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 %).
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.
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.