Chapter 9
Water on Land/Running Water
  •  Deals with the HYDROSPHERE
  •  The aqueous envelope of the Earth
  •  Includes bodies of waters & aqueous vapor in the atmosphere
  •  essential to life (animals & plants)
  •  H2O is 60 % of our bodies
  •  H2O covers 70 % of earth surface
  •  Rests in oceans, lakes, rivers, glacier, etc.
  •  If earth were flat, H2O would cover it up to 3000 m deep
  •  Fortunately, H2O is concentrated in depressions all over earth surface.

    • (Figure here)

     Units of Measurement

  •  Various units e.g., gallons, acre-feet, etc.
  •  Once acre-foot = water required to cover one acre of land, one foot deep (Figure here)


    • 1 Acre-foot = 325,851 gallons

    Uses: Everything!!!!!

    The Hydrologic Cycle

  • Describes circulation of H2O falling as rain, flowing to oceans, infiltrating to groundwater, evaporating back to the atmosphere, condenses & falling back as rain: (Figure here)
  • Ocean has 97 % of H2O on earth, But salty & not useful to plants & animals
  •  Remaining 3 % is fresh H2O
  •  75 % of the 3 % in glaciers ice and snow


    • Processes (and Rainfall)
    Evaporation:

     Liquid to vapor below BOILING POINT

    Sublimation:
     Solid H2O (ice) to vapor directly, mainly on bright, windy days ( snow -> vapor)

    Humidity:
     Amount of H2O vapor in air (Warm air is more than cold air.)

    Saturation Point:
     Air is at saturation point when it contains as much H2O as it can hold at that temperature (T).

    Relative Humidity:
     Actual amount of H2O in air relative to saturation point at that temp (T).

    Condensation:
     H2O molecules aggregate about saturation point => called CONDENSATION

    Dew Point:
     Temperature at which condensation begins.

    Rainfall:
    With enough condensation, rainfall occurs!!! (main source of H2O supply)

     Rainfall is unevenly distributed:

  •  Due to effects of winds & topography (hills & valleys)
  •  Rainfall is more at the tropics and on windward side of mountains.


    •  (figure here)

    Compartments (e.g. River System)

  •  River is an important geologic agent for (1) Water Supply (2) shaping the landscape by eroding and depositing materials on ground surface (3) flooding
  •  To evaluate these effects of a river, we need to know some factors of the river, e.g., DISCHARGE and GRADIENT.


    • Discharge: Amount of water flowing past a point in the river channel for a given period of time.

  • Discharge evaluated through the Discharge Equation:


    •  Q = V X A

     (Discharge = Velocity X Cross-sectional area)
    (Figure here)
    Q = Discharge of river in cubic feet of water per second (cfs)
    V = Velocity of water in feet per second (ft/sec)
    A = Area of channel in square feet (ft2)

    Quiz :

    1. 1. Q = 18 cfs, A = 1 sq. yd. (yd2)

      2. V = ?
    2. Q = 20 cfs, V = 5 ft/min

      3. A = ?
  • In general, the greater the discharge, the better the water supply and more erosion.
    1. Velocity - discharge relation
    2.  Depth - discharge relation
    3.  Width - discharge relation
    (Figure here)
    Gradient: Longitudinal profile or side view of a river:

     Gradient = Vertical drop (rise) = 10 = 1:10

    Horizontal dist ance (run) 100
  • The smaller the gradient, the less the level of erosion


    • Features of stream

  •  Depositional OR erosional


    • Erosional:

    Meander: S-shaped features along river

    (figure here)

    Oxbow lake: Erosion and deposition produce tight meanders and eventually oxbow lakes form.

    Depositional:

    Alluvium: Sediments deposited by streams
    Deltas: Triangular shaped sediments found where water runs into standing bodies of H2O

  • Usually good as reservoirs for H2O (aquifers) and oil.


    • Various shapes:

    1.  Stream - dominated
    2.  Wave - dominated
    3.  Tide - domintated
    (figure here)

    FLOOD PLAINS:

  • Gradient of a stream decreases in its lower reaches
  •  High precipitation may provide large volumes of H2O to cause flooding in these reaches
  •  The FLAT AREAS flanking the valley, on which sediments are deposited during flooding are the flood plains.

    • (figure here)

    Flooding ??? (Read up) + Lab ////// FLOOD PREDICTION !!!!!!!

     http://www.wes.army.mil/EL/flood/gifs.html 1993 Missippi / missouri Rivers

     ** many other Erosion features !!! will not discuss all.

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