World water resources. Natural resources

The water resources considered are surface runoff (rivers, lakes and other bodies of water), underground runoff (underground and groundwater), glacier water, and precipitation, which are sources of water to meet economic and domestic needs. Water is a unique type of resource. It combines the nature of both exhaustible (groundwater) and inexhaustible (surface runoff) reserves. Water in nature is in continuous movement, so its distribution across the territory, seasons and years is subject to significant fluctuations.

Russia has significant reserves of fresh water. River waters are most widely used in the national economy. The rivers of Russia belong to the basins of three oceans, as well as to the internal Caspian basin, which occupies most of the European part of Russia. Most of the rivers in Russia belong to the Arctic Ocean basin. The rivers flowing into the northern seas are the longest and deepest. The longest river is the Lena (4400 km), the deepest river is the Yenisei. In the southern parts of Siberia the rivers are swift and rapid. The largest hydroelectric power stations in the country were built on these sections - Krasnoyarsk and Sayano-Shushenskaya on the Yenisei, Novosibirsk on the Ob, Irkutsk, Bratsk, Ust-Ilimsk on the Angara, etc. The rivers of the European part of the Arctic Ocean basin - Pechora, Mezen, Northern Dvina, Onega - are much shorter than Siberian rivers. Many rivers belong to the Pacific Ocean basin. The main rivers of this basin are the Amur and its tributaries the Zeya, Bureya, and Ussuri.

The Atlantic Ocean basin occupies the smallest area of ​​the entire country. Rivers flow west to the Baltic Sea (Neva) and south to the Azov and Black Sea (Don, Kuban, etc.). The Neva occupies a special place. This short river (74 km) carries a huge amount of water - four times more than the Dnieper, which is over 2000 km long.

Most of European Russia is occupied by the internal basin of the Caspian Sea. The rivers Volga, Ural, Terek and others flow into the Caspian Sea. In European Russia, the longest river is the Volga (3530 km). There are many hydroelectric power stations on the Volga: Volzhskaya named after. Lenin, Saratov, Volzhskaya named after. XXI Congress of the CPSU, etc.

The main consumers of water resources in our country are water supply, hydropower, and artificial irrigation.

Water supply is a set of different ways of using water resources by industry, utilities and the population with a large share of irreversible losses and varying degrees of pollution. It is this aspect of water use that creates the problem of qualitative deterioration and reduction of water reserves, which becomes increasingly aggravated as production grows. Solving it requires the redistribution of water resources between regions, careful use of reserves, the construction of treatment facilities, the widespread use of closed cycles of water use, etc.

Hydropower uses the energy of flowing water, the reserves of which are then completely returned to the watercourse. Russia has the world's largest hydropower reserves, which account for about 1/10 of the world's reserves. Russia's hydropower resources are distributed unevenly. Most of them are located in Siberia and the Far East, with the main hydropower reserves concentrated in the basins of the Yenisei, Lena, Ob, Angara, Irtysh and Amur rivers. The Lena ranks first among Russian rivers in terms of hydropower reserves. The rivers of the North Caucasus are rich in hydropower resources. A significant part of the country's technically possible hydropower resources is located in the Volga and Central regions of Russia, where the hydropower reserves of the Volga basin are especially large.

River flow and glacier resources are used for artificial irrigation. The main irrigation areas are arid territories: the North Caucasus, Trans-Volga region.

The article contains information about the planet's water resources. Statistical data on the water content on the planet is provided. Ways to prevent a global catastrophe are being clarified.

What are the Earth's water resources?

Water resources are the totality of the waters of the hydrosphere, including the World Ocean, as well as the surface and hidden waters of the continents.

Water is the most abundant substance on the planet. Water suitable for drinking is of the greatest importance - without it, human existence is not possible. The main features of the resource are that it has no analogues or alternatives. Humanity has always used water in various areas of its activities: domestic and agricultural industries, industry.

It is not easy to determine how many water reserves the Earth contains. This is explained by the fact that water is in constant motion and is capable of changing its state to:

• liquid;
• hard;
• gaseous.

The Earth's total water resources are defined as the free water that is present in all known states and atmosphere.

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Rice. 1. Glaciers of Antarctica.

The planet contains about 1.386 billion km. cube water. But a significant part of the total volume (97.5%) is salt water and only 2.5% is fresh. The main share of fresh water (68.7%) is found in the ice of Antarctica, the Arctic, and mountainous regions.

Inland waters and water resources in general were once considered renewable resources due to the water cycle and its ability to purify. These specific features of life-giving moisture have given rise to a widespread myth about the immutability and inexhaustibility of the resource.

However, now the situation has changed greatly. In most parts of the world, the consequences of prolonged and incorrect human impact on the most valuable resource have been identified. Over the past three decades, there has been a massive human-caused change in the water cycle, which has negatively impacted its quality and potential as a natural resource.

The volume of water resources, their geography and temporal distribution depend not only on natural climatic fluctuations.

Rice. 2. Human water pollution.

Due to the positive and negative impacts of humans on the planet, many parts of the world's water resources are simply becoming depleted and heavily polluted. This circumstance is now the main factor that significantly slows down economic development, and at the same time population growth. Therefore, the topic and issue regarding the irrational use of water resources is more relevant today than ever.

Water conservation

Water resources require rational use by every inhabitant of the Earth, enterprise and state.

Rice. 3. Cleaning the ocean surface from an oil spill.

To prevent irreversible consequences on the planet, it is necessary to involve all segments of the population in the problem and create a legislative framework that will promote concern for water resources on the part of both individuals and enterprises.

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Water resources are water suitable for human use. Water resources are concentrated in surface and underground water bodies, atmosphere and soil (Table 2.1). Actively used water resources form the water fund.

Characteristics of world water reserves

Water features		Fresh water reserves, %	Resume time	Use for water consumption
				not used
Groundwater				drinking purposes
				not used
				widespread use
Soil moisture				consumption by plants
Atmospheric moisture				not used
				not used
				widespread use

Water fund - withtotality of water bodies in within the territory of the Russian Federation, included or subject to inclusion in the state water cadastre. The most widely used are rivers, underground aquifers and lakes, which contain 55% of the resource. Lakes and groundwater, in addition to the resource, are characterized by static (secular) reserves, which amount to about 54,068 km 3 (Table 2.2).

Total water resources of Russia

(according to the Center for Register and Cadastre)

	Average annual volume of renewable flow		Static stocks
River flow*
Groundwater
Soil moisture

*Including 227 km 3 /year of river flow coming from the territory of other states.

Fig.2.1 The ratio of water resources concentrated in water fund objects.

Fresh water reserves concentrated in the Russian Federation are estimated at 50 km 3 . The water supply to the population in this case is about 1000 l/day*person, with an average water requirement of about 200 l/day*person. However, the uneven distribution of water resources and the settlement of people are of decisive importance in the water supply of the population and economic sectors. In the most developed areas of the European part of the country, where up to 80% of the population and production potential are concentrated, less than 10% of water resources are concentrated.

Information about water bodies is presented in the State Water Register. The State Water Register is a constantly replenished and updated systematic collection of data on water bodies and their use. It is created for the purpose of information support for the integrated and targeted use of water bodies, their protection, planning and development of measures to prevent the negative impact of water and eliminate its consequences.

The State Water Register contains information:

about water bodies and their basins, the features of their water regime, their physical-geographical, morphometric and other features;

on water management systems and the use of water bodies for water consumption and wastewater disposal;

on water protection zones and coastal protective strips, other zones with special conditions for their use;

on the provision of water bodies for use and on water use agreements.

Surface water resources

Swamps occupy 140.8 million hectares, which is about 8% of the country's territory. The main massifs are concentrated in the North-Western region, in the north of the Central region, in the south of the Ural and Siberian regions. About 3000 km 3 of static reserves of natural water are concentrated in swamps. The average long-term exploitation resources of wetlands are about 300 km 3 /year. Swamps contain a large amount of water, but of poor quality, which does not allow it to be used even for technical purposes. The required water treatment is currently too expensive, so swamp waters in the Russian Federation are not used for water consumption purposes.

Swamps play an important role in the formation of the hydrological and hydrochemical regime of rivers. The slow water exchange of swamps makes it possible to accumulate runoff from the drainage area during snowmelt and rainfall and redistribute it throughout the year, making the flow regime more uniform. Therefore, swamps lead to a decrease in the flow of floods and floods and an increase in runoff volumes during low-water periods.

Fig.2.2 Area of ​​swamps, as a percentage of the area of ​​the federal subjects

(http://www.peatlands.ru/?file=home.php&page=home&lang=ru).

Swamps are a kind of biological filter that reduces the pollution of surface runoff and thereby regulates the hydrochemical regime of runoff.

Glaciers are essential accumulators of fresh water. In Russia, the bulk of glaciers are concentrated on the Arctic islands and mountainous regions. Glaciers perform the function of redistributing runoff and precipitation and regulating the flow of mountain rivers. Of interest for use are the glaciers of mountainous regions, which determine the water content of mountain rivers.

Fig.2.3 Distribution of glaciers on the territory of Russia, km 2.

The possibility of using iceberg water is being considered. Transporting an iceberg with a volume of 10 billion m3 to California (USA) and creating a special reservoir where melt water from the iceberg will accumulate will require no more than 1 million dollars, and the cost of the resulting water will be no less than 100 million dollars. Using glacier fresh water is much more profitable than desalinating salt water or transporting fresh water from remote areas.

Lakes. On the territory of Russia there are 2.7 million lakes with a total fresh water reserve of 26.5 thousand km 3. The deepest freshwater lake in the world is Baikal. Its depth reaches more than 1.5 km. It contains 23 thousand. km 3 of water, or 20% of global and 87% of national fresh water reserves. Lakes are unevenly distributed throughout Russia. The Northwestern region is considered the land of lakes.

In nature, lakes perform the following main functions:

accumulating - substances flowing from the catchment area and transported by rivers accumulate in lakes;

regulating - lakes take on part of the runoff coming from the catchment area, reducing the height of floods and floods, creating a more uniform intra-annual river flow regime.

Characteristics of large lakes in Russia

	Area, km 2	Average depth, m	Water reserve, km 3	Resource, km 3 / year
Caspian
Baikal
Ladoga
Onega
Zaysan
Khanka
Taimyr

Currently, the lakes serve as a source of drinking, industrial and agricultural water supply. The lakes are used for tourism, recreation, and sports. Lakes have always been used for fishing purposes.

Groundwater resources They have a higher degree of protection from technogenic pollution, therefore their ecological condition, compared to surface waters, is much better, which determines their maximum use for domestic and drinking water supply.

Natural groundwater resources are approximately 790 km 3 /year. Potential exploitable resources are about 316 km 3 /year. More than a third of potential resources are concentrated in the European part of the country. Small reserves of fresh groundwater are concentrated in the Northwestern region, in the south of the Volga region, in the Southern and certain regions of the Central regions. In the country as a whole, the degree of development of groundwater reserves does not exceed 19%.

In a number of countries (for example, Hungary, Iceland), thermal underground waters are widely used for heat supply and electricity generation. Russia has very significant potential resources of such waters in the Far Eastern and Siberian regions, but their proven reserves and use are small.

By the beginning of 2000, 60 thermal water deposits had been explored in Russia, including 5 deposits with an operational resource of 315 thousand m 3 /day. Water was extracted from 28 fields with an annual volume of 34 million m 3. The total capacity of Russian geothermal stations and installations is slightly more than 500 MW.

Rice. 2.4 Structure of the use of thermal groundwater, %.

(http://www.5ballov.ru/referats/preview/41779/1)

Groundwater plays a huge role in nature, participating in almost all physical and geographical processes occurring in the lithosphere. Thanks to their movement, dissolved substances are transferred, and plants receive nutritious salts and moisture. Groundwater actively influences the formation of relief: landslides, erosion; cause waterlogging under certain conditions. They participate in feeding rivers and lakes, being the most stable part of the flow.

Rivers. In Russia there are over 3 million rivers with a total length of more than 9.5 million km. The total volume of river flow in the country is 4043 km 3 /year.

River flow is formed due to surface and underground feeding. Surface runoff is formed in the drainage area as a result of rainfall and snow melting. The time it takes for surface runoff to reach rivers from the most remote points of the drainage area depends on the terrain, the density of the river network and the water-physical properties of soils, and is approximately 1…15 days. As the runoff passes over the surface of the catchment area, it acquires a specific hydrological regime and forms its hydrochemical composition due to the leaching of substances from the soil. Thus, the specific leaching of phosphorus from the catchment area occupied by mixed forests is about 0.056 kg/ha, meadows contribute about 0.1 kg/ha to the river, and for lowland swamps this value is 0.4 kg/ha. The volume of phosphorus leaching from agricultural areas varies within 1 – 5 kg/ha, i.e. 3-100 times more than from natural lands.

Main characteristics of large rivers in Russia.

	Catchment area, thousand km 2	Length, km	Average long-term flow rate, m 3 /s	Runoff volume, km 3
Western Dvina

Fig.2.5 Length of natural watercourses as a percentage of their total length.

(Classification of rivers by length:

streams – length up to 10 km,

small rivers 10…100 km,

medium rivers 100…300 km,

large – more than 300 km).

Thus, the qualitative and quantitative flow of rivers is determined by the conditions that develop in the catchment area, which allows us to consider it an indicator of the condition and a measure of the use of the catchment area.

The underground flow is divided into two components: groundwater (the flow of the first unconfined aquifer) and interlayer flow. Ground flow is more inert compared to surface flow and allows one to take into account mainly seasonal changes. At the same time, groundwater runoff, as well as surface runoff, can serve as an indicator of the state of the catchment area and the conditions of human economic activity. The most constant in terms of quantity and quality is the flow of groundwater itself, i.e. waters of the second and underlying aquifers. It provides the river with a certain background component, guaranteeing the minimum volume of water in the river and its quality. Seasonal changes in flow are important for a river ecosystem, since the functions of the river change significantly seasonally.

The summer low-water period is characterized by relatively low flow rates, depths and flow rates of water. This creates a favorable temperature regime, the water is saturated with oxygen, which promotes the growth and development of aquatic biota. The biomass of plant organisms increases due to the absorption of nutrients, which leads to a decrease in their concentration in water, i.e. is happening self-purification of water.

In the autumn period, active vegetation ends, which is accompanied by a decrease in the growth of biomass of aquatic organisms. The water temperature decreases, which is accompanied by: an increase in water transparency, due to a decrease in plankton biomass and sedimentation of suspended substances to the bottom; increasing the oxygen content in water due to increasing the solubility limit; a decrease in the intensity of physical and chemical processes. All this prepares conditions for overwintering biota.

Winter period peace, before the next stage of active life, which begins in the spring.

Spring is characterized by high flow rates, depths and speeds of water flow. Thus, the spring period accounts for up to 60-80 times the volume of annual runoff. Rapid flows of water have a high transport capacity, which allows rivers to be cleared of sediments and sediments ( self-purification of the river), which are carried to water meadows, deposited in oxbow lakes or redistributed along the river bed. At the same time, due to runoff from the catchment area, especially from floodplains, the water is saturated with nutrients.

Most large rivers flow through the plains. Plain rivers have wide valleys and slight slopes, which determines a calm flow regime with low speeds. For example, the Ob River has the lowest average slope, which is 0.00004, and the Yenisei has the highest slope of lowland rivers, which in some areas reaches 0.00037.

Reservoirs. Reservoirs make it possible to ensure guaranteed water supply through the redistribution of water resources. Currently in Russia there are 2,290 reservoirs with a capacity of over 1 million m3 and 30 thousand small reservoirs and ponds. The total capacity of the reservoirs is 800 km 3 . Large and especially large objects include 325 reservoirs (with a capacity of more than 10 million m3). The largest number of reservoirs is located in the Volga region - 600, Central Black Earth - 434, Ural - 383. The largest reservoirs are located in the Asian part of Russia. Thus, the average volume of one reservoir in the Siberian region reaches 26.4 km 3, in the Far East - 7.4 km 3, and for example in the Volga region - 1.4 km 3.

Along with the positive role of reservoirs, it should be noted their negative impact on the environment, which consists, for example, in the following:

flooding and flooding of land;

coastal destruction;

intensification of landslide phenomena, the zone of which includes many settlements, including such large ones as Volgograd, Saratov, Ulyanovsk;

deterioration of the technical condition of waterworks, most of which are in need of ongoing repairs, and hundreds are in a pre-emergency condition.

Water management zoning of the territory

Water management zoning of the territory is intended for the implementation of activities: planning the use of water resources, operation of water management systems, protection and restoration of water bodies, in particular, for the development of “Schemes for the integrated use and protection of water bodies”. Zoning is carried out on the basis of information on hydrographic units (river basin and sub-basins of rivers flowing into the main river) basin districts.

The basin district is the main management unit in the field of use and protection of water bodies, consisting of river basins and associated groundwater bodies and seas.

1 – Barents-Belomorsky 2 – Belomorsky 3 – Dvinsko-Pechersky

4 – Verkhne-Volzhsky 5 – Oksky 6 – Dnieper 7 – Kama 8 – Donskoy

9 – Kuban 10 – Western Caspian 11 – Lower Volga 12 – Ural

13 – Irtysh 14 – Lower Ob 15 – Upper Ob 16 – Yenisei

17 – Lensky 18 – Amursky 9 – Angaro-Baikalsky 20 – Anadyro-Kalymsky

Fig. 2.8 Basin districts in Russia

SELF-CONTROL QUESTIONS

Water resources and their main characteristics

What is the State Water Register?

Water management zoning of the territory

Territorial division of Russia and the main characteristics of water resources of the territories

Characteristics of surface water resources: swamps, glaciers, lakes, rivers, reservoirs.

Groundwater resources and their characteristics

If you look at our planet from space, the Earth appears as a blue ball completely covered with water. And the continents are like small islands in this endless ocean. This is understandable. Water occupies 70.8% of the planet's entire surface, leaving only 29.2% of land. The watery shell of our planet is called the hydrosphere. Its volume is 1.4 billion cubic meters.

Water appeared on our planet about 3.5 billion years ago in the form of vapor, which was formed as a result of degassing of the mantle. Currently, water is the most important element in the Earth's biosphere, since it cannot be replaced by anything. Fortunately, water resources are considered inexhaustible because scientists have come up with a way to desalinate salt water.

The main purpose of water as a natural resource is to support the life of all living things - plants, animals and humans. It is the basis of all life on our planet, the main supplier of oxygen in the most important process on Earth - photosynthesis.

Water is the most important factor in climate formation. By absorbing heat from the atmosphere and releasing it back, water regulates climate processes.

It is impossible not to note the role of water sources in the modification of our planet. From time immemorial, people have settled near reservoirs and water sources. Water serves as one of the main means of communication. There is an opinion among scientists that if our planet were entirely dry land, then, for example, the discovery of America would be delayed for several centuries. And we would hardly have learned about Australia for another 300 years.

Types of Earth's water resources

The water resources of our planet are the reserves of all water. But water is one of the most common and most unique compounds on Earth, since it is present in three states at once: liquid, solid and gaseous. Therefore, the Earth's water resources are:

. Surface waters (oceans, lakes, rivers, seas, swamps)

. Groundwater.

. Artificial reservoirs.

. Glaciers and snowfields (frozen water from glaciers in Antarctica, the Arctic and highlands).

. Water contained in plants and animals.

. Atmospheric vapors.

The last 3 points relate to potential resources, because humanity has not yet learned to use them.

Fresh water is the most valuable; it is used much more widely than sea, salt water. Of the total water reserves in the world, 97% of water comes from seas and oceans. 2% of fresh water is contained in glaciers, and only 1% is fresh water reserves in lakes and rivers.

Use of water resources

Water resources are the most important component of human life. People use water in industry and at home.

According to statistics, most water resources are used in agriculture (about 66% of all fresh water reserves). About 25% is used by industry and only 9% goes to meet the needs of utilities and households.

For example, to grow 1 ton of cotton, about 10 thousand tons of water are needed, for 1 ton of wheat - 1,500 tons of water. To produce 1 ton of steel, 250 tons of water are required, and to produce 1 ton of paper, at least 236 thousand tons of water are needed.

A person needs to drink at least 2.5 liters of water per day. However, on average, 1 person in large cities spends at least 360 liters per day. This includes the use of water in sewers, water supply, for watering streets and extinguishing fires, for washing vehicles, etc., etc.

Another option for using water resources is water transport. Over 50 million tons of cargo are transported annually in Russian waters alone.

Don't forget about fisheries. Breeding marine and freshwater fish plays an important role in the economies of countries. Moreover, fish farming requires clean water, saturated with oxygen and free of harmful impurities.

An example of the use of water resources is also recreation. Who among us doesn’t like to relax by the sea, barbecue on the river bank or swim in the lake? In the world, 90% of recreational facilities are located near water bodies.

Water conservation

Today there are only two ways to preserve water resources:

1. Preservation of existing fresh water reserves.

2. Creation of more advanced collectors.

The accumulation of water in reservoirs prevents its flow into the world's oceans. And storing water, for example, in underground cavities, allows you to protect water from evaporation. The construction of canals allows us to solve the issue of delivering water without it seeping into the ground. New methods of irrigating agricultural land are also being developed that make it possible to use wastewater.

But each of these methods has an impact on the biosphere. Thus, the reservoir system prevents the formation of fertile silt deposits. The canals impede the replenishment of groundwater. And water filtration in canals and dams is the main risk factor for swamps, which leads to disturbances in the planet’s ecosystem.

Today, the most effective measure for protecting water resources is considered to be the method of wastewater treatment. Various methods can remove up to 96% of harmful substances from water. But this is often not enough, and the construction of more advanced treatment facilities often turns out to be economically unprofitable.

Water pollution problems

Population growth, development of production and agriculture - these factors have led to a shortage of fresh water for humanity. The share of polluted water resources is growing every year.

Main sources of pollution:

. Industrial wastewater;

. Wastewater from municipal routes;

. Drains from fields (when the water is oversaturated with chemicals and fertilizers);

. Disposal of radioactive substances in water bodies;

. Drains from livestock complexes (such water contains a lot of biogenic organic matter);

. Shipping.

Nature provides for the self-purification of reservoirs, which occurs due to the water cycle in nature, due to the life activity of plankton, irradiation with ultraviolet rays, and the sedimentation of insoluble particles. But all these processes can no longer cope with the mass of pollution that human activity brings to the planet’s water resources.

Contents of the article

WATER RESOURCES, waters in liquid, solid and gaseous states and their distribution on Earth. They are found in natural bodies of water on the surface (oceans, rivers, lakes and swamps); in the subsoil (groundwater); in all plants and animals; as well as in artificial reservoirs (reservoirs, canals, etc.).

The water cycle in nature.

Although the world's total supply of water is constant, it is constantly being redistributed and is therefore a renewable resource. The water cycle occurs under the influence of solar radiation, which stimulates the evaporation of water. In this case, the minerals dissolved in it precipitate. Water vapor rises into the atmosphere, where it condenses, and thanks to gravity, the water returns to the earth in the form of precipitation - rain or snow. Most precipitation falls over the ocean and only less than 25% falls 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.

Gravity promotes the redistribution of liquid moisture from higher to lower areas, both on the earth's surface and under it. Water, initially 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 the geographical location and size of parts of the world. For example, South America receives almost three times as much annual precipitation as Australia, and almost twice as much as North America, Africa, Asia, and Europe (listed in order of decreasing annual precipitation). Some of this moisture returns 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 over the earth's surface and eventually reaches the ocean with river runoff.

Within continents, precipitation also varies greatly from place to place. For example, in Africa, in Sierra Leone, Guinea and Cote d'Ivoire, more than 2000 mm of precipitation falls annually, in most of central Africa - from 1000 to 2000 mm, but in some northern regions (Sahara and Sahel deserts) the amount precipitation is only 500–1000 mm, and in southern Botswana (including the Kalahari Desert) and Namibia - less than 500 mm.

Eastern India, Burma and parts of Southeast Asia receive more than 2000 mm of rainfall per year, and most of the rest of India and China receive between 1000 and 2000 mm, with northern China receiving only 500–1000 mm. Northwestern India (including the Thar Desert), Mongolia (including the Gobi Desert), Pakistan, Afghanistan and much of the Middle East receive less than 500 mm of annual rainfall.

In South America, annual precipitation 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 receives less than 500 mm. In some areas of Central America located to the north, over 2000 mm of precipitation falls per year, in the southeastern regions of the USA - from 1000 to 2000 mm, and in some areas of Mexico, in the northeast and Midwest of the USA, in eastern Canada - 500–1000 mm mm, while in central Canada and the western United States it is less than 500 mm.

In the far north of Australia, annual rainfall is 1000–2000 mm, in some other northern areas it ranges from 500 to 1000 mm, but most of the mainland and especially its central regions receive less than 500 mm.

Much of the former USSR also receives less than 500 mm of precipitation per year.

Time cycles of water availability.

At any point on the globe, river flow experiences daily and seasonal fluctuations, and also changes at intervals of several years. These variations are often repeated in a certain sequence, i.e. are cyclical. For example, water flows in rivers whose banks are covered with dense vegetation tend to be higher at night. This is because from dawn to dusk vegetation uses groundwater for transpiration, resulting in a gradual reduction in river flow, but its volume increases again at night when transpiration stops.

Seasonal cycles of water availability depend on the distribution of precipitation throughout the year. For example, in the Western United States, snow melts together in the spring. India receives little rainfall in winter, but heavy monsoon rains begin in midsummer. 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. This may be due to the cyclical nature of solar activity. Information on the cyclicity of precipitation and river flow is used in forecasting water availability and frequency of droughts, as well as in planning water protection activities.

WATER SOURCES

The main source of fresh water is precipitation, but two other sources can also be used for consumer needs: groundwater and surface water.

Underground springs.

Approximately 37.5 million km 3, or 98% of all fresh water in liquid form, is 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 the aquifers and the power of the pumps pumping out the water. Groundwater reserves in the Sahara are estimated at approximately 625 thousand km 3 . Under modern conditions, they are not replenished by surface fresh waters, but are depleted when pumped out. Some of the deepest groundwater is never included in the general water cycle, and only in areas of active volcanism does such water erupt in the form of steam. However, a significant mass of groundwater still penetrates the earth's surface: under the influence of gravity, these waters, moving along waterproof, inclined 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 also extracted by plant roots and then enter the atmosphere through the process of transpiration.

The water table represents the upper limit of available groundwater. If there are slopes, the groundwater table intersects with the earth's surface, and a source is formed. If groundwater is under high hydrostatic pressure, then artesian springs are formed at the places where they reach 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 on aquifers. However, in wells drilled to greater depths, to the level of pressure artesian waters, 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 impervious shale formations, and only rarely are they concentrated in underground cavities or underground streams. To correctly select the location for drilling a well, information about the geological structure of the area is usually required.

In some parts of the world, increasing consumption of groundwater is having serious consequences. Pumping a large volume of groundwater, incomparably exceeding its natural replenishment, leads to a lack of moisture, and lowering the level of this water requires greater costs for expensive electricity used to extract it. In places where the aquifer is depleted, the earth's surface begins to subside, and there it becomes more difficult to restore water resources naturally.

In coastal areas, over-abstraction of groundwater leads to the replacement of fresh water in the aquifer with seawater and saline water, thereby degrading local freshwater sources.

The gradual deterioration of groundwater quality as a result of salt accumulation can have even more dangerous consequences. Sources of salts 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 over a long distance.

Indiscriminate release or disposal of toxic chemicals causes them to leak into aquifers that provide drinking or irrigation water. In some cases, only a few years or decades are enough for harmful chemicals to enter groundwater and accumulate there in noticeable quantities. However, once the aquifer has been contaminated, it will take 200 to 10,000 years to naturally cleanse itself.

Surface sources.

Only 0.01% of the total volume of fresh water in liquid state is concentrated in rivers and streams and 1.47% in lakes. To store water and constantly provide it to consumers, as well as to prevent unwanted floods and generate electricity, dams have been built on many rivers. The Amazon in South America, the Congo (Zaire) in Africa, the Ganges with the Brahmaputra in southern Asia, the Yangtze in China, the Yenisei in Russia and the Mississippi and Missouri in the USA have the highest average water flows, and therefore the greatest energy potential.

Natural freshwater lakes holding 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 lands, navigation, recreation, fishing and, unfortunately, for the discharge of domestic and industrial wastewater. Sometimes, due to gradual filling with sediment or salinization, lakes dry up, but in the process of evolution of the hydrosphere, new lakes form in some places.

The water level of even “healthy” lakes can decrease throughout the year as a result of water runoff through the rivers and streams flowing from them, due to water seeping into the ground and its evaporation. Restoration of their levels usually occurs due to precipitation and the influx of fresh water from rivers and streams flowing into them, as well as from springs. However, as a result of evaporation, salts coming with river runoff accumulate. Therefore, after thousands of years, some lakes can become very salty and unsuitable for many living organisms.

USING WATER

Water consumption.

Water consumption is growing rapidly everywhere, but not only due to an increase in population, but also due to urbanization, industrialization and especially the development of agricultural production, in particular irrigated agriculture. By 2000, daily global water consumption 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 has been lost forever.

Water quality,

used for various purposes, is determined depending on the quantitative and qualitative content of dissolved salts (i.e. its mineralization), as well as organic substances; solid suspensions (silt, sand); toxic chemicals and pathogenic microorganisms (bacteria and viruses); smell and temperature. Typically, fresh water contains less than 1 g/l of dissolved salts, brackish water contains 1–10 g/l, and salt water contains 10–100 g/l. Water with a high salt content is called brine, or brine.

Obviously, for navigation purposes, water quality (salinity of sea water reaches 35 g/l, or 35‰) is not significant. Many species of fish have adapted to life in salt water, but others live only in fresh water. Some migratory fish (such as salmon) begin and complete their life cycles 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, may proceed based on the use of low-quality water. Water for domestic purposes must be of high quality, but not absolutely pure, since such water is too expensive to produce, and the lack of dissolved salts makes it tasteless. In some areas of the world, people are still forced to use low-quality muddy water from open reservoirs and springs for their daily 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 with regard to 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 foam formation is impaired; an insoluble residue remains on washed items, giving them a matte gray tint. Calcium carbonate from hard water forms scale (lime crust) in kettles and boilers, which reduces their service life and the thermal conductivity of the walls. The water is softened by adding sodium salts that replace calcium and magnesium. In soft water (containing less than 6 mg/l of calcium and magnesium carbonates), soap foams well and is more suitable for washing and washing. Such water should not be used for irrigation, since excess sodium is harmful to many plants and can disrupt the loose, clumpy structure of soils.

Although elevated concentrations of trace elements are harmful and even poisonous, small amounts of them can have beneficial effects on human health. An example is water fluoridation to prevent caries.

Reuse of water.

Used water is not always completely lost; some or even all of it can be returned to the cycle and reused. For example, water from a bath or shower passes through sewer pipes to city wastewater treatment plants, where it is treated and then reused. Typically, more than 70% of urban runoff returns to rivers or underground aquifers. Unfortunately, in many large coastal cities, municipal and industrial wastewater is simply dumped into the ocean and not recycled. Although this method eliminates the cost of cleaning them and returning them to circulation, there is a loss of potentially usable water and pollution of marine areas.

In irrigated agriculture, crops consume huge amounts of water, sucking it up with their roots and irreversibly losing up to 99% in the process of transpiration. However, when irrigating, farmers typically use more water than is needed for their crops. Part of it flows to the periphery of the field and returns to the irrigation network, and the rest seeps into the soil, replenishing groundwater reserves, which can be pumped out using pumps.

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 Great Britain almost all crops are provided with moisture from precipitation. In the United States, 10% of agricultural land is irrigated, mostly in the west of the country. A significant portion 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, besides Egypt, a significant share of irrigated land is in Sudan (22%), Swaziland (20%) and Somalia (17%), and in America - in Guyana (62%), Chile (46%), Mexico (22% ) and in Cuba (18%). In Europe, irrigated agriculture is developed in Greece (15%), France (12%), Spain and Italy (11% each). In Australia, approx. 9% agricultural land and approx. 5% – in the former USSR.

Water consumption by different crops.

To obtain high yields, a lot of water is required: for example, growing 1 kg of cherries requires 3000 liters of water, rice - 2400 liters, corn on the cob and wheat - 1000 liters, green beans - 800 liters, grapes - 590 liters, spinach - 510 l, potatoes - 200 l and onions - 130 l. The approximate amount of water spent just on growing (and not on processing or preparing) food crops consumed daily by one person in Western countries is approx. 760 l, for lunch (lunch) 5300 l and for dinner - 10,600 l, which is a total of 16,600 l per day.

In agriculture, water is used not only to irrigate crops, but also to replenish groundwater reserves (to prevent the groundwater level from dropping too quickly); for washing out (or leaching) salts accumulated in the soil to a depth below the root zone of cultivated crops; for spraying against pests and diseases; frost protection; fertilization; reducing air and soil temperatures in summer; for caring for livestock; evacuation of treated wastewater used for irrigation (mainly grain crops); and processing of harvested crops.

Food industry.

Processing of different food crops requires different amounts of water depending on the product, production technology and the availability of sufficient quality water. In the USA, from 2000 to 4000 liters of water are consumed to produce 1 ton of bread, and in Europe - only 1000 liters and only 600 liters in some other countries. Preserving fruits and vegetables requires 10,000 to 50,000 liters of water per ton in Canada, but only 4,000 to 1,500 in Israel, where water is a great scarcity. The “champion” in terms of water consumption is lima beans, 70,000 liters of water are consumed in the USA to preserve 1 ton of them. Processing 1 ton of sugar beet requires 1,800 liters of water in Israel, 11,000 liters in France and 15,000 liters in the UK. Processing 1 ton of milk requires from 2000 to 5000 liters of water, and to produce 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 huge volume of raw materials processed. The production of each ton of pulp and paper requires an average of 150,000 liters of water in France and 236,000 liters in the USA. The newsprint production process in Taiwan and Canada uses approx. 190,000 liters of water per 1 ton of product, 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 required, and motor gasoline requires two-thirds less.

Textile industry

requires a lot of water for soaking raw materials, cleaning and washing them, bleaching, dyeing and finishing fabrics and for other technological processes. To produce each ton of cotton fabric, from 10,000 to 250,000 liters of water are required, for woolen fabric - up to 400,000 liters. The production of synthetic fabrics requires significantly more water - up to 2 million liters per 1 ton of product.

Metallurgical industry.

In South Africa, when mining 1 ton of gold ore, 1000 liters of water are consumed, in the USA, when mining 1 ton of iron ore, 4000 liters and 1 ton of bauxite - 12,000 liters. Iron and steel production in the United States requires approximately 86,000 L of water for every ton of production, but up to 4,000 L of this is deadweight loss (mainly evaporation), and therefore approximately 82,000 L of water can be reused. Water consumption in the iron and steel industry varies significantly across countries. To produce 1 ton of pig iron in Canada, 130,000 liters of water are spent, to smelt 1 ton of pig iron in a blast furnace in the USA - 103,000 liters, steel in electric furnaces in France - 40,000 liters, and in Germany - 8000–12,000 liters.

Electric power industry.

To produce electricity, hydroelectric power plants use the energy of falling water to drive hydraulic turbines. In the USA, 10,600 billion liters of water are consumed daily at hydroelectric power plants.

Wastewater.

Water is necessary for the evacuation of domestic, industrial and agricultural wastewater. Although about half of the population, such as the United States, is served by sewer systems, wastewater from many homes is still simply dumped into septic tanks. But increasing awareness of the consequences of water pollution through such outdated sewer systems has stimulated the installation of new systems and the construction of water treatment plants to prevent pollutants from infiltrating into groundwater and untreated wastewater flowing into rivers, lakes and seas.

WATER SHORTAGE

When water consumption exceeds water supply, the difference is usually compensated by its reserves in reservoirs, since usually both demand and water supply vary by season. A negative water balance occurs when evaporation exceeds precipitation, so a moderate decrease in water reserves is common. Acute shortage occurs when water flow is insufficient due to prolonged drought or when, due to poor planning, water consumption continually increases at a faster rate than expected. Throughout history, humanity has suffered from water shortages from time to time. In order not to experience a shortage of water even during droughts, many cities and regions try to store it in reservoirs and underground collectors, but at times additional water-saving measures are necessary, as well as its normalized consumption.

OVERCOMING WATER SCARCITY

Flow redistribution is aimed at providing water to those areas where it is scarce, and water conservation is aimed at reducing irreplaceable water losses and reducing local demand for it.

Redistribution of runoff.

Although traditionally many large settlements arose near permanent water sources, nowadays some settlements are also created in areas that receive water from afar. Even when the source of the supplementary water supply is within the same state or country as the destination, technical, environmental or economic problems arise, but if the imported water crosses state borders, the potential complications increase. For example, spraying silver iodide into clouds causes an increase in precipitation in one area, but it may cause a decrease in precipitation in other areas.

One of the large-scale flow transfer projects proposed in North America involves diverting 20% ​​of excess water from the northwestern regions to arid regions. 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 facilitate the development of navigation in the interior regions, 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 grand plan for the transfer of flow is associated with the construction of the Grand Canadian Canal, through which water would be directed from the northeastern regions of Canada to the western ones, and from there to the United States and Mexico.

The project of towing icebergs from Antarctica to arid regions, for example, to the Arabian Peninsula, is attracting much attention, which will annually provide fresh water to 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 places of consumption, which is technically feasible through the use of electrodialysis, freezing and various distillation systems. The larger the desalination plant, the cheaper it is to obtain fresh water. But as the cost of electricity increases, desalination becomes economically unviable. 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 USA. Numerous smaller demonstration plants have been built in other countries.

Protection of water resources.

There are two widespread ways to conserve water resources: preserving existing supplies of usable water and increasing its reserves by constructing more advanced collectors. The accumulation of water in reservoirs prevents its flow into the ocean, from where it can only be extracted again through the process of the water cycle in nature or through desalination. Reservoirs also make it easier to use water at the right time. Water can be stored in underground cavities. In this case, there is no loss of moisture due to 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; using more efficient irrigation methods 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 one or another impact on the environment. For example, dams spoil the natural beauty of unregulated rivers and prevent the accumulation of fertile silt deposits on floodplains. Preventing water loss as a result of filtration in canals can disrupt the water supply of wetlands and thereby adversely affect the state of their ecosystems. It may also prevent groundwater recharge, thereby affecting water supplies to other consumers. And to reduce the volume of evaporation and transpiration by agricultural crops, it is necessary to reduce the area under cultivation. The latter measure is justified in areas suffering from water shortages, where savings are being made by reducing irrigation costs due to the high cost of energy required to supply water.

WATER SUPPLY

The sources of water supply and reservoirs themselves are important only when water is delivered in sufficient volume to consumers - to residential buildings and institutions, to fire hydrants (devices for collecting water for fire needs) and other public utility facilities, industrial and agricultural facilities.

Modern water filtration, purification and distribution systems are not only convenient, but also help prevent the spread of water-borne diseases such as typhoid and dysentery. A typical city 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 station where its volume and flow rate are recorded. The water then enters the water tower, where it is passed through an aeration plant (where impurities are oxidized), a microfilter to remove silt and clay, and a sand filter to remove remaining impurities. Chlorine, which kills microorganisms, is added to the water in the main pipe before entering the mixer. Ultimately, purified water is pumped into a storage tank before being sent to the distribution network to consumers.

The pipes at the central waterworks are usually cast iron and have a 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, water supply systems in agricultural areas must have a large capacity, especially in arid conditions. Water from the reservoir is directed into a lined, or more often unlined, main canal and then through branches into distribution irrigation canals of various types to farms. Water is released onto the fields as a spill or through irrigation furrows. Because many reservoirs are located above irrigated land, water flows primarily by gravity. Farmers who store their own water pump it from wells directly into ditches or storage ponds.

For sprinkling or drip irrigation, which has been practiced recently, low-power pumps are used. In addition, there are giant center-pivot irrigation systems that pump water from wells in the middle of the field directly into a pipe equipped with sprinklers and rotating in a circle. The fields irrigated in this way appear from the air as giant green circles, some of them reaching 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 from the deep Nubian aquifer.