Water for people.pdf - WHO Thailand Digital Repository

6 8 / A L O O K A T T H E W O R L D ’ S F R E S H W A T E R R E S O U R C E SThe Natural Water CycleTable 4.1: The distribution of water across the globeVolume, % of total volume % of Volume recycled RenewalLocation (10 3 km 3 ) in hydrosphere freshwater annually (km 3 ) period yearsOcean 1,338,000 96.5 – 505,000 2,500Groundwater (gravity and capillary) 23,400 1 1.7 16,700 1,400Predominantly fresh groundwater 10,530 0.76 30.1Soil moisture 16.5 0.001 0.05 16,500 1Glaciers and permanent snow cover: 24,064 1.74 68.7Antarctica 21,600 1.56 61.7Greenland 2,340 0.17 6.68 2,477 9,700Arctic Islands 83.5 0.006 0.24Mountainous regions 40.6 0.003 0.12 25 1,600Ground ice (permafrost) 300 0.022 0.86 30 10,000Water in lakes: 176.4 0.013 – 10,376 17Fresh 91.0 0.007 0.26Salt 85.4 0.006 –Marshes and swamps 11.5 0.0008 0.03 2,294 5River water 2.12 0.0002 0.006 43,000 16 daysBiological water 1.12 0.0001 0.003 –Water in the atmosphere 12.9 0.001 0.04 600,000 8 daysTotal volume in the hydrosphere 1,386,000 100 –Total freshwater 35,029.2 2.53 1001 Excluding groundwater in the Antarctic estimated at 2 million km 3 , including predominantly freshwater of about 1 million km 3 .This table shows great disparities: between the huge volume of saltwater and the tiny fraction of freshwater; between the large volumes of water contained by the glaciers and the water stored in the aquifers;and between the amount of groundwater and the small volumes of water in rivers, lakes and reservoirs.Source: Shiklomanov, forthcoming.Figure 4.1: The global hydrological network by typeDischarge64,000 (11%)Evaporation4,000 (2%)Sediment discharge18,000 (3%)Water quality102,000 (17%)Observationwell level146,000 (25%)Precipitation198,000 (34%)Groundwater192,000 (32%)Observationwell quality44,000 (8%)This figure shows the number of monitoring stations that make up the global hydrological network.Source: WMO, 1995.