Themes of the Day:

• The Hydrologic Cycle
• Features of Rivers & Streams

The Hydrologic Cycle

• Mainly driven by solar energy (and gravity, of course)
• Reservoirs:
  • Oceans and Seas (saltwater) - 97.5%
  • Ice Caps and Glaciers (freshwater) - 1.8%
  • Groundwater (mostly freshwater) - 0.62%
  • Rivers and Lakes (mostly freshwater) - 0.02%
  • Atmospheric (freshwater) - 0.001%
• Processes:
  • Evaporation
  • Precipitation
  • Infiltration
  • Groundwater Flow
  • Runoff
  • Transpiration (perspiration)
• Orographic Precipitation - rain shadows
• USA Precipitation & Runoff
• Water Usage and Droughts - Cadillac Desert, by Mark Reisner

Features of Rivers & Streams

• Drainage Basins, Streams, Rivers, Source (Headwaters), Mouth, Tributaries, Distributaries
• Valley, Flood Plain, Levees, Channel, Bed, Banks
• Braided Rivers - choked with sediment (glacial outwash, deserts)
• Meandering Rivers - usually low gradient
  Features:
  • Meandering channel
  • Cutbanks - erosion on outside of a meander bend
  • Point Bars - deposition on inside of a meander bend - sand and gravel deposits
  • Levees - natural (or artificial) embankment between river and flood plain - Development A -> B -> C
  • Cutoff - when a river short circuits a meander bend
  • Oxbow Lake - a cutoff meander bend - will often silt up
  • Flood Plain - flat lying areas adjacent to river subject to flooding during high water - often well suited for agriculture - silt and mud deposited here
• Deltas
  Features:
  • Distributaries
  • Topset, Foreset, and Bottomset beds
  • Progradation
  • Delta abandonment, migrating deltas - Mississippi vs. Atchafalaya
• Alluvial Fans