<P> However, fresh groundwater is of great value, especially in arid countries such as India . Its distribution is broadly similar to that of surface river water, but it is easier to store in hot and dry climates because groundwater storages are much more shielded from evaporation than are dams . In countries such as Yemen, groundwater from erratic rainfall during the rainy season is the major source of irrigation water . </P> <P> Because groundwater recharge is much more difficult to accurately measure than surface runoff, groundwater is not generally used in areas where even fairly limited levels of surface water are available . Even today, estimates of total groundwater recharge vary greatly for the same region depending on what source is used, and cases where fossil groundwater is exploited beyond the recharge rate (including the Ogallala Aquifer) are very frequent and almost always not seriously considered when they were first developed . </P> <P> The total volume of water on Earth is estimated at 1.386 billion km3 (333 million cubic miles), with 97.5% being salt water and 2.5% being fresh water . Of the fresh water, only 0.3% is in liquid form on the surface . In addition, the lower mantle of inner earth may hold as much as 5 times more water than all surface water combined (all oceans, all lakes, all rivers). </P> <Table> <Tr> <Th> Source of water </Th> <Th> Volume of water in km3 (cu mi) </Th> <Th>% total water </Th> <Th>% salt water </Th> <Th>% fresh water </Th> <Th>% liquid surface fresh water </Th> </Tr> <Tr> <Td> Oceans </Td> <Td> 7018133800000000000 ♠ 1,338,000,000 (321,000,000) </Td> <Td> 96.5 </Td> <Td> 99.0 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Pacific Ocean </Td> <Td> 7017669880000000000 ♠ 669,880,000 (160,710,000) </Td> <Td> 48.3 </Td> <Td> 49.6 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Atlantic Ocean </Td> <Td> 7017310410900000000 ♠ 310,410,900 (74,471,500) </Td> <Td> 22.4 </Td> <Td> 23.0 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Indian Ocean </Td> <Td> 7017264000000000000 ♠ 264,000,000 (63,000,000) </Td> <Td> 19.0 </Td> <Td> 19.5 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Southern Ocean </Td> <Td> 7016718000000000000 ♠ 71,800,000 (17,200,000) </Td> <Td> 5.18 </Td> <Td> 5.31 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Arctic Ocean </Td> <Td> 7016187500000000000 ♠ 18,750,000 (4,500,000) </Td> <Td> 1.35 </Td> <Td> 1.39 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Ice and snow </Td> <Td> 7016243640000000000 ♠ 24,364,000 (5,845,000) </Td> <Td> 1.76 </Td> <Td> </Td> <Td> 69.6 </Td> <Td> </Td> </Tr> <Tr> <Td> Glaciers </Td> <Td> 7016240640000000000 ♠ 24,064,000 (5,773,000) </Td> <Td> 1.74 </Td> <Td> </Td> <Td> 68.7 </Td> <Td> </Td> </Tr> <Tr> <Td> Antarctic ice sheet </Td> <Td> 7016216000000000000 ♠ 21,600,000 (5,200,000) </Td> <Td> 1.56 </Td> <Td> </Td> <Td> 61.7 </Td> <Td> </Td> </Tr> <Tr> <Td> Greenland ice sheet </Td> <Td> 7015234000000000000 ♠ 2,340,000 (560,000) </Td> <Td> 0.17 </Td> <Td> </Td> <Td> 6.68 </Td> <Td> </Td> </Tr> <Tr> <Td> Arctic islands </Td> <Td> 7013835000000000000 ♠ 83,500 (20,000) </Td> <Td> 0.006 </Td> <Td> </Td> <Td> 0.24 </Td> <Td> </Td> </Tr> <Tr> <Td> Mountain ranges </Td> <Td> 7013406000000000000 ♠ 40,600 (9,700) </Td> <Td> 0.003 </Td> <Td> </Td> <Td> 0.12 </Td> <Td> </Td> </Tr> <Tr> <Td> Ground ice and permafrost </Td> <Td> 7014300000000000000 ♠ 300,000 (72,000) </Td> <Td> 0.022 </Td> <Td> </Td> <Td> 0.86 </Td> <Td> </Td> </Tr> <Tr> <Td> Groundwater </Td> <Td> 7016234000000000000 ♠ 23,400,000 (5,600,000) </Td> <Td> 1.69 </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Saline groundwater </Td> <Td> 7016128700000000000 ♠ 12,870,000 (3,090,000) </Td> <Td> 0.93 </Td> <Td> 0.95 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Fresh groundwater </Td> <Td> 7016105300000000000 ♠ 10,530,000 (2,530,000) </Td> <Td> 0.76 </Td> <Td> </Td> <Td> 30.1 </Td> <Td> </Td> </Tr> <Tr> <Td> Soil moisture </Td> <Td> 7013165000000000000 ♠ 16,500 (4,000) </Td> <Td> 0.0012 </Td> <Td> </Td> <Td> 0.047 </Td> <Td> </Td> </Tr> <Tr> <Td> Lakes </Td> <Td> 7014176400000000000 ♠ 176,400 (42,300) </Td> <Td> 0.013 </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Saline lakes </Td> <Td> 7013854000000000000 ♠ 85,400 (20,500) </Td> <Td> 0.0062 </Td> <Td> 0.0063 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Caspian Sea </Td> <Td> 7013782000000000000 ♠ 78,200 (18,800) </Td> <Td> 0.0056 </Td> <Td> 0.0058 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Other saline lakes </Td> <Td> 7012720000000000000 ♠ 7,200 (1,700) </Td> <Td> 0.00052 </Td> <Td> 0.00053 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Fresh water lakes </Td> <Td> 7013910000000000000 ♠ 91,000 (22,000) </Td> <Td> 0.0066 </Td> <Td> </Td> <Td> 0.26 </Td> <Td> 87.0 </Td> </Tr> <Tr> <Td> African Great Lakes </Td> <Td> 7013300700000000000 ♠ 30,070 (7,210) </Td> <Td> 0.0022 </Td> <Td> </Td> <Td> 0.086 </Td> <Td> 28.8 </Td> </Tr> <Tr> <Td> Lake Baikal </Td> <Td> 7013236150000000000 ♠ 23,615 (5,666) </Td> <Td> 0.0017 </Td> <Td> </Td> <Td> 0.067 </Td> <Td> 22.6 </Td> </Tr> <Tr> <Td> North American Great Lakes </Td> <Td> 7013221150000000000 ♠ 22,115 (5,306) </Td> <Td> 0.0016 </Td> <Td> </Td> <Td> 0.063 </Td> <Td> 21.1 </Td> </Tr> <Tr> <Td> Other fresh water lakes </Td> <Td> 7013152000000000000 ♠ 15,200 (3,600) </Td> <Td> 0.0011 </Td> <Td> </Td> <Td> 0.043 </Td> <Td> 14.5 </Td> </Tr> <Tr> <Td> Atmosphere </Td> <Td> 7013129000000000000 ♠ 12,900 (3,100) </Td> <Td> 0.00093 </Td> <Td> </Td> <Td> 0.037 </Td> <Td> </Td> </Tr> <Tr> <Td> Swamps </Td> <Td> 7013114700000000000 ♠ 11,470 (2,750) </Td> <Td> 0.00083 </Td> <Td> </Td> <Td> 0.033 </Td> <Td> 11.0 </Td> </Tr> <Tr> <Td> Rivers </Td> <Td> 7012212000000000000 ♠ 2,120 (510) </Td> <Td> 0.00015 </Td> <Td> </Td> <Td> 0.0061 </Td> <Td> 2.03 </Td> </Tr> <Tr> <Td> Biological water </Td> <Td> 7012112000000000000 ♠ 1,120 (270) </Td> <Td> 0.000081 </Td> <Td> </Td> <Td> 0.0032 </Td> <Td> </Td> </Tr> </Table>

What is the percentage of salt water in the world