The hydrosphere (frae Greek ὕδωρ - hudōr, "watter"[1] an σφαῖρα - sphaira, "sphere"[2]) in pheesical geografie describes the combined mass o watter foond on, unner, an ower the surface o a planet.

Igor Shiklomanov, the man selectit bi the Unitit Naitions tae dae its warld inventory o watter resoorces,[3] estimatit that thare are 1386 million cubic kilometres o watter on yird.[4] This includes watter in liquid an frozen furms in grundwatters, glaciers, oceans, lochs an streams. Saline watter accoont for 97.5% o this amoont. Fresh watter acoonts for anly 2.5%. O this fresh watter 68.7% is in the "furm o ice an permanent snow cover in the Arctic, the Antarctic, an in the muntainous regions. Next, 29.9% exists as fresh grundwatters. Anly 0.26% o the tot amount o fresh watters on the Yird are concentrated in lochs, reservoirs an river seestems whaur thay are maist easily accessible for oor economic needs an absolutely vital for watter ecoseestems."[4] The tot mass o the Yird's hydrosphere is aboot 1.4 × 1018 tonnes, which is aboot 0.023% o the Yird's tot mass. Aboot 20 × 1012 tonnes o this is in the Yird's atmosphere (the volume o ane tonne o watter is approximately 1 cubic metre). Approximately 75% o the Yird's surface, an aurie o some 361 million square kilometers (139.5 million square miles), is covered bi ocean. The average salinity o the Yird's oceans is aboot 35 grams o saut per kilogram o sea watter (3.5%) [5]


  1. ὕδωρ, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  2. σφαῖρα, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus
  3. Marq de Villiers (2003). Water: The Fate of Our Most Precious Resource (2 ed.). Toronto, Ontario: McClelland & Stewart. pp. 453. ISBN 978-0-7710-2641-6. OCLC 43365804., revised 2003|Governor General's Award (1999)
  4. a b World Water Resources: A New Appraisal and Assessment for the 21st Century (Report). UNESCO. 1998. Archived frae the original on 27 September 2013. Retrieved 13 Juin 2013.
  5. Kennish, Michael J. (2001). Practical handbook of marine science. Marine science series (3rd ed.). CRC Press. p. 35. ISBN 0-8493-2391-6.