Water resources are one of the most important treasures of the Earth. But they are very limited. Indeed, although ¾ of the planet’s surface is occupied by water, most of it is the salty World Ocean. A man needs fresh water.
Its resources are also mostly inaccessible to people, as they are concentrated in the glaciers of the polar and mountainous regions, in swamps, underground. Only a small part of the water is convenient for human use. These are fresh lakes and rivers. And if in the first, water is delayed for decades, then in the second it is renewed approximately every two weeks.
River runoff: what does this concept mean?
This term has two main meanings. Firstly, it means the entire volume of water flowing into the sea or ocean during the year. This is its difference with the other term "river flow", when the calculation is carried out for a day, hours or seconds.
The second value is the amount of water, dissolved and suspended particles carried by all the rivers flowing in this region: the mainland, country, region.
Surface and underground river runoff are distinguished. In the first case, we mean water flowing into the river on the earth's surface. And underground - these are springs and keys, beating under the channel. They also replenish the water in the river, and sometimes (during the summer low water or when the surface is icebound) they are its only source of nutrition. Together, these two species make up the total river flow. When they talk about water resources, they mean it.
Factors Affecting River Runoff
This question has already been studied enough. Two main factors can be named: the terrain and its climatic conditions. In addition to them, several other additional ones are highlighted, including human activities.
The main reason for the formation of river flow is the climate. It depends on the ratio of air temperature and precipitation what volatility is in a given area. River formation is possible only with excessive moisture. If the evaporation exceeds the amount of precipitation, there will be no surface runoff.
The climate determines the nutrition of rivers, their water and ice regimes. Precipitation provides replenishment of moisture. Low temperatures reduce evaporation, and when freezing soils, the flow of water from underground sources is reduced.
The relief affects the size of the catchment area of the river. Depends on the shape of the earth’s surface in which direction and at what speed moisture will flow. If there are closed depressions in the relief, not rivers, but lakes will form. The slope of the terrain and the permeability of the rocks affect the ratio between the parts of the precipitation that flows into the water and leaks underground.
The significance of rivers for humans
Nile, Indus with Ganges, Tiger and Euphrates, Yellow River and Yangtze, Tiber, Dnieper ... These rivers have become the cradle for different civilizations. Since the inception of mankind, they have served for him not only as a source of water, but also as channels of penetration into new unexplored lands.
Thanks to river runoff, irrigated agriculture is possible, which feeds almost half the world's population. High water consumption also means rich hydropower potential. River resources are used in industrial production. Especially water-intensive are the production of synthetic fibers and the manufacture of pulp and paper.
River transport is not the fastest, but cheap. It is best suited for the transport of bulk goods: forests, ores, petroleum products, etc.
A lot of water is taken for household needs. Finally, rivers are of great recreational importance. These are places of rest, restoration of health, a source of inspiration.
The deepest rivers in the world
The largest volume of river flow is from the Amazon. It is almost 7000 km 3 per year. And this is not surprising, because the Amazon is full-flowing all year due to the fact that its left and right tributaries flow at different times. In addition, it collects water from an area the size of almost the whole of mainland Australia (more than 7,000 km 2 )!
In second place is the African Congo River with a drain of 1445 km 3 . Located in the equatorial belt with daily showers, it never gets shallow.
The following are the resources of the full river flow: the Yangtze is the longest in Asia (1080 km 3 ), Orinoco (South America, 914 km 3 ), Mississippi (North America, 599 km 3 ). All three are very spilled during rains and pose a considerable threat to the population.
On the 6th and 8th places in this list are the great Siberian rivers - the Yenisei and Lena (624 and 536 km 3, respectively), and between them - the South American Parana (551 km 3 ). Closing the top ten is another South American river Tokantins (513 km 3 ) and African Zambezi (504 km 3 ).
Water resources of the world
Water is the source of life. Therefore, it is very important to possess its reserves. But they are distributed unevenly on the planet.
The provision of countries with river flow resources is as follows. The top ten most water-rich countries are Brazil (8,233 km 3 ), Russia (4,5 thousand km 3 ), the USA (more than 3 thousand km 3 ), Canada, Indonesia, China, Colombia, Peru, India, Congo .
Areas poorly secured in tropical dry climates: North and South Africa, countries of the Arabian Peninsula, Australia. There are few rivers in the inland regions of Eurasia, therefore, among the low-income countries, Mongolia, Kazakhstan, and Central Asian states.
If the population using this water is taken into account, the indicators change somewhat.
Resource availability of river flow| The largest | Smallest |
| Countries | Security (m 3 / person) | Countries | Security (m 3 / person) |
| French guiana | 609 thousand | Kuwait | Less than 7 |
| Iceland | 540 thousand | United Arab Emirates | 33.5 |
| Guyana | 316 thousand | Qatar | 45.3 |
| Suriname | 237 thousand | Bahamas | 59.2 |
| Congo | 230 thousand | Oman | 91.6 |
| Papua New Guinea | 122 thousand | Saudi Arabia | 95.2 |
| Canada | 87 thousand | Libya | 95.3 |
| Russia | 32 thousand | Algeria | 109.1 |
The densely populated countries of Europe with full-flowing rivers are no longer so rich in fresh water: Germany - 1326, France - 3106, Italy - 3052 m 3 per capita with an average value for the whole world - 25 thousand m 3 .
Cross-border flow and problems associated with it
Many rivers cross the territory of several countries. In this regard, difficulties arise in the sharing of water resources. This problem is especially acute in areas of irrigated agriculture. In them, almost all the water is taken to the fields. A neighbor downstream may not get anything.
For example, the Amu Darya River, which belongs to Tajikistan and Afghanistan in its upper reaches, and Uzbekistan and Turkmenistan in the middle and lower reaches, has not brought its waters to the Aral Sea in recent decades. Only with good neighborly relations between neighboring states can its resources be used to the benefit of all.
Egypt receives 100% of river water from abroad, and a reduction in the flow of the Nile due to the abstraction of water upstream can adversely affect the state of agriculture in the country.
In addition, various pollutants “travel” along the borders of countries along with water: garbage, plant effluents, fertilizers and pesticides washed off from the fields. These problems are relevant for countries lying in the Danube basin.
Rivers of Russia
Our country is rich in large rivers. There are especially many of them in Siberia and the Far East: Ob, Yenisei, Lena, Amur, Indigirka, Kolyma, etc. And the river flow is the largest in the eastern part of the country. Unfortunately, only a small fraction of them is used so far. Part goes for domestic needs, for the work of industrial enterprises.
These rivers have enormous energy potential. Therefore, the largest hydroelectric power plants are built on Siberian rivers. And they are indispensable as transport routes and for rafting the forest.
The European part of Russia is also rich in rivers. The largest of them is the Volga, its runoff is 243 km 3 . But 80% of the population and economic potential of the country are concentrated here. Therefore, water scarcity is sensitive, especially in the southern part. The runoff of the Volga and some of its tributaries is regulated by reservoirs; a cascade of hydroelectric power plants is built on it. The river with its tributaries is the main part of the Unified Deepwater System of Russia.
In the context of the growing worldwide water crisis, Russia is in favorable conditions. The main thing is to prevent pollution of our rivers. Indeed, according to economists, clean water can become a more valuable commodity than oil and other minerals.