Hydrology as a science

6.THE DISTRIBUTION OF LAND AND WATER ON EARTH
Of the total area of ​​the globe (510 million km2), 361 million km2 or 71% is occupied by the World Ocean. The land area is 149 million km2 or 29% of it. The total area of ​​all inland water bodies on land is less than 3 percent of its total area, and glaciers account for about 10 percent.
The total volume of water on Earth is more than 1 billion 386 million km3. Of this, 1 billion 338 million km3 is in the world's oceans, 234 million km3 in the Earth's crust, 26 million km3 in glaciers, 176 thousand km3 in lakes, and 2.1 thousand km3 in rivers (Table 1).
The total freshwater resources on Earth are estimated at 35 million km3, which is 2.3% of the total volume of water on Earth. More than 68% of fresh water is in the glaciers of Antarctica and Greenland, and 30% is groundwater. Currently, the amount of fresh water available is about 0.3% of the total volume of water on Earth.

6. YERDA ER VA SUVNING TARQATISHI
Yer sharining umumiy maydonining (510 mln km2) 361 mln km2 yoki 71%ini Jahon okeani egallaydi. Er maydoni 149 mln km2 yoki 29% ni tashkil qiladi. Quruqlikdagi barcha ichki suv havzalarining umumiy maydoni uning umumiy maydonining 3 foizidan kamrog'ini, muzliklar esa taxminan 10 foizni tashkil qiladi.
Yerdagi suvning umumiy hajmi 1 milliard 386 million km3 dan ortiq. Shundan 1 mlrd 338 mln km3 jahon okeanida, 234 mln km3 yer qobig’ida, 26 mln km3 muzliklarda, 176 ming km3 ko’llarda, 2,1 ming km3 daryolarda (1-jadval).
Yerdagi umumiy chuchuk suv resurslari 35 million km3 deb baholanadi, bu Yerdagi umumiy suv hajmining 2,3% ni tashkil qiladi. Chuchuk suvning 68% dan ortigʻi Antarktida va Grenlandiya muzliklarida, 30% esa yer osti suvlaridir. Hozirgi vaqtda mavjud chuchuk suv miqdori Yerdagi umumiy suv hajmining taxminan 0,3% ni tashkil qiladi.

7.THE WATER CYCLE IN NATURE
The large water cycle involves all types of water circulation in continents and oceans. The return of water from land to the oceans or adjacent seas in the form of river flows completes the process of the great water cycle. Thus, the Earth's oceans, atmospheric moisture and waters are interconnected as a single system. Some of the river water that forms on the land surface flows into the oceans and seas, while some remains inside the continents. Much of the land surface (78 percent) slopes toward the Earth’s oceans, where the rivers flow that forms there flows into the oceans. This part of the land is called the oceanic or marginal flow areas. Areas where rivers do not flow into the ocean are called inland flow zones or closed zones. On the globe, marginal flow areas are 117 million km², and inland flow areas are 32 million km². Examples of the largest inland flow areas are the Aral-Caspian Basin, Lake Chad in Africa, the Sahara Desert, the deserts of Arabia and Central Australia.