Hydrologic Cycle/Water Balances

Earth’s Water Covers approximately 75% of the surface Volcanic emissions Only known substance that naturally exists as a gas, liquid, and solid at surface temperatures and pressures

One estimate of global water distribution Volume (1000 km 3 ) Percent of Total Water Percent of Fresh Water Oceans, Seas, & Bays1,338, Ice caps, Glaciers, & Permanent Snow 24, Groundwater23, Fresh(10,530)(0.76)30.1 Saline(12,870)(0.94)- Soil Moisture Ground Ice & Permafrost Lakes Fresh(91.0)(0.007).26 Saline(85.4)(0.006)- Atmosphere Swamp Water Rivers Biological Water Total1,385, 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

Fresh Water

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

Hydrologic Cycle In the hydrologic cycle, individual water molecules travel between the oceans, water vapor in the atmosphere, water and ice on the land, and underground water. (Image by Hailey King, NASA GSFC.)

Florida

U.S. total, surface- water, and ground-water withdrawals, /circ1268/htdocs/text-total.html

U.S. total water withdrawals by category,

Trends in population and freshwater withdrawals by source,

Water (Mass) Balance In – Out = Change in Storage –Totally general –Usually for a particular time interval –Many ways to break up components –Different reservoirs can be considered

Water (Mass) Balance Principal components: –Precipitation –Evaporation –Transpiration –Runoff P – E – T – Ro = Change in Storage Units?

Ground Water (Mass) Balance Principal components: –Recharge –Inflow –Transpiration –Outflow R + Q in – T – Q out = Change in Storage