HYDROLOGIC CYCLE AND FRESHWATER SUPPLY



HYDROLOGIC CYCLE

"The continuous circulation of water through abiotic environment from ocean to atmosphere than atmosphere to land and than back to the oceans is called hydrologic cycle. It is complex cycle."

Hydrologic cycle maintains a balance of water among oceans, land and atmosphere. 

Sea Water

Sea Water accounts a large portion of water on earth surface. Almost 97 % of water of earth surface is found in the oceans. The oceans consist of dissolved salts. Sea water is too saline that if this saline water is given to plants, the plants will die. Humans can also not utilize this water for drinking purpose. 

Fresh Water

The percentage of freshwater on the earth surface is very low. Only 2.5 % fresh water is there on earth but from this 2.5 %,  1.97 % water is in frozen form in polar ice or glaciers that is not in use for humans; 0.5 % water is available in ground water; Only 0.03 % water is available in lakes, rivers, streams, soil moisture and atmosphere. It can been seen from the values that less than 1 % water is available to humans.
  • Surface Water
Surface water is a fresh water present in lakewetlands are the areas that are covered with water for some part of the year. Surface water is refilled by runoff of precipitation or rainfall. Thus it can be said that this is a renewable resource although it is finite. Watershed is the land area that is drained by river and its tributaries.
s, streams, ponds, reservoirs and wetlands. While
  • Groundwater
Earth surface has underground formations like pathways for the flow of water. Rain water or snow melted water seeps through soil and they make their ways in the soil through cracks in rocks until no impermeable layer restrict them. These form the groundwater. Groundwater make its way toward rivers, oceans or springs.
  • Aquifers
The porous layers of rocks that stores the water are called aquifers. These can be confined aquifers or unconfined aquifers. Confined aquifers are those aquifers that are formed between the impermeable rock layers. While unconfined aquifers are those aquifers in which upper layer of rocks is permeable that allows the water to seep down and replace the aquifer. The upper limit of the unconfined aquifers below which the water is saturated is known as water table.

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