Useful volume of the reservoir. Reservoirs of Russia

More than a hundred large objects have been built on the territory of Russia - accumulations of water artificially created with the help of dams. In this article, we will consider in detail what a reservoir is, its main characteristics, and the role of its influence on the environment.

Reservoir - what is it?

What is a reservoir? This is a component of the landscape artificially created by man. The hydrological river regime is regulated in accordance with the necessary requirements. The use of accumulated water in the reservoir is determined by economic needs.

The role of artificial reservoirs

Russia occupies vast areas of the Eurasian continent. Its territories extend from the shores of the Arctic Ocean to the southern steppes and deserts. Not everywhere there is an abundance of rivers and lakes that fully satisfy human needs. The national economy requires large amounts of fresh water. Artificial reservoirs have long been used for domestic needs of the population and irrigation of crops. The Egyptian Sadd el-Kafara, built before our era, is considered the oldest man-made reservoir. Since the beginning of the 20th century, the construction of such reservoirs has become widespread. Now there are more than 60 thousand artificially created reservoirs on the planet. The largest reservoirs in the world are Nasser in Egypt on the Nile River, Volta in Ghana, in Russia Kuibyshevskoye on the Volga and Bratskoye on the Angara.

Purpose

The total area of ​​all reservoirs in the world created by man throughout history is more than 400 thousand square kilometers. Most reservoirs are located in Europe, Asia and North America. What is a reservoir for people, other than large reserves of water used for basic domestic and economic needs? The operation of artificial reservoirs allows for a more reasonable use of water resources - the accumulated ones are used for soil irrigation, water supply to the population and industry, hydropower and transport routes. Also used for flood prevention.

Reservoirs are often favorite places for recreation and fishing. However, despite the positive economic effect, the construction of dams often causes negative consequences that affect the ecology of adjacent territories.

Categories of artificial reservoirs

Reservoirs can be divided according to several criteria:

• structure;
• location in a river basin;
• filling method;
• degree of water level regulation;
• geographical location.

Based on the nature of the reservoir bed, they are divided into:

1. Valley - a valley, blocked by a dam, is a bed. The direction of the bottom slope from the top to the dam is the main feature that defines this reservoir. The depth increases towards the dam. There can be channel and floodplain-valley.
2. Basin - located in lowlands isolated from the sea with the help of dams.

By location in the river basin:

1. Horse riding.
2. Grassroots.
3. Cascade is a stepped system on a river bed.

By water filling:

1. Liquid.
2. Zaprudnye.

By the nature of water level regulation:

1. Perennial - filling of the bed can occur over several years.
2. Daily - the level is constantly regulated.
3. Seasonal - water discharge occurs at certain times of the year. Seasonal flows are used to artificially irrigate agricultural lands in the spring and summer and reduce the possible risk of flooding.

Winter drops in level are dangerous for the flora and fauna of the reservoir created with the help of the dam. If seasonal runoff occurs at the reservoir in winter, layers of ice settling on the dried bottom crush a large number of fish.

By geographical location:

1. Plain is a wide reservoir, the height of the water level is no more than 30 meters.
2. Mountain - the level increase can reach more than 300 meters.
3. Predgornoe - indicators are within 100 meters.
4. Primorskoye - pressure of several meters, built in sea bays.

What is a reservoir for a fisherman and a tourist?

Changing the river bed has a negative impact on fish spawning. Due to changes in the food supply and places where populations gather, the species composition is gradually becoming poorer. Valuable species are disappearing. However, fishing in the reservoir is often successful.

Large reservoirs are characterized by their own microclimate. Large freshwater reservoirs are often called the sea. Waves appear on the open water surface, which, due to the absence of natural obstacles in the form of islands, are very high. Not only residents of the surrounding banks prefer to relax on the reservoir; picturesque landscapes and rich fauna attract numerous tourists and travelers.

Impact on the environment

The construction of reservoirs may adversely affect the natural conditions of the surrounding area. The most serious negative consequences of the construction of large reservoirs are flooding of land, rising groundwater levels, and swamping of coastal zones. The total area of ​​the territories that went under water is approximately 240 thousand square kilometers. Siltation of reservoirs is the process of formation of large sediments at the bottom, leading to a decrease in water level. It is also assumed that the additional load in the form of the mass of accumulated water volumes can lead to an increase in the level of seismicity.

The construction of reservoirs entails many different consequences. In the process of creating and operating dams, construction should be carefully planned and environmental forecasts should be taken into account.

Lecture 9. Useful volume of the reservoir. Justification of the optimal reservoir drawdown depth.

9.1 Useful volume of annual regulation reservoir

The main task of the annual regulation reservoir is to increase the amount of energy and power of the hydroelectric power station during the low-water period of the year due to excess water retained in the reservoir during floods. The first issue that must be resolved by us is the issue of dividing the entire volume of the annual regulation reservoir into two parts - useful and dead volumes. Having the full volume of the reservoir, it is necessary to divide it into these two volumes, i.e., decide the issue of determining the depth of drawdown of the reservoir or set the ULV mark. When solving this problem, we will assume that the FSL mark of the reservoir is known and that the reservoir can always be filled during a flood, with the exception of very rare cases when particularly unfavorable hydrological conditions occur. We will not take these cases into account for now.

The task is to find the maximum drawdown depth of the reservoir at which the greatest energy effect at the hydroelectric power station can be obtained. If we accepted that the reservoir can be filled every year, then here we can consider the period of emptying the reservoir separately. The general solution to the problem can be obtained as follows.

As the emptying of the reservoir increases, the amount of energy that is obtained from the use of the reservoir also increases. This energy depends only on the depth to which the reservoir will be drained, and practically does not depend on the length of time during which the reservoir is emptied, the magnitude of the transit flow or other factors.

The generation of a hydroelectric power station in the presence of a reservoir can be represented as consisting of two parts: electricity generation due to the transit flow of the river flowing during the drawdown of the reservoir, and generation due to the drawdown of the reservoir

E hydroelectric power station =E IN +E TR (11-2)

The amount of transit energy from a hydroelectric power station depends, of course, on the volume of transit flow, i.e., on the magnitude of transit water flows and the duration of the period of emptying the reservoir. But it also depends on the pressure, i.e., on the drawdown depth of the reservoir. Finally, it depends on the operating mode of the reservoir. With rapid drawdown of the reservoir at the beginning of the low-water period, as, for example, shown in Fig. 1.1, most of the transit flow passes at a relatively low pressure and therefore produces a small energy effect. The drainage is mainly at the end of the low-water season, shown in Fig. 1.2, allows you to pass almost the entire transit flow at high pressure and, therefore, receive more energy from the hydroelectric power station.

Rice. 1.1 Fig. 1.2

Let us know the hydrological characteristics of the low-water season, during which the reservoir is emptied. By setting some simple conditional mode of operation of a hydroelectric power station (for example, when regulating the flow rate of water passed through the turbines of a hydroelectric power station to a constant value), we can determine the amount of energy that the hydroelectric power station produces at various operating levels by the end of the low-water season. The results of such calculations can be presented graphically in the form of a curve of the dependence of the transit energy of a hydroelectric power station on the depth of drawdown of the reservoir, shown in Fig. 2

The energy characteristics of the reservoir are plotted on the same graph. The deeper the reservoir is drained, i.e., the larger its useful volume is assumed to be, the greater the amount of energy obtained from the reservoir and the less transit energy becomes. The decrease in transit energy is explained by a decrease in pressure as the drawdown of the reservoir deepens. By summing up the energy of the reservoir and transit energy for different drawdown depths, we obtain the total energy value of the hydroelectric power station for the entire period of emptying the reservoir. It is obvious that for the given hydrological conditions and for the adopted regulation regime, the reservoir drawdown depth at which the hydroelectric power station produces the greatest amount of energy turns out to be the most profitable. Further deepening of the drawdown of the reservoir, although it would increase its useful volume and the regulated flow used by the hydroelectric power station, the pressure would decrease so much that the total amount of energy generated by the hydroelectric power station would not increase, but decrease.

If the characteristics of the transit flow change during the emptying of the reservoir, then the curve of the dependence of transit energy on the depth of drainage of the reservoir will take a different form and take a different position on the graph. In Fig. In Fig. 2, the dotted line shows such a curve obtained with a reduced transit flow, and the curve of the total energy of the hydroelectric power station for this case. From the above graph it can be seen that in this case the most advantageous value of the useful volume of the reservoir increases. This is very easily explained by the fact that with a decrease in transit flow, the energy of the reservoir accounts for the majority of the total energy of the hydroelectric power station. Let us note here that a change in the magnitude of the transit flow can occur even if the hydrological characteristics remain unchanged, but with a change in the duration of the emptying of the reservoir.

If we, without changing the volume and distribution of transit flow, adopted a different regulatory regime, then the shape of the curve of the dependence of transit energy on the depth of the maximum drawdown of the reservoir at the end of the low-water season would change. At the same time, the shape of the total curve of the total energy of the hydroelectric power station would also change. Consequently, we would have received a different mark for the most profitable reservoir drawdown. If the control regime changes significantly during reservoir emptying, the change in the most advantageous reservoir drawdown depth can also be significant. From Fig. 1.1 and 1.2 it follows that when the reservoir is emptied early, its deep drawdown is less profitable than when it is emptied late.

The influence of various conditions on the position of the most favorable drawdown depth of a reservoir, which has a certain characteristic of its own, was discussed above. But comparing different reservoirs with each other, it is not difficult to see that the maximum depth of their drawdown, under the same other conditions, depends on the type of their characteristics - volumetric and energy. For example in Fig. Figure 3 plots the volumetric characteristics of two reservoirs that have the same total volume at the same FSL level. From this graph it is clear that at the drawdown depth indicated in the drawing, the useful volume of the reservoir is A makes up the majority of its total volume. For reservoir B at the same drawdown depth, the useful volume is only a small part of the entire total volume of the reservoir. Further deepening of the drawdown noticeably increases its useful volume and, therefore, gives a large energy effect, while for the reservoir A deepening the drawdown only very little increases the regulated water flow.

For a mixed dam-diversion scheme, water-energy calculations to determine the most advantageous reservoir drawdown depth are carried out in the same way as for a dam scheme. These calculations must, of course, take into account the entire head, both that created by the dam and that created by the diversion. It is clear that in a dam-diversion scheme the useful volume of the reservoir constitutes a significantly larger part of its total volume, and the dead volume is much smaller than in a dam scheme. The dead volume may be negligible.

From all that has been said above, let us dwell on one very important point. For a given reservoir, the most advantageous drawdown depth depends very much on the volume of transit flow. But in different hydrological years, the volume of transit flow during the low-water season, when the reservoir is emptied, is not the same. Consequently, the drawdown depth of the reservoir should also be different in different hydrological years.

If we had the opportunity to obtain a fairly reliable forecast of the natural flow regime of the river for the upcoming low-water season, then a preliminary determination of the most favorable depth of reservoir drawdown in each individual year would not present any fundamental difficulties. However, in the absence of a preliminary forecast of river flow, it becomes impossible. But if it is impossible for practically every single year to establish its own special most advantageous reservoir drawdown depth, then this means that one depth of maximum reservoir drawdown, identical for all years, should be determined, regardless of the difference in hydrological characteristics in all these years.

Of particular importance is the use of an annual regulation reservoir to increase the energy and power of hydroelectric power stations during emptying of the reservoir in low-water years. Therefore, determining the maximum drawdown depth of a reservoir should be carried out with a small volume of transit flow. In this case, we get, as can be seen from Fig. 2, a greater depth of the maximum drawdown of the reservoir, which we will consider the same for all hydrological years. With this solution to the problem, in high-water years, the amount of energy generated by a hydroelectric power station may turn out to be slightly less than the maximum possible. But, as we will see later, the energy lost in this way can be, if not completely, then partially compensated if we apply different regulatory regimes in different hydrological years. Indeed, in high-water years, there is no need to quickly empty the reservoir at the beginning of the low-water season, as in low-water years, since the large amount of transit flow allows the hydroelectric station to operate with the power required for the energy system, no less than the guaranteed one, while taking only relatively a small amount of water. At the end of the low-water season, when only a small part of the transit flow remains unused, the drawdown of the reservoir can be quickly brought to a constant maximum level, as a result of which additional energy will be obtained.

Although we have come to the conclusion that the maximum working depth should be determined based on a low-water year, this conclusion cannot yet be considered complete, since we still need to decide which year should be chosen from among the low-water ones as the design year. The choice of the calculation year cannot, of course, be made arbitrarily, since the calculation year must meet certain conditions, i.e., the conditions for the best use of hydroelectric power plants in the energy system. Of the two main requirements imposed by the energy system on hydroelectric power plants, in this case the first one is of greatest importance - achieving the greatest security in the operation of the energy system. Methods for satisfying the second main requirement of the energy system - the largest amount of energy generated by hydroelectric power plants - will be discussed further.

Taking as the initial condition for determining the most favorable maximum depth of reservoir drawdown the achievement of the greatest security in the operation of the energy system, we at the same time resolve the issue of the reservoir emptying regime, which we previously accepted as conditional. Since the greatest security, as we established earlier, is achieved when the hydroelectric power station operates according to a guaranteed power schedule, it follows that the regulation regime during emptying of the reservoir must correspond to the operation of the hydroelectric power station according to this schedule.

If the composition of the existing energy system is known, then a guaranteed schedule of the average daily power of a hydroelectric power station can always be constructed. Having a fairly complete hydrological characteristic of the river, we can calculate the regulation for a long series of years when the hydroelectric power station operates according to a guaranteed schedule of average daily power. As a result of this calculation, a graph of changes in the water level in the reservoir over all these years will be obtained. In Fig. Figure 4 shows combined curves of changes in water level in the reservoir over several years, and here only those sections of the curves that are of interest to us in this case are highlighted, i.e., those related to the time of emptying of the reservoir.

The shallower the year, the greater the amount of water that needs to be taken from the reservoir to obtain guaranteed power at the hydroelectric power station. Therefore, the shallower the year, the deeper the reservoir is drained. However, in especially low-water years, no deep drawdown of the reservoir will make it possible for the hydroelectric power station to operate according to a guaranteed schedule during the entire period of emptying the reservoir due to a significant decrease in pressure during deep drawdown. The curve of changes in water level in the reservoir for such a case is shown in Fig. 4 dotted line. Obviously, in such particularly low-water years, disruptions to the normal operation of the energy system cannot be avoided. Therefore, we exclude all such years from further consideration.

From among the remaining years, we will take the year with the least water, in which the depth of the reservoir drawdown is greatest. If we had used the reservoir to a lesser extent this year, the hydroelectric power station would not have been able to operate according to the guaranteed schedule due to a lack of water. A deeper drawdown of the reservoir this year is not required to obtain guaranteed capacity and it cannot provide additional energy, since the operation of a hydroelectric power station with an average daily capacity greater than the guaranteed one would lead to premature emptying of the reservoir and an excessive reduction in the pressure of the hydroelectric power station. Thus, we come to the conclusion that the drawdown depth we obtained is the limit to which the annual regulation reservoir can be emptied annually. That part of the total volume of the reservoir, which is contained between the maximum drawdown mark and the NPL mark, represents the useful volume of the reservoir.

When determining the maximum drawdown depth of the reservoir using the method described above, we took the guaranteed schedule of the average daily power of the hydroelectric power station as the initial condition. But since a hydroelectric power station, which has a reservoir of annual regulation, simultaneously carries out daily regulation, then during the hours of the daily peak load of the energy system it must develop a power greater than the daily average. With deep drawdown of the reservoir and a significant decrease in pressure, the available power of the hydroelectric power station can be equal to or even greater than the guaranteed average daily power. In such cases, despite the fact that the hydroelectric power station can operate according to the guaranteed average daily power schedule, a disruption of the normal operation of the energy system still occurs. Consequently, in this case, the maximum drawdown mark for the annual regulation reservoir, up to which it must be emptied annually, must lie higher than that which we determined earlier. Based on the annual schedule of the guaranteed peak power of a hydroelectric power station and the characteristics of the turbines installed on it, it is not difficult to determine what minimum pressure is necessary to have and, therefore, what water level in the reservoir must be maintained on any calendar date for the entire time the reservoir is emptying. The dependence of the required minimum water level in the reservoir on time is plotted in Fig. 5. The same graph shows a curve of the dependence of the water level in the reservoir on time when the hydroelectric power station operates according to the guaranteed schedule of average daily power. Of all such curves in Fig. 5 shows only two. One of them, shown as a solid line, was obtained in a hydrological year when the drawdown of the reservoir by the end of the low-water season exactly coincides, as can be seen from the graph, p. permissible drawdown under the condition of obtaining the required peak "power at the hydroelectric power station. This depth of drawdown of the reservoir should be considered as the limiting one, i.e., as the one to which the reservoir is emptied annually. In the same drawing, the dotted line shows the curve of the dependence of the water level in the reservoir on time , which was previously adopted to determine the operating depth based on the average daily power.

The greatest load on the energy system, when a hydroelectric power station is required to participate in the power balance with its entire total displacement capacity, in most cases does not coincide in time with the greatest emptying of the reservoir. The annual peak load of the energy system usually occurs at the end of December and beginning of January, and the complete emptying of the reservoir occurs at the end of the low-water season, i.e. in the spring, before the onset of the flood. In this regard, during the deepest drawdown of the reservoir, the guaranteed peak power is slightly less than the maximum. This makes it possible to increase reservoir utilization by the end of the low-water season. Such a case is shown in Fig. 5.

For low-pressure hydroelectric power plants, in which the pressure and available power of the hydroelectric power station depend on fluctuations in the water level in the downstream, when determining the maximum drawdown depth of the reservoir, the unsteady nature of water movement in the downstream of the hydroelectric power station during daily regulation should be taken into account. A large, but short-term increase in the load of a hydroelectric power station does not have a significant effect on the magnitude of the pressure and, consequently, the available power of the hydroelectric power station. Therefore, for low-pressure hydroelectric power plants, peak operating power mode and frequency regulation in the energy system seem to be more advantageous, since they make it possible to slightly increase the useful volume of the annual regulation reservoir used by such hydroelectric power plants, and at the same time the amount of energy generated by the hydroelectric power station.

If the displacement capacity of a hydroelectric power station includes reserve power, in particular, if a load reserve of the energy system is installed at the hydroelectric power station, then its value should, of course, be taken into account when determining the operating depth of the annual regulation reservoir, which is permissible under the condition of obtaining the required peak power at the hydroelectric power station.

Limitations on the drawdown depth of an annual regulation reservoir can be caused by other reasons than those noted above and which depend on the characteristics of the turbines installed at the hydroelectric power station. One of these additional reasons may be siltation of the reservoir with sediment, filling not only the dead volume determined by energy conditions, but also part of the useful volume of the reservoir. Another example of limiting the drawdown depth of a reservoir can be found in dam-diversion schemes. Such a case is shown in Fig. 6.

If the dam of such a hydroelectric power station is high enough, then the reservoir could have a very large usable volume if the maximum drawdown mark is determined on the basis of the energy calculations outlined above. In this case, the pressure diversion tunnel would have to occupy the height position shown in the dotted line in the drawing. But then, with a long tunnel length and a large slope, the internal pressure in its lower part at the connection with the turbine pipeline would be extremely large at a time when the reservoir is filled to the low level. This would require strengthening and therefore increasing the cost of the tunnel lining, which may not be economically viable. For this reason, to reduce the internal pressure in the tunnel, it has to be located higher, as shown in the drawing with solid lines. Since the ULV in the reservoir must be higher than the water intake openings of the diversion, this leads to a decrease in the useful volume of the reservoir.

Also, restrictions on the drawdown depth of an annual regulation reservoir may be caused by the operating conditions of other water consumers.

Finally, when choosing the reservoir drawdown depth, the equipment that will be installed at the hydroelectric power station should be taken into account. There is no turbine that works equally well at a head of 100 m and 50 m. In general, the ratio of the minimum pressure to the maximum turbine pressure for RO turbines is 0.6; for vertical submarines and PLDs – 0.5; for horizontal PL-0.35. This means that if you divide the minimum pressure at the selected operating depth by the maximum pressure of the proposed equipment, you should get a number no less than the indicated ones. For example, if the pressure at a hydroelectric power station at a NPL is 110 m, then when installing a RO115 turbine, the reservoir should be activated at no lower than 46 m, (115 * 0.6 = 69 m), less can be activated (and for rigid-blade turbines, the smaller the pressure fluctuations, the better), more - no.

9.2 Justification of the optimal reservoir drawdown depth

Above, we have already considered the energy characteristic or electricity generation curve for the period of emptying the reservoir, depending on the depth of the reservoir drainage.

For ease of perception, the total energy was obtained as the sum of two components: the energy of the transit runoff and the energy due to the drawdown of the reservoir.

It was noted that the value Esrab grows to a certain limit h O , after which the decrease in pressure is not compensated by an increase in the used flow and the total production decreases.

If the transit flow changes during the period of reservoir drawdown, then the position of the curve will also change. The dotted curve corresponds to a smaller value during the operation of the transit flow. Such a decrease may be a consequence of both lower water content and a shorter period of reservoir drawdown. The curve of the total energy of the hydroelectric power station also took a new position. The maximum output in this case corresponds to a different operating depth h o1 .

The curve of the total annual electricity generation of the hydroelectric power station in Fig. 1 has a similar character. 7

However, from a comparison of the two mentioned curves it is clear that the maximum annual production occurs at a lower final drawdown depth than the production during the period of emptying the reservoir. This is due to the fact that during the period of filling the reservoir, production decreases due to a decrease in both pressure and flow.

In Fig. The 7-dotted curves show the generation of hydroelectric power plants, taking into account additional generation at other hydroelectric power stations of the cascade. Taking into account the effect at the underlying stations of the cascade, the operating depth ensuring maximum output is greater.

So, each combination of initial conditions (transit flow, operation mode and duration, cascade scheme, etc.) corresponds to its own reservoir operation depth, at which the maximum values ​​of the guaranteed annual electricity generation of the hydroelectric power station will occur.

However, this operating depth cannot be definitively accepted as optimal. Analysis of the graphs presented above provides only the zone within which the optimal reservoir drawdown depth should be sought. To substantiate it, in addition to changes in energy indicators, it is necessary to take into account other consequences of the drawdown of the reservoir.

Along with an increase in output, provided and installed capacity, an increase in useful volume leads to an increase in costs. Thus, a deeper final drawdown of the reservoir is associated with a greater depth of water intake and an increase in the cost of gates and hydraulic structures. An increase in the installed capacity of the designed hydroelectric power station is also associated with additional capital investments and costs. . These are the costs of expanding the hydroelectric power station building, increasing the total power of generators, electrical parts, turbine equipment, etc.

Additional costs for turbine equipment are caused by an increase in wheel diameter or the number of turbines. Both measures are used to increase the installed power and compensate for the decrease in the available power of the turbines when the design pressure decreases due to deeper drawdown of the reservoir. With a cascade scheme for using a watercourse, an increase in the useful volume of the reservoir of the designed hydroelectric power station may lead to the feasibility of increasing the installed capacity at the lower hydroelectric power stations of the cascade. This also involves additional capital investment and costs.

Finally, with the integrated use of a watercourse, additional capital investments and costs for related activities may be required. Thus, additional capital investments caused by an increase in the depth of reservoir drawdown when moving from one option to another represent the sum

Additional costs and reduced costs are determined similarly. All economic indicators are used in calculations taking into account the time factor. Accordingly, for the option of the designed hydroelectric power station, replacement options are calculated, for which changes in capital investments, costs and expenses are also determined during the sequential transition from the previous option to the next one.

In general, the costs of the replaced options or their changes A3 replacement represent the sum of the costs (or increments) of the replaced power plants, fuel and related activities

The minus sign at the second term can occur when transitioning between options in the zone from /g 0G od To ha (Fig. 7), i.e. when, with increasing operating depth, the power continues to increase, and the annual output is already beginning to decrease.

However, it must be borne in mind that a decrease in output is not always identical to a decrease in fuel economy. The fact is that specific fuel economy b w in different seasons of the year it is different, in particular, in winter, higher than in the spring-summer period. Therefore, with an increase in production during the period of reservoir drawdown (in winter) and a decrease in it during the period of filling reservoirs, despite the general decrease in annual production, the total fuel economy may not decrease, but increase. To correctly assess this component of costs, it is obviously necessary to carry out calculations to determine fuel savings separately by season.

All indicators for the replaced options should be determined according to the full effect on the designed hydroelectric power station and other hydroelectric power stations of the cascade, taking into account the different times of its receipt and use.

The rationale for the optimal drawdown depth of the reservoir is made according to one of the following conditions:

according to the equality of cost increment when the operating depth changes by the value Δh

according to the equality of the payback period for additional capital investments of a standard value with an increase in operating time by Δh

When designing hydraulic structures with reservoirs of long-term regulation, it is necessary to additionally carry out calculations to determine the timing of its initial filling and the regime for the hydroelectric station to reach its design energy output.

The main characteristics of a reservoir are volume, surface area and changes in water levels under operating conditions. When reservoirs are created, river valleys change significantly, as well as the hydrological regime of the river within the backwater. Changes in the hydrological regime caused by the creation of reservoirs also occur in the downstream (part of the river adjacent to the dam, sluice) of hydraulic structures. Sometimes such changes are noticeable over tens or even hundreds of kilometers. One of the consequences of creating reservoirs is a reduction in floods. As a result, conditions for fish spawning and grass growth in floodplains deteriorate. When creating reservoirs, the speed of river flow also decreases, which causes siltation of reservoirs.

Krasnoyarsk Reservoir (photo by Maxim Gerasimenko)

Reservoirs are distributed unevenly across Russia: in the European part there are more than a thousand, and in the Asian part there are about a hundred. The total volume of Russian reservoirs is about one million m2. Artificial reservoirs have greatly changed the main river - and some of its tributaries. 13 reservoirs have been created on them. Their construction began in the middle of the 19th century, when a water retaining dam was built in the upper reaches of the river. Almost a hundred years later it was flooded Ivankovskoye Reservoir, which is often called the Moscow Sea. From here begins a canal connecting the river with the capital.

Rybinsk Reservoir (photo by Evgeny Gusev)

Rybinsk Reservoir The area is comparable to the largest lakes. As a result of the flooding of the wide valleys of the left tributaries of the Volga (Sheksna and Mologa), a reservoir was formed up to 60 km wide and 140 km long, replete with many bays, and.

Dam Kuibyshev Reservoir raised the water level in the Volga by 26 m and flooded the river floodplain over an area of ​​almost 6.5 thousand km2. When creating the reservoir, about 300 settlements had to be moved to a new location, and the city of Sviyazhsk turned out to be an island. Quite large storms are even possible on this reservoir (wave heights sometimes exceed 3 m).

Fifteen of the world's largest reservoirs are located in and in the Far East. Their construction took place in the second half of the last century. Dams were built mainly on high-water rivers: , Vilyue, Zeya. At the same time, relatively small areas were flooded. The length of most reservoirs in this area is significant: from 150 km ( Kolymskoye) up to 565 km ( Bratskoe). But the width is relatively small, with the exception of some areas where the water spills up to 15-33 km. After the device Baikal Reservoir A 60-kilometer section of the Angara became almost one with, and the lake level rose by a meter.

Sayano-Shushenskoye Reservoir (photo by Pavel Ivanov)

The largest reservoir is Bratskoe has a rather peculiar shape: wide reaches here are combined with long winding bays. The amplitude of level fluctuations reaches 10 m. The reservoir is of great importance for shipping and timber rafting, as well as for water supply.

Sayano-Shushenskoye Reservoir flooded the Yenisei valley for more than 300 km, but its width was small - up to 9 km. Fluctuation of levels - up to 40 m. Dam Krasnoyarsk reservoir is located on a narrow (up to 800 m wide) site in the Yenisei valley. It is notable for its unique lift. When ships approach the dam, they enter a chamber filled with water, which carries them through the dam downstream. Vessels going upstream have to be raised to a height of one hundred meters for this purpose.

The created reservoirs made it possible to improve the quality of municipal and industrial water supply in large cities and large cities. The parameters of the country's reservoirs vary widely: the total volume is from 1 to 169 million m2. The area of ​​the water surface is from 0.2 - 0.5 to 5900 km2. Length, width, maximum and average depths differ significantly. The maximum length of large plain and plateau reservoirs reaches 400 - 565 km, mountain reservoirs 100 - 110 km, and width - up to several tens of kilometers. The deepest reservoirs from 200 - 300 m are located in the valleys of large mountain rivers (Ingurskoye, Chirkeyskoye) to 70 - 105 m - in plateau and foothill areas (Bratskoye, Krasnoyarskoye, Boguchanskoye, Bukhtarminskoye). In large lowland reservoirs, depths do not exceed 20 - 30 m.

Reservoirs of Russia

The largest reservoirs in Russia

- artificial reservoirs, created, as a rule, in river valleys for the accumulation and storage of water for use in the national economy.

Reservoirs have similarities with and: with the first - in appearance and slow water exchange, with the second - in the progressive nature of water movement. At the same time, they also have their own distinctive features:

• Reservoirs experience significantly greater fluctuations in water levels throughout the year than rivers and lakes, which are associated with artificial regulation of flow - accumulation and discharge of water;
• water flow leads to less heating of water than in lakes;
• small reservoirs freeze earlier, and large ones - later than rivers, but both open later than rivers;
• the mineralization of reservoir waters is greater than that of rivers, etc.

People began to build the first reservoirs that served to irrigate fields even before our era in the valleys of the Nile, Tigris and Euphrates, Indus, Yangtze, etc. In the Middle Ages, reservoirs were no longer only in Asia and Africa, but also in Europe and America. In modern times, reservoirs began to be used not only for irrigation, but also for industrial water supply and for the development of river transport. In modern times, another function of reservoirs has been to generate electricity.

A huge number of reservoirs were built after. From that time until today, their number around the world has increased fivefold. It was during this period that the largest reservoirs in the world were created. Reservoir creation peaked in most regions of the world in the 1960s, followed by a gradual decline.

Currently, more than 60 thousand reservoirs are in operation around the globe.

The main parameters of reservoirs are the surface area, water volume, depth and amplitude of fluctuations in water levels under operating conditions.

The area of ​​the water surface of all reservoirs in the world is 400 thousand km 2. The Victoria Reservoir (Owen-Fole) in East Africa (Uganda) is considered the largest in terms of surface area. It also includes Lake Victoria (68,000 km 2), the level of which rose by 3 m as a result of the construction of the Owen-Fole dam on the Victoria Nile River in 1954. The second place is occupied by the Volta Reservoir, located in the Republic of Ghana (West Africa). Its mirror area is 8482 km2.

The length of some of the largest reservoirs reaches 500 km, width - 60 km, maximum depth - 300 m. The deepest reservoir in the world is Boulder Dam on the river. Colorado (average depth 61 m).

The total volume of the world's reservoirs is 6,600 km 3 , and the useful volume, that is, suitable for use, is 3,000 km . 95% of the water in reservoirs comes from reservoirs with a volume of more than 0.1 km 3 . The largest reservoir in terms of water volume is also the Victoria Reservoir (204.8 km 3). The Bratsk Reservoir, located on the Angara River, follows it (169.3 km 3).

Based on the volume of water and the area of ​​the water surface, reservoirs are divided into large, very large, large, medium, small and small.

The largest reservoirs have a total water volume of more than 500 km 3 . There are 15 of them in total. They are found in all regions of the world except Australia.

According to their genesis, reservoirs are divided into valley-river, lake, located at groundwater outlets, in river estuaries.

For reservoirs lake type(for example, Rybinsk) is characterized by the formation of water masses that are significantly different in their physical properties from the properties of tributary waters. Currents in these reservoirs are most associated with winds. Valley-river reservoirs (for example, Dubossary) have an elongated shape, the currents in them, as a rule, are runoff; The water mass is close in its characteristics to river waters.

Purpose of reservoirs

For a specific purpose, reservoir waters can be used for irrigation, water supply, hydropower generation, navigation, recreation, etc. Moreover, they can be created for a single purpose or for a set of purposes.

More than 40% of reservoirs are concentrated in the temperate zone of the Northern Hemisphere, where most economically developed countries are located. A significant number of reservoirs are also located in the subtropical zone, where their creation is associated primarily with the need for land irrigation. Within the tropical, subequatorial and equatorial zones, the number of reservoirs is relatively small, but since large and largest ones predominate among them, their share in the total volume of all reservoirs is more than 1/3.

The economic importance of reservoirs is great. They regulate flow, reducing flooding and maintaining proper river levels throughout the rest of the year. Thanks to a cascade of reservoirs on rivers, unified deep-water transport routes are created. Reservoirs are areas for recreation, fishing, fish farming, and waterfowl breeding.

But along with the positive significance of the reservoir, they cause undesirable but inevitable consequences: flooding of lands above the dam, especially rich floodplain meadows; flooding and even waterlogging of lands above the dam in the zone of influence of reservoirs due to rising groundwater levels; drainage of lands below the dam; deterioration of water quality in reservoirs due to a decrease in self-purifying ability and excessive development of blue-green algae; Reservoir dams prevent fish from spawning, causing damage to fisheries, etc.

At the same time, the construction of reservoirs causes irreparable harm to nature: flooding and underwatering of fertile lands, swamping of adjacent territories, processing of banks, dehydration of floodplain lands, changes in microclimate, genetic migration routes of fish in rivers are interrupted, etc. In addition, their construction in flat areas is associated with deforestation and the need to resettle many thousands of people. Of course, we are talking more about large reservoirs here.

The construction of reservoirs is, in fact, the most important way for humanity to survive on our planet. The role of reservoirs at all times has been enormous: from storing water for domestic needs, irrigating farmland, fighting floods in ancient times to generating electricity today. Man built the first reservoirs more than 3 thousand years ago in Ancient Egypt, Mesopotamia and China. Later, such structures began to be erected in India, Iran, and Syria.

We present a selection of the world's five largest hydroelectric reservoirs. Enjoy the views!

1. Victoria, b. Neil (Uganda, Owen Falls hydroelectric station)
   Total volume: 205 km 3
   Area: 76,000 km2 (comparable to the area of ​​a country such as the Republic of Panama)
   Length: 320 km
   Width: 275 km
   Maximum depth: 83 m
   Dam height: 31 m
   Year of construction start: 1947
   Year completed: 1954
2. Bratskoye, r. Angara (Russia, HPP "Bratskaya")
   Total volume: 169 km 3
   Area: 5470 km 2
   Length: 570 km (equal to the distance between the two European capitals Prague and Budapest)
   Width: 25 km
   Maximum depth: 150 m
   Dam height: 124.5
   Year of construction start: 1955
   

   

3. Kariba, b. Zambezi (Zambia, Zimbabwe, Kariba hydroelectric station)
   Total volume: 160 km 3
   Area: 4450 km 2
   Length: 220 km
   Width: 40 km
   Maximum depth: 78 m
   Dam height: 126 (this is the height of four nine-story buildings)
   Year of construction start: 1957
   Year completed: 1963

   

4. Nasser, b. Nile (Egypt, Sudan, Aswan hydroelectric complex)
   Total volume: 157 km 3
   Area: 5120 km 2
   Length: 550 km
   Width: 35 km
   Maximum depth: 130 m (this is ten times the depth of the Sea of ​​Azov at its lowest point)
   Dam height: 111 m
   Year of construction start: 1960
   Year completed: 1970

   

5. Volta, b. Volta (Ghana, Akosombo hydroelectric station)
   Total volume: 147 km 3
   Area: 8500 km2 (occupies almost 4% of Ghana)
   Length: 400 km
   Maximum depth: 80 m
   Dam height: 111 m
   Year of construction start: 1961
   Year completed: 1967

   

It is interesting that the next largest five reservoirs are located in Russia: Krasnoyarsk, Zeyskoye, Ust-Ilimskoye, Kuibyshevskoye, Baikalskoye (Irkutskoye).