Water table
Nature Zone Total moistening (atm precipitation, river runoff), the minimum
Annual
increase in plant mass, kg / ha
Tundra and tundra 300-350 10-40
Middle taiga 460-470 40-80
Deciduous forests 550-600 80-100
Forest-steppe 580 100-150
Steppe 465 90-140
Subtropical semi-desert 320 10-25
Restricting the tropical savanna 920 150-300
Evergreen tropical forests 1320 300-500
From this table it is clearly visible uneven distribution of water resources in natural areas of the planet. A specific locations on Earth, these differences may be much higher. For example, in India there is a meteorological station Cherapundzhi, where the annual rainfall record rainfall – 23 mm thousand, and in Peru at weather stations in La Zhoya did not get a single millimeter of rain per year. Therefore, on Earth as many other deserts I drylands. Whole areas where prosperity, or even in excess of a variety of natural resources – the sun’s heat, fertile and suitable for the cultivation of the soil – has not enough water, precipitation.
But along with many areas on Earth and territories in which there is constant surplus of water – is primarily wetlands and wetlands. Here, as a rule, already in short supply will be the sun’s heat and the ability to take the surface (drain) the excess water.
Scientists know not only such long-term periods of change of dry and wet years, but centuries-old cycles of change in moisture over large areas. As a result, during wet periods is offensive to the forest steppe, a dry – desert seizing new territory.
Often, precipitation is unevenly and in different seasons of the year. There are areas (these areas are primarily the so-called monsoon), where the dry season can not fall out over many months, a drop of rain, and then replaced by a severe drought come torrential tropical downpours. But in zovah with quite a mild climate, including in most areas of Russia in the spring after the snow melts the lion’s share of the annual runoff is held in the rivers. And for its regulation, ie for a more equitable distribution of the seasonal year, are on the rivers of the reservoir, and the creeks and streams – ponds and reservoirs.
Even in highly industrialized countries such as France, more than 20 million residents of small towns, not to mention the rural people throw all sorts of waste into rivers. And according to the American specialist D. Bard, the total amount of funds needed for water purification in
U.S. should be around 40 billion dollars, and in the 70-ies. XX century. for these purposes are spent 50 times less.
Arctic, in connection with what are called “island”. These same ice sheet, scale commensurate with the mainland and so-called “continental”, can now be seen only in Antarctica and Greenland.
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