1. General questions

1.1 Describe the water resources of the Earth

1.2 Describe the interactions between flow, channel and transport facilities

1.3 Name the main hydrological characteristics of water flows and methods for their determination

1.4 Describe sediment movements and channel processes

1.5 Describe the methods of engineering hydrometric surveys on watercourses

2. Questions on the option (Option No. 3)

3. Tasks according to the option (Option No. 10)

Literature

Appendix No. 1 20

1. General issues

water flow channel calculation

1.1 Describe the water resources of the Earth

Water resources of the Earth are waters suitable for practical use. These include almost all water the globe- river, lake water, sea, underground, soil moisture, ice of mountain glaciers and polar "caps", as well as atmospheric water vapor - the only exception is water that is physically or chemically associated with minerals or biomass.

However, from the point of view of water supply, water resources should include only those natural waters that can be used at a given level of technological development in a specific state of a water source. The most valuable for the economy and human needs are the fresh waters of the land.

In practice, water resources are called reserves of surface and groundwater of any territory.

Water resources are distributed over the Earth's surface very unevenly - for example, the largest number fresh water have South America and Australia; At the same time, the densely populated countries of Asia with significant development potential are experiencing an increasingly acute shortage of fresh and, especially, potable water. Fresh water reserves on Earth are estimated at 35 million km 3, which is no more than 2.5% of the total water reserves on Earth; at the same time, fresh waters of rivers, the most widely used in human activities, account for only 0.006% of all water reserves.

Since ancient times, various methods of artificial regulation of river flow have been used to meet the economic needs of a person, such as the construction of dams and the creation of reservoirs; construction of artificial reservoirs (ponds and lakes) filled during the period of high water and spring snowmelt, etc. However, this is often associated with various negative phenomena - flooding and withdrawal from economic activity large areas, deterioration of water quality, clogging and swamping of the banks of reservoirs and small rivers, pollution of rivers and the death of a significant part of the aquatic fauna.

The total total capacity of the operated reservoirs of the world is about 5000 km 3 (useful volume is 2000 km 3). This is approximately equal to 11% of the annual runoff from the land surface. The volume (capacity) of water in the reservoir, concluded between the minimum and maximum levels of water during normal operating conditions is called the usable volume.

In second place in terms of intensity of use are groundwater, and in third place are the waters of lakes containing more than 0.25% of the Earth's water reserves. The main volume of water (1338 km 3, or 96.5%) is contained in the World Ocean, which occupies more than 71% of the globe, but it is salty and unsuitable for most economic and technological processes. To use it, it must be desalinated.

To study the water resources of individual states and global water resources, streamline information about them and prevent their irrational use, a set of water accounting data on quantitative and qualitative indicators has been created and is regularly updated - the so-called water cadastre; for use in science, construction, and other types of economic activity, catalogs of water resources, methodological and regulatory publications are published.

1.2 Describe the interaction of flow, channel and transport facilities

The set of processes of interaction between the water flow and the channel is called the channel process. At each moment of time, the speed and direction of the flow of water is determined by the shape of the channel; under the conditions of an eroded channel (if the velocities are higher than the erosive ones), a change in shape occurs, the channel deepens - the flow cross section increases, and the velocity decreases. If the velocities are lower than the erosive ones, sedimentation occurs, the channel becomes shallow and the velocity increases.

IN vivo the channel process depends on the flow of water and its change over time, the flow and size of sediments, is determined by the relief, structure and location of geological layers, and the presence of vegetation. Under the influence of human economic activity, channel processes change - as a rule, during the construction of transport or hydraulic structures, the living section of the river narrows, the depths change in certain sections of the alignment, and the roughness of the banks also changes. As a result of these changes, channel deformations occur.

When the flow is constrained under bridges, the intensity of the channel process and the development of deformations depend on the degree of such constraint. The most dangerous deformations should be recognized as local erosion near the bridge supports and regulatory structures, which violate their stability. To prevent the development of undesirable deformations, it is necessary to study the natural channel processes of the river and provide for the least possible restriction of the flow and displacement of the existing channel during construction. This is the main task of hydrological research.

When designing bridges, their openings should, as a rule, be no less than the width of the channel under the bridge, and take into account the possibility of channel displacement within the bridge opening and its approach to the abutments. The depth of the foundations of the supports should be calculated from the maximum values ​​​​of the household depth at the support; and under unfavorable conditions, it should be assigned more than is required only under the conditions of erosion.

For calculation maximum depths local erosion, a number of techniques have been developed and are described in the regulatory literature. Often, in order to reduce the cost and speed up construction, it is necessary to reduce the required depth of foundations - in this case, various regulatory structures are designed that reduce the intensity of the channel process, and sometimes they also give the supports specific streamlined outlines. The method of combating unwanted deformations of the channel is selected based on the characteristics of the soils that make up the channel and the water flow. In this case, it should be taken into account that downstream of the bridge, an alluvium from the soil carried out from the section of the channel constrained by the bridge will form. Such alluvium causes shallowing of the channel, can threaten navigation and adversely affect the ecosystem of the river.

1.3 Name the main hydrological characteristics of water flows and methods for their determination

The main hydrological characteristics of water flows are: current velocities, slopes; water flow rates, dependence of levels on flow rates; area, depth and width of the channel and floodplain depending on water levels; as well as the trajectories of jets, ice floes, ships and caravans.

Methods for determining the characteristics of flows are different depending on which characteristic is being determined. Thus, levels and slopes are determined by direct or remote observation at water-measuring posts, flow rates - by special devices (turntables) or floats of various designs, flow trajectories - also by observation of floats, ice floes or other objects floating in the stream. Observation can be carried out with the help of geodetic instruments.

The depths of the stream are found by immersing lots in water at various points in the channel, or using acoustic equipment (echo sounders). Other geometric characteristics are obtained by direct measurement with a surveying instrument.

To determine the flow rate, an analytical or graphic methods, having previously determined the speeds and depths on the verticals in the design range. The speed of the water flow is measured with turntables from a rod if the depth is less than 3 m or with a cable with a load.

1.4 Describe sediment movements and channel processes

River sediments are called solid mineral particles, regardless of size, carried by the flow of water and forming deposits under certain conditions. The intensity of the formation, transport and deposition of sediments depends on the energy of the flowing water and the nature of the rocks that make up the channel. At the same time, erosion is most often observed in the upper reaches of the rivers, and deposition (accumulation) is observed in the lower reaches.

Sediment can be divided according to the nature of their movement and sedimentation into bottom and suspended. Bottom sediments are the largest particles that move without separation from the bottom (drawn) or with a separation for a short time (semi-suspended). Such sediments are relief-forming and largely form the stream bed.

Suspended sediments - a set of the smallest particles of soil that are in suspension for a long time and move at a speed close to the speed of the current. The highest concentration of these particles is observed in the bottom layer. The degree of saturation of water with sediment particles is determined by the turbidity of the water, kg/m 3 (concentration). This indicator depends on the energy of the flow and varies significantly both along the length of the river, and along the width and vertically.

Knowing the distribution of water turbidity and flow velocity in any section, it is possible to determine the sediment flow, that is, the amount of sediment carried by flows per unit time; as well as the transporting capacity of the flow - the amount of transported sediments of a certain grain composition without bottom deformations. Thus, the transport capacity of the flow is equal to the maximum flow rate of sediments, at which their settling and weighing are balanced, and the average turbidity of the flow is constant.

With relatively large particle sizes and a significant flow velocity, mass sediment movement along the bottom begins, and so-called microforms are formed - asymmetric formations similar to ripples on the water surface. They can be with short curvilinear ridges (rifles) or with long straight ones (flat ridges). Their formation is due to the appearance of vortex zones in the flow behind random bottom irregularities, which cause rarefaction and the appearance of lift on the bottom surface. Bottom soil particles rise and form a micro-ridge, which causes a further increase in the lifting force and the development of unevenness, some suspended particles are transferred below the primary corrugation and form a new unevenness. The process can be clearly observed on the sandbar at low flow rates. With an increase in speed, the dimensions of the corrugations grow, the vortex zones increase, and mass weighing of particles begins, which leads to the formation of flat ridges.

Looking at our planet from above outer space, immediately suggests a comparison with a blue ball, which is completely covered with water. The continents at this time seem like small islands in this endless ocean. This is quite natural, because water occupies 79.8% of the entire surface, and 29.2% falls on land. The water shell of the Earth is called the hydrosphere, its volume is 1.4 billion m 3.

Water resources and their purpose

Water resources- it is suitable for use in the economy of the water of rivers, lakes, canals, reservoirs, seas and oceans. This also includes groundwater, soil moisture, swamps, glaciers, and atmospheric water vapor.

Water arose on the planet about 3.5 billion years ago and initially it had the form of vapors that were released during the degassing of the mantle. Today, water is the most important element in the Earth's biosphere, because nothing can replace it. However, recently, water resources have ceased to be considered limited, because scientists have managed to desalinate salt water.

Purpose of water resources- support the vital activity of all life on Earth (human, plants and animals). Water is the basis of all living things and the main supplier of oxygen in the process of photosynthesis. Water also takes part in climate formation - taking heat from the atmosphere in order to give it away in the future, thereby regulating climatic processes.

We should also remember that water sources play an honorable role in the modification of our planet. People have always settled near reservoirs or water sources. Thus, water promotes communication. There is a hypothesis among scientists that if there were no water on Earth, the discovery of America would be postponed by several centuries. And Australia would still be unknown today.

Types of water resources

As already said water resources is all the water on the planet. But on the other hand, water is the most common and most specific compound on Earth, because only it can exist in three states (liquid, gaseous and solid).

The earth's water resources are made up of:

• surface water(oceans, seas, lakes, rivers, swamps) is the most valuable source of fresh water, but the thing is that these objects are distributed quite unevenly over the Earth's surface. So, in the equatorial zone, as well as in the northern part of the temperate zone, water is in excess (25 thousand m 3 per year per person). And the tropical continents, which consist of 1/3 of the land, are very acutely aware of the shortage of water reserves. Based on this situation, their agriculture develops only under the condition of artificial irrigation;
• groundwater;
• reservoirs created artificially by man;
• glaciers and snowfields (frozen water of the glaciers of Antarctica, the Arctic and snowy mountain peaks). It contains the largest part of fresh water. However, these reserves are practically inaccessible for use. If all the glaciers are distributed over the Earth, then this ice will cover the earth with a ball 53 cm high, and having melted it, we thereby raise the level of the World Ocean by 64 meters;
• moisture what is found in plants and animals;
• vapor state of the atmosphere.

Water consumption

The total volume of the hydrosphere is striking in its quantity, however, only 2% of this figure is fresh water, moreover, only 0.3% is available for use. Scientists have calculated the fresh water resources that are necessary for all mankind, animals and plants. It turns out that the supply of water resources on the planet is only 2.5% of the water of the required volume.

Around the world, about 5 thousand m 3 are consumed annually, while more than half of the water consumed is irretrievably lost. In percentage terms, the consumption of water resources will have the following characteristics:

• agriculture - 63%;

• industrial water consumption - 27% of the total;

• household needs take 6%;
• reservoirs consume 4%.

Few people know that it takes 10,000 tons of water to grow 1 ton of cotton, 1,500 tons of water to grow 1 ton of wheat, 250 tons of water to produce 1 ton of steel, and 1 ton of paper requires at least 236,000 tons of water.

A person per day should consume at least 2.5 liters of water, but on average this person spends in major city not less than 360 liters per day, since this figure includes all kinds of water use, including watering the streets, washing vehicles and even fire fighting.

But the consumption of water resources does not end there. This is evidenced, for example, by water transport or the process of breeding both marine and fresh fish. Moreover, for breeding fish, you will need exceptionally clean water, saturated with oxygen and without the content of harmful impurities.

A huge example of the use of water resources are recreational areas. There is no such person who would not like to relax by the pond, relax, swim. In the world, almost 90% of recreational areas are located near water bodies.

The need to protect water resources

Considering the current situation, we can conclude that water requires a careful attitude towards itself. Currently, there are two ways to save water resources:

• reduce fresh water consumption;
• creation of modern collectors of high quality.

The conservation of water in reservoirs limits its flow into the world's oceans. Storing water underground helps prevent evaporation. The construction of canals can easily solve the problem of water delivery without its penetration into the ground. Humanity is also thinking about the latest methods of irrigating agricultural land, allowing to moisten the territory using wastewater.

But each of the above ways actually affects the biosphere. The system of reservoirs, for example, does not allow the formation of fertile silt deposits, channels interfere with the replenishment of groundwater. Therefore, today one of the most effective ways save water resources is wastewater treatment. Science does not stand still in this regard, and various methods allow to neutralize or remove up to 96% of harmful substances.

The problem of water pollution

Population growth, the rise of production and agriculture ... These factors contributed to the shortage of fresh water. In addition to everything, the share of polluted water resources is also growing.

Main sources of pollution:

• industrial effluents;
• sewage from utility lines;
• plums from the fields (meaning when they are oversaturated with chemicals and fertilizers;
• disposal of radioactive substances near water bodies;
• effluents coming from livestock complexes (water is characterized by an excess of biogenic organic matter);
• shipping.

Nature provides for the self-purification of water bodies. This happens due to the presence of plankton in the water, the ingress of ultraviolet rays into the water, and the settling of insoluble particles. But unfortunately, pollution is much greater and nature alone is not able to cope with such a mass of harmful substances that man and his activities provide to water resources.

Extraordinary sources of drinking water

Recently, mankind has thought about how to use non-traditional sources of water resources. Here are the main ones:

• tow icebergs from the Arctic or Antarctica;
• carry out desalination of sea waters (actively used at the moment);
• condense the water of the atmosphere.

In order to obtain fresh water by desalination of salt water, desalination stations are installed on ships. In the whole world, there are already about a hundred such units. The world's largest producer of such water is Kuwait.

Fresh water has recently acquired the status of a world commodity, it is transported in tankers using long-distance water pipelines. This scheme has been successful in the following areas:

• the Netherlands receives water from Norway;
• Saudi Arabia receives a resource from the Philippines;
• Singapore imports from Malaysia;
• water is pumped from Greenland and Antarctica to Europe;
• The Amazon transports drinking water to Africa.

One of the latest achievements is installations with the help of which the heat from nuclear reactors is used simultaneously for desalination sea ​​water and electricity generation. At the same time, the price of one liter of water costs a little, since the productivity of such installations is quite large. Water that has passed through this path is recommended to be used for irrigation.

Reservoirs can also help overcome fresh water scarcity by regulating river flow. In total, more than 30 thousand reservoirs have been built in the world. In most countries, there are projects for the redistribution of river flow through its transfer. But, the largest such programs have been rejected due to environmental considerations.

Water resources of the Russian Federation

Our country has a unique water resource potential. However, their main drawback is their extreme uneven distribution. So, if we compare the Southern and Far Eastern federal districts Russia, they differ from each other by 30 times in terms of the size of local water resources, and 100 times in terms of water supply.

Rivers of Russia

Thinking about the water resources of Russia, first of all, it should be noted the rivers. Their volume is 4,270 km3. There are 4 water basins on the territory of Russia:

• the seas of the Arctic and Arctic Oceans, as well as the large rivers flowing into them (Northern Dvina, Pechora, Ob, Yenisei, Lena, Kolyma);
• the seas of the Pacific Ocean (Amur and Anadyr);
• seas Atlantic Ocean(Don, Kuban, Neva);
• the internal basin of the Caspian Sea and the flowing Volga and Ural.

Since in the central regions the population density is greater than, for example, in Siberia, this leads to the disappearance of small rivers and water pollution in general.

Lakes and swamps of Russia

Half of all fresh water in the country falls on lakes. Their number in the country is approximately 2 million. Of these, large:

• Baikal;
• Ladoga;
• Onega;
• Taimyr;
• Khanka;
• Vats;
• Ilmen;
• White.

A special position should be given to Lake Baikal, because 90% of our fresh water reserves are concentrated in it. In addition to being the deepest lake on earth, it is also characterized by a unique ecosystem. Baikal is also included in the UNESCO list of natural heritage.

The lakes of the Russian Federation are used for irrigation and as sources for water supply. Some of the listed lakes have a decent supply of therapeutic mud and therefore they are used for recreation purposes. As well as for rivers, lakes are characterized by their uneven distribution. They are mainly concentrated in the North-Western part of the country (Kola Peninsula and the Republic of Karelia), the Ural region, Siberia and Transbaikalia.

The swamps of Russia also play an important role, although many people treat them disrespectfully, draining them. Such actions lead to the death of entire huge ecosystems, and as a result of this, rivers do not have the opportunity to cleanse themselves naturally. The swamps also feed the rivers, act as their controlled object during floods and floods. And of course, swamps are a source of peat reserves.

These elements of water resources are distributed in the North-West and North-Central parts of Siberia, the total area of ​​swamps in Russia is 1.4 million km2.

As you can see, Russia has a large water resource potential, but we should not forget about the balanced use of this resource, treat it with care, because anthropogenic factors and huge consumption lead to pollution and depletion of water resources.

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Despite the fact that about 70% of the earth's surface is covered with water, it is still a very valuable resource. Especially when it comes to quality. What is water resources? What is their structure and world reserves? What are the most pressing water resource issues today? All this will be discussed in the article.

What is water resources?

Geographic, as you know, consists of five spheres: litho-, atmo-, bio-, techno- and hydrospheres. What is water resources? This is all the water that is contained in the hydrosphere. It is found in oceans and seas, lakes and rivers, glaciers and reservoirs, in the soil and in the air (in the form of water vapor).

About 70% of the earth's surface is covered with water. Only 2.5% of this volume is fresh water, which humanity needs. IN absolute values- this is at least 30 million cubic kilometers, which is thousands of times higher than the needs of world civilization. However, one should not forget that the main part of these reserves is contained in the "ice shells" of the Antarctic, the Arctic and Greenland. In addition, the state of water resources available to man is often unsatisfactory.

Structure of planetary water resources

The water resources of the planet are divided into two classes:

• waters of the oceans;
• land (or surface) waters.

Rivers, lakes, reservoirs and glaciers hold only four percent of the world's waters. Moreover, most of them (in terms of volume) are confined to glaciers. And the largest "reservoir" of fresh water on the planet is Antarctica. Underground flows are also classified as water resources of the Earth, but their quantitative estimates vary greatly in numbers.

Pure - the most valuable for humans and any other living organisms. Its protection and rational use is one of the critical tasks humanity on present stage.

Renewal of water resources

Features of water resources are the possibility of self-purification and renewal. However, the renewability of water depends on several factors, in particular, on the type of hydrological object.

So, for example, water in rivers is completely renewed in about two weeks, in a swamp - in five years, and in a lake - in 15-17 years. This process takes the longest time in ice sheets (on average, it takes 10 thousand years), and as quickly as possible - in the biosphere. In a living organism, water goes through a full cycle of renewal in a few hours.

Distribution of water resources by macro-regions and countries

In terms of total water resources in the world, the Asian region is the leader. It is followed by South America, North America and Europe. The poorest corner of the planet in terms of water resources is Australia.

However, there is one important nuance here. So, if we calculate the volume of water reserves per capita of the mainland or part of the world, then a completely different picture emerges. Australia ranks first in this calculation, while Asia is in last place. The fact is that in Asia the population is growing at a rapid pace. Today it has already reached the milestone of four billion people.

Which countries can not worry about water? Below is the top five countries with the largest reserves of fresh water. This:

1. Brazil (6950 km 3).
2. Russia (4500 km 3).
3. Canada (2900 km 3).
4. China (2800 km 3).
5. Indonesia (2530 km 3).

It is worth noting the uneven distribution of water resources on Earth. So, in the equatorial and temperate climatic zones, they are even in abundance. But in the so-called "arid" (tropical and subtropical climate), the population experiences an acute shortage of life-giving moisture.

Water resources and people

Water is in demand in everyday life, energy, industry, and recreation. Using this resource may be accompanied by retrieving it from natural source(for example, from the riverbed) or pass without it (for example, for the operation of water transport).

The largest consumers of water resources are:

• Agriculture;
• industrial and energy enterprises;
• communal area.

Domestic water consumption is constantly growing. According to environmentalists, in large metropolitan areas of economically developed countries, one person uses at least 300 liters of liquid daily. Such a level of consumption may lead to a shortage of this resource in the near future.

Pollution and depletion of world waters

Pollution of water resources is very acute. To date, it has reached catastrophic levels in some regions of the planet.

Every year, millions of tons of chemicals, oil and oil products, phosphorus compounds, and municipal solid waste enter the World Ocean. The latter form huge out of debris. The waters of the Persian Gulf, Northern and caribbean very oily. Already about 3% of the surface of the North Atlantic is covered with an oil film, which has a detrimental effect on the living organisms of the ocean.

A big problem is also the reduction of the planet's water resources. However, the deterioration of the quality of life-giving moisture is no less dangerous. After all, one cubic meter of untreated sewage can fall into the natural riverbed and spoil tens of cubic meters of clean water.

In the developing countries of the world, according to statistics, every third inhabitant suffers from poor-quality drinking water. She serves main reason many diseases of the population of the "arid belt" of Africa and Latin America.

Main types and sources of pollution of world waters

In ecology, water pollution is understood as the excess of the maximum permissible concentrations of substances contained in them (harmful chemical compounds). There is also such a thing as the depletion of water resources - the deterioration of water quality under constant activity.

There are three main types of water pollution:

• chemical;
• biological;
• thermal;
• radiation.

Any substance that enters a hydrological object as a result of human activity can act as a pollutant. At the same time, this substance significantly worsens natural qualities water. One of the most dangerous modern pollutants is oil, as well as products from it.

Sources of pollution can be permanent, periodic or seasonal. They can be of both anthropogenic and natural origin, be point, linear or areal.

The largest source of pollution are the so-called That is, those that are formed as a result of industrial, construction or municipal human activities. They are usually oversaturated with harmful organic and inorganic substances, heavy metals and microorganisms. There are industrial (including mine), municipal, agricultural and other types of wastewater.

Characteristics of Russia's water resources

Russia is one of the countries in the world that does not experience water shortages. The modern water resources of the country are 2.5 million rivers and streams, about two million lakes and hundreds of thousands of swamps. The territory of Russia is washed by twelve seas. A huge amount of fresh water is stored in glaciers (mountain and subpolar).

To improve water supply on the territory of our state, thousands of reservoirs of various sizes have been created. In general, they contain about 800 km 3 of fresh water. These objects not only serve as artificial reservoirs of a valuable natural resource, but also regulate the regime of rivers, prevent floods and floods. Thus, their importance cannot be overestimated.

Among the main problems of water resources in Russia, the following should be highlighted:

• irrational water use;
• deterioration in the quality of drinking water;
• unsatisfactory condition of hydroelectric facilities and hydraulic structures.

Finally...

What is water resources? This is all the water that is contained in the hydrosphere. The countries with the largest reserves of water resources are Brazil, Russia, Canada, China, Indonesia and the USA.

In modern realities, the problem of pollution and irrational use of world waters is becoming very relevant, and in some regions it is especially acute. Its solution is impossible without the consolidation of the efforts of all countries of the planet and the effective implementation of joint global projects.

Message on the topic

Earth's water resources

students

Ι course group 251(b)

Sazonova Daria

Kazan 2006.

1. general characteristics water resources

2. Water balance of the Earth

3. Hydrosphere as a natural system

4. World Ocean

5. Land waters

6. Water management

7. Sources of water pollution

8. Measures for the protection and economical use of water resources

9. International Decade: "Water for Life".

1. General characteristics of water resources.

The water shell of the globe - oceans, seas, rivers, lakes - is called the hydrosphere. It covers 70.8% of the earth's surface. The volume of the hydrosphere reaches 1370.3 mln. rivers, swamps and lakes.

The aquatic environment includes surface and ground waters. Surface waters are mainly concentrated in the ocean, with a content of 1 billion 338 million km3 - about 98% of all water on Earth. The surface of the ocean (water area) is 361 million km2. It is approximately 2.4 times larger than the land area of ​​the territory, which occupies 149 million km2. The water in the ocean is salty, and most of it (more than 1 billion km3) maintains a constant salinity of about 3.5% and a temperature of approximately 3.7° C. Noticeable differences in salinity and temperature are observed almost exclusively in the surface water layer, as well as in the marginal and especially in the Mediterranean seas. The content of dissolved oxygen in water decreases significantly at a depth of 50-60 meters.

Groundwater can be saline, brackish (lower salinity) and fresh; existing geothermal waters have an elevated temperature (more than 30 ° WITH.). For the production activities of mankind and its household needs, fresh water is required, the amount of which is only 2.7% of the total volume of water on Earth, and a very small share of it (only 0.36%) is available in places that are easily accessible for extraction. Most of the fresh water is found in snows and freshwater icebergs found in areas mostly in the Antarctic Circle. The annual global freshwater river runoff is 37.3 thousand km3. In addition, a part of groundwater equal to 13 thousand km3 can be used. Unfortunately, most of the river flow in Russia, amounting to about 5000 km3, falls on the marginal and sparsely populated northern territories. In the absence of fresh water, salty surface or underground water is used, producing its desalination or hyperfiltration: it is passed under a large pressure drop through polymer membranes with microscopic holes that trap salt molecules. Both of these processes are very energy intensive, therefore, the proposal is of interest, which consists in using freshwater icebergs (or parts of them) as a source of fresh water, which for this purpose are towed along the water to shores that do not have fresh water, where they organize their melting. According to the preliminary calculations of the developers of this proposal, the production of fresh water will be about half as energy-intensive as compared to desalination and hyperfiltration. An important circumstance inherent in the aquatic environment is that infectious diseases are mainly transmitted through it (approximately 80% of all diseases). However, some of them, such as whooping cough, chickenpox, tuberculosis, are transmitted through the air. To combat the spread of disease through the aquatic environment, the World Health Organization (WHO) has declared the current decade the decade of drinking water.

2. The water balance of the earth.

To imagine how much water is involved in the cycle, we characterize the various parts of the hydrosphere. More than 94% of it is the oceans. The other part (4%) is groundwater. At the same time, it should be taken into account that most of them belong to deep brines, and fresh waters make up 1/15 of the share. The volume of ice of polar glaciers is also significant: in terms of water, it reaches 24 million km, or 1.6% of the volume of the hydrosphere. Lake water is 100 times less - 230 thousand km., And the riverbeds contain only 1200 m. of Water, or 0.0001% of the entire hydrosphere. However, despite the small volume of water, rivers play a very important role: they, like groundwater, satisfy a significant part of the needs of the population, industry and irrigated agriculture. There is quite a lot of water on Earth. The hydrosphere makes up about 1/4180 of the mass of our planet. However, the share of fresh water, excluding water bound in polar glaciers, accounts for a little more than 2 million km, or only 0.15% of the total volume of the hydrosphere.

3. Hydrosphere as a natural system

The hydrosphere is a discontinuous water shell of the Earth, a combination of seas, oceans, continental waters (including groundwater) and ice sheets. Seas and oceans occupy about 71% of the earth's surface, they contain about 96.5% of the total volume of the hydrosphere. The total area of ​​all inland water bodies of land is less than 3% of its area. Glaciers account for 1.6% of water reserves in the hydrosphere, and their area is about 10% of the area of ​​the continents.

The most important property of the hydrosphere is the unity of all types of natural waters (the World Ocean, land waters, water vapor in the atmosphere, groundwater), which is carried out in the process of the water cycle in nature. The driving forces of this global process are the thermal energy of the Sun coming to the Earth's surface and the force of gravity, which ensures the movement and renewal of natural waters of all kinds.

Under the influence of solar heat, water in nature makes a continuous cycle. Water vapor, which is lighter than air, rises to the upper layer of the atmosphere, condenses into tiny droplets, forming clouds of which water returns to the earth's surface in the form of precipitation, rain, snow. The water that falls on the surface of the globe is partly

directly into natural water bodies, partially collected in the upper layer

soils, forming surface and groundwater.

Evaporation from the surface of the World Ocean and from the land surface is the initial link in the water cycle in nature, ensuring not only the renewal of its most valuable component - fresh water on land, but also their high quality. An indicator of the activity of natural water exchange is the high rate of their renewal, although various natural waters are renewed (replaced) at different rates. The most mobile agent of the hydrosphere is river waters, the renewal period of which is 10-14 days.

The predominant part of the hydrospheric waters is concentrated in the World Ocean. The world ocean is the main closing link of the water cycle in nature. It releases most of the evaporating moisture into the atmosphere. The aquatic organisms that inhabit the surface layer of the World Ocean provide the return to the atmosphere of a significant part of the free oxygen of the planet.

The huge volume of the World Ocean testifies to the inexhaustibility of the planet's natural resources. In addition, the World Ocean is a collector of land river waters, annually receiving about 39 thousand m3 of water. The pollution of the World Ocean, which has been outlined in some areas, threatens to disrupt the natural process of moisture circulation in its most critical link - evaporation from the surface of the ocean.

4. World Ocean.

The average depth of the World Ocean is 3700 m, the greatest is 11022 m (Marian Trench). The volume of waters of the World Ocean, as mentioned above, cubic meters. km.

Almost all substances known on Earth are dissolved in sea water, but in different quantities. Most of them are difficult to detect due to their low content. The main part of salts dissolved in sea water is chlorides (89%) and sulfates (almost 11%), much less carbonates (0.5%). Salt ( NaCl) gives water a salty taste, magnesium salts (MqCl) - bitter. The total amount of all salts dissolved in water is called salinity. It is measured in thousandths - ppm (% o).

The average salinity of the World Ocean is about 35% o.

The salinity of water in the ocean depends primarily on the ratio of precipitation and evaporation. Reduce the salinity of river waters and waters of melting ice. In the open ocean, the distribution of salinity in the surface layers of water (up to 1500 m) has a zonal character. In the equatorial zone, where there is a lot of precipitation, it is lower, in tropical latitudes it is higher.

Inland seas differ markedly in salinity. The salinity of the water in the Baltic Sea is up to 11%o, in the Black Sea - up to 19%o, and in the Red - up to 42%o. This is explained by the different ratio of the inflow (atmospheric precipitation, river runoff) and consumption (evaporation) of fresh water, i.e., climatic conditions. Ocean - heat regulator

The highest temperature at the surface of the water in the Pacific Ocean is 19.4 ° C; The Indian Ocean has 17.3 °C; Atlantic - 16.5 ° С. With such average temperatures, the water in the Persian Gulf regularly heats up to 35 °C. The water temperature tends to decrease with depth. Although there are exceptions due to the rise of deep warm waters. An example is the western part of the Arctic Ocean, where the Gulf Stream invades. At a depth of 2 km throughout the entire water area of ​​the World Ocean, the temperature usually does not exceed 2-3 °C; in the Arctic Ocean it is even lower.

The World Ocean is a powerful heat accumulator and a regulator of the Earth's thermal regime. If there were no ocean, the average surface temperature of the Earth would be - 21 ° C, that is, it would be 36 ° lower than that which is in reality.

Currents of the oceans

The waters of the ocean are in constant motion under the influence of various forces: cosmic, atmospheric, tectonic, etc. The most pronounced are surface sea ​​currents, predominantly of wind origin. But 3 currents that arise due to different mass densities are very common. Currents in the World Ocean are subdivided according to the direction prevailing in them into zonal (going to the west and east) and meridional (carrying water to the north and south). Currents going towards neighboring, more powerful currents are called countercurrents. Equatorial currents (along the equator) are specially distinguished. Currents that change their strength from season to season, depending on the direction of coastal monsoons, are called monsoons.

The most powerful in the entire World Ocean is the Circumpolar, or Antarctic, circular current, due to strong and stable westerly winds. It covers a zone of 2500 km in width and kilometer depths, carrying about 200 million tons of water every second. For comparison, the largest river in the world, the Amazon, carries only about 220,000 tons of water per second.

In the Pacific Ocean, the strongest is the South Trade Wind Current, heading from east to west, at a speed of 80-100 miles per day. To the north of it there is a countercurrent, and even to the north - the Northern trade wind current from east to west. Knowing the direction of the currents, the locals have long used them for their movements. Following them, T. Heyerdahl used this knowledge for his famous trip to the Kon-Tiki. Analogues of the trade winds (literally "favorable to moving") currents and countercurrents are found in the Indian and Atlantic oceans.

Of the meridional currents, the most famous are the Gulf Stream and Kuroshio, which carry 75 and 65 million tons of water per second, respectively.

Many areas of the World Ocean (western coasts of North and South America, Asia, Africa, Australia) are characterized by upwelling, which can be caused by wind-driven surface waters from the coast. Rising deep waters are often rich in nutrients, and upwelling sites are associated with a zone of high biological productivity.

The role of the ocean in people's lives

It is difficult to overestimate the role of the World Ocean in the life of mankind. It largely determines the face of the planet as a whole, including its climate, the water cycle on Earth. In the ocean, there were vital waterways connecting the continents and islands. Its biological resources are colossal. More than 160 thousand species of animals and about 10 thousand species of algae live in the World Ocean. The annual reproducible number of commercial fish is estimated at 200 million tons, of which approximately 1/3 is caught. More than 90% of the world's catch comes from the coastal shelf, especially in the temperate and high latitudes of the Northern Hemisphere. The share of the Pacific Ocean in the world catch is about 60%, the Atlantic - about 35%.

The shelf of the World Ocean has huge reserves of oil and gas, large reserves of iron-manganese ores and other minerals. Mankind is just beginning to use the energy resources of the World Ocean, including the energy of the tides. The World Ocean accounts for 94% of the volume of the hydrosphere. Desalination of sea waters is associated with the solution of many water problems of the future.

Unfortunately, humanity does not always wisely use natural resources World Ocean. In many areas, its biological resources are depleted. A significant part of the water area is polluted with anthropogenic waste, primarily oil products.

Land waters are water, rivers, lakes, swamps, glaciers. They contain 3.5% of the total amount of water in the hydrosphere. Of these, only 2.5% is fresh water.

Groundwater is located in the rock masses of the upper part of the earth's crust in a liquid, solid and vapor state. Their main mass is formed due to seepage from the surface of rain, melt and river waters.

According to the conditions of occurrence, groundwater is divided into:

1) soil, located in the uppermost, soil layer;

2) ground, lying on the first permanent water-resistant layer from the surface;

3) interstratal, located between two water-resistant layers;

The latter are often pressure and then are called artesian.

Groundwater feeds rivers and lakes.

Rivers are constant water streams flowing in depressions developed by them - channels.

The most important characteristic of rivers is their feeding. There are four power sources: snow, rain, glacial and underground.

The regime of rivers largely depends on the feeding of rivers, i.e., the change in the amount of water discharge by the seasons of the year, level fluctuations, and changes in water temperature. The water regime of the river is characterized by water flow and runoff. The flow rate is the amount of water passing through the cross section of the flow in one second. The flow of water over a long time - a month, a season, a year - is called a runoff. The volume of water that rivers carry on average per year is called their water content. The most abundant river in the world is the Amazon, at its mouth the average annual water flow is 220,000 cubic meters. m/s. In second place is the Congo (46,000 cubic meters per second), then the Yangtze. In our country, the most abundant river is the Yenisei (19,800 cubic meters per second). Rivers are characterized by a very uneven distribution of runoff over time. Most rivers in Russia carry 60-70% of the volume of water in a relatively short period of spring floods. At this time, melt water flows down the frozen and well-moistened surface of the watersheds with the least loss of filtration and evaporation.

It is during the flood period that rivers most often overflow their banks and flood the surrounding areas. In summer and winter, low water is usually observed - low water, when the rivers are fed by groundwater, the resources of which are also largely replenished in the spring. In summer, most of the precipitation is spent on evaporation; only a small part of atmospheric precipitation reaches the level of groundwater, and even more so, rivers. In winter, precipitation accumulates in the form of snow. Only in autumn there are small floods on Russian rivers.

The rivers of the Far East and the Caucasus differ from the plain rivers of Russia in terms of hydrological regime. The first spill in the fall - during the monsoon rains; on the Caucasian rivers, the maximum water discharges are observed in summer, when high-mountain glaciers and snowfields melt.

The flow of rivers varies from year to year. Often there are low-water and high-water periods when the river is characterized by low or, on the contrary, high water content. For example, in the 1970s, low water was observed on the Volga, in connection with which the level of the inland Caspian Sea, for which the Volga is the main supplier of water, was rapidly falling. Since 1978, a phase of increased humidity began in the Volga basin, its runoff annually began to exceed the long-term average, and the level of the Caspian Sea began to rise, as a result of which coastal areas were flooded. Most of the rivers in Russia are annually covered with ice. The duration of freeze-up in the north of Russia is 7-8 months (from October to May). The opening of rivers from ice - ice drift - is one of the most impressive sights, often accompanied by flooding.

Rivers have played an outstanding role in the history of mankind, the formation and development of human society is associated with them. Since historical times, rivers have been used as communication routes, for fishing and fish farming, timber rafting, field irrigation and water supply. People have long settled along the banks of rivers - this is also confirmed by folklore, in which the Volga is called "mother", and Amur - "father". The river is the main source of hydropower and the most important transport route. Rivers are of great aesthetic and recreational importance as an integral element of the environment. The wide involvement of rivers in economic circulation has led to the complete transformation of many of them. The flow of such rivers as the Volga, Dnieper, Angara is largely regulated by reservoirs. Many of them, especially those flowing in the southern regions, where there is a great need for irrigation, are dismantled for the needs of irrigation. For this reason, the Amu Darya and Syr Darya no longer flow into the Aral Sea, and it is rapidly drying up.

One of the worst results anthropogenic impact on the rivers - their mass pollution with sewage and other wastes of economic activity. The threat of qualitative depletion of river water resources can be avoided if a complex of water management measures is implemented, including not only traditional wastewater treatment, but also such cardinal measures as changing production technology in order to reduce water consumption and waste generation many times over.

Lakes are natural reservoirs in land depressions (hollows), filled within the lake bowl (lake bed) with heterogeneous water masses and not having a one-sided slope. Lakes are characterized by the absence of a direct connection with the oceans. Lakes occupy about 2.1 million km2, or almost 1.4% of the land area. This is about 7 times the surface of the Caspian Sea - largest lake peace.

A swamp is a piece of land with excessive stagnant soil moisture, overgrown with moisture-loving vegetation. Swamps are characterized by the accumulation of undecomposed plant residues and the formation of peat. Bogs are distributed mainly in the Northern Hemisphere, especially in flat areas where permafrost soils are developed, and occupy an area of ​​about 350 million hectares.

Glaciers are moving natural accumulations of ice of atmospheric origin on the earth's surface; are formed in those areas where solid atmospheric precipitation is deposited more than it melts and evaporates. Within the glaciers, areas of nutrition and ablation are distinguished. Glaciers are divided into terrestrial ice sheets, shelf and mountain. The total area of ​​modern glaciers is approx. 16.3 million km2 (10.9% land area), total ice volume approx. 30 million km3.

6. Water resources management.

One of the directions for solving water problems is to attract the currently underused water resources of desalinated waters of the World Ocean, groundwater and glacier waters for the purposes of water supply. At present, the share of desalinated water in the total volume of world water supply is small - 0.05%, which is explained by the high cost and significant energy intensity of desalination processes. Even in the United States, where the number of desalination plants has increased 30-fold since 1955, desalinated water accounts for only 7% of water consumption.

In Kazakhstan, in 1963, the first experimental-industrial distiller was put into operation in the city of Aktau (Shevchenko). Due to the high cost, desalination is used only where surface or underground fresh water resources are completely absent or extremely difficult to access, and their transportation is more expensive compared to water desalination.

increased mineralization directly on the spot. In the future, water desalination will be carried out in a single technical complex with the extraction of useful components from it: sodium chloride, magnesium, potassium, sulfur, boron, bromine, iodine, strontium, non-ferrous and rare metals, which will increase the economic efficiency of desalination plants.

An important reserve of water supply is groundwater. The greatest value for society is fresh groundwater, which makes up 24% of the volume of the fresh part of the hydrosphere. Brackish and saline underground waters can also serve as a reserve in water supply when they are used in a mixture with fresh water or after their artificial desalination. Factors limiting underground water intake include:

1) the uneven distribution of their distribution over the territory of the earth;

2) difficulties in processing saline groundwater;

3) rapidly declining rates of natural renewal since

increase in the depth of aquifers.

Utilization of water in the solid phase (ice, ice sheets) is assumed, firstly, by increasing the water yield of mountain glaciers, and secondly, by transporting ice from the polar regions. However, both of these methods are practically difficult to implement and the environmental consequences of their implementation have not yet been studied.

Thus, at the present stage of development, the possibilities of attracting additional volumes of water resources are limited. The uneven distribution of water resources across the globe should also be pointed out. The highest availability of river and underground runoff resources falls on the equatorial belt of South America and Africa. In Europe and Asia,

where 70% of the world's population lives, only 39% of river waters are concentrated. the largest rivers of the world are Amazon (annual flow 3780 km3), Congo (1200 km3), Mississippi (600 km3), Zamberi (599 km3), Yangtze (639 km3), Ayeyarwaddy (410 km3), Mekong (379 km3), Brahmaputra (252 km3) ) . In Western Europe, the average annual surface runoff is 400 km3, including about 200 km3 in the Danube, 79 km3 on the Rhine, and 57 km3 on the Rhone. The largest lakes in the world are the Great American Lakes (total area - 245 thousand km3), Victoria (68 thousand km3), Tanganyika (34 thousand km3), Nyasa (30.8 thousand km3).

The Great American Lakes contain 23,000 km3 of water, the same amount as Baikal. To characterize the distribution of hydro resources, the volume of total river flow per unit of territory (1 km3) and population is calculated. 5.2 km3 of total sustainable runoff (including regulated by reservoirs) falls on 1 million inhabitants of the USSR against 4 km3 for the total

the globe; 19 km3 of total river flow versus 13 km3; 4.1 sustainable groundwater flow versus 3.3 km3. The average water supply per 1 km2 is 212 thousand m3 in the CIS, and 278 thousand m3 in the world. The main ways to manage water resources are the creation of reservoirs and the territorial transfer of runoff.

7. Sources of pollution of water resources.

The Earth's hydrosphere is of great importance in the exchange of oxygen and carbon dioxide with the atmosphere. Oceans and seas have a softening, regulating effect on air temperature, accumulating heat in summer and giving it back to the atmosphere in winter. Warm and cold waters circulate and mix in the ocean. The biomass of the vegetation of the oceans and seas is many times

smaller than land, but animal biomass is at least an order of magnitude greater. Oceans and seas absorb carbon dioxide. The hydrosphere is an important food source for humans and other land dwellers. The catch of fish, which at the beginning of this century was 3 million tons per year, now reaches 80 million tons. This growth is associated with the progress of technology, the widespread use of special trawlers, seiners with hydroacoustic devices for detecting accumulations of fish, equipment for impact on her

light, electricity.

There were fish pumps, nylon nets, trawl fishing, freezing and canning of fish on board. As a result of the increased catch, its composition deteriorated, the share of herring decreased,

Sardine, salmon, cod, flounder, halibut and increased proportions of tuna, mackerel, sea bass and bream. With significant investments, it is really possible to increase the catch of seafood to 100-130 million tons. These figures include, for example, krill-small crustaceans, whose reserves are huge in the southern seas. Krill contains protein, these crustaceans can be used for food and other purposes. A large number of fish are caught. Not for food, but for food

livestock or processed into fertilizer. For a number of years, especially after the war, a significant part of the whales has been exterminated, and some of their species are on the verge of complete destruction. By international agreement, further whale fishing is limited. The destruction of the inhabitants of the oceans and seas due to their unreasonable catch raises the question of the advisability of the transition from extensive fishing to artificial breeding of fish. In this regard, we may recall the transition from hunting and gathering fruits and roots in the earlier stages of the development of society to the breeding of animals and plants.

8. Measures for the protection and economical use of water resources.

Serious measures are being taken to prevent growing pollution water bodies sewage. Waste water is water discharged after use in domestic and industrial human activities. By their nature, pollution is divided into mineral, organic, bacteriological and biological. The criterion for the harmfulness of wastewater is the nature and degree of restriction of water use. The quality of natural waters in Kazakhstan is standardized in places of water use. The developed normative indicators - the maximum permissible concentrations of harmful substances in the water of water bodies for various purposes - refer to the composition of water in reservoirs, and not to the composition of wastewater.

In accordance with the Regulations on the state accounting of waters and their

use (1975), primary accounting of wastewater discharged into water bodies is carried out by water users themselves. This control is exercised by the majority of water users unsatisfactorily. This is evidenced by the fact that only 20% of the discharged wastewater is controlled by hydraulic

equipment, and the rest - by indirect methods. Currently, the transition to the system of standards for maximum allowable emissions (MAE) is being carried out. The MPE values ​​are determined for each specific emission source so that the total emissions from all sources in the region do not exceed the MPC standard. The use of MPE standards will facilitate the planning and control of environmental activities, increase

responsibility of the enterprise for compliance with environmental requirements, eliminate conflict situations. Of the total amount of wastewater, 69% is conditionally clean, 18% is polluted and 13% is normatively purified. There are no strict criteria for dividing industrial wastewater into normatively treated, polluted and conditionally clean. Raw wastewater needs to be repeatedly diluted with clean water.

water. Particularly polluting are the production of the oil refining, pulp and paper and chemical industries. Regulatory purified water

The main market method of regulation of environmental activities is pollution charges. There are two types of payment per unit of emissions and payment for the use of public wastewater treatment plants. The fee level in the first case is determined by the desired quality of the environment. The mechanism of such a board automatically ensures the optimal allocation of resources. The fee for the use of treatment facilities includes

the basic fee for the discharge of standard wastewater, the additional fee for excess discharge, the fee for transporting water and the service fee for the water inspection. To assess the pollution of river waters, the indicator of conditional pollution is used. The amount of the fee depends on the age of the treatment plant, the ability of water bodies to self-purify, as well as the composition of the effluent. The fee mechanism is most efficient under pure competition, where each firm seeks to minimize unit costs.

release. In the conditions of monopolies, firms may not set themselves such a goal, therefore, in monopolized industries, methods of direct administrative regulation gain advantages.

10. International Decade Water for Life

4,000 children die every day due to diseases caused by undrinkable water; 400 million children do not have even the bare minimum of safe water necessary for life; as many as 2.6 billion people live without sanitation - all of which defy the UN's fight for clean water.

The United Nations Children's Fund (UNICEF) has highlighted the fact that lack of clean water is responsible for at least 1.6 million of the 11 million preventable child deaths each year. Nearly three children die every minute due to diseases caused by unfit water, such as diarrhea and typhoid fever. In sub-Saharan Africa, where one in five children die before age five, 43% of children drink unsafe water, risking illness and death with every sip.

The Office of the United Nations High Commissioner for Refugees (UNHCR) spoke about the situation in Zhegriyad - the "Valley of Death" in Somalia. It got its name from the fact that every year people die of thirst here, especially drivers whose trucks or cars break down on the way to Djibouti.

This is just a small part of the challenge facing UNHCR, an organization that is trying to help 17 million people in more than 116 countries. In Tindouf, Algeria, a project is currently under way to improve the water supply of the Smara camp in the heart of the Sahara Desert, where tens of thousands of Western Saharan refugees live.

In another camp in eastern Chad, where more than 200,000 refugees are fleeing the conflict in Sudan's Darfur, UNHCR continues to provide water to refugees by delivering water, drilling wells, digging wells and using high technology to find additional sources of water.

On March 22, 2005, the UN celebrated World Water Day by proclaiming International Decade "Water for Life". Data on the scale of the problem and the stories of specific people, apart from the speeches of the leaders of the organizations of the UN system, is what makes us realize how difficult it will be for the world to achieve one of the Millennium Development Goals: by 2015, to halve the number of people who are deprived clean drinking water and minimum sanitary conditions.

List of used literature:

1. Geography. Complete exam preparation course. Moscow. AST-press; 2004

2., "Environmental Protection"

3. B. Nebel "Environmental Science" Moscow. "Science" 2002

4. Great Soviet Encyclopedia. Moscow. "Soviet Encyclopedia", 1972

WATER RESOURCES

WATER RESOURCES

water suitable for domestic use. Especially important are fresh water resources, which make up less than 3% of the total volume of the hydrosphere. Available fresh water resources are extremely unevenly distributed: in Africa, only 10% of the population is provided with a regular water supply, while in Europe this figure exceeds 95%. The situation with water in the big cities of the world (Paris, Tokyo, Mexico City, New York) is becoming more and more tense. The deficit is associated with an increase in the consumption of reserves and with pollution of the hydrosphere.

Brief geographical dictionary. EdwART. 2008 .

Water resources

usable fresh water contained in rivers, lakes, reservoirs, glaciers, groundwater, and soil moisture. Atmospheric vapors, salty waters of the oceans and seas, not used in the economy, are potential water resources. The total volume of water resources is estimated at 1.4 billion km³, of which only 2% is fresh water, and only 0.3% is technically available for use. Water intake from all sources is approx. 4000 km³ per year. Water resources are used in the energy sector, for land irrigation, industrial, agricultural, domestic water supply, and also as transport routes. When using water resources, their quantity either does not change at all (for example, in hydropower, water transport), or part of them is withdrawn (for irrigation, public water supply). This part constitutes irretrievable losses for the given territory. At the same time, the total reserves of water resources on Earth are inexhaustible, since they are continuously renewed in the process of global water cycle. Available sustainable river flow of approx. 9000–12,000 km³ per year, is a renewable land water resource that can be withdrawn for households. needs. In terms of the total value of renewable water resources, Brazil, Russia, Canada, China, the USA, Indonesia, Bangladesh, and India are in the lead. In a number of districts, there is a quantitative and qualitative (due to pollution) depletion of water resources. OK. 1 /3 of the world's population lives in countries experiencing a shortage of fresh water. In the deficit zone is 50% ter. Asia, 20% of Europe, approx. 30% Sev. America, almost all of Australia. Districts with an excess of water resources are located in the equatorial and subpolar latitudes, as well as in many areas of the temperate zone. Surface runoff in Russia is 10% of the world. However, 90% is bass. Sev. Arctic and Pacific Oceans, at the same time on the bass. The Azov and Caspian Seas, where more than 80% of the population lives, account for less than 8% of the annual river runoff.

Geography. Modern illustrated encyclopedia. - M.: Rosman. Under the editorship of prof. A. P. Gorkina. 2006 .

Water resources

water in liquid, solid and gaseous state and their distribution on Earth. They are found in natural water bodies on the surface (oceans, rivers, lakes and swamps); in the bowels (groundwater); in all plants and animals; as well as in artificial reservoirs (reservoirs, canals, etc.).
Water is the only substance that exists in nature in liquid, solid and gaseous states. The value of liquid water varies significantly depending on location and application. Fresh water is more widely used than salt water. Over 97% of all water is concentrated in the oceans and inland seas. Still ok. 2% is accounted for by fresh waters contained in ice sheet and mountain glaciers, and only less than 1% is accounted for by fresh waters of lakes and rivers, underground and groundwater.
Water, the most abundant compound on Earth, has unique chemical and physical properties. Since it easily dissolves mineral salts, living organisms absorb nutrients with it without any significant changes in their own chemical composition. Thus, water is necessary for the normal functioning of all living organisms. The water molecule consists of two hydrogen atoms and one oxygen atom. Its molecular weight is only 18, and its boiling point reaches 100°C at atmospheric pressure 760 mmHg Art. At higher altitudes, where the pressure is lower than at sea level, water boils at lower temperatures. When water freezes, its volume increases by more than 11%, and expanding ice can rupture water pipes and pavements and erode rock, turning it into loose soil. In terms of density, ice is inferior to liquid water, which explains its buoyancy.
Water also has unique thermal properties. When its temperature drops to 0°C and it freezes, 79 calories are released from each gram of water. During nighttime frosts, farmers sometimes spray their gardens with water to protect buds from frost damage. When water vapor condenses, each gram of it gives off 540 calories. This heat can be used in heating systems. Due to its high heat capacity, water absorbs a large amount of heat without changing the temperature.
Water molecules are linked by "hydrogen (or intermolecular) bonds" when the oxygen of one water molecule combines with the hydrogen of another molecule. Water is also attracted to other hydrogen- and oxygen-containing compounds (the so-called molecular attraction). The unique properties of water are determined by the strength of hydrogen bonds. Cohesive and molecular attraction forces allow it to overcome gravity and, due to capillarity, rise up through small pores (for example, in dry soil).
DISTRIBUTION OF WATER IN NATURE
As the temperature of the water changes, hydrogen bonds between its molecules, which in turn leads to a change in its state - from liquid to solid and gaseous.
Since liquid water is an excellent solvent, it is rarely completely pure and contains minerals in a dissolved or suspended state. Only 2.8% of the total 1.36 billion km only 0.6% - in liquid. Approximately 98% of liquid fresh water is concentrated underground. The salt waters of the oceans and inland seas, which occupy more than 70% of the earth's surface, make up 97.2% of all the waters of the Earth. see also OCEAN.
The water cycle in nature. Although the total supply of water in the world is constant, it is constantly redistributed, and thus it is a renewable resource. The water cycle is influenced by solar radiation which stimulates the evaporation of water. At the same time, mineral substances dissolved in it are deposited. Water vapor rises into the atmosphere, where it condenses, and due to gravity, the water returns to earth in the form of precipitation - rain or snow ( see also RAIN). Most of the precipitation falls over the ocean and less than 25% over land. About 2/3 of this precipitation enters the atmosphere as a result of evaporation and transpiration, and only 1/3 flows into rivers and seeps into the ground. see also HYDROLOGY.
Gravity contributes to the redistribution of liquid moisture from higher to lower areas both on the earth's surface and below it. Water, originally set in motion by solar energy, moves in the seas and oceans in the form of ocean currents, and in the air - in clouds.
Geographical distribution of precipitation. The volume of natural renewal of water reserves due to precipitation varies depending on geographical location and sizes of parts of the world. For example, South America receives nearly three times as much annual rainfall as Australia and nearly twice as much as North America, Africa, Asia and Europe (listed in descending order of annual rainfall). Part of this moisture is returned to the atmosphere as a result of evaporation and transpiration by plants: in Australia this value reaches 87%, and in Europe and North America- only 60%. The rest of the precipitation flows down the earth's surface and eventually reaches the ocean with river runoff.
Within the continents, rainfall also varies greatly from place to place. For example, in Africa, on the territory of Sierra Leone, Guinea and Côte d "Ivoire, more than 2000 mm of precipitation falls annually, in most of central Africa - from 1000 to 2000 mm, but at the same time in some northern regions (Sahara and Sahel desert) the amount rainfall is only 500-1000 mm, and in the south - Botswana (including the Kalahari Desert) and Namibia - less than 500 mm.
Eastern India, Burma and part of Southeast Asia receive over 2000 mm of precipitation per year, while most of the rest of India and China receive between 1000 and 2000 mm, while northern China receives only 500–1000 mm. Northwestern India (including the Thar Desert), Mongolia (including the Gobi Desert), Pakistan, Afghanistan and most of the Middle East receive less than 500 mm of precipitation annually.
In South America, the annual rainfall in Venezuela, Guyana and Brazil exceeds 2000 mm, most of the eastern regions of this continent receive 1000–2000 mm, but Peru and parts of Bolivia and Argentina receive only 500–1000 mm, and Chile less than 500 mm. In some areas of Central America located to the north, more than 2000 mm of precipitation falls annually, in the southeastern regions of the United States - from 1000 to 2000 mm, and in some areas of Mexico, in the northeast and Midwest of the United States, in eastern Canada - 500–1000 mm, while in central Canada and the western United States it is less than 500 mm.
In the far north of Australia, the annual rainfall is 1000-2000 mm, in some other northern regions it varies from 500 to 1000 mm, but most of the mainland and especially its central regions receive less than 500 mm.
For the most part former USSR it also receives less than 500 mm of precipitation per year.
Time cycles of water availability. At any point in the world, river runoff experiences daily and seasonal fluctuations, and also changes with a frequency of several years. These variations are often repeated in a certain sequence, i.e. are cyclic. For example, discharges in rivers with heavily vegetated banks tend to be higher at night. This is because, from dawn to dusk, vegetation uses groundwater for transpiration, resulting in a gradual decrease in river flow, but its volume increases again at night when transpiration stops.
Seasonal cycles of water supply depend on the distribution of precipitation throughout the year. For example, in the Western United States, snowmelt occurs in the spring. In India, there is little rainfall in winter, and heavy monsoon rains begin in mid-summer. Although the average annual river flow is almost constant over a number of years, it is extremely high or extremely low once every 11–13 years. Perhaps this is due to the cyclical nature of solar activity. Information about the cyclicity of precipitation and river runoff is used in forecasting water availability and the frequency of droughts, as well as in planning water protection activities.
WATER SOURCES
The main source of fresh water is atmospheric precipitation, but two other sources can also be used for consumer needs: groundwater and surface water.
Underground sources. Approximately 37.5 million km 3 or 98% of all fresh water in the liquid state falls on groundwater, and approx. 50% of them lie at depths of no more than 800 m. However, the volume of available groundwater is determined by the properties of aquifers and the capacity of pumps pumping water. Groundwater reserves in the Sahara are estimated at about 625 thousand km3. IN modern conditions they are not replenished by surface fresh water, but are depleted when pumped out. Some of the deepest underground waters are never included in the general water cycle at all, and only in areas of active volcanism do such waters erupt in the form of steam. However, a significant amount of groundwater still penetrates the earth's surface: under the influence of gravity, these waters, moving along waterproof sloping rock layers, emerge at the foot of the slopes in the form of springs and streams. In addition, they are pumped out by pumps, and are also extracted by plant roots and then enter the atmosphere through the process of transpiration.
The groundwater table represents the upper limit of available groundwater. In the presence of slopes, the groundwater mirror intersects with the earth's surface, and a source is formed. If groundwater is under high hydrostatic pressure, then artesian springs are formed in the places where they come to the surface. With the advent of powerful pumps and the development of modern drilling technology, the extraction of groundwater has become easier. Pumps are used to supply water to shallow wells installed in aquifers. However, in wells drilled to a greater depth, to the level of artesian pressure water, the latter rise and saturate the overlying groundwater, and sometimes come to the surface. Groundwater moves slowly, at a speed of several meters per day or even per year. They are usually found in porous pebbly or sandy horizons or relatively impermeable shale beds, and only rarely are they concentrated in underground cavities or in underground streams. For right choice well drilling sites usually require information about the geological structure of the territory.
In some parts of the world, the growing demand for groundwater is having serious consequences. Pumping out a large volume of groundwater, incomparably greater than their natural recharge, leads to a lack of moisture, and lowering the level of these waters requires more expensive electricity used to extract them. In places where the aquifer is depleted, the earth's surface begins to subside, and the restoration of water resources in a natural way is complicated there.
In coastal areas, excessive abstraction of groundwater leads to the replacement of fresh water in the aquifer with salt water, and thus degradation of local fresh water sources occurs.
Gradual deterioration of groundwater quality as a result of salt accumulation can have even more dangerous consequences. Salt sources can be both natural (for example, the dissolution and removal of minerals from soils) and anthropogenic (fertilization or excessive watering with water with a high salt content). Rivers fed by mountain glaciers usually contain less than 1 g/l of dissolved salts, but the mineralization of water in other rivers reaches 9 g/l due to the fact that they drain areas composed of salt-bearing rocks for a long distance.
The indiscriminate discharge or disposal of toxic chemicals causes them to seep into aquifers that provide drinking or irrigation water. In some cases, just a few years or decades are enough for harmful chemicals to get into groundwater and accumulate there in tangible quantities. However, if an aquifer was once polluted, it would take 200 to 10,000 years for it to naturally clean itself.
surface sources. Only 0.01% of the total volume of fresh water in the liquid state is concentrated in rivers and streams and 1.47% in lakes. Dams have been built on many rivers to store water and provide it continuously to consumers, as well as to prevent unwanted floods and generate electricity. The Amazon in South America, the Congo (Zaire) in Africa, the Ganges with the Brahmaputra in South Asia, the Yangtze in China, the Yenisei in Russia, and the Mississippi with the Missouri in the USA have the highest average water consumption and, consequently, the highest energy potential. see also river .
Natural freshwater lakes containing approx. 125 thousand km 3 of water, along with rivers and artificial reservoirs, are an important source of drinking water for people and animals. They are also used for irrigation of agricultural land, navigation, recreation, fishing and, unfortunately, for the discharge of domestic and industrial wastewater. Sometimes, due to the gradual filling with sediments or salinization, the lakes dry up, but in the process of evolution of the hydrosphere, new lakes are formed in some places.
The water level even in “healthy” lakes can decrease during the year as a result of water flow through the rivers and streams flowing from them, due to water infiltration into the ground and its evaporation. The restoration of their level usually occurs due to precipitation and the inflow of fresh water from rivers and streams flowing into them, as well as from springs. However, as a result of evaporation, salts that come with river runoff accumulate. Therefore, after millennia, some lakes can become very salty and unsuitable for many living organisms. see also lake .
USE OF WATER
Water consumption. Water consumption is growing rapidly everywhere, but not only because of increasing population, but also due to urbanization, industrialization and especially the development of agricultural production, in particular irrigated agriculture. By 2000, the world's daily water consumption had reached 26,540 billion liters, or 4,280 liters per person. 72% of this volume is spent on irrigation, and 17.5% on industrial needs. About 69% of irrigation water is lost irretrievably.
water quality, used for different purposes is determined depending on the quantitative and qualitative content of dissolved salts (i.e. its mineralization), as well as organic matter; solid suspensions (silt, sand); toxic chemicals and pathogens (bacteria and viruses); odor and temperature. Typically, fresh water contains less than 1 g/l of dissolved salts, brackish water 1–10 g/l, and saline water 10–100 g/l. Water with a high salt content is called brine, or brine.
Obviously, for navigational purposes, water quality (seawater salinity reaches 35 g/l, or 35‰) is not essential. Many species of fish have adapted to life in salt water, but others live only in fresh water. Some migratory fish (such as salmon) start and end their life cycle in inland fresh waters but spend most of their lives in the ocean. Some fish (like trout) need cold water, while others (like perch) prefer warm water.
Most industries use fresh water. But if such water is in short supply, then some technological processes, such as cooling, can proceed based on the use of low-quality water. Water for domestic purposes should be of high quality, but not absolutely pure, since such water is too expensive to produce, and the absence of dissolved salts makes it tasteless. In some parts of the world, people are still forced to use low-quality muddy water from open reservoirs and springs for everyday needs. However, in industrialized countries, all cities are now supplied with piped, filtered and specially treated water that meets at least minimum consumer standards, especially in terms of potability.
An important characteristic of water quality is its hardness or softness. Water is considered hard if the content of calcium and magnesium carbonates exceeds 12 mg/l. These salts are bound by some components of detergents, and thus foaming worsens, an insoluble residue remains on the washed items, giving them a dull gray tint. Hard water calcium carbonate forms scale (limescale) in kettles and boilers, which reduces their service life and the thermal conductivity of the walls. Water is softened by adding sodium salts to replace calcium and magnesium. In soft water (containing less than 6 mg/l of calcium and magnesium carbonates), the soap lathers well and is more suitable for washing and washing. Such water should not be used for irrigation, as excess sodium is harmful to many plants and can disturb the loose, cloddy soil structure.
Although elevated concentrations of trace elements are harmful and even poisonous, their small content can have a beneficial effect on human health. An example is water fluoridation to prevent caries.
Reuse of water. Used water is not always completely lost, part of it or even all of it can be returned to the circulation and reused. For example, water from a bath or shower through sewer pipes enters urban treatment facilities where it is processed and then reused. Typically, more than 70% of urban runoff returns to rivers or aquifers. Unfortunately, in many large coastal cities, municipal and industrial wastewater is simply dumped into the ocean and not disposed of. Although this method eliminates the cost of cleaning and returning them to circulation, there is a loss of potentially usable water and pollution of marine areas.
In irrigated agriculture, crops consume a huge amount of water, sucking it out by the roots and irretrievably losing up to 99% in the process of transpiration. However, when irrigating, farmers usually use more water than is needed for crops. Part of it flows to the periphery of the field and returns to the irrigation network, while the rest seeps into the soil, replenishing groundwater reserves that can be pumped out.
Use of water in agriculture. Agriculture is the largest consumer of water. In Egypt, where there is almost no rain, all agriculture is based on irrigation, while in the UK, almost all crops are provided with moisture from precipitation. In the US, 10% of agricultural land is irrigated, mostly in the west of the country. A significant part of agricultural land is artificially irrigated in the following Asian countries: China (68%), Japan (57%), Iraq (53%), Iran (45%), Saudi Arabia (43%), Pakistan (42%), Israel ( 38%), India and Indonesia (27% each), Thailand (25%), Syria (16%), Philippines (12%) and Vietnam (10%). In Africa, apart from Egypt, a significant proportion of irrigated land is in Sudan (22%), Swaziland (20%) and Somalia (17%), and in America - in Guyana (62%), Chile (46%), Mexico (22%). ) and Cuba (18%). In Europe, irrigated agriculture is developed in Greece (15%), France (12%), Spain and Italy (11% each). Australia irrigates approx. 9% agricultural land and approx. 5% - in the former USSR.
Water consumption by different cultures. To obtain high yields, a lot of water is required: for example, 3,000 liters of water are spent on growing 1 kg of cherries, 2,400 liters of rice, 1,000 liters of corn on the cob and wheat, 800 liters of green beans, 590 liters of grapes, and 510 liters of spinach. l, potatoes - 200 l and onions - 130 l. Approximate amount of water used only for growing (and not for processing or cooking) food crops consumed daily by one person in Western countries is for breakfast approx. 760 liters, for lunch (lunch) 5300 liters and for dinner - 10 600 liters, which is 16 600 liters per day.
In agriculture, water is used not only to irrigate crops, but also to recharge groundwater (to prevent the groundwater level from dropping too quickly); for leaching (or leaching) of salts accumulated in the soil to a depth below the root zone of cultivated crops; for spraying against pests and diseases; frost protection; fertilizer application; decrease in air and soil temperature in summer; for the care of livestock; evacuation of treated wastewater used for irrigation (mainly cereals); and processing of harvested crops.
Food industry. The processing of different food crops requires different amounts of water depending on the product, the manufacturing technology and the availability of water of the appropriate quality in sufficient volume. In the United States, 2,000 to 4,000 liters of water are used to produce 1 ton of bread, while in Europe it is only 1,000 liters and only 600 liters in some other countries. Preserving fruits and vegetables requires between 10,000 and 50,000 liters of water per ton in Canada, while in Israel, where water is a severe shortage, only 4,000–1,500. The “champion” in terms of water consumption is lima beans, for the conservation of 1 ton of which in the USA 70,000 liters of water are consumed. Processing 1 tonne of sugar beet consumes 1,800 liters of water in Israel, 11,000 liters in France and 15,000 liters in the UK. The processing of 1 ton of milk requires from 2000 to 5000 liters of water, and the production of 1000 liters of beer in the UK - 6000 liters, and in Canada - 20,000 liters.
Industrial water consumption. The pulp and paper industry is one of the most water-intensive industries due to the sheer volume of raw materials processed. The production of each ton of pulp and paper uses an average of 150,000 liters of water in France and 236,000 liters in the United States. The process of producing newsprint in Taiwan and Canada consumes approx. 190,000 liters of water per 1 ton of production, while the production of a ton of high-quality paper in Sweden requires 1 million liters of water.
Fuel Industry. To produce 1,000 liters of high-quality aviation gasoline, 25,000 liters of water are needed, and motor gasoline requires two-thirds less.
Textile industry requires a lot of water for soaking raw materials, cleaning and washing, bleaching, dyeing and finishing fabrics and for other technological processes. For the production of each ton of cotton fabric, from 10,000 to 250,000 liters of water are needed, for woolen - up to 400,000 liters. The production of synthetic fabrics requires much more water - up to 2 million liters per 1 ton of products.
Metallurgical industry. In South Africa, the extraction of 1 ton of gold ore consumes 1,000 liters of water; in the USA, the extraction of 1 ton of iron ore is 4,000 liters and 1 ton of bauxite is 12,000 liters. The production of iron and steel in the United States requires approximately 86,000 liters of water per ton of product, but up to 4,000 liters of this is a deadweight loss (mainly to evaporation), and therefore approximately 82,000 liters of water can be reused. Water consumption in the iron and steel industry varies considerably by country. 130,000 liters of water are spent on the production of 1 ton of pig iron in Canada, 103,000 liters of water are spent on smelting 1 ton of pig iron in a blast furnace in the USA, 40,000 liters of steel in electric furnaces in France, and 8,000–12,000 liters in Germany.
Power industry. Hydroelectric power plants use the energy of falling water to generate electricity, driving hydraulic turbines. In the United States, hydroelectric power plants consume 10,600 billion liters of water daily ( see also HYDROPOWER).
Wastewater. Water is necessary for the evacuation of domestic, industrial and agricultural wastewater. While about half of the population in the United States, for example, is served by sewer systems, effluent from many homes is still simply dumped into septic tanks. But growing awareness of the consequences of water pollution through such outdated sewer systems has spurred the construction of new systems and the construction of wastewater treatment plants to prevent pollutants from infiltrating into groundwater and untreated runoff into rivers, lakes and seas ( see also WATER POLLUTION).
WATER DEFICIENCY
When water demand exceeds water supply, the difference is usually offset by storage in reservoirs, as both demand and supply usually vary seasonally. A negative water balance is formed when evaporation exceeds precipitation, so a moderate decrease in water reserves is a common occurrence. Acute scarcity occurs when the water supply is insufficient due to prolonged drought or when, due to poor planning, water consumption is constantly growing at a faster rate than expected. Throughout history, humanity has suffered from time to time due to lack of water. In order not to lack water even during droughts, in many cities and regions they try to store it in reservoirs and underground collectors, but sometimes additional water-saving measures are needed, as well as its normalized consumption.
OVERCOMING WATER SHORTAGE
The redistribution of runoff is aimed at providing water to those areas where it is not enough, and the protection of water resources is aimed at reducing irreplaceable water losses and reducing the need for it on the ground.
Redistribution of runoff. Although traditionally many large settlements arose near permanent water sources, at present some settlements are also created in areas that receive water from afar. Even where the source of the supplemental water supply is within the same state or country as the destination, there are technical, environmental, or economic problems, but if the imported water crosses national boundaries, the potential complications increase. For example, spraying silver iodide on clouds results in increased rainfall in one area, but this can result in reduced precipitation in other areas.
One of the major water transfer projects proposed in North America is to divert 20% of excess water from the northwest to arid areas. At the same time, up to 310 million m 3 of water would be redistributed annually, a through system of reservoirs, canals and rivers would contribute to the development of navigation in the interior, the Great Lakes would receive an additional 50 million m 3 of water annually (which would compensate for the decrease in their level), and up to 150 million kW of electricity would be generated. Another grandiose plan for the transfer of runoff is associated with the construction of the Great Canadian Canal, through which water would be directed from the northeastern regions of Canada to the western regions, and from there to the USA and Mexico.
Much attention is drawn to the project of towing icebergs from Antarctica to arid regions, for example, to the Arabian Peninsula, which will make it possible to annually provide fresh water 4 to 6 billion people or irrigate approx. 80 million hectares of land.
One of the alternative methods of water supply is the desalination of salt water, mainly ocean water, and its transportation to the places of consumption, which is technically feasible due to the use of electrodialysis, freezing and various systems distillation. The larger the desalination plant, the cheaper it is to obtain fresh water. But with the increase in the cost of electricity, desalination becomes economically unprofitable. It is used only in cases where energy is readily available and other methods of obtaining fresh water are impractical. Commercial desalination plants operate on the islands of Curacao and Aruba (in the Caribbean), Kuwait, Bahrain, Israel, Gibraltar, Guernsey and the United States. Numerous smaller demonstration plants have been built in other countries.
Protection of water resources. There are two widely used ways to conserve water resources: maintaining existing supplies of usable water and increasing its supply by building better collectors. The accumulation of water in reservoirs prevents it from flowing into the ocean, from where it can only be extracted again through the natural water cycle or through desalination. Reservoirs also make it easier to use water at the right time. Water can be stored in underground cavities. At the same time, there is no loss of moisture for evaporation, and valuable land is saved. The preservation of existing water reserves is facilitated by channels that prevent water from seeping into the ground and ensure its efficient transportation; more than effective methods irrigation using wastewater; reducing the volume of water flowing from fields or filtering below the root zone of crops; careful use of water for domestic needs.
However, each of these methods of conserving water resources has some impact on the environment. For example, dams spoil the natural beauty of unregulated rivers and prevent the accumulation of fertile silt on floodplains. Prevention of water losses as a result of filtration in canals can disrupt the water supply of swamps and thus adversely affect the state of their ecosystems. It may also prevent groundwater recharge, thus affecting the water supply of other users. And to reduce the volume of evaporation and transpiration by agricultural crops, it is necessary to reduce the area under crops. The latter measure is justified in areas suffering from water shortages, where it is carried out a savings regime by reducing irrigation costs due to the high cost of energy needed to supply water.
WATER SUPPLY
The sources of water supply and reservoirs themselves matter only when water is delivered in sufficient volume to consumers - to residential buildings and institutions, to fire hydrants (devices for extracting water for fire needs) and other public utilities, industrial and agricultural facilities.
Modern systems for filtering, purifying and distributing water are not only convenient, but also help prevent the spread of water-borne diseases such as typhoid and dysentery. A typical urban water supply system involves drawing water from a river, passing it through a coarse filter to remove most of the pollutants, and then through a measuring post, where its volume and flow rate are recorded. After that, the water enters the water tower, from where it passes through the aeration unit (where impurities are oxidized), a microfilter to remove silt and clay, and a sand filter to remove the remaining impurities. Chlorine, which kills microorganisms, is added to the water in the main pipe before entering the mixer. Ultimately, before being sent to the distribution network for consumers, treated water is pumped into a storage tank.
Pipes at the central waterworks are usually cast iron, of large diameter, which gradually decreases as the distribution network expands. From street water mains with pipes with a diameter of 10–25 cm, water is supplied to individual houses through galvanized copper or plastic pipes.
Irrigation in agriculture. Since irrigation requires huge amounts of water, the water supply systems of agricultural areas must have a large capacity, especially in arid conditions. Water from the reservoir is directed to a lined, and more often unlined main canal and then through branches to distribution irrigation canals of various types to farms. Water is released to the fields by flooding or by irrigation furrows. Because many reservoirs are located above irrigated land, water mostly flows by gravity. Farmers who store water themselves pump it from wells directly into canals or storage reservoirs.
For sprinkler irrigation or drip irrigation practiced in Lately use low power pumps. In addition, there are giant central-pivot irrigation systems that pump water from wells right in the middle of the field directly into a pipe equipped with sprinklers and rotating in a circle. From the air, fields irrigated in this way appear to be giant green circles, some of which reach a diameter of 1.5 km. Such installations are common in the US Midwest. They are also used in the Libyan part of the Sahara, where more than 3,785 liters of water per minute are pumped out of the deep Nubian aquifer.

Encyclopedia Around the World. 2008 .