Presentation on theme: "Runoff Processes. What happens when we go from a landscape that looks like this … Photo credit: Vermont Land Trust to this? Photo credit: Stowe Mountain."— Presentation transcript:
Hydrologic Cycle Describes the cycling of water through the atmosphere, biosphere and lithosphere. Includes the processes of: Condensation Precipitation Infiltration Evapotranspiration Runoff
Condensation: Phase change of water from gaseous to liquid state.
Precipitation: Flux of water from atmosphere to earth surface.
Evapotranspiration: Flux of water from earth surface to atmosphere. Evaporation: flux from free water surfaces Transpiration: flux from free water surfaces Phase change from liquid to gas Energy consumed in phase change = latent heat
Infiltration Influenced by: Soil characteristics Land cover Precipitation rate Vertical movement of water into the soil profile.
Runoff Flux of water through the lithosphere to rivers, streams, ocean. Includes: Overland flow Subsurface flow
Soil permeability (tendency to soak up water) Rainfall intensity low high lowhigh humid regions arid regions subsurface flow overland flow Adapted from: Dunne & Leopold. Water in Environmental Planning. Geographical patterns in runoff … but how do these patterns in runoff influence landforms?
V-shaped valley of a humid, temperate landscape Photo credit: Field Studies Council, UK Badland topography of an arid landscape Photo credit: National Park Service … landforms reflect dominant runoff processes
Stream gauging station, H.J. Andrews Experimental Forest, Oregon Hydrograph: plot of runoff over time
time Runoff A A A B B timeRunoff B Paired watershed studies
A A B B Runoff - A Runoff - B Paired watershed studies
A A B B time Runoff A timeRunoff B Paired watershed studies
A A B B Peak streamflow A Peak streamflow B Before clearing After clearing
time Runoff before after Hydrologic effects of deforestation / development Higher peak stream flows Greater annual water yield Lower base flows Faster runoff
Hydrologic effects of deforestation First year increases in water yield after forest harvesting Adapted from Hornbeck et al., 1993. Journal of Hydrology, 150:323-344
Hydrologic effects of deforestation from: Brown et al., 2005. A review of paired catchment studies for determining changes in water yield resulting from alterations in vegetation. J Hydrology 310: 28-61..