any of those encountered, 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 10), by the percentage of each month A% (Table 11), calculate the estimated discharge for each month.

Horac v = Horaces A % v / 100% (30)

The data obtained are entered in table. 12 “Estimated expenses by months” and on graph paper, an estimated hydrograph R-80% of the river under study is built (Fig. 11).

Table 12. Estimated costs (m3/s) by months

Intra-annual runoff distribution

Systematic ( daily) observations of water levels were started in our country around 100 years back. Initially, they were conducted in a small number of points. At present, we have data on the flow of rivers for 4000 hydrological posts. These materials are of a unique nature, making it possible to track changes in runoff over a long period; they are widely used in calculating water resources, as well as in the design and construction of hydraulic and other industrial facilities on rivers, lakes and reservoirs. To solve practical issues, it is necessary to have observational data on hydrological phenomena for periods of time from 10 before 50 years and more.

Hydrological stations and posts located on the territory of our country form the so-called state hydrometeorological network. It is under the jurisdiction of Roskomgidromet and is designed to meet the needs of all sectors of the national economy according to data on the regime of water bodies. For the purpose of systematization, observation materials at posts are published in official reference publications.

For the first time, hydrological observation data were summarized in the State Water Cadastre USSR (GVK). It included guides to water resources the USSR (regional, 18 volumes), information about water levels on rivers and lakes the USSR(1881-1935, 26 volumes), materials on the regime of rivers ( 1875-1935, 7 volumes). With 1936 materials of hydrological observations began to be published in hydrological yearbooks. Currently, there is a unified nationwide system for accounting for all types of natural waters and their use on the territory of the Russian Federation.

The primary processing of data on daily water levels given in the Hydrological Yearbooks is to analyze the intra-annual distribution of runoff and build a graph of water level fluctuations for the year.

The nature of the change in runoff during the year and the regime of water levels due to these changes mainly depend on the conditions for feeding the river with water. According to B.D. Zaikova rivers are divided into three groups:

With spring floods, formed as a result of snow melting on the plains and low mountains;

With high water in the warmest part of the year, arising from the melting of seasonal and perpetual mountain snows and glaciers;

With rainfall.

The most common are rivers with spring floods. The following phases of the water regime are typical for this group: spring flood, summer low water, autumn water rise, winter low water.

During the period spring flood in the rivers of the first group, due to the melting of snow, the flow of water increases significantly, and its level rises. The amplitude of fluctuations in water levels and the duration of floods on the rivers of this group differ depending on the factors of the underlying surface and factors of a zonal nature. For example, the Eastern European type of intra-annual runoff distribution has a very high and sharp spring flood and low water discharges in the rest of the year. This is explained by the insignificant amount of summer precipitation and strong evaporation from the surface of the steppe basins of the Southern Trans-Volga region.

Western European type The distribution is characterized by a low and extended spring flood, which is a consequence of the flat relief and severe waterlogging of the West Siberian Lowland. The presence of lakes, swamps and vegetation within the boundaries of the drainage basin leads to the equalization of the flow throughout the year. This group also includes the East Siberian type of runoff distribution. It is characterized by relatively high spring floods, rain floods in the summer-autumn period, and extremely low winter low water. This is due to the influence of permafrost on the nature of the feeding of the river.

The amplitude of fluctuations in water levels in medium and large rivers of Russia is quite significant. She reaches 18 m on the upper Oka and 20 m on the Yenisei. With such filling of the channel, vast areas of river valleys are flooded.

The period of low levels that change little over time during the summer is called the period summer low water when groundwater is the main source of river nutrition.

In autumn, surface runoff increases due to autumn rains, which leads to water rise and education summer-autumn rain flood. The increase in runoff in autumn is also facilitated by a decrease in evaporation during this period of time.

Phase winter low water in the river begins with the appearance of ice and ends with the beginning of the rise in water levels from spring snowmelt. During the winter low water in the rivers, a very small flow is observed, since from the moment of the onset of stable negative temperatures, the river is fed only by groundwater.

The rivers of the second group are distinguished Far Eastern and Tien Shan types of intra-annual runoff distribution. The first of them has a low, strongly stretched, comb-like flood in the summer-autumn period and a low runoff in the cold part of the year. The Tien Shan type is distinguished by a smaller amplitude of the flood wave and a secure runoff in the cold part of the year.

Near the rivers of the third group ( Black Sea type) rain floods are evenly distributed throughout the year. The amplitude of fluctuations in water levels is strongly smoothed near rivers flowing from lakes. In these rivers, the boundary between high water and low water is hardly noticeable, and the volume of runoff during high water is comparable to the volume of runoff during low water. For all other rivers, the main part of the annual flow passes during the flood.

The results of observations over the levels for the calendar year are presented as level fluctuation chart(Fig. 3.5). In addition to the course of levels, the graphs show the phases of the ice regime with special symbols: autumn ice drift, freeze-up, spring ice drift, and also show the values ​​of the maximum and minimum navigational water levels.

Usually, the graphs of fluctuations in water levels at a hydrological post are combined for 3-5 years on one drawing. This makes it possible to analyze the river regime for low-water and high-water years and to trace the dynamics of the onset of the corresponding phases of the hydrological cycle for a given period of time.

Water regime rivers is characterized by a cumulative change in time levels and volumes of water in the river. Water level ( H) - height water surface rivers relative to a constant zero mark (ordinary or zero of the graph of a water gauge station). Among the fluctuations in water levels in the river, long-term ones are identified, due to secular climate changes, and periodic: seasonal and daily. In the annual cycle of the water regime of rivers, several characteristic periods are distinguished, called the phases of the water regime. For different rivers, they are different and depend on climatic conditions and the ratio of food sources: rain, snow, underground and glacial. For example, the rivers of temperate continental climate (Volga, Ob, etc.) have the following four phases: spring flood, summer low water, autumn rise of water, winter low water. high water- a long-term increase in the water content of the river that repeats annually in the same season, causing a rise in the level. In temperate latitudes, it occurs in spring due to intensive snowmelt.

low water- a period of long-term low levels and flow of water in the river with the predominance of underground feeding ("low water"). Summer low water is due to intense evaporation and seepage of water into the ground, despite the greatest amount of precipitation at this time. Winter low water is the result of the lack of surface nutrition, rivers exist only due to groundwater.

Floods- short-term non-periodic rises in water levels and an increase in the volume of water in the river. Unlike floods, they occur in all seasons of the year: in the warm half of the year they are caused by heavy or prolonged rains, in winter - by melting snow during thaws, at the mouths of some rivers - due to the surge of water from the seas where they flow. In temperate latitudes, the autumn rise of water in rivers is sometimes called the flood period; it is associated with a decrease in temperature and a decrease in evaporation, and not with an increase in precipitation - there is less than in summer, although cloudy rainy weather is more common in autumn. Autumn floods along the Neva River in St. Petersburg are caused primarily by the surge of water from the Gulf of Finland by westerly winds; the highest flood of 410 cm occurred in St. Petersburg in 1824. Floods are usually short-term, the rise in water level is lower, and the volume of water is less than during floods.

One of the most important hydrological characteristics of rivers is river runoff, which is formed due to the inflow of surface and groundwater from the catchment area. A number of indicators are used to quantify the flow of rivers. The main one is the flow of water in the river - the amount of water that passes through the living section of the river in 1 second. It is calculated according to the formula Q=v*ω, where Q- water consumption in m 3 / s, v is the average speed of the river in m/s. ω - open area in m 2. Based on the data of daily expenses, a calendar (chronological) graph of fluctuations in water consumption is built, called a hydrograph.

The flow modification is the volume of runoff (W in m 3 or km 3) - the amount of water flowing through the living section of the river for a long period (month, season, most often a year): W \u003d Q * T, where T is a period of time. The volume of runoff varies from year to year, the average long-term runoff is called the runoff rate. For example, the annual flow rate of the Amazon is about 6930 km3, which is about >5% of the total annual flow of all rivers. the globe, Volga - 255 km 3. The annual volume of runoff is calculated not for the calendar, but for the hydrological year, within which the full annual hydrological cycle of the water cycle is completed. In regions with cold snowy winters, November 1 or October 1 is taken as the beginning of the hydrological year.

Drain module(M, l / s km 2) - the amount of water in liters flowing from 1 km 2 of the basin area (F) per second:

(10 3 is a multiplier for converting m 3 into liters).

The river flow module allows you to find out the degree of water saturation of the basin area. He is zoned. largest modulus runoff near the Amazon - 30,641 l / s km 2; near the Volga, it is 5670 l / s km 2, and near the Nile - 1010 l / s km 2.

runoff layer (Y) is the water layer (in mm) evenly distributed over the catchment area ( F) and flowing down from it behind certain time(annual runoff layer).

Runoff coefficient (To) is the ratio of the volume of water flow in the river ( W) to the amount of precipitation ( X) falling on the area of ​​the basin ( F) for the same time, or the ratio of the runoff layer ( Y) to the precipitation layer ( X) that fell on the same area ( F) for the same period of time (immeasurable value or expressed in%):

K=W/(x*F)* 100%, or K=Y/x*100%.

The average runoff coefficient of all the Earth's rivers is 34%. i.e., only one third of the precipitation that falls on land flows into rivers. The runoff coefficient is zonal and varies from 75-65% in tundra and taiga zones to 6-4% in semi-deserts and deserts. For example, for the Neva it is 65%, and for the Nile it is 4%.

The concept of runoff regulation is related to the water regime of rivers: the smaller the annual amplitude of water discharges in the river and the water levels in it, the more the runoff is regulated.

Rivers are the most mobile part of the hydrosphere. Their runoff is an integral characteristic of the water balance of the land area.

The amount of river runoff and its distribution during the year is affected by the complex natural factors and human economic activity. Among natural conditions the main one is climate, especially precipitation and evaporation. With heavy rainfall, the flow of rivers is large, but one must take into account their type and the nature of the fallout. For example, snow will provide more runoff than rain because there is less evaporation in winter. Heavy precipitation increases the runoff compared to continuous precipitation with the same amount. Evaporation, especially intense, reduces runoff. Apart from high temperature, it is promoted by wind and lack of air humidity. The statement of the Russian climatologist A. I. Voeikov is true: “Rivers are a product of the climate.”

Soils affect runoff through infiltration and structure. Clay increases surface runoff, sand reduces it, but increases underground runoff, being a moisture regulator. The strong granular structure of soils (for example, in chernozems) contributes to the penetration of water deep into, and on structureless loose loamy soils, a crust often forms, which increases surface runoff.

very important geological structure river basin, especially material composition rocks and the nature of their occurrence, since they determine the underground feeding of rivers. Permeable rocks (thick sands, fractured rocks) serve as moisture accumulators. The flow of rivers in such cases is greater, since a smaller proportion of precipitation is spent on evaporation. The runoff in karst areas is peculiar: there are almost no rivers there, since precipitation is absorbed by funnels and cracks, but at their contact with clays or shale, powerful springs are observed that feed the rivers. For example, the karsted Crimean yaila itself is dry, but powerful springs gush at the foot of the mountains.

Relief influence ( absolute altitude and slopes of the surface, density and depth of dissection) is large and varied. The runoff of mountain rivers is usually greater than that of flat rivers, since in the mountains on the windward slopes there is more abundant precipitation, less evaporation due to lower temperatures, due to the large slopes of the surface, the path and time for the precipitation to reach the river are shorter. Due to the deep erosive incision, underground nutrition is more abundant from several aquifers at once.

Influence of vegetation - different types forests, meadows, crops, etc. - ambiguous. In general, vegetation regulates runoff. For example, a forest, on the one hand, enhances transpiration, delays precipitation by tree crowns (especially coniferous forests snow in winter), on the other hand, more precipitation usually falls over the forest, under the canopy of trees the temperature is lower and evaporation is less, the snow melts longer, the infiltration of precipitation into the forest floor is better. To reveal the influence of different types of vegetation in pure form it is very difficult due to the joint compensating effect of various factors, especially within large river basins.

The influence of lakes is unequivocal: they reduce the flow of rivers, since there is more evaporation from the water surface. However, lakes, like swamps, are powerful natural flow regulators.

The impact of economic activity on the stock is very significant. Moreover, a person affects both directly the runoff (its value and distribution in the year, especially during the construction of reservoirs), and the conditions for its formation. When creating reservoirs, the regime of the river changes: during the period of excess water, they are accumulated in reservoirs, during the period of shortage, they are used for various needs, so that the flow of rivers is regulated. In addition, the flow of such rivers is generally reduced, because evaporation from the water surface increases, a significant part of the water is spent on water supply, irrigation, watering, and underground nutrition decreases. But these inevitable costs are more than offset by the benefits of reservoirs.

When water is transferred from one river system to another, the flow changes: in one river it decreases, in another it increases. For example, during the construction of the Moscow Canal (1937), it decreased in the Volga, and increased in the Moskva River. Other transport channels for water transfer are not usually used, for example, the Volga-Baltic, White Sea-Baltic, numerous channels Western Europe, China, etc.

Of great importance for the regulation of river flow are the activities carried out in the river basin, because its initial link is the slope flow in the catchment area. The main activities carried out are as follows. Agroforestry - forest plantations, irrigation and drainage - dams and ponds in beams and streams, agronomic - autumn plowing, snow accumulation and snow retention, plowing across the slope or contour on hills and ridges, grassing slopes, etc.

In addition to the intra-annual runoff variability, its long-term fluctuations occur, apparently associated with 11-year cycles. solar activity. On most rivers, high-water and low-water periods lasting about 7 years are clearly traced: for 7 years, the water content of the river exceeds the average values, floods and low water are high, for the same number of years the water content of the river is less than the average annual values, water discharges in all phases of the water regime are small.

Literature.

1. Lyubushkina S.G. General geography: Proc. allowance for university students enrolled in special. "Geography" / S.G. Lyubushkina, K.V. Pashkang, A.V. Chernov; Ed. A.V. Chernov. - M. : Education, 2004. - 288 p.