LECT1 (Intro) - AOM 4643 INTRODUCTION Hydrologic science...

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AOM 4643 - INTRODUCTION Hydrologic science focuses on the global hydrologic cycle and the processes involved in the land phase of that cycle. It is the geoscience that describes and predicts: spatial and temporal distribution of water in the terrestrial, oceanic and atmospheric compartments of the global water system movement of water on and under earth’s land surfaces and the physical/ chemical/ biological processes that accompany, conduct or affect movement Applied or engineering hydrology uses this understanding to design and operate flood control, water supply, irrigation and drainage, pollution abatement, wildlife protection systems. i.e., for planning and management of water resources. The hydrologic cycle describes the continuous circulation of water from land and sea to the atmosphere and back again. The concept is based on mass balance and is simply that water changes state and is transported in a closed system which extends approximately 1 km down into the earth’s crust and about 15 km up into the atmosphere. The cycle is only closed earth-wide, not on a watershed or continental scale. Thus practicing hydrologists are typically faced with an open system. The energy required to keep the hydrologic cycle going is provided by the sun .
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Definitions: precipitation - movement of water from the atmosphere to the earth as rain or snow evapotranspiration - combined consumptive evaporative process by which water is released to the atmosphere through vegetation and soil throughfall - water not intercepted by vegetation interflow - water at shallow depths within soil structure infiltration - precipitated water “absorbed” by soil surface percolation - water movement into deep aquifers exfiltration - rising of soil moisture due to tension and capillary forces overland flow - precipitated water which moves over the land surface ultimately infiltrating into the ground or discharging into streams as surface runoff. sublimation - release of water from snowpack and icecaps directly to the atmosphere as vapor On a global scale: Ocean activity dominates the global hydrologic cycle -- receiving 79% of the earth’s rainfall and contributing 88% of the evapotranspiration. More rainfall falls on the oceans than land (because of larger surface area). But land receives more water than it evaporates; oceans evaporate more water than receive as precipitation. Excess water on land returns to ocean as surface and groundwater outflow to balance the system. Distribution of water throughout the earth: oceans - approximately 97% fresh water - 3% ice caps 2% (as recently as 18,000 years ago, glaciation at peak, ice caps had all freshwater - 3%, other periods ice caps - 0%), groundwater 0.6%, lakes, rivers, streams, etc. 0.4% volume storage in system volumetric flow rate through system 0.001% 8.2 days 97% 2650 yr GW 0.6% 4790 yr 0.4% T r = S/Q
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human - water residence time 14 days biological water ± 1/2 volume in river waters Atmospheric water accounts for approximately 0.001% of the total water volume at any
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This note was uploaded on 03/27/2012 for the course AOE 4643 taught by Professor Graham during the Fall '11 term at University of Florida.

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LECT1 (Intro) - AOM 4643 INTRODUCTION Hydrologic science...

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