1. One estimate of global water distribution Volume (1000 km 3 ) Percent of Total Water Percent of Fresh Water Oceans, Seas, & Bays1,338,00096.5- Ice caps, Glaciers, & Permanent Snow 24,0641.7468.7 Groundwater23,4001.7- Fresh(10,530)(0.76)30.1 Saline(12,870)(0.94)- Soil Moisture16.50.0010.05 Ground Ice & Permafrost3000.0220.86 Lakes176.40.013- Fresh(91.0)(0.007).26 Saline(85.4)(0.006)- Atmosphere 12.90.0010.04 Swamp Water11.470.00080.03 Rivers2.120.00020.006 Biological Water1.120.00010.003 Total1,385,984100.0 Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823. http://earthobservatory.nasa.gov/Library/Water/

2. Fresh Water

3. Hydrologic Cycle Powered by energy from the sun Evaporation 90% of atmospheric water Transpiration 10% Evaporation exceeds precipitation over oceans Precipitation exceeds evaporation over continents All water stored in atmosphere would cover surface to a depth of 2.5 centimeters 1 m average annual precipitation http://earthobservatory.nasa.gov/Library/Water/

4. U.S. total, surface- water, and ground-water withdrawals, 2000 http://water.usgs.gov/pubs/circ/ 2004/circ1268/htdocs/text-total.html

5. U.S. total water withdrawals by category, 2000 http://water.usgs.gov/pubs/circ/2004/circ1268/htdocs/text-total.html

6. Basin Hydrologic Cycle Charbeneau, 2000.

7. Basin Hydrologic Cycle – GW/SW Interaction

8. U.S. Hydrogeologic Units

9. Figure 15.1

10. Types of Porous Media Freeze and Cherry, 1979. n = V V / V T = Vol Voids / Total Vol

11. Bedient et al., 1999., Porosity

12. Two Confined Aquifers with Different Heads Charbeneau, 2000. Groundwater will tend to flow from the top aquifer to the bottom aquifer. We can’t make any conclusion about horizontal head gradients from this picture.

13. Other Aquifer Features

14. Atmospheric Water Vapor (kg/m 2 ) Sea Surface Temperature (K) From Held and Soden, 2000 ITCZ

15. SPCZ Annual Mean Salinity

16. IPCC 2007 Report, Linear trends in precipitable water (in % per decade).