Global Distribution of Water — Definition, Sources

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Glac­i­er — Water

Water is distributed across various region of earth. Oceans cover roughly 70% of the area of the earth, They reflect blue light and hence the earth appears blue from space.Therefore Earth is also referred as blue planet. the total volume of water on Earth is estimated at 1.386 billion km3 . (333million cubic miles). Out of the total water available only 3% of water is freshwater and remaining 97% is saline.Average salinity is 35% (or 3.5 %). this is equivalent to 34 grams of salt dissolved in 1 kg of seawater 35000 mg of salt ions Dissolved per litre of sea water. water with the salinity level between 0.35% and 1% is referred as its marginal water.The ratio of salt water to freshwater on Earth is around 40 to 1 %Of the total freshwater about 69% exist in the form of ice, snow 30% as groundwater and less than 1% (about 0.3 %) as liquid.This means that only 1% of water is available for use by humans and rest 99% is underground.Of the total liquid surface freshwater 87% is contained in lakes 11% ‚in Swamps and 2% in Rivers.Approximately 680,000 km2 of fresh water is present in the form of glacier and permanent snow /ice Cover.stop these include water resources present As Ice sheets in the Antarctic ‚Arctic and Greenland. This water is not accessible. melting Glacier provide a natural source of river water and groundwater.

Fresh­wa­ter is defined as water with salin­i­ty less than 1% that of ocean that is blue around 0.35% rivers and lakes pro­vide an excel­lent source of fresh­wa­ter for human use.Surface waters include lakes as well as Ponds, Reser­voir ‚rivers and streams and wetland.The flow of water into these water bod­ies come from rainfall,runoff ‚melt­ing snow ice,and base flow from under­ground water sys­tems. sur­face water account for small vol­ume 0.3 % of the earth­’s total fresh­wa­ter resources for stop Lake store the largest vol­ume of fresh sur­face water 90,000km.This accounts for 40 times more than water found in rivers or streams. lakes are esti­mat­ed to cov­er a total area of about 2.7 mil­lion km2.This rep­re­sent around 2% of the land sur­face exclud­ing polar regions. most­ly lakes are small but worlds 145 lakes are esti­mat­ed to con­tain over 95% of the of all Lake freshwater.Lake Baikal( Rus­sia )is the world’s largest deep­est lake which con­tain 27% of the fresh­wa­ter con­tain in lakes .Lake water pro­vide many ser­vices such as fish­ing, recre­ation ‚trans­port and water sup­ply for the world’s pop­u­la­tion. The total vol­ume of water stored in riv­er and stream is esti­mat­ed that about 2,120km2. a large area of sub sur­face ‚porous rock that hold water is an Aqua fire. Aquifires are com­mon­ly drilled and have Wells installed in them to pro­vide water for agri­cul­ture and per­son­al use.

Wet­lands are water sat­u­rat­ed envi­ron­ment and are and com­mon­ly char­ac­ter­ized as swamps, bogs, marsh­es, Mires and lagoons. wet­land cov­er and area about four times greater than the world’s lakes.The cov­er total of about 6% of the earth­’s land sur­face. water is used main­ly for irri­ga­tion (68%) pub­lic sup­ply (21% )and indus­try (11 %).

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Ocean Water

Water exist­ing in the voids of the geo­log­i­cal stra­tum below the sur­face of earth is called ground­wa­ter. it is found enclosed in pores and fis­sures of rocks. out of total 13,84,12,000cubic km of water exist­ing on Earth about 8,00,0043cubic km is groundwater.Groundwater com­pris­es 95% ‚sur­face water 3.5% and soil mois­ture 1.5%. out of all the fresh water on the earth only 0.36% is read­i­ly avail­able to use.Around 61,234 cubic metre of water exist in the form of soil mois­ture. ground water and soil mois­ture togeth­er con­stituent the sub­sur­face water fall stop ground­wa­ter is 0.58% of the total water resources avail­able in nature. It is locat­ed up to the depth of 4 km below the Earth­’s surface.Most of the ground­wa­ter orig­i­nat­ed as mete­oric water from pre­cip­i­ta­tion in the form of rain or snow.Rain or snow melt infil­trates the ground and moves down­ward to form groundwater.Groundwater is stored in dif­fer­ent lay­ers of earth by in fil­tra­tion through pores and fis­sures of per­me­able rocks. it is present in all small spaces( pore space) between min­er­al grains and sub­sur­face of Rock of sediments.The main source of ground­wa­ter is rain­fall. it infil­trates through seep­age slow­ly into Earth and col­lects there. it is also called plu­ton­ic water. Oth­er source of ground­wa­ter include seep­age from sur­face water (lakes ‚rivers, Reser­voir and swamps) irri­ga­tion and under­ground waste water treat­ment sys­tem (sep­tic tank).Morris ET Al 2003 report­ed that ground­wa­ter sys­tem pro­vide 25 to 40% of world’s drink­ing water.Groundwater is an impor­tant part of the water cycle because sur­face and atmos­pher­ic water goes under­ground through rain­fall ‚riv­er and lakes.

Groundwater mainly comes from three sources.

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Ground­wa­ter

i) Meteoric Water 

This is the main source of ground­wa­ter. this water is received in the form of rain and snow hence it is called met­ric or shoot­ing star water.Water infil­trates down through Rock ‚joints,pores, fis­sures of Rock and it stored in the form of groundwater.Groundwater can direct­ly derived from atmos­pher­ic mois­ture via con­den­sa­tion of water vapour from cir­cu­lat­ing air present in pore spaces. This is also known as con­den­sa­tion of water. it is a basic source of water in arid and semi-arid areas.

The dif­fer­ence in the tem­per­a­ture between land and air dur­ing sum­mers cause a dif­fer­ence of pres­sure between the water vapour in the atmos­phere and the soil. this result in pen­e­tra­tion of water vapour into soil.Seepage of water from lakes rivers ocean and also man made chan­nels add to ground­wa­ter. this occurs main­ly in humid regions.

ii) Connate Water

What to con­tained in pores and cav­i­ties of sed­i­men­ta­ry rocks under seas and lakes is called con­nate water. it is also called sed­i­ment water. it is a sec­ond impor­tant source of ground­wa­ter. this water is entrapped in the inter­stices of sed­i­men­ta­ry and vol­canic Rock at the time of depo­si­tion. this water is high­ly cen­tralised and salty.

iii) Magmatic water

Water that gets con­vert­ed to Vapour after con­den­sa­tion as a result of vol­canic action at the time of enter­ing hard rock is called Mag­mat­ic water.Hot Mag­ma enters Rock due to vol­canic action after which its vapour drops a con­densed and con­vert­ed into water.This is called mag­mat­ic water.Springs, Wells, and gey­sers a source of such waters. it is gen­er­at­ed in the inte­ri­or of the earth but con­se­quent­ly trav­els to the upper lay­ers of Earth­’s surface.

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