Water water resources. Water resources of the planet and their reserves. Geographical distribution of precipitation
WATER RESOURCES LAND
Until relatively recently, water, like air, was considered one of the free gifts of nature, only in areas of artificial irrigation it always had a high price. Recently, attitudes towards land water resources have changed. This is explained by the fact that fresh water resources account for only 2.5% of the total volume of the hydrosphere. In absolute terms, this is a huge value (30-35 million m3), which exceeds the current needs of humanity by more than 10 thousand times! However, the overwhelming majority of fresh water is, as it were, conserved in the glaciers of Antarctica, Greenland, in the ice of the Arctic, in mountain glaciers and forms a kind of “emergency reserve” that is not yet available for use.
Indicators:
96.5% - salty waters of the World Ocean; 1% - saline groundwater; 2.5% - fresh water resources.
Fresh water: 68.7 - glaciers; 30.9% - groundwater.
Table 11. Distribution of global freshwater resources by major region.
The data in this table allows us to draw interesting conclusions. First of all, about how the ranking of countries according to the first indicator does not coincide with their placement according to the second. It can be seen that Asia has the largest fresh water resources, and Australia and Oceania have the smallest, while in terms of their specific supply they change places. Of course, it’s all about the population, which in Asia has already reached 3.7 billion people, and in Australia barely exceeds 30 million. If we discount Australia, then South America will be the region with the most fresh water supply in the world. And it is no coincidence, because this is where the Amazon is located - the deepest river in the world.
Individual countries differ even more in their reserves and availability of fresh water. Based on the principle of “the best,” we will show which of them belong to the category of the richest and poorest in fresh water.
Table 12. Top ten countries by freshwater resources.
In it, the ranking of resources also does not coincide with the ranking of specific provision, and in each individual case such a difference can be explained. For example, in China and India there is a huge population, therefore, low security per capita. But there are countries in the world that are even less supplied with fresh water, where there is less than 1 thousand m 3 of water per capita (i.e., the amount that a resident of a large European or American city consumes in about two days). The most striking examples of this kind can be found in the sub-Saharan part of Africa (Algeria - 520 m3, Tunisia - 440 m3, Libya - 110 m3) and in the Arabian Peninsula (Saudi Arabia - 250 m3, Kuwait - 100 m3).
These individual examples are interesting because they allow us to make an important generalization: at the end of the 20th century. approximately 2/5 of our planet's population experiences a chronic lack of fresh water. In this case, we are talking mainly about those developing countries that are located in the Earth's arid belt. It should also be taken into account that even the available fresh water in these countries is so polluted that it is the main cause of most diseases.
The main consumer of fresh water is agriculture, where irrecoverable water consumption is very high, especially for irrigation. Industrial, energy and municipal water consumption is also growing all the time. In economically developed countries, a city dweller uses 300-400 liters of water per day. Such an increase in consumption with unchanged river flow resources creates a real threat of fresh water shortage.
In this case, it is necessary to take into account not only the quantity, but also the quality of water. In developing countries, every third person suffers from a lack of drinking water. Consumption of contaminated water is the source of 3/4 of all diseases and 1/3 of all deaths. In Asia, more than 1 billion people do not have access to clean water, in sub-Saharan Africa - 350 million and in Latin America - 100 million people.
But, in addition, fresh water supplies on Earth are distributed extremely unevenly. In the equatorial zone and in the northern part of the temperate zone it is available in abundance and even in excess. The most water-rich countries are located here, with more than 25 thousand m3 per capita per year. In the arid zone of the Earth, which covers about 1/3 of the land area, water shortages are especially acute. Here are the most water-scarce countries, where per capita there is less than 5 thousand m 3 per year, and agriculture is possible only with artificial irrigation.
There are several ways to solve humanity's water problem. The main one is reducing the water intensity of production processes and reducing irretrievable water losses. First of all, this applies to such technological processes as the production of steel, synthetic fiber, pulp and paper, cooling of power units, and irrigation of rice and cotton fields. The construction of reservoirs that regulate river flow is of great importance for solving the water problem. Over the past fifty years, the number of reservoirs on the globe has increased approximately 5 times. In total, more than 60 thousand reservoirs have been created in the world, the total volume of which (6.5 thousand km 3) is 3.5 times greater than the one-time volume of water in all the rivers of the globe. Taken together, they occupy an area of 400 thousand km 2, which is 10 times larger than the area of the Sea of Azov. Such large rivers as the Volga, Angara in Russia, Dnieper in Ukraine, Tennessee, Missouri, Columbia in the USA, and many others, have actually turned into cascades of reservoirs. Large and large reservoirs play a particularly important role in transforming river flow. The problem is that the main source of satisfying humanity’s needs for fresh water has been and remains river (channel) waters, which determine the planet’s “water ration” - 40 thousand km 3 . It's not that significant, especially considering that you can actually use about 1/2 of this amount.
In terms of the number of large reservoirs, the United States, Canada, Russia, and some countries in Africa and Latin America stand out.
Table 13. Largest reservoirs in the world by volume of water (countries)
In the USA, Canada, Australia, India, Mexico, China, Egypt, and a number of CIS countries, numerous projects for the territorial redistribution of river flow through its transfer have been implemented or are being designed. However, recently the largest inter-basin transfer projects have been canceled for economic and environmental reasons. In the countries of the Persian Gulf, the Mediterranean, Turkmenistan, the Caspian Sea, the southern USA, Japan, and the islands of the Caribbean, seawater desalination is used; The world's largest producer of such water is Kuwait. Fresh water has already become a global trade commodity: it is transported in sea tankers and through long-distance water pipelines. Projects are being developed to tow icebergs from Antarctica, which sends 1,200 million tons of fresh water preserved in them to the countries of the arid zone every polar summer.
You know that river flow is also widely used to generate hydropower. World hydropower potential, suitable for use, is estimated at almost 10 trillion kWh. possible electricity generation. About 1/2 of this potential falls on just 6 countries: China, Russia, USA, Congo (formerly Zaire), Canada, Brazil.
Table 14 . World economic hydro potential and its use
|
Regions |
Total |
Including used, % |
|
|
billion kWh |
V % |
||
|
CIS |
1100 |
11,2 |
|
|
Foreign Europe |
|||
|
Foreign Asia |
2670 |
27,3 |
|
|
Africa |
1600 |
16,4 |
|
|
North America |
1600 |
16,4 |
|
|
Latin America |
1900 |
19,4 |
|
|
Australia and Oceania |
|||
|
The whole world |
Basic concepts: geographical (environmental) environment, ore and non-metallic minerals, ore belts, mineral basins; structure of the world land fund, southern and northern forest belts, forest cover; hydropower potential; shelf, alternative energy sources; resource availability, natural resource potential (NRP), territorial combination of natural resources (TCNR), areas of new development, secondary resources; environmental pollution, environmental policy. Skills and abilities: be able to characterize the natural resources of the country (region) according to plan; use various methods of economic assessment of natural resources; characterize the natural prerequisites for the development of industry and agriculture of the country (region) according to the plan; give a brief description of the location of the main types of natural resources, identify countries as “leaders” and “outsiders” in terms of endowment with one or another type of natural resources; give examples of countries that do not have rich natural resources, but have achieved a high level of economic development and vice versa; give examples of rational and irrational use of resources. | ||
The aquatic environment includes surface and groundwater. Surface water is mainly concentrated in the ocean, containing 1 billion 375 million km3 - about 98% of all water on Earth. The ocean surface (water area) is 361 million km2. It is approximately 2.4 times larger than the land area of the territory, occupying 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 layer of water, 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 (less salinity) and fresh; existing geothermal waters have an elevated temperature (more than 30°C). 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 contained in snow and freshwater icebergs found in areas mainly in the Antarctic Circle. The annual global river flow of fresh water 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, occurs in the infertile and sparsely populated northern territories. In the absence of fresh water, salty surface or underground water is used, desalinating it or hyperfiltrating it: passing it under a high pressure difference through polymer membranes with microscopic holes that trap salt molecules. Both of these processes are very energy-intensive, so an interesting proposal is to use freshwater icebergs (or parts thereof) as a source of fresh water, which for this purpose are towed through the water to shores that do not have fresh water, where they are organized to melt. According to preliminary calculations by the developers of this proposal, obtaining fresh water will be approximately half as energy intensive as 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, for example, whooping cough, chickenpox, tuberculosis, are transmitted through the air. To combat the spread of diseases through water, the World Health Organization (WHO) has declared this decade the Decade of Drinking Water.
WATER RESOURCES, in ó 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.).Water is the only substance that exists in nature in liquid, solid and gaseous states. The meaning 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% comes from fresh water contained in cover and mountain glaciers, and only less than 1% comes from fresh water in 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 together with it without any significant changes in their own chemical composition. Thus, water is necessary for the normal functioning of all living organisms. A 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. On bó 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 the expanding ice can rupture water pipes and pavements and erode rock into loose soil. Ice is less dense than liquid water, which explains its buoyancy.Water also has unique thermal properties. When her temperature drops to
0 ° C and it freezes, then 79 calories are released from each gram of water. During night frosts, farmers sometimes spray their gardens with water to protect the buds from frost damage. When water vapor condenses, each gram of it releases 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 temperature.Water molecules are held together 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 (called molecular attraction). The unique properties of water are determined by the strength of hydrogen bonds. The forces of adhesion and molecular attraction allow it to overcome gravity and, due to capillarity, to rise up through small pores (for example, in dry soil).
DISTRIBUTION OF WATER IN NATUREWhen the temperature of water changes, the hydrogen bonds between its molecules also change, which in turn leads to a change in its state from liquid to solid and gaseous. see also WATER, ICE AND STEAM.
Since liquid water is an excellent solvent, it is rarely absolutely pure and contains minerals in a dissolved or suspended state. Only 2.8% of 1.36 billion km
3 of all the water available on Earth is fresh, and bó The majority of it (about 2.2%) is in the solid state in mountain and cover glaciers (mainly in Antarctica) and only 0.6% is in the liquid state. Approximately 98% of liquid fresh water is concentrated underground. The salty waters of the oceans and inland seas, which occupy more than 70% of the earth's surface, make up 97.2% of all the earth's waters. see also OCEAN.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 (see also RAIN). Bó 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. see also HYDROLOGY.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). Part 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 receives more than 2000 mm of precipitation annually, most of central Africa receives between 1000 and 2000 mm, but in some northern regions (the Sahara and Sahel deserts) precipitation amounts to only 500–1000 mm, and in southern Botswana (including the desert Kalahari) and Namibia less than 500 mm.Eastern India, Burma and parts of Southeast Asia receive more than 2000 mm of precipitation per year, a b
ó most of the rest of India and China are from 1000 to 2000 mm, with northern China only 500 to 1000 mm. In the territory of northwestern India (including the Thar Desert), Mongolia (including the Gobi Desert), Pakistan, Afghanistan andó Most of the Middle East receives less than 500 mm of rainfall annually.In South America, annual precipitation in Venezuela, Guyana and Brazil exceeds 2000 mm, b
ó Most of the eastern regions of this continent receive 1000-2000 mm, but Peru and some areas 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, 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 - 5001000 mm, while in central Canada and the western USA less than 500 mm.In the far north of Australia, annual precipitation is 10002000 mm, in some other northern regions it ranges from 500 to 1000 mm, but
ó Most of the mainland and especially its central regions receive less than 500 mm.ó Most 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 SOURCESThe 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 in b
ó greater depth, 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 out a large volume of groundwater, which incomparably exceeds its natural replenishment, leads to a lack of moisture, and lowering the level of these waters requires
ó higher costs for expensive electricity used to extract them. In places where the aquifer is depleted, the earth's surface begins to subsidence, and there it becomes more difficult to restore water resources naturally.In coastal areas, excessive groundwater withdrawal 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. see also RIVER.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 for breakfast 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; application of fertilizers; 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 varying 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 from 10,000 to 50,000 liters of water per ton in Canada, but in Israel, where water is a great scarcity, only 40001500. 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 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 1000 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 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 needed, and 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 are consumed 12,000 liters. Iron and steel production in the US requires approximately 86,000 liters of water for every ton of production, but up to 4,000 liters of this is deadweight loss (mainly evaporation), and therefore approximately 82,000 liters 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 stations (see also HYDROPOWER). 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 everything wouldó Greater 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 the infiltration of pollutants into groundwater and the release of untreated wastewater into rivers, lakes and seas (see also WATER POLLUTION). WATER SHORTAGEWhen 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 is formed when evaporation exceeds precipitation, so a moderate decrease in water reserves is a common occurrence. Acute shortage occurs when water supply 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 needed, as well as its normalized consumption.
OVERCOMING WATER SCARCITYFlow redistribution is aimed at providing water to those areas where it is scarce, and water resource protection 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 would be redistributed annually 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. 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.
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 1025 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 orders 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 reservoirs.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.
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Water resources and their importance
water natural economic
If you look at our planet from space, the Earth appears as a blue ball completely covered with water. Water covers the earth's surface, forming the World Ocean and the endless icy deserts of the polar regions. The watery shell of our planet is called the hydrosphere.
Water resources mean the entire variety of water suitable for economic use. Among natural resources, water resources occupy one of the most important places.
The main purpose of water as a natural resource is to support the life of all living things - plants, animals and humans.
Water sources play an important role in the transformation of our planet. From time immemorial, people have settled near reservoirs and water sources. Water is also the creator of natural landscapes and serves as one of the important means of communication.
Water is the most important factor in climate formation.
A special role belongs to inland reservoirs and watercourses, which are transport arteries and sources of food resources.
Types of water resources
The water resources of our planet are the reserves of all water. Water is one of the most common and most unique compounds on Earth, as it is present in three states at once: liquid, solid and gaseous. Based on this, the main types of water resources can be identified.
There are also potential water resources such as:
* Glaciers and snowfields (frozen water from glaciers in Antarctica, the Arctic and highlands).
* Atmospheric vapors.
But people have not yet learned to use these resources.
Use of water.
When we talk about the Earth's water resources, we usually mean the planet's supply of fresh water.
Water is the most important component of human life. A special place in the use of water resources is occupied by water consumption for the needs of the population.
According to statistics, most water resources are used in agriculture (about 66% of all fresh water reserves).
Don't forget about fisheries. Breeding marine and freshwater fish plays an important role in the economy of many countries.
Water bodies also serve as a favorite vacation spot for people. Who among us doesn’t like to relax by the sea, barbecue on the river bank or swim in the lake? In the world, about 90% of all recreational facilities are located near bodies of water.
Based on all this, the question arises: How much water is there in the modern biosphere? Is the supply of fresh water inexhaustible?
It turns out that the entire volume of the hydrosphere is approximately 1.4 billion cubic meters. Of this, 94% comes from the salty waters of the seas and oceans. And the remaining 6% is distributed between groundwater, rivers, lakes, streams, and glaciers.
Currently, the availability of water per person per day varies greatly in different countries of the world.
In order to find out how each of us can help save water, I looked at water consumption for household needs, using the example of residents of Russia, and this is what we learned.
Water consumption of Russian residents for sanitary and domestic needs
Thus, the higher the degree of home improvement, the greater the water consumption.
The growth of cities and population, the development of production and agriculture - these factors have led to a shortage of fresh water for humanity. In a number of countries with developed economies, the threat of water shortages is brewing. The shortage of fresh water on earth is growing quite quickly. The share of polluted water resources is growing every year.
In recent years, environmentalists in all countries have been sounding the alarm. Due to man's careless attitude towards water resources, great changes are occurring on Earth that are harmful to human health and lead to the death of animals and plants.
I monitored water consumption in our school, at home and in our neighbors. And here's what it turned out: in everyday life, water is not used sparingly. A huge amount of water is wasted unnecessarily. For example: a leaking washbasin (or faucet), leaking heating system pipes, unfinished water in a glass…. etc.
We don’t think at all about the fact that there may be a shortage of fresh water.
As a result of my research, I came to the conclusion that each of us, being in our home, at work or at school, can at least slightly help preserve fresh water supplies on our planet.
Thus, my hypothesis turned out to be correct. To achieve my goal - to develop a careful attitude towards water, based on the results of my work, I compiled a reminder that will help save water.
Water is a wonderful gift of nature. We are used to it being all around us - in raindrops, snowdrifts, in rivers and lakes, in swamps, glaciers, gushing out in cold springs from the slopes or at the bottom of the river. Water is needed for all living things, as well as in inanimate nature.
And as it turns out, fresh water supplies are not endless.
It is mistakenly believed that humanity has inexhaustible reserves of fresh water at its disposal and that they are sufficient for all needs. This is a deep misconception.
The problem of fresh water shortage arose for the following main reasons:
· intensive increase in demand for water due to the rapid growth of the planet's population and the development of industries that require huge amounts of water resources.
· loss of fresh water due to reduced water flow in rivers.
· pollution of water bodies with industrial and domestic wastewater.
The world needs sustainable water management practices, but we are not moving fast enough in the right direction. Humanity is too slow to understand the scale of the danger created by a careless attitude towards the environment.
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