Earth: The Water Planet

Planetary Temperature and Energy in the Climate System Sources? Geothermal Heat Flow (cooling of Earth’s hot interior) –0.075 W/m^2 (Watt = Energy Flux, J/s) –100’ x 100’ = 1000m^2 = 75 Watt total Solar radiation –~1366 W/m^2 incoming (what sets this?) –~1000 W/m^2 reaches surface Remember: Conserve Energy

The Water Planet

The Fate of Solar Insolation planetary albedo = 30% Earth and Atmosphere absorb 45% + 25% = 70% of solar insolation

Solar Energy Drives Hydrologic Cycle

Hydrologic Cycle Questions How does the WATER Cycle compare to the Hydrologic Cycle? On an annual, global average, how do ET and P compare? P >> ET, P > ET, P = ET, P < ET What about over land? Amazon rainforest: how does total P compare to moisture flux from oceans (more, equal, less) – and why? As we will learn, most rainfall on land soaks into the ground, only impermeable areas (rock, urban areas) or particularly intense rainfall cause direct runoff. Given this why do we have rivers?

Hydrologic Cycle

Hydrologic Cycle: Conservation of Mass Atmosphere 12.7 Ocean 1,335,040 Surface Water 300 Groundwater 15, {40} {+40} {-40} Reservoir Volumes: 1000 km 3 Fluxes: 1000 km 3 /yr Residence Time = Volume/Flux (yr)

Discussion of Reading Any questions, points of clarification in (a) A&A chap 1, (b) Allen, 2008? What are some Big Questions in Geomorphology? What are the Guiding Principles to the Study of Geomorphology outlined by Anderson and Anderson?

Willett, 1999 JGR Beaumont et al., 2001 Nature Numerical Simulations: Strong Climate-Tectonics Coupling

Overview/Guidelines (Chapter 1) Many interacting processes: wind, rain, runoff, ice, heat/cool, freeze/thaw, chemical attack – all modulated by life; all event-driven, variable Interaction of different timescales Hillslopes and Channels (+ floodplains) Our Approach: Conservation (of mass [water, sediment, atoms], energy, momentum) Transport Rules (flow of water, mud, ice, transport of sediment, etc) Event Size, Frequency and Duration (storms, floods, climate variations, etc)

NET RADIATION (INCOMING SHORTWAVE MINUS OUTGOING LONGWAVE)

AIR TEMPERATURE (Mean Monthly)

PRECIPITABLE WATER VAPOR (in air column)

PRECIPITATION (Mean Monthly)

EFFECTIVE PRECIPITATION (Ppt - Evap)

Atmospheric Rivers

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 {  h/  l = (h 1 – h 2 )/  l } 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 ? ?  h/  l

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 Next: Controls on Hydrographs

San Gabriel Mtns: Mean Daily Q Mean Daily Runoff = Q/A = ~225 mm/yr (~33% of MAP)

San Gabriel Mtns: Q 10

Hydrologic Process Transforms Distribution of Rainfall

Hurricane Irene Hydrological Response

North Carolina

Maryland

New Jersey

Pennsylvannia

New York

Massachusetts

New Hamshire

From Perron et al., Nature 2009 Predicted L c Observed A c 1/2