Introduction to hydrosphere: water cycle and water reservoirs

what is hydrosphere?

           ‘Hydro’ is a Greek word that means water. The hydrosphere is the total water available under or near the surface of the Earth. most of the earth’s water occurs in the ocean. the rest of the earth’s water resides in lakes, streams, glaciers, ice sheets, groundwater, biosphere, and atmosphere.

Surprisingly, the hydrosphere is only 0.03% of the earth’s total mass. The frozen parts of water including glaciers, ice sheets, and ice caps are collectively called the cryosphere.   around 97 percent of water resides in the ocean. and the rest of the 3 % of water resides in the glacier, groundwater, lake, river, and biosphere.

Hydrologic cycle or water cycle

The hydrologic cycle or water cycle is the most familiar and important cycle of the earth system. the large water bodies such as the ocean play a major role in the hydrologic cycle. Through the water cycle, hydrosphere interacts with the atmosphere, biosphere, and lithosphere. In the hydrologic cycle, water continuously moves from one reservoir to another. the reservoirs are the storage places of water.

water cycle, hydrosphere

In the water cycle, the sun is the main source that causes evaporation of water from the ocean and land surface water. now, the atmosphere gets water vapor that moves with the flowing air. Due to atmospheric changes, the water vapor undergoes the condensed and changed into a liquid or solid-state. the condensed water comes to earth as precipitation due to gravity. this precipitation may be rain or snow. Water also evaporates from the lithosphere and biosphere. some of the water flows back to the ocean as runoff.

Water Reservoirs: water storage places

1. ocean

         About 97 % of the water of hydrosphere is in the ocean. Around 71 % of the earth’s surface area is covered by the ocean and the rest of the 29% is the continent. The Pacific Ocean, Atlantic Ocean, Indian ocean, the Southern Ocean, and the Arctic Ocean are the five oceans. Among these, the Pacific Ocean is the largest ocean that covers more than 30 percent of the earth.

 the Mariana Trench is the deepest point, about 11,033m deep in the Pacific Ocean. the average depth of the ocean is about 3.7 Km. the ocean plays a crucial role in the earth’s weather and climate pattern.  the seawater contains an average 3.5 percent dissolved slat that makes seawater undrinkable.

2. Glaciers

       A glacier is the thick mass of ice that consists of recrystallized snow along with air and sediment. Due to the accumulation of snow, the deeper snow feels pressure and it recrystallizes into denser ice. When the mass of dense snow and ice increases, the gravitational pull causes the frozen mass to move, known as the glacier.

Glacier contains around 69 percent of the total freshwater on earth. The glacial ice can be as large as a continent, such as Greenland and Antarctica ice sheets. Most glacial ice today is found in the Polar Regions.

3. Groundwater

 groundwater is the term for water beneath the earth’s surface. It is the most important source of freshwater.  the water comes beneath the surface by infiltration of water down through the soil. very deep in the crust groundwater normally found saline. Saline groundwater is usually found at very deep in the crust. Out of the total freshwater, groundwater contains around 24 percent freshwater.

Apart from these, rivers and lakes are also water reservoirs. the water in the biosphere is negligible because it contains a very small percentage of the hydrosphere.

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