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Explore the hydrologic cycle, flood discharge, and groundwater flow. Learn about Darcy's Law and the factors influencing water movement in Earth's systems.
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Hydrologic Cycle: Conservation of Mass Atmosphere 12.7 {+40} {-40} 73 113 373 413 Surface Water 300 30-38 Ocean 1,335,040 2-10 Groundwater 15,300 {40} Reservoir Volumes: 1000 km3 Fluxes: 1000 km3/yr Residence Time = Volume/Flux (yr)
Simplest Model: Q = C R_i A (Storm Response)
What Sets Flood Discharge (thus shear stress exerted on the bed)?
Runoff Essentials • Simple Empirical Model: Q = C R_i A • Runoff Pathways – basic properties and controls, hydrograph implications • Infiltration Capacity (velocity) • The Importance of Saturation State • The Variable Source Area Concept
Runoff Essentials • Simple Empirical Model: Q = C R_i A • Runoff Pathways – basic properties and controls, hydrograph implications • Infiltration Capacity (velocity) • The Importance of Saturation State • The Variable Source Area Concept
What is Hydraulic Head? • The total force driving flow of groundwater • Why does Water stay still in a cup or bowl? • What can make water in pipes flow? • Elevation: flow downhill (gravity) • Pressure: use pumps to create pressure and drive water uphill (or just faster) • Elevation Head + Pressure Head • GW Elevation head = elevation * density * gravity (potential energy per unit volume) • GW Pressure head = weight of overlying water (per unit volume)
Darcy’s Law • Darcy’s law provides an accurate description of the flow of ground water in almost all hydrogeologic environments. • = the basis of a pretty good job
Darcy’s Law V = – K (∆h/∆L) Q = VA (A = cross-section area) Q = – KA (∆h/∆L) Q/A = – K (∆h/ ∆L)
Darcy’s Experiment (1856): Flow rate determined by Difference in Hydraulic Head per flow path length { Dh/Dl = (h1 – h2)/Dl } Group Project: Sketch Out What Darcy Did to Discover His Famous Equation Extra Credit to first Team that can make a sketch of experimental data that would support Darcy’s Law and satisfactorily explain it to me
Sketch of Experimental Data Dh/Dl ? ?
Rainfall Intensity and Initial Conditions Vivoni et al. (2007)