For determining water flow in the river still to be determined average speed of the river. 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, i.e. 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 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. To convert cubic meters to liters, we multiply the flow rate by 1000, S is the pool area.

For determining river runoff coefficient need to know annual flow rivers and the volume of water deposited in the area of ​​the 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 to multiply the area of ​​​​the basin, expressed in square kilometers, by the thickness of the layer of precipitation (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, which becomes very shallow in summer, dries up, loses water in ponds and disappears 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 information);

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 tachymeter bathometer must be lowered vertically into the water to a certain depth, so that the opening of the tachymeter bathometer 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

At general characteristics rivers 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 the shortest distance between the source and the mouth is only 233 km, hence the sinuosity 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

Water regime rivers is characterized by a cumulative change in time levels and volumes of water in the river. Water level ( H) - the height of the water surface of the river relative to the constant zero mark (ordinary or zero of the graph of the 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 water rise, 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 low levels and water flow in the river with the predominance of underground nutrition (“low water”). Summer low water is due to intense evaporation and seepage of water into the ground, despite the largest number rainfall 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, in 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 reduction 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 a flood.

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 modification of the flow 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 drain is an integral characteristic water balance land areas.

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 the material composition of 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.

The influence of the relief (absolute height and slopes of the surface, density and depth of dissection) is great and varied. The runoff of mountain rivers is usually greater than that of the plains, 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 very difficult due to the joint compensatory action 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.

Influence economic activity 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 transferring water from one river system in another, the flow changes: in one river it decreases, in the other 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.

Great value for regulation river flow have activities carried out in the river basin, because its initial link is the slope runoff 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.

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, and are widely used in calculating water resources, as well as in the design and construction of hydrotechnical and other industrial facilities on rivers, lakes and reservoirs. For solutions 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 administered by Roskomgidromet and is designed to meet the needs of all industries. National economy according to the 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 USSR (regional, 18 volumes), information about water levels on rivers and lakes USSR(1881-1935, 26 volumes), materials on the regime of rivers ( 1875-1935, 7 volumes). FROM 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.

Primary processing data on daily water levels, given in the Hydrological Yearbooks, is to analyze the intra-annual distribution of runoff and plot the fluctuations in water levels 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. For this group, the following phases of the water regime are characteristic: 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 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 over given period time.

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 flow, flow modulus, and flow coefficient.

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

Drain module they call the amount of water expressed in liters (y), flowing on average in 1 second from the area of ​​​​the river basin in 1 km 2:

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

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

To determine the runoff modulus, it is necessary to know the water discharge and the area of ​​the basin upstream of the target, according to which the water discharge of the given river was determined. The area of ​​a river basin can be measured from a map. For this, the following methods are used:

• 1) planning
• 2) breakdown into elementary figures and calculation of their areas;
• 3) measuring the area with a palette;
• 4) calculation of areas using geodetic tables

It is easiest for students to use the third method and measure the area using a palette, i.e. transparent paper (tracing paper) with squares printed on it. Having a map of the studied area of ​​the map on a certain scale, you can 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 apply the map to the palette, 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 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.

Q - water consumption, l. To convert cubic meters to liters, we multiply the flow rate by 1000, S pool area, km 2.

To determine the river runoff coefficient, it is necessary to know the annual runoff 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 ​​this pool is easy to determine. To do this, you need to multiply the area of ​​​​the basin, expressed in square kilometers, by the thickness of the layer of precipitation (also in kilometers). For example, the thickness will be equal to p if precipitation in a given area was 600 mm per year, then 0 "0006 km and the runoff coefficient will be equal to:

Qr 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.

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, which becomes very shallow in summer, dries up, loses water in pores and disappears from the surface);

b) the time of high water, if any;

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

d) the duration of the freezing of the river, if it occurs (according to their own 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 disk out of plywood and paint it white, 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 cm 3; 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 for a student to make a bathometer-tachymeter. 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 tachymeter bathometer must be lowered vertically into the water to a certain depth, so that the opening of the tachymeter bathometer is directed downstream. Having lowered to a certain depth, the bar must be rotated by 180 and held for about 100 seconds in order to draw water, and then again turn the bar by 180 °. runoff water regime river

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.

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 water temperature in the river is 18 °.

Study in certain areas on certain nature of the riverbed. When examining sections 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) draw and, if possible, measure the islands, shoals, middles, side channels;

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

e) 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.

General characteristics of the river and its use. With a general description of the river, you need to find out:

a) which part of the river is mainly eroding and which is 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 the shortest distance between the source and the mouth is only 233 km, hence the tortuosity coefficient:

K - sinuosity coefficient, L - river length, 1 - shortest distance between source and mouth

Meander study It has great importance for timber rafting and shipping;

c) Non-squeezing river fans formed at the mouths of tributaries or produce temporary flows.

Find out how the river is used for navigation and timber rafting; if the hand is not navigable, then find out why, it serves as an obstacle (shallow, rapids, are there waterfalls), are there dams and other artificial structures on the river; whether the river is used for irrigation; what transformations need to be done to use the river in the national economy.

Determining the nutrition of the river. It is necessary to find out the types of river nutrition: groundwater, rain, lake or marsh from melting snow. For example, r. Klyazma is fed, ground, snow and rain, of which ground supply is 19%, snow - 55% and rain. - 26 %.

The river is shown in Figure 2.

m 3

Conclusion: During this practical session, as a result of calculations, the following values ​​characterizing the river flow were obtained:

Drain module? = 177239 l / s * km 2

Runoff coefficient b = 34.5%.

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 of hydrological analogy, geographic interpolation and hydrological and hydrogeological. Probabilistic-statistical analysis: method of moments, maximum likelihood method, quantifier method, correlation and regression analysis, factor analysis, principal component method, discriminant analysis method. Methods of analysis of computational mathematics: systems of algebraic equations, differentiation and integration of functions, partial differential equations, Monte Carlo method. Mathematical modeling of 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 hydrological data: rectilinear, exponential and exponential graphical dependencies.

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. River basin water balance equation. 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. The impact of economic activity on river flow: the creation of reservoirs and ponds, the redistribution of flow between river basins, the irrigation of agricultural fields, the drainage of swamps and wetlands, agroforestry activities in river catchments, 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 (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. Degree of reliability of hydrological input 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. Conditions for the formation of 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.

The practical significance of 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 the intra-annual distribution of runoff: lakes, swamps, river floodplains, 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 of catastrophic floods. Genetic groups of maximum water flow rates. Estimated availability of maximum water flow rates depending on the capital class of a 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 in the formation of the maximum flow of floods. genetic theory formation of the 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. Minimum runoff formation factors: precipitation, temperature, evaporation, connection of aeration zone waters, 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 erosion cut river channels, 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 of 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 graphical 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 long-term runoff Qо´, and the coefficient of variation Cv 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 in sufficient corresponding to the empirical distribution if the following inequality holds:

IQo - Qo´I< 0,02·Qо.

The root mean square 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).