River water levels, general concepts. Water levels in Altai rivers

This information about the effect of water level on fish biting is based on observations and practice, and cannot be proven or disproved by any theory. Changing water levels cause fish to change their behavior. Accordingly, depending on the amount of water in the reservoir, fishing can be successful or not very successful. Fish reacts to change external factors instantly, guided by her instincts - but how will she behave when the water level drops in summer?.. What should we expect from the rise and fall of water in a lake and pond?

A small gradual decrease in water level in summer in bets and lakes, as a rule, does not affect the bite in any way, and even activates carp fish

Natural drop in water level

On small rivers, lakes and rivers, the water level changes more significantly throughout the year than on large reservoirs. Rain or drought immediately noticeably changes the level of a small reservoir. The fish in them are quite calm about such fluctuations; apparently, they are simply accustomed to this as a natural, non-dangerous process. In large bodies of water, minor seasonal drops in water levels also do not cause special emotions in fish.

But it should be noted that the same drop in water level in small and large reservoirs can cause completely different reactions in fish. For example, a drop in level of half a meter during a drought in a rural pond will not affect the behavior of the fish in any way. At the same time, a drop of water in the reservoir by half a meter will most likely be perceived as an unusual and emergency situation, and will lead to a complete lack of activity of underwater inhabitants.

Change in water volume - a more accurate characteristic

Here it is more appropriate to talk about changes in the volume of water. Let’s agree that the volume of lost water will be the same for a pond in which the level drops by half a meter and for a reservoir with a drop in level of 10 cm. And this will most likely not cause an acute reaction from the fish. But if water leaves the reservoir in such a volume that its level drops by 1 meter, then the fish will stop actively biting. If the same volume is taken from the pond, and the level drops by 5 meters, all biting there will also stop.

It has been noticed that a decrease in water during a drought, the withdrawal of a certain volume of water from a reservoir, which happens every year, activates the fish (if due to a decrease in the volume of water there is no critical drop in oxygen - death), the food supply of reservoirs decreases and it is caught more actively.

Natural rise in water level

Rising water levels usually have a beneficial effect on the bite in all bodies of water. This is the time of melting snow and the time of summer rains. True, in early spring the fish are more likely guided by completely different instincts; they are preparing for spawning, and seasonal fluctuations don’t bother them. In summer, rains are very favorable for fish. At this time, there is a large influx of fresh water rich in oxygen and food into the reservoirs. An increase in water level is always accompanied by increased feeding of fish; it also actively explores shallow waters previously inaccessible to it.

In reservoirs with stable water levels, there are generally fewer problems with biting

Water level regulation

Here you can make a division into planned-habitual regulation and emergency regulation.

A rapid drop in water in a reservoir, not related to natural phenomena, always leads to a complete cessation of fish biting.

The same is observed in regulated reservoirs and during periods of sharp increases in levels above normal. Fish stop being caught until the water level in the reservoir stabilizes at a certain level. Then the fish masters the new food supply, and the bite resumes with renewed vigor.

But in individual reservoirs, where the discharge and rise of water occurs cyclically, for example, according to the operating plan of a hydroelectric power station, the fish have developed their own completely unique cycle of movement through the reservoir and feeding. There, the fish react sensitively to both the beginning of the discharge and the rise of water and migrate in accordance with the water level and the speed of the currents. Usually, when water falls, it concentrates on the channel edges, but does not stop being caught. When it rises, it enters shallow waters, but finding migrating schools can be problematic.

It is also necessary to note the practice of pre-spring water release at many reservoirs. While the discharge is in progress, the fish usually freezes. Then the uncontrollable biting begins, due to a sharp reduction in the food supply. With a lack of oxygen, due to the decreased volume of water, the bite freezes.

When pumping the pond down to a small puddle for the upcoming catch, carp, crucian carp, etc. freeze at the bottom and even bury themselves in the silt. Therefore, catching in this way is often semi-effective; mainly horse fish and silver carp are taken. After filling the pond, it is again full of fish.

Good bite on restored, newly filled reservoirs

It is not uncommon for a bet to dry out, or to be specially drained, to a small puddle or stream in the center, and it remains in this state for half a season or even years. Then, for some reason, it fills with water again. In the next two or three years, at the newly filled headquarters, there is an active feeding of all the carp fish that have been sitting in the mud for a long time. A similar period of fish activity also occurs in newly created reservoirs made on small rivers in which carp fish were found.

Where fish activity persists as water levels change

So, we can draw some conclusions.
If there is information about an artificial rapid decrease in the water level within a few hours, then fish will most likely not be caught in such a reservoir for another day or two after the low level has stabilized. If the level, on the contrary, rises, then for several hours there is also nothing to expect a bite there, but then it gradually normalizes, and after the level stabilizes, the fish enters shallow waters.

By the way, this phenomenon brings money. But not everyone. With an abundance of fishermen, they simply start dumping water on the paid pond. The fishermen leave after ten hours, not understanding what’s going on. Then the reset is stopped and the stakes are filled again. The bite resumes with good energy, and the remaining anglers then talk about their big catches and the time when the fish arrived.

With slow decreases and increases in the level, the fish, as a rule, do not stop biting, but can migrate throughout the reservoir.
The most favorable time for fishing is summer thunderstorms with heavy rains that fill the drying reservoir.

Slope of the riverbed. The most characteristic feature of any river is the continuous movement of water from source to mouth, which is called current. The reason for the flow is the inclination of the channel, along which, obeying the force of gravity, the water moves at a greater or lesser speed. As for the speed, it is directly dependent on the slope of the riverbed. The slope of the channel is determined by the ratio of the difference in heights of two points to the length of the section located between these points. So, for example, if from the source of the Volga to Kalinin 448 km, and the difference in height between the source of the Volga and Kalin and the nom is 74.6 m, then the average slope of the Volga in this section is 74.6 m, divided by 448 km, i.e. 0.00017. This means that for every kilometer of the length of the Volga in this section the fall is 17 cm.

Longitudinal profile of the river. Let us plot the length of different sections of the river along a horizontal line, and the heights of these sections along vertical lines. By connecting the ends of the verticals with a line, we get a drawing of the longitudinal profile of the river (Fig. 112). If you do not pay special attention to the details, the longitudinal profile of most rivers can be simplistically represented as a descending, slightly concave curve, the slope of which progressively decreases from source to mouth.

The slope of the longitudinal profile of the river is not the same for different sections of the river. So, for example, for the upper section of the Volga, as we have already seen, it is equal to 0.00017, for the section located between Gorky and the mouth of the Kama it is 0.00005, and for the section from Stalingrad to Astrakhan it is 0.00002.

The Dnieper is approximately the same, where in the upper section (from Smolensk to Orsha) the slope is 0.00011, and in the lower section (from Kakhovka to Kherson) 0.00001. In the area where the rapids are located (from Lotsmanskaya Kamenka to Nikopol), the average slope of the longitudinal profile of the river is 0.00042, i.e. almost four times greater than between Smolensk and Orsha.

The examples given show that the longitudinal profile of different rivers is far from the same. The latter is understandable: the longitudinal profile of the river reflects the relief, geological structure and many other geographical features of the area.

For example, consider the “steps” on the longitudinal profile of the river. Yenisei. Here we see sections of large slopes in the area of ​​​​the intersection of the Western Sayan, then the Eastern Sayan and, finally, at the northern end of the Yenisei Ridge (Fig. 112). The stepped nature of the river's longitudinal profile. The Yenisei indicates that uplifts in the areas of these mountains occurred (geologically) relatively recently, and the river has not yet had time to level out the longitudinal curve of its bed. The same can be said about the Bureinsky Mountains, cut through by the river. Cupid.

So far we have talked about the longitudinal profile of the entire river. But when studying rivers, it is sometimes necessary to determine the slope of the river in a given small area. This slope is determined directly by leveling.

Cross profile of the river. In the transverse profile of a river we distinguish two parts: the transverse profile of the river valley and the transverse profile of the river itself. We already have an idea of ​​the transverse profile of the river valley. It is obtained as a result of ordinary terrain surveying. To get an idea of ​​the profile of the river itself, or, more precisely, the river bed, it is necessary to measure the depths of the river.

Measurements are made either manually or mechanically. For manual measurements, a mark or hand lot is used. The basting is a pole made of flexible and durable wood (spruce, ash, hazel) of round cross-section with a diameter of 4-5 cm, length from 4 to 7 m.

The lower end of the basting is finished with iron (iron protects against splitting and helps with its weight). The basting is colored in white and is marked to tenths of a meter. The zero division corresponds to the lower end of the basting. Despite the simplicity of the device, basting gives accurate results.

Depth measurements are also carried out using a hand survey. The flow of the river causes the lot to deviate from the vertical by a certain angle, which forces an appropriate correction to be made.

Measurements on small rivers are usually made from bridges. On rivers reaching 200-300 m width, with a current speed of no more than 1.5 m per second, measurements can be made from a boat along a cable stretched from one bank of the river to the other. The cable should be taut. When the river width is more than 100 m it is necessary to anchor a boat in the middle of the river to support the cable.

On rivers whose width is more than 500 m, the measurement line is determined by the channel signs placed on both banks, and measurement points are determined by goniometric instruments from the shore. The number of measurements along the target depends on the nature of the bottom. If the bottom topography changes quickly, there should be more measurements; if the bottom is uniform, there should be fewer. It is clear that the more measurements, the more accurate the river profile is obtained.

To draw a river profile, a horizontal line is drawn, on which measurement points are plotted to scale. A perpendicular line is drawn down from each estrus, on which the depths obtained from measurements are also plotted in scale. By connecting the lower ends of the verticals, we get a profile. Due to the fact that the depth of rivers is very small compared to the width, when drawing a profile, the vertical scale is taken larger than the horizontal one. Therefore, the profile is distorted (exaggerated), but more visual.

Having a river bed profile, we can calculate the cross-sectional area (or water cross-sectional area) of the river (Fm 2 ), width of the river (B), length of the wetted perimeter of the river ( Rm), greatest depth (hmaxm ), average river depth ( hcpm) and the hydraulic radius of the river.

Live cross section of the river called the cross section of a river filled with water. The channel profile obtained as a result of measurements gives an idea of ​​the living cross-section of the river. The living cross-sectional area of ​​a river is for the most part calculated analytically (less often determined from a drawing using a planimeter). To calculate the living cross-sectional area ( Fm 2) take a drawing of the transverse profile of the river, on which the verticals divide the area of ​​​​the living cross-section into a series of trapezoids, and the coastal sections have the form of triangles. The area of ​​each individual figure is determined using formulas known to us from geometry, and then the sum of all these areas is taken.

The width of the river is simply determined by the length of the upper horizontal line representing the surface of the river.

Wetted perimeter - this is the length of the river bottom line on the profile from one edge of the river bank to the other. It is calculated by adding the length of all segments of the bottom line on the drawing of the living cross-section of the river.

Hydraulic radius is the quotient of dividing the open cross-sectional area by the length of the wetted perimeter ( R= F/R m).

Average depth - this is the quotient of dividing the living cross-sectional area

rivers by river width ( h Wed = F/ Bm).

For lowland rivers, the value of the hydraulic radius is usually very close to the value of the average depth ( R≈ hcp).

Greatest depth is restored based on measurement data.

River level. The width and depth of the river, the open cross-sectional area and other values ​​we give can remain unchanged only if the river level remains unchanged. In reality, this never happens, because the river level changes all the time. From this it is quite clear that when studying a river, measuring the fluctuations in river level is the most important task.

For the water-measuring station, an appropriate section of the river with a straight channel is selected, the cross-section of which is not complicated by shoals or islands. Observation of river level fluctuations is usually carried out using foot rod. A foot rod is a pole or rod, divided into meters and centimeters, installed near the shore. The zero of the foot rod is taken (if possible) to be the lowest level of the river in a given place. The zero selected once remains constant for all subsequent observations. The zero of the foot rod is associated with a constant rapper .

Observation of level fluctuations is usually carried out twice a day (at 8 and 20 hours). At some posts, self-recording limnigraphs are installed, which provide a continuous record in the form of a curve.

Based on the data obtained from observations of the foot rod, a graph of level fluctuations is drawn for one period or another: for a season, for a year, for a number of years.

River flow speed. We have already said that the speed of the river flow is directly dependent on the slope of the riverbed. However, this dependence is not as simple as it might seem at first glance.

Anyone who is at least a little familiar with the river knows that the speed of the current near the banks is much less than in the middle. Boatmen know this especially well. Whenever a boatman has to go up a river, he sticks to the bank; when he needs to quickly go down, he stays in the middle of the river.

More accurate observations made in rivers and artificial streams (having a regular trough-shaped channel) showed that the layer of water immediately adjacent to the channel, as a result of friction against the bottom and walls of the channel, moves at the lowest speed. The next layer has a higher speed, because it does not come into contact with the riverbed (which is motionless), but with the slowly moving first layer. The third layer has an even greater speed, etc. Finally, the highest speed is found in the part of the flow furthest from the bottom and walls of the channel. If we take a cross section of the flow and connect places with the same flow speed with lines (isotachs), then we will get a diagram that clearly depicts the location of layers of different speeds (Fig. 113). This peculiar layered flow movement, in which the speed successively increases from the bottom and walls of the channel to the middle part, is called laminar. Typical features of laminar flow can be briefly characterized as follows:

1) the speed of all particles in the flow has one constant direction;

2) the speed near the wall (at the bottom) is always zero, and with distance from the walls it gradually increases towards the middle of the flow.

However, we must say that in rivers where the shape, direction and character of the channel are very different from the regular trough-shaped bed of an artificial stream, regular laminar movement is almost never observed. Even with just one bend of the channel, as a result of the action of centrifugal forces, the entire system of layers moves sharply towards the concave bank, which in turn causes a number of other

movements. If there are protrusions at the bottom and along the edges of the channel, vortex movements, countercurrents and other very strong deviations arise, further complicating the picture. Particularly strong changes in the movement of water occur in shallow places of the river, where the current is divided into jets arranged in a fan-shape.

In addition to the shape and direction of the channel, an increase in flow speed has a great influence. Laminar movement, even in artificial flows (with a regular bed), changes sharply with increasing flow speed. In fast-moving flows, longitudinal helical jets appear, accompanied by small vortex movements and a kind of pulsation. All this greatly complicates the nature of the movement. Thus, in rivers, instead of laminar movement, a more complex movement is most often observed, called turbulent. (We will dwell in more detail on the nature of turbulent movements later when considering the conditions for the formation of a flow channel.)

From all that has been said, it is clear that studying the speed of river flow is a complex matter. Therefore, instead of theoretical calculations, one often has to resort to direct measurements.

Measuring current speed. The simplest and most accessible way to measure current speed is to measure using floats. By observing (with a clock) the time a float passes by two points located along the river at a certain distance opposite each other, we can always calculate the required speed. This speed is usually expressed in meters per second.

The method we have indicated makes it possible to determine the speed of only the uppermost layer of water. To determine the speed of deeper layers of water, two bottles are used (Fig. 114). In this case, the top bottle gives an average speed between both bottles. Knowing the average speed of water flow on the surface (the first method), we can easily calculate the speed at the desired depth. If V 1 will be the speed on the surface, V 2 - average speed, A V - the required speed, then V 2 =( V 1 + V)/2 , where the required speed comes from v = 2 v 2 - v 1 .

Incomparably more accurate results are obtained when measuring with a special device called turntables. There are many types of turntables, but the principle of their design is the same and is as follows. The horizontal axis with a bladed propeller at the end is movably mounted in a frame that has a steering feather at the rear end (Fig. 115). The device, lowered into the water, obeys the rudder, stands just against the current,

and the bladed propeller begins to rotate along with the horizontal axis. There is an endless screw on the axis that can be connected to the counter. Looking at the watch, the observer turns on the counter, which begins to count the number of revolutions. After a certain period of time, the counter turns off, and the observer determines the flow speed by the number of revolutions.

In addition to the above methods, they also use special bathometers, dynamometers, and, finally, chemical methods known to us from studying the speed of groundwater flow. An example of a bathometer is the bathometer of Prof. V. G. Glushkova, which is a rubber cylinder, the hole of which faces the flow. Amount of water, which manages to get into the cylinder per unit time, makes it possible to determine the flow speed. Dynamometers measure the force of pressure. The pressure force allows you to calculate the speed.

When it is necessary to obtain a detailed understanding of the distribution of velocities in the cross section (live section) of the river, proceed as follows:

1. The transverse profile of the river is drawn, and for convenience, the vertical scale is taken 10 times larger than the horizontal one.

2. Vertical lines are drawn along those points where current velocities were measured at different depths.

3. On each vertical, the corresponding depth in scale is marked and the corresponding speed is indicated.

By connecting points with the same speeds, we obtain a system of curves (isotaches), which gives a visual representation of the distribution of speeds in a given living section of the river.

Average speed. For many hydrological calculations, it is necessary to have data on the average speed of water flow in the living section of the river. But determining the average speed of water is a rather difficult task.

We have already said that the movement of water in a stream is not only complex, but also uneven over time (pulsation). However, based on a number of observations, we always have the opportunity to calculate the average flow speed for any point in the living cross-section of the river. Having the value of the average speed at a point, we can plot the distribution of speeds along the vertical we have taken. To do this, the depth of each point is plotted vertically (from top to bottom), and the flow speed horizontally (from left to right). We do the same with other points of the vertical we took. By connecting the ends of the horizontal lines (depicting velocities), we get a drawing that gives a clear idea of ​​the velocities of currents at various depths of the vertical we have taken. This drawing is called a velocity graph or velocity hodograph.

According to numerous observations, it was revealed that to obtain a complete picture of the vertical distribution of current velocities, it is enough to determine the velocities at the following five points: 1) on the surface, 2) at 0.2h, 3) by 0.6h, 4) by 0.8hand 5) at the bottom, counting h - vertical depth from surface to bottom.

The velocity hodograph gives a clear idea of ​​the change in velocities from the surface to the bottom of the flow along a given vertical. The lowest velocity at the bottom of the flow is mainly due to friction. The greater the roughness of the bottom, the sharper the current speeds decrease. IN winter time When the surface of the river is covered with ice, friction also occurs on the surface of the ice, which is also reflected in the speed of the flow.

The velocity hodograph allows us to calculate the average speed of the river flow along a given vertical.

The average vertical flow velocity of the free cross-section of the flow can most easily be determined using the formula:

where ώ is the area of ​​the velocity hodograph, and H is the height of this area. In other words, to determine the average vertical velocity of the flow across the live cross section of the flow, you need to divide the area of ​​the velocity hodograph by its height.

The area of ​​the velocity hodograph is determined either using a planimeter or analytically (i.e., breaking it down into simple figures - triangles and trapezoids).

The average flow rate is determined in various ways. Most in a simple way is the multiplication of the maximum speed (V max) by roughness coefficient (p). The roughness coefficient for mountain rivers can be approximately considered 0.55, for rivers with a bed lined with gravel, 0.65, for rivers with an uneven sandy or clay bed, 0.85.

To accurately determine the average flow velocity of the live cross-section of the flow, various formulas are used. The most commonly used is the Chezy formula.

Where v - average speed of the live flow section, R - hydraulic radius, J- surface flow slope and WITH- speed coefficient. But here, determining the speed coefficient presents significant difficulties.

The speed coefficient is determined using various empirical formulas (i.e., obtained based on the study and analysis of a large number of observations). The simplest formula is:

Where n- roughness coefficient, a R - the hydraulic radius already familiar to us.

Consumption. Amount of water in m, flowing through a given living section of a river per second is called river flow(for this item). Theoretically, consumption (A) It’s easy to calculate: it’s equal to the cross-sectional area of ​​the river ( F), multiplied by the average current speed ( v), i.e. A= Fv. So, for example, if the cross-sectional area of ​​a river is 150 m 2, and speed 3 m/sec, then consumption will be 450 m 3 per second. When calculating the flow rate, a cubic meter is taken as a unit of water quantity, and a second is taken as a unit of time.

We have already said that theoretically the river flow for one point or another is not difficult to calculate. Fulfilling this task in practice is much more difficult. Let us dwell on the simplest theoretical and practical methods most often used in the study of rivers.

There are many different ways to determine the flow of water in rivers. But all of them can be divided into four groups: volumetric method, mixing method, hydraulic and hydrometric.

Volumetric method successfully used to determine the flow of the smallest rivers (springs and streams) with a flow rate of 5 to 10 l (0,005- 0,01 m 3) per second. Its essence is that the stream is dammed and the water flows down the gutter. A bucket or tank is placed under the gutter (depending on the size of the stream). The volume of the vessel must be accurately measured. The filling time of the vessel is measured in seconds. The quotient of dividing the volume of the vessel (in meters) by the time of filling the vessel (in seconds) as. times and gives the desired value. The volumetric method gives the most accurate results.

Mixing method is based on the fact that at a certain point in the river a solution of some salt or paint is introduced into the stream. By determining the salt or paint content at another, lower flow point, the water flow rate is calculated (the simplest formula

Where q - consumption saline solution, k 1 - concentration of the salt solution at release, to 2- concentration of the salt solution at the underlying point). This method is one of the best for stormy mountain rivers.

Hydraulic method based on application various kinds hydraulic formulas for the flow of water both through natural channels and artificial weirs.

Let us give a simple example of a spillway method. A dam is built, the top of which has a thin wall (made of wood, concrete). A rectangular spillway with precisely defined dimensions of the base is cut into the wall. Water flows over the spillway, and the flow rate is calculated using the formula

(T - weir coefficient, b - width of the spillway threshold, H- pressure above the edge of the weir, g -gravity acceleration), With the help of a weir it is possible to measure flow rates from 0.0005 to 10 with great accuracy m 3 /sec. It is especially widely used in hydraulic laboratories.

Hydrometric method is based on measuring the living cross-sectional area and flow velocity. It is the most common. The calculation is carried out according to the formula, as we have already discussed.

Stock. The amount of water flowing through a given living section of a river per second is called flow. The amount of water flowing through a given living section of a river over a longer period is called drain. The amount of runoff can be calculated per day, per month, per season, per year and even over a number of years. Most often, runoff is calculated over seasons, because seasonal changes for most rivers are particularly strong and characteristic. Of great importance in geography are the values ​​of annual runoff and, in particular, the value of the average annual runoff (runoff calculated from long-term data). The average annual flow makes it possible to calculate the average river flow. If flow is expressed in cubic meters per second, then annual flow (to avoid very large numbers) is expressed in cubic kilometers.

Having information about the flow rate, we can obtain data about the flow for a given period of time (by multiplying the flow rate by the number of seconds of the given time period). The amount of runoff in this case is expressed volumetrically. The flow of large rivers is usually expressed in cubic kilometers.

For example, the average annual flow of the Volga is 270 km 3, Dnepra 52 km 3, Obi 400 km 3, Yeniseya 548 km 3, Amazon 3787 km, 3 etc.

When characterizing rivers, the ratio of the amount of runoff to the amount of precipitation falling on the area of ​​the basin of the river we have taken is very important. The amount of precipitation, as we know, is expressed by the thickness of the water layer in millimeters. Consequently, to compare the amount of runoff with the amount of precipitation, it is necessary to express the amount of runoff also by the thickness of the water layer in millimeters. To do this, the amount of runoff for a given period, expressed in volumetric measures, is distributed evenly over the entire area of ​​the river basin lying above the observation point. This value, called the runoff height (A), is calculated by the formula:

A is the height of the drain, expressed in millimeters, Q - consumption, T- time period, 10 3 serves to convert meters to millimeters and 10 6 to convert square kilometers to square meters.

The ratio of the amount of runoff to the amount of precipitation is called runoff coefficient. If the runoff coefficient is denoted by the letter A, and the amount of precipitation expressed in millimeters is h, That

The runoff coefficient, like any ratio, is an abstract quantity. It can be expressed as a percentage. So, for example, for r. Neva A=374 mm, h= 532 mm; hence, A= 0.7, or 70%. In this case, the river runoff coefficient. The Neva allows us to say that of the total amount of precipitation falling in the river basin. Neva, 70% flows into the sea, and 30% evaporates. We see a completely different picture on the river. Nile. Here A=35 mm, h =826 mm; therefore a=4%. This means that 96% of all precipitation in the Nile basin evaporates and only 4% reaches the sea. Already from the given Examples it is clear how important the runoff coefficient is for geographers.

Let us give as an example the average value of precipitation and runoff for some rivers in the European part of the USSR.

In the examples we have given, the amount of precipitation, runoff values, and, consequently, runoff coefficients are calculated as annual averages based on long-term data. It goes without saying that runoff coefficients can be derived for any period of time: day, month, season, etc.

In some cases, flow is expressed as liters per second per 1 km 2 pool area. This flow value is called drain module.

The value of the average long-term runoff can be plotted on a map using isolines. On such a map, runoff is expressed in runoff modules. It gives an idea that the average annual runoff on the flat parts of the territory of our Union has a zonal character, and the amount of runoff decreases to the north. From such a map you can see how important relief is for runoff.

River feeding There are three main types of river feeding: feeding by surface waters, feeding by groundwater and mixed feeding.

Recharge by surface waters can be divided into rain, snow and glacial. Rain feeding is typical for rivers in tropical regions, most monsoon regions, as well as many areas Western Europe characterized by a mild climate. Snow feeding is typical for countries where a lot of snow accumulates during the cold period. This includes most of the rivers of the USSR territory. In spring, they are characterized by powerful floods. It is especially necessary to highlight the snows of high mountainous countries, which provide the greatest amount of water at the end of spring and in summer time. This nutrition, called mountain snow nutrition, is close to glacial nutrition. Glaciers, like mountain snow, provide water mainly in the summer.

Groundwater recharge occurs in two ways. The first way is to feed the rivers with deeper aquifers that emerge (or, as they say, wedge out) into the river bed. This is a fairly sustainable food for all seasons. The second way is nutrition groundwater alluvial strata directly connected to the river. During periods of high water standing, the alluvium is saturated with water, and after the water declines, it slowly returns its reserves to the river. This diet is less sustainable.

Rivers that receive their nutrition from surface water alone or groundwater alone are rare. Rivers with mixed feeding are much more common. In some periods of the year (spring, summer, early autumn) surface water is of predominant importance for them, in other periods (winter or during periods of drought) ground water becomes the only source of nutrition.

We can also mention rivers fed by condensation waters, which can be both surface and underground. Such rivers are more common in mountainous areas, where accumulations of boulders and stones on peaks and slopes condense moisture in noticeable quantities. These waters can influence the increase in runoff.

River feeding conditions at different times of the year. Pain in winterMost of our rivers are fed exclusively by groundwater. This feeding is quite uniform, so the winter flow for most of our rivers can be characterized as the most uniform, decreasing very slightly from the beginning of winter to spring.

In spring, the nature of the flow and, in general, the entire regime of rivers changes dramatically. Precipitation accumulated over the winter in the form of snow quickly melts, and huge quantities of meltwater flow into rivers. The result is a spring flood, which, depending on the geographical conditions of the river basin, lasts for a more or less long time. We will talk about the nature of spring floods a little later. In this case, we note only one fact: in the spring, a huge amount of spring melted snow water is added to the ground supply, which increases the runoff many times. So, for example, for the Kama the average flow rate in spring exceeds the winter flow by 12 and even 15 times, for the Oka it is 15-20 times; The flow of the Dnieper near Dnepropetrovsk in the spring in some years exceeds the winter flow by 50 times; in small rivers the difference is even more significant.

In the summer, rivers (in our latitudes) are fed, on the one hand, by groundwater, and on the other, by direct runoff of rainwater. According to the observations of academician Oppokova in the upper Dnieper basin, this direct runoff of rainwater during the summer months reaches 10%. In mountainous areas, where flow conditions are more favorable, this percentage increases significantly. But it reaches a particularly large magnitude in those areas that are characterized by widespread permafrost. Here, after each rain, the river level rises quickly.

In autumn, as temperatures drop, evaporation and transpiration gradually decrease, and surface runoff (rainwater runoff) increases. As a result, in autumn the runoff, generally speaking, increases until the moment when liquid precipitation(rains) give way to hard (snow). Thus, in the fall, like

we have ground plus rain feeding, and rain feeding gradually decreases and by the beginning of winter it stops altogether.

This is the course of feeding of ordinary rivers in our latitudes. In high mountainous countries, melt water from mountain snows and glaciers is added in the summer.

In desert and dry-steppe areas, melt water from mountain snow and ice plays a dominant role (Amu Darya, Syr Darya, etc.).

Fluctuations in water levels in rivers. We have just talked about the feeding conditions of rivers at different times of the year and, in connection with this, noted how the flow changes at different times of the year. These changes are most clearly shown by the curve of fluctuations in water levels in rivers. Here we have three graphs. The first graph gives an idea of ​​the fluctuations in river levels in the forest zone of the European part of the USSR (Fig. 116). The first graph (Volga river) is characterized by

rapid and high rise with a duration of about 1/2 month.

Now pay attention to the second graph (Fig. 117), typical for rivers in the taiga zone Eastern Siberia. There is a sharp rise in the spring and a series of rises in the summer due to rain and the presence of permafrost, which increases the speed of runoff. The presence of the same permafrost, which reduces winter ground nutrition, leads to especially low water levels in winter.

The third graph (Fig. 118) shows a curve of river level fluctuations in the taiga zone of the Far East. Here, due to the permafrost, there is the same very low level during the cold period and continuous sharp fluctuations in the level during warm periods. They are caused by snowmelt in spring and early summer, and later by rain. The presence of mountains and permafrost accelerates runoff, which has a particularly dramatic effect on level fluctuations.

The nature of fluctuations in the levels of the same river in different years is not the same. Here is a graph of fluctuations in p levels. Kama for different years (Fig. 119). As you can see, the river has very different patterns of fluctuations in different years. True, the years of the most dramatic deviations from the norm are selected here. But here we have a second graph of fluctuations in p levels. Volga (Fig. 116). Here all the fluctuations are of the same type, but the range of fluctuations and the duration of the spill are very different.

In conclusion, it must be said that the study of fluctuations in river levels, in addition to scientific significance, also has enormous practical significance. Demolished bridges, destroyed dams and coastal structures, flooded, and sometimes completely destroyed and washed away villages have long forced people to pay close attention to these phenomena and begin to study them. It is no wonder that observations of fluctuations in river levels have been carried out since ancient times (Egypt, Mesopotamia, India, China, etc.). River navigation, the construction of roads, and especially railways, required more accurate observations.

Observation of fluctuations in river levels in Russia began, apparently, a very long time ago. In the chronicles, starting with XV c., we often find indications of the height of the river floods. Moscow and Oka. Observations of fluctuations in the level of the Moscow River were made daily. At first XIX V. daily observations were already carried out at all major piers of all navigable rivers. From year to year the number of hydrometric stations has continuously increased. In pre-revolutionary times, we had more than a thousand water measuring posts in Russia. But these stations achieved special development during Soviet times, which is easy to see from the table below.

Spring flood. During the period of spring snowmelt, the water level in the rivers rises sharply, and the water, usually overflowing the channel, overflows its banks and often floods the floodplain. This phenomenon, characteristic of most of our rivers, is called spring flood.

The timing of the flood depends on climatic conditions terrain, and the duration of the flood period, in addition, depends on the size of the basin, individual parts of which may be under different climatic conditions. So, for example, for r. On the Dnieper (according to observations near the city of Kyiv), the duration of the flood is from 2.5 to 3 months, while for the tributaries of the Dnieper - Sula and Psyol - the duration of the flood is only about 1.5-2 months.

The height of the spring flood depends on many reasons, but the most important of them are: 1) the amount of snow in the river basin at the beginning of melting and 2) the intensity of spring melting.

The degree of water saturation of the soil in the river basin, permafrost or soil thaw, spring precipitation, etc. are also of some importance.

Most large rivers in the European part of the USSR are characterized by a spring rise in water up to 4 m. However, in different years the height of the spring flood is subject to very strong fluctuations. So, for example, for the Volga near the city of Gorky, water rises reach 10-12 m, near Ulyanovsk until 14 m; for r. Dnieper for 86 years of observations (from 1845 to 1931) from 2.1 m up to 6-7 and even 8.53 m(1931).

The highest rises in water lead to floods, which cause great damage to the population. An example is the flood in Moscow in 1908, when a significant part of the city and the Moscow-Kursk railway were under water for tens of kilometers. A number of Volga cities (Rybinsk, Yaroslavl, Astrakhan, etc.) experienced very severe flooding as a result of an unusually high rise in the river water. Volga in the spring of 1926

On large Siberian rivers, due to congestion, the water rise reaches 15-20 meters or more. So, on the river Yenisei up to 16 m, and on the river Lena (near Bulun) up to 24 m.

Floods. In addition to periodically recurring spring floods, there are also sudden rises in water caused by either precipitation heavy rains, or for any other reasons. These sudden rises of water in rivers, in contrast to periodically recurring spring floods, are called floods. Floods, unlike floods, can occur at any time of the year. In flat areas, where the slope of the rivers is very small, these floods can cause sharp increases in levels, mainly in small rivers. In mountainous conditions, floods also occur on larger rivers. Particularly severe floods are observed in our area. Far East, where, in addition to mountain conditions, we have sudden prolonged downpours, giving more than 100 in one or two days mm precipitation. Here, summer floods often take on the character of strong, sometimes destructive floods.

It is known that forests have a huge influence on the height of floods and the nature of runoff in general. First of all, they ensure the slow melting of snow, which lengthens the duration of the flood and reduces the height of the flood. Besides, forest floor(fallen leaves, pine needles, mosses, etc.) retains moisture from evaporation. As a result, the surface runoff coefficient in the forest is three to four times less than in the arable land. Hence, the height of the flood decreases to 50%.

In order to reduce spills and generally regulate flows in the USSR, the government paid special attention to the preservation of forests in river feeding areas. Resolution (from 2/VII1936) provides for the conservation of forests on both banks of the rivers. At the same time, in the upper reaches of the rivers, forest strips of 25 km width, and in the lower reaches 6 km.

The possibilities for further combating spills and developing measures to regulate surface runoff in our country are, one might say, unlimited. The creation of forest shelterbelts and reservoirs regulates flow over vast areas. The creation of a huge network of canals and colossal reservoirs back in to a greater extent subordinates the flow to the will and greatest benefit of a person in a socialist society.

Low water. During the period when the river lives almost exclusively due to groundwater feeding in the absence of nutrition rainwater, the river level is at its lowest. This period of the lowest water level in the river is called low water. The beginning of low water is considered to be the end of the decline in the spring flood, and the end of low water is the beginning of the autumn rise in level. This means that the low-water period or low-water period for most of our rivers corresponds to the summer period.

Freezing of rivers. Rivers of cold and temperate countries in cold period years are covered with ice. Freezing of rivers usually begins near the coast, where the current is weakest. Subsequently, crystals and ice needles appear on the surface of the water, which, collecting in large quantities, form the so-called “fat”. As the water cools further, ice floes appear in the river, the number of which gradually increases. Sometimes continuous autumn ice drift lasts for several days, and in calm frosty weather the river “rises” quite quickly, especially at bends where a large number of ice floes accumulate. After the river is covered with ice, it switches to feeding on groundwater, and the water level often drops and the ice on the river sag.

The ice gradually thickens by growing from below. The thickness of the ice cover, depending on climate conditions, can be very different: from several centimeters to 0.5-1 m, and in some cases (in Siberia) up to 1.5- 2 m. From the melting and freezing of fallen snow, the ice can thicken on top.

The outlets of a large number of springs bringing warmer water, in some cases lead to the formation of a “polynya,” i.e., an ice-free area.

The freezing process of a river begins with the cooling of the upper layer of water and the formation of thin films of ice known as lard As a result of the turbulent nature of the flow, water is mixed, which leads to cooling of the entire mass of water. In this case, the water temperature can be slightly below 0° (on the Neva River up to - 0°.04, on the Yenisei River -0°.1): Supercooled water creates favorable conditions for the formation of ice crystals, resulting in the so-called deep ice. Deep ice formed at the bottom is called bottom ice. Deep ice in suspension is called Suga. Suga can be suspended or float to the surface.

Bottom ice, gradually growing, breaks away from the bottom and, due to its lower density, floats to the surface. At the same time, bottom ice, breaking away from the bottom, takes with it part of the soil (sand, pebbles and even stones). Bottom ice that floats to the surface is also called slush.

The latent heat of ice formation is quickly consumed, and the river water remains supercooled all the time, right up to the formation of the ice cover. But once the ice cover forms, heat loss to the air largely stops and the water is no longer supercooled. It is clear that the formation of ice crystals (and therefore deep ice) stops.

At significant current speeds, the formation of ice cover slows down greatly, which in turn leads to the formation of deep ice in huge quantities. As an example, we can point to p. Hangar. There's sludge here. And. bottom ice, clogging the channel, forms gluttons. Blockage of the riverbed leads to a high rise in water levels. After the formation of ice cover, the process of formation of deep ice is sharply reduced, and the river level quickly decreases.

The formation of ice cover begins from the coast. Here, with a lower current speed, ice is more likely to form (zaberegi). But this ice is often carried away by the current and, together with the mass of slush, causes the so-called autumn ice drift. Autumn ice drift is sometimes accompanied by congestion, i.e., the formation of ice dams. Jams (like ice jams) can cause significant water rises. Congestion usually occurs in narrowed sections of the river, at sharp turns, on riffles, and also near artificial structures.

On large rivers flowing north (Ob, Yenisei, Lena), the lower reaches of the rivers freeze earlier, which contributes to the formation of especially powerful jams. The rising water level in some cases can create conditions for the occurrence of reverse flows in the lower sections of the tributaries.

From the moment the ice cover forms, the river enters a period of freeze-up. From this point on, the ice slowly grows from below. In addition to temperatures, the thickness of the ice cover is greatly influenced by the snow cover, which protects the river surface from cooling. On average, the ice thickness on the territory of the USSR reaches:

Polynyas. It is not uncommon for some sections of the river to not freeze in winter. These areas are called polynyas. The reasons for their formation are different. Most often they are observed in areas fast current, at the outlet of a large number of springs, at the site of factory water discharge, etc. In some cases, such areas are also observed when a river exits a deep lake. So, for example, R. Angara at the exit from the lake. Baikal for 15 kilometers, and in some years even 30, does not freeze at all (the Angara “sucks in” the warmer water of Lake Baikal, which does not soon cool down to the freezing point).

Opening up of rivers. Under the influence of spring sun rays The snow on the ice begins to melt, causing lens-shaped accumulations of water to form on the surface of the ice. Streams of water flowing from the shores increase the melting of ice, especially near the coast, which leads to the formation of edges.

Usually, before the autopsy begins, there is ice movement. At the same time, the ice begins to move and then stops. The moment of movement is the most dangerous for structures (dams, dikes, bridge abutments). Therefore, ice near structures breaks off in advance. The beginning of a rise in water breaks up the ice, which ultimately leads to ice drift.

The spring ice drift is usually much stronger than the autumn one, which is determined significantly a large number water and ice. Ice jams in spring are also greater than in autumn. They reach especially large sizes on northern rivers, where the opening of rivers begins from the top. The ice brought by the river lingers in the lower areas, where the ice is still strong. As a result, powerful ice dams are formed, which in 2-3 hours raise the water level by a few meters. The subsequent dam failure causes very severe destruction. Let's give an example. The Ob River opens near Barnaul at the end of April, and near Salekhard at the beginning of June. The ice thickness near Barnaul is about 70 cm, and in the lower reaches of the Ob there are about 150 cm. Therefore, congestion is quite common here. When jams form (or, as they call it here, “jams”), the water level rises by 4-5 in 1 hour m and drops just as quickly after the ice dams break through. Enormous flows of water and ice can destroy forests over large areas, destroy banks, and create new channels. Congestion can easily destroy even the strongest structures. Therefore, when planning structures, it is necessary to take into account the locations of structures, especially since traffic jams usually occur in the same areas. To protect structures or winter anchorages of the river fleet, the ice in these areas is usually blasted.

The rise of water during congestion on the Ob reaches 8-10 m, and in the lower reaches of the river. Lena (near the town of Bulun) - 20-24 m.

Hydrological year. The flow and other characteristic features of river life, as we have already seen, are different at different times of the year. However, the seasons in the life of the river do not coincide with the usual calendar seasons. So, for example, winter season for the river it begins from the moment when rain feeding stops and the river switches to winter ground feeding. Within the territory of the USSR this moment in northern regions occurs in October, and in the south in December. Thus, there is no one precisely established moment suitable for all rivers of the USSR. The same must be said regarding other seasons. It goes without saying that the beginning of the year in the life of a river, or, as they say, the beginning of the hydrological year cannot coincide with the beginning calendar year(January 1). The beginning of the hydrological year is considered to be the moment when the river transitions to exclusively groundwater feeding. For different places in the territory of even one of our states, the beginning of the hydrological year cannot be the same. For most rivers in the USSR, the beginning of the hydrological year falls on the period from 15/XIup to 15/XII.

Climatic classification of rivers. Already from what has been said O rivers at different times of the year, it is clear that climate has a huge impact on rivers. It is enough, for example, to compare the rivers Eastern Europe with the rivers Western and Southern Europe to notice the difference. Our rivers freeze in the winter, open in the spring and give an exceptionally high rise in water during the spring flood. The rivers of Western Europe very rarely freeze and give almost no spring floods. As for the rivers of Southern Europe, they do not freeze at all, and their water levels are highest in winter. We find an even sharper difference between the rivers of other countries lying in other climatic regions. It is enough to recall the rivers of the monsoon regions of Asia, the rivers of northern, central and southern Africa, the rivers of South America, Australia, etc. All this taken together gave our climatologist Voeikov the basis to classify rivers depending on the climatic conditions in which they are located. According to this classification (slightly modified later), all rivers on Earth are divided into three types: 1) rivers fed almost exclusively by meltwater from snow and ice, 2) rivers fed only by rainwater, and 3) rivers fed by both methods indicated above .

Rivers of the first type include:

a) rivers of deserts bordered by high mountains with snowy peaks. Examples include: Syr-Darya, Amu-Darya, Tarim, etc.;

b) rivers of the polar regions (northern Siberia and North America), located mainly on islands.

Rivers of the second type include:

a) rivers of Western Europe with more or less uniform rainfall: Seine, Main, Moselle, etc.;

b) rivers of Mediterranean countries with winter floods: rivers of Italy, Spain, etc.;

c) rivers of tropical countries and monsoon regions with summer floods: Ganges, Indus, Nile, Congo, etc.

Rivers of the third type, fed by both melt and rainwater, include:

a) rivers of the East European, or Russian, plain, Western Siberia, North America and others with spring floods;

b) rivers receiving food from high mountains, with spring and summer floods.

There are other newer classifications. Among them, it is worth noting the classification M. I. Lvovich, who took as a basis the same classification of Voeikov, but for the purpose of clarification took into account not only qualitative, but also quantitative indicators of river feeding sources and the seasonal distribution of flow. So, for example, it takes the annual runoff and determines what percentage of the runoff is due to one or another power source. If the runoff value of any source is more than 80%, then this source is given exceptional importance; if the flow rate is from 50 to 80%, then it is preferential; less than 50% - predominant. As a result, he gets 38 groups of river water regimes, which are combined into 12 types. These types are as follows:

1. Amazonian type - almost exclusively rain-fed and the predominance of autumn runoff, i.e. in those months when temperate zone are considered autumn (Amazon, Rio Negro, Blue Nile, Congo, etc.).

2. Nigerian type - predominantly rain fed with a predominance of autumn runoff (Niger, Lualaba, Nile, etc.).

3. Mekong type - almost exclusively rain-fed with a predominance of summer runoff (Mekong, upper reaches of Madeira, Marañon, Paraguay, Parana, etc.).

4. Amur - predominantly rain fed with a predominance of summer runoff (Amur, Vitim, upper reaches of the Olekma, Yana, etc.).

5. Mediterranean - exclusively or predominantly rain fed and the dominance of winter runoff (Moselle, Ruhr, Thames, Agri in Italy, Alma in Crimea, etc.).

6. Oderian - predominance of rain nutrition and spring runoff (Po, Tissa, Oder, Morava, Ebro, Ohio, etc.).

7. Volzhsky - mainly snow-fed with a predominance of spring runoff (Volga; Mississippi, Moscow, Don, Ural, Tobol, Kama, etc.).

8. Yukon - predominant snow supply and dominance of summer runoff (Yukon, Kola, Athabasca, Colorado, Vilyui, Pyasina, etc.).

9. Nura - predominance of snow supply and almost exclusively spring runoff (Nura, Eruslan, Buzuluk, B. Uzen, Ingulets, etc.).

10. Greenland - exclusively glacial feeding and short-term runoff in summer.

11. Caucasian - predominant or predominantly glacial feeding and dominance of summer runoff (Kuban, Terek, Rhone, Inn, Aare, etc.).

12. Loansky - exclusive or predominant nutrition from groundwater and uniform distribution of flow throughout the year (Loa River in northern Chile).

Many rivers, especially those that have longer length and a large feeding area, may turn out to be their own separate parts in different groups. For example, the Katun and Biya rivers (from the confluence of which the Ob is formed) are fed mainly by meltwater from mountain snow and glaciers with rising water in the summer. In the taiga zone, the tributaries of the Ob are fed by melted snow and rainwater with overflows in the spring. In the lower reaches of the Ob, tributaries belong to the rivers of the cold zone. The Irtysh River itself has complex character. All this, of course, must be taken into account.

In this article we will talk about how an increase or decrease in the water level in a reservoir can affect the behavior of fish and, accordingly, their bite. It would seem, how can this lead to changes in the behavior of fish? But a fish is not a particularly intelligent creature, but rather an instinctive one, so an increase or decrease in the water level in a reservoir acts as a kind of sign for fish that some changes are taking place in their normal habitat, which may indicate a possible danger. These changes entail a reaction from the fish in the form of a decrease in their activity and a cessation of biting.

Constantly fluctuating water levels are the worst conditions for fishing. With a large and sharp increase in water level, the bite becomes weak, because the fish is forced to constantly change its location. In calmer places, a high water level for a long time is the key to a good bite, since fish find shelter in such places. A sharp drop in water level reduces the bite, and a decrease in water level to normal, which occurs gradually, can contribute to a good catch.

The water level in a reservoir remains stable only for short periods of time. Increases or decreases in level are quite common occurrences and apply to both large and small bodies of water. The reasons for such changes are. These often include prolonged droughts, floods and frequent rains, as well as spring melting of ice and snow. A consistently average water level in the river ensures that the fish bite well, because nothing forces them to be less active.

Natural decrease in water level in a reservoir

Typically, the catalyst that causes a decrease in water levels is prolonged drought and lack of precipitation. Also, the water level depends on the size of the reservoir, because in small reservoirs the water level fluctuates much more often than in large ones. But the fish behave calmer with such decreases in small lakes, rivers and rates. This is explained by the fact that changes in the habitat for fish are not uncommon, but rather have become commonplace. Therefore, when the water level drops in small reservoirs, fish bite quite well. Its activity in such cases can only be affected by significant changes in the reservoir. These include an increase in water temperature, a decrease in the composition of oxygen in it, which may be followed by the death of fish. But with normal oxygen levels in the reservoir, the bite will be normal. But when the water level decreases in large bodies of water, for example, reservoirs, a significant decrease in fish activity can be observed.

This can be explained by a change in the volume of water due to even a slight decrease in its level. At the same time, the fish react quite quickly to changes, behave less actively, freeze on the edge of the reservoir, and the bite stops for some time. Thus, we can conclude that fish respond not to changes in water level, but, by and large, to changes in the volume of water in the reservoir.

Natural increase in water level in a reservoir

The next option for changes in a reservoir is an increase in water level, which can affect the activity and bite of fish. Most often, the water in the reservoir arrives during the melting of snow and ice in early spring or during the period of frequent rains and floods in the summer.

In the spring, the water level in reservoirs rises to , therefore, due to natural factors, the fish does not react to the changes in any way and bites quite well, because its food supply also increases. There may be no bite during this season either due to atmospheric changes, or due to the inability of anglers to monitor parking and catch fish in a separate body of water. In summer, the influx of water into reservoirs is very favorable for fish.

Firstly, due to the presence of water, reservoirs are enriched with oxygen, and secondly, the volume of the fish’s habitat increases, which causes an increase in its activity, and, accordingly, biting. Small fish mainly occupy shallow-water habitual places, since there is plenty of food in such places. Large fish mainly stick to hogs near deep places. From these places, roach, perch, and pike make periodic “raids” to the coastal zone in order to profit from crustaceans, small fish and larvae. Pike can generally stick to the shore, since there is a better oxygen regime here, and not leave this place until the edges form. Roach and bream occupy deep places at mid-water.

When the water is mixed due to runoff, which allows the bottom layer to be enriched with oxygen, the bream goes to the bottom and feeds there. When the water level becomes uniform, that is, the release of water is completed and stabilized, the fish are redistributed again. Therefore, before you start fishing, it is better to familiarize yourself in advance with the water discharge regime at the selected reservoir. If the discharge intensifies, then it is better not to catch, but if it happened 3-4 days before fishing, then it is better to start looking for fish from deep places and deep hogs at mid-water. After this, the fish moves closer to the shore.

Monitoring water levels in reservoirs

There are not only natural reservoirs in which the water level rises and falls due to natural conditions and processes, but also reservoirs in which the water level is regulated by man. Such reservoirs include reservoirs and various canals. Changes in water levels in such regulated reservoirs can be either planned or emergency. This most often depends on the melting of ice and snow in the spring, as well as flood rains in the summer and fall. Therefore, when there is an unplanned change in the water level in a reservoir, it is discharged and accumulated.

For fish, the regulation of water levels in reservoirs by artificial means is a surprise and also acts as a signal that something bad is happening in their habitat. Fish simply does not know how to behave in such situations. The negative reaction of fish is quite clearly manifested at the end of winter, when before the start of melt water entering the reservoirs, planned water discharges from reservoirs are carried out. It is also fair to note that in reservoirs that have existed for decades, for example in reservoirs near Moscow, adult fish have already become accustomed to the actions of the Mosvodokanal and a change in water level that occurs unexpectedly is no longer perceived as a natural disaster.

Most often, when water is released in regulated reservoirs, the fish become less active, freeze and stop biting for a while. After the water level in the river rises, the bite is restored as the fish begins to develop a new food base. But this applies more to small reservoirs, because in large reservoirs that have existed for many years, fish simply get used to such changes in water level and behave quite naturally, both when water is discharged and when it accumulates.

In regulated reservoirs, artificial changes in water levels can also be cyclical, which are carried out to generate and obtain electricity. Such reservoirs include rivers, canals and reservoirs on which hydroelectric power stations are located. Often, the operation of a hydroelectric power station to regulate the water level is planned in such a way as to excessively accumulate the water level in the reservoir, and then, due to its sudden release, produce maximum quantity electricity. The most successful example of such work is a hydroelectric power station on the Volga, in which water is stored on weekends and released on weekdays. In such reservoirs, fish react sharply to changes in water level. When water is released, schools of fish gather on the riverbed edges, and when the water level rises, the fish move closer to the shore to develop a new food supply.

When water levels drop in dammed rivers, lakes, streams and ponds, changes in fish behavior are observed. The reaction of fish can be expressed either in a sharp increase in biting when the water rises, or in a sharp absence of biting when it is released. For example, the bite can increase instantly during a rainstorm with rising water levels, and end literally after 10 minutes when the water level begins to rise. By artificially changing the water level, the bite can be regulated by the owners of such reservoirs in order to make a profit from the fishermen.

Artificially lowering the water level

Water discharge in regulated reservoirs occurs at the end of winter, before the melting of ice and snow. The reservoir is cleared of water to a certain level in order to avoid sudden and excessive accumulation of water in the spring during the arrival of melt water. Such water discharge also helps clean the reservoir bed. During such changes in the reservoir, the bite increases, as the food supply for fish is significantly reduced. At the same time, the oxygen regime deteriorates. And if the fish perceive a decrease in water level as a signal of danger, their activity will sharply decrease and the fish will sit at the bottom for some time.

Where and when is the best time to fish?

During a gradual rise in the water level, the bite does not stop, but often increases due to the supply of oxygen. But the peculiarity of such changes is that the fish move and localize closer to the shore, because in shallow water they find fresh places to feed.

Low water levels in the river are not the direct cause of poor bite; the water during such a period is prone to temperature fluctuations. During drought, a moderate increase in water level can cause heavy biting.

The fish bite is also affected not only by a decrease or increase in the water level in the reservoir, but also by its temperature and oxygen content, flow and turbidity of the water. Therefore, when going fishing, you should take into account all these factors in order not only to predict the time of a good bite, but also to ensure yourself a wonderful catch.

To summarize, it should be noted that minor changes in the water level of a reservoir do not entail any special changes in the behavior of fish. With a gradual decrease in water level, the fish does not react to the changes in any way and only gradually moves deeper into the reservoir. But with sharp drops and discharges of water, the fish becomes less active, localizes on the underwater edges and stops biting. This reaction will be observed within 24 hours, after which the fish will adapt to the changes and the bite will resume.

In my opinion, a more correct formulation of the question should look a little different: how does a change in water level affect the fish bite? This problem is so complicated that it is unlikely that it will be possible to reveal all the subtleties within the framework of a separate article, but I will try to derive general patterns.

Danger signal

A sharp change in the water level in a reservoir is almost always a signal of danger for fish. This is a kind of wake-up call, a signal that something is happening somewhere and an adequate action needs to be taken. When the alarm clock rings, a person wakes up and begins to act according to a plan drawn up in advance. But the person sets the alarm himself. Fish do not wait for a call, do not plan their actions and react to changes in living conditions as soon as they happen, so we can easily trace how changes in water level affect the fish’s bite. Accumulated observations allow us to identify specific examples of the connection between water level and fish behavior.

Period of constant water level

During this period, the water remains at a relatively stable, constant level. This is observed quite rarely. And the smaller the reservoir, the less often the water level in it remains completely unchanged. Enough to pass good rain or, conversely, no precipitation occurs for two weeks, as the level changes noticeably. But, as practice shows, it is in small bodies of water that fish react quite painlessly to minor changes in the level: they are simply accustomed to them. If the water level in a small river or pond drops a few centimeters, this usually does not affect the bite. But in a large river, a decrease in the water level by the same few centimeters can lead to a complete cessation of biting. That is, it would be more correct to correlate the degree of fish reaction not with the water level, but with the change in its volume. The conclusion is this: in small bodies of water, the behavior of fish noticeably changes during strong, visually observable fluctuations in water level, but in large bodies of water, the same reaction can be caused by a much smaller change in level. Therefore, determining a stable water level in a reservoir is a relative concept.

If fluctuations in the water level in the reservoir in which you fish do not affect the bite, then we can assume that the level remains unchanged (from the point of view of fish behavior).

Increasing water level in a reservoir

I would characterize the second situation as a period of rapid increase in the mass of water and, as a consequence, an increase in its level in the reservoir. This happens during high water, but since it is associated with the spawning period, certain fish behavior is determined genetically. An increase in the water level in this situation leads to the fact that the food supply increases many times, and the fish begin to feed intensively. The lack of a bite at this time is due either to sudden changes in the atmosphere, or even more often to the fact that the angler cannot find a fish site or adapt to the fishing conditions. Summer floods also lead to a sharp increase in water levels. During them, the activity of fish in search of food always increases. A decrease in its activity may be associated with atmospheric phenomena and a sharp change in water transparency. Reservoirs with clayey banks become cloudy after a heavy rain literally within tens of minutes.

Changes in water level in regulated reservoirs

Reservoirs are divided into those in which changes in water level are associated only with natural processes, and those where regulation is carried out by humans.

In regulated reservoirs, changes in water levels depend on two factors: on planned accumulations and subsequent releases of water, which are carried out depending on flood rains, and on the speed of spring melting of ice. For fish, artificial regulation of the water level is unpredictable and unexpected, and it has an extremely negative attitude towards it. The fish simply does not know how to behave in this situation. The negative reaction of fish is especially clearly observed at the end of winter, when planned water discharges from reservoirs are carried out before melt water begins to flow into reservoirs. To be fair, it should be noted that in reservoirs that have existed for decades, such as those near Moscow, adult fish are already accustomed to the actions of the Mosvodokanal and an unexpected change in water level is not perceived as a natural disaster.

On small bodies of water, the behavior of fish noticeably changes during strong, visually observable fluctuations in water level, but on large bodies of water, the same reaction can be caused by a much smaller change in level. Therefore, determining a stable water level in a reservoir is a relative concept.

In addition to the accumulation and release of water in reservoirs associated with the influence of natural factors, there is regulation of the volume of water in order to generate electricity. This applies to those rivers on which hydroelectric power stations are located. A classic example is the Volga. All Volga dams operate in maximum water discharge mode weekdays. On Saturday and Sunday, water is accumulated above the dam for the purpose of subsequent release on weekdays for maximum hydroelectric power generation.

When water accumulates above the dam, that is, in the reservoir basin, below the dam the water level drops and the flow slows down. Above the dam, the water level increases, and the flow also slows down, until it stops completely.

What happens in the end? Below the dam the fish move away from coastal zone and stands on the riverbed edges. Above the dam, the fish scatter throughout the area with standing water, and finding them becomes very problematic. On the Volga, over several decades, fish have become accustomed to this spillway regime and behave completely adequately to artificial changes in water level. Therefore, in the reservoirs of the Volga cascade, fishing is worst on weekends, in conditions of the weakest current. And it’s most effective on Wednesday and Thursday, when the current reaches its maximum speed. Moreover, this applies to fishing both from a boat and from the shore. When the question concerns the behavior of fish in “younger” reservoirs, then in order to predict the bite and optimize the search for fish, it is necessary to take into account the age factor of the regulated reservoir. In “young” reservoirs, during the first years of their existence, there is a constant restructuring of the hydrodynamic regime, changes in the food supply, spawning, feeding and wintering areas, so that the fish are not up to the “level”.

Dammed streams

In small dammed lakes and ponds that are formed after the creation of a simple dam, for example, to create a “fire” pond in a summer cottage, a sharp change in the water level causes a more pronounced reaction from the fish. For example, the bite can begin almost instantly with the rise in water level during a rainstorm and end literally 10 minutes after the water level in the pond begins to rise. On some “cultural” reservoirs the following action is practiced. When a lot of fishermen gather who have paid for the pleasure of catching crucian carp and crucian carp, the pond owners lower the water level by several centimeters. The biting either stops completely or becomes extremely cautious. When most fishermen leave the pond, complaining about the weather and the lack of bite, the water level quietly rises. Carp and crucian carp begin to bite on everything at once. The remaining fishermen are glad that they “waited” for the fish to come. The next day, word spreads that the bite began only at six in the evening, and the reputation of the pond was saved.

Natural level reduction

Another characteristic period of change in water level is observed after a long drought, when the water flow decreases sharply. Pisces take this very calmly. A possible decrease in feeding activity occurs not due to a decrease in water level, but due to an increase in temperature, stratification of water and a deterioration in the oxygen regime, which can lead to death. If the oxygen content in the water remains normal, then when the water level in lakes and small rivers decreases, the activity of fish even increases, since it is partially deprived of its food supply in the coastal zone.

Decrease in reservoir levels at the end of winter

It’s another matter when the water level decreases at the end of winter in regulated reservoirs. Here, water is routinely discharged, freeing the reservoir for melt water, as well as for the purpose of flushing the riverbed from bottom sediments. During this period, on the one hand, the concentration of fish increases sharply, which leads to food competition and improved biting, on the other hand, the oxygen regime worsens, and the fish perceives a decrease in water level as a signal of danger. Therefore, days of good biting can be interspersed with complete lack of biting, which, among other things, can be associated with changes in the weather.

Where to look for fish

It is almost impossible to consider all the options for fish dislocation, but we will still try to draw a few basic conclusions. When the water level slowly decreases over several days, the activity of the fish does not change. The fish gradually migrates to deeper places, using underwater edges as intermediate stopover sites.

In the reservoirs of the Volga cascade, fishing is worst on weekends, in conditions of the weakest current. And the most effective time is on Wednesday and Thursday, when the current reaches its maximum speed. Moreover, this applies to fishing both from a boat and from the shore.

When the water level slowly rises, the fish also actively feed, but at the same time they try to occupy the smallest places that are richest in food. It is worth noting that in almost all situations, predators also follow “peaceful” fish.

A particularly pronounced desire for small places is observed at night. So, for example, at sunset, when the water level in the Volga was rising, I often caught bream under the shore from a depth of no more than 1 m. But it becomes more difficult to find fish sites at this time.

In the event of a sharp, rapid drop in water level, the bite worsens everywhere, often for several days. If the water level rises sharply, the bite subsides for several hours, but then returns to normal. The best place For fishing there will be a border between a direct stream of water and a quiet coastal part. Until the water level stabilizes, fish are in no hurry to go out into shallow water for several hours. In addition to level fluctuations, the associated changes in current strength and water turbidity have no less influence on the bite. Taking into account these factors, as well as weather conditions, a forecast for the upcoming fishing is built. Judging by my experience, with any changes in water level, even taking into account its possible turbidity, but with stable weather You can always find a spot of active fish and be with a catch.

LOW - prolonged seasonal standing of low water levels in the river, due to weakening of surface flow and the transition of the river, mainly to ground feeding

(Bulgarian language; Български) - extreme oligohydramnios

(Czech language; Čeština) - období malé vodnosti

(German; Deutsch) - Niedrigwasser

(Hungarian; Magyar) - kisviz

(Mongolian) - tataal

(Polish language; Polska) - niżówka

(Romanian language; Român) -etiaj

(Serbo-Croatian language; Srpski jezik; Hrvatski jezik) - period niskog vodostaja

(Spanish; Español) - estiaje

(English language; English) - low water

(French; Français) - basses eaux

low water level during the inter-flood period, when the river is fed mainly by groundwater, as well as the period when this level remains.

Construction dictionary.

Synonyms:

See what "MEZEN" is in other dictionaries:

low water- Prolonged seasonal standing of low water levels in the river, due to the weakening of surface flow and the transition of the river, mainly to groundwater feeding. [ Terminological dictionary on construction in 12 languages ​​(VNIIIS Gosstroy USSR)]… … Technical Translator's Guide

Annually recurring seasonal low (low) water levels in rivers. In temperate and high latitudes, a distinction is made between summer and winter low water... Big Encyclopedic Dictionary

Low water, low water, female. (region also Mezhnya, male). 1. Intermediate level water in a river, lake (special). The water rose above low water. 2. Midsummer (region). Small rivers dry up during low water. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary

The period (at least 10 days) of the intra-annual cycle during which the lowest water levels are observed in the river. In temperate and high latitudes, a distinction is made between summer and winter low water. Ecological encyclopedic dictionary. Chisinau: Main editorial office... ... Ecological dictionary

MEGENE, and, female. (specialist.). Low water level in a river or lake, as well as the period when this level remains. | adj. low water, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

- (river) a constant water level, established in the summer for a long period. Samoilov K.I. Marine dictionary. M. L.: State Naval Publishing House of the NKVMF of the USSR, 1941 ... Marine Dictionary

Noun, number of synonyms: 3 summer (10) the lowest water level in the river (1) ... Dictionary of synonyms

Low water- the lowest water level in the river... Source: RD 51 2 95. Regulations for meeting environmental requirements for the placement, design, construction and operation of underwater crossings of main gas pipelines (approved by Order of RAO Gazprom... ... Official terminology

Low water- stable periods of the intra-annual cycle, during which low water content is observed, due to a sharp decrease in water inflow from the catchment area. Source: MI 1759 87: GSI. Water flow in rivers and canals. Measurement technique... ... Dictionary-reference book of terms of normative and technical documentation

low water- Low water level in a river or lake, accompanied by low water availability... Dictionary of Geography

LOW- the period of the lowest water level in reservoirs. For middle zone In the European part of the USSR, the period of M. usually occurs in the summer after the passage of the spring flood and continues until the beginning of the autumn floods. Establishing the value ... ... Pond fish farming

Books

• Nikolay Baykov. Novels and short stories, Nikolai Baykov. The book includes stories and short stories “On the Jurassic River”, “Strict Earth”, “Free Fall”, “Mezhen” and others, the heroes of which raise virgin soil, herd cattle, harvest crops and work on factory floors,…