Chapter 9 Outline

Chapter 9 Outline - Chapter 9: Water Resources The...

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Chapter 9: Water Resources The Hydrologic Cycle A Hydrologic Cycle Model Hydrologic cycle - operated for bils yrs fr lower atmos kms below Earth’s surface; involves circulation/ transformation of water thruout Earth’s atmos, hydrosphere, lithosphere, biosphere; hydro cyc model simplified model of this complex sys; 97%+ Earth’s water in ocean; (see pg. 247 ) here: Most evap’tn, precip occur; rest evap on land, incl transpiration ; of 86% evap rising fr ocean, 66% combos w/12% advected (moving horiz’lly) fr land to=>78% of all precip that falls back to ocean; rest 20% of moisture evap’d fr ocean + 2% land-derived moisture= the 22% of all precip tht falls over land Surface Water Precip reaching earth’s surface flows overland or soaks into soil; along way, interception occurs when precip hits ground cover; intercepted water tht drains across plant leaves, dwn thr stems= stem flow , can be impt moisture route to ground surface; precip falling directly to ground= throughfall Water soaks into subsurface thru infiltration - penetration of soil surface; further permeates soil thru downward movement- percolation ; atmos’ic advection of water vapor fr sea<-->land unbalanced- 20% moves inland, 12% moves sea; but this balanced by the 8% land runoff tht flows sea Most of this runoff (95%) fr dynamic surface waters (rivers, streams) tht wash across land as overland flow/streamflow- rest slow-moving subsurface groundwater; residence time for water molc in hydro cyc determines its relative imptce in affecting Earth’s climates: Water’s short time in transit thru atmos (10 days)=>temporary fluctuations in reg wthr patterns; long 1000s yrs in deep-ocean circ/groundwater aquifers/glacial ice=>moderate temp, climatic changes- work as system memory - long pers over which heat energy sotred, released buffer effects of sys changes over time; Global Energy and Water Cyc Experiment observes/describes hydro cyc Soil-Water-Budget Concept Soil-water budget can be est’d for any area of earth’s surface; key- measuring precip input/its distribution to satisfy demands of plants re: evap, soil moisture storage; budget can examine any time frane; precip input must balance w/output of evap, transpiration, runoff. . Soil-moisture storage accepts deposits, w/drawals of water; can=>surplus/deficit/balance as result The Soil-Water-Balance Equation Object of Charles W. Thornthwaite’s water-balance methodology= account for ways in which this supply is distributed; precip receipt must fully balance expenditures; see pg. 248 Precipitation (PRECIP) Input Earth’s moisture supply= precipitation (PRECIP/P); forms= rain, sleet, snow, hail, dew, frost, fog; the 22% tht falls on land examined here; precip measured w/rain gauge- lg measuring cup to measure water by depth/weight/volume; incl windshield to prevent inaccuracies due to undercatch Actual Evapotranspiration (ACTET) Evaporation - net movement of free water molcs away fr wet surface
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Chapter 9 Outline - Chapter 9: Water Resources The...

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