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Earth Science, 13e. Tarbuck & Lutgens. Running Water and Groundwater Earth Science, 13e Chapter 5. Stanley C. Hatfield Southwestern Illinois College.

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earth science 13e

Earth Science, 13e

Tarbuck & Lutgens

running water and groundwater earth science 13e chapter 5

Running Water and GroundwaterEarth Science, 13eChapter 5

Stanley C. Hatfield

Southwestern Illinois College

slide3

Li River, China’s Guilin DistrictNote karst topography, in which groundwater has dissolved large volumes of limestone (more later).

earth as a system the hydrologic cycle
Earth as a system: the hydrologic cycle
  • Illustrates the circulation of Earth’s water supply
  • Processes involved in the cycle
    • Precipitation
    • Evaporation
    • Infiltration
    • Runoff
    • Transpiration
running water
Running water
  • Drainage basin
    • Land area that contributes water to a river system
    • A divide separates drainage basins
running water1
Running water
  • Streamflow
    • Factors that determine

velocity

      • Gradient, or slope
      • Channel characteristics
        • Shape
        • Size
        • Roughness
      • Discharge – volume of water flowing in the stream (generally expresses as cubic feet per second)
gradient slope
Gradient (slope)
  • Parts of lower Mississippi: 10 cm/km
  • Mountain streams: 40 m/km
  • Steeper gradient has more energy,  more velocity
discharge
Discharge
  • Measured in m3 or ft3 per second
  • Changes over time due to amount of precipitation in drainage basin
measuring stream velocity
Measuring stream velocity

1 kph – 30 kph

Straight – highest at center

Curved– highest at outer bank

running water2
Running water
  • Upstream-downstream changes
    • Profile
      • Cross-sectional view of a stream
      • From head (source) to mouth
        • Profile is a smooth curve
        • Gradient decreases from the head to the mouth
      • Factors that increase downstream
        • Velocity
        • Discharge
running water3
Running water
  • Upstream-downstream changes
    • Profile
      • Factors that increase downstream
        • Channel size
      • Factors that decrease downstream
        • Gradient, or slope
        • Channel roughness
running water4
Running water
  • The work of streams
    • Earth’s most important erosional agent
      • Downcut, widen streams
      • Transport sediment which can erode banks, channel, bedrock
  • MG: Sediment transport by streams
running water5
Running water
  • Transportation – transported material is called the stream’s load
    • Dissolved load
      • From groundwater, dispersed through flow
      • Expressed in ppm
      • Velocity of streamflow has no effect on stream’s ability to carry dissolved load
      • Precipitation only if water chemistry changes
running water6
Running water
  • Transportation – transported material is called the stream’s load
    • Suspended load
      • Biggest portion of river’s load
      • Usually fine particles s/a silt, clay but could be sand or gravel, especially during flood (which can also increase quantity)
      • Controlled by flow velocity and settling velocity (speed @ which particle falls through still fluid)
        • Slow settling + high flow = longer suspension
    • Bed load
running water7
Running water
  • Suspended load, Colorado River
running water8
Running water
  • Transportation – transported material is called the stream’s load
    • Bed load – solids are to large to be carried in suspension, settle along stream bed
      • Erosional action – move by rolling, sliding, saltation (jumping or skipping)
      • < 10% of total load
running water9
Running water
  • The work of streams
    • Transportation
      • Load is related to a stream’s
        • Competence
          • maximum particle size
          • increases proportionately to square of velocity (swift streams have greater competence
        • Capacity
          • maximum load
          • related to discharge
running water10
Running water
  • The work of streams
    • Transportation
      • Deposition
        • Caused by a decrease in velocity
        • Competence is reduced
        • Sediment begins to drop out
      • Stream sediments
        • Known as alluvium
        • Well-sorted deposits
running water11
Running Water
  • Bedrock channels vs. alluvial channels
    • Bedrock – headwater, steep
    • May contain rapids/waterfalls
      • Rapid
        • section of river where river bed has a relatively steep gradient 
        • increase in water velocity and turbulence
        • river becomes shallower and has some rocks exposed above the flow surface
running water13
Running Water
  • Bedrock channels vs. alluvial channels
    • Bedrock – headwater, steep
    • May contain rapids/waterfalls
      • Waterfall – place where water flows over a vertical drop in the course of a stream or river
running water14
Running Water
  • Bedrock channels vs. alluvial channels
    • Alluvial – loosely consolidated sediment (alluvium)
      • Meandering
        • mostly suspended load
        • evolve over time as bends migrate floodplain
        • most erosion @ outside of bend
running water15
Running Water

Cut bank – zone of active erosion

Point bar – coarser material deposited

running water17
Running Water
  • Braided Streams
    • Complex network of diverging channels
    • Coarse grains are transported as bed load
slide32

South-looking photograph showing diamond-shaped bars and meandering braided stream channels, East Fork Toklat River, Alaska Range, Denali National Park, Alaska.

South-looking photograph showing diamond-shaped bars and meandering braided stream channels, East Fork Toklat River, Alaska Range, Denali National Park, Alaska.

Rakaia River, South Island New Zealand

running water18
Running water
  • Base level
    • Lowest point a stream can erode to
    • Two general types
      • Ultimate – sea level
      • Temporary, or local
    • Changing causes readjustment of the stream – deposition or erosion
running water19
Running water
  • Stream valleys
    • Valley sides are shaped by
      • Weathering
      • Overland flow
      • Mass wasting
    • Characteristics of narrow valleys
      • V-shaped
      • Downcutting toward base level
running water20
Running water
  • Stream valleys
    • Characteristics of narrow valleys
      • Features often include
        • Rapids
        • Waterfalls
    • Characteristics of wide valleys
      • Stream is near base level
        • Downward erosion is less dominant
        • Stream energy is directed from side to side
running water21
Running water
  • Stream valleys
    • Characteristics of narrow valleys
      • Features often include
        • Rapids
        • Waterfalls
    • Characteristics of wide valleys
      • Stream is near base level
        • Downward erosion is less dominant
        • Stream energy is directed from side to side
running water22
Running water
  • Features produced by deposition
    • Deltas
      • exist in ocean or lakes
      • formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river
      • Human activities s/a diversion of water, damscan radically alter delta ecosystems
        • dams block sedimentation which can cause the delta to erode away
        • use of water upstream can greatly increase salinity levels as less fresh water flows to meet the salty ocean water
        • Nile Delta and Colorado River Delta are some of the most extreme examples of the ecological devastation caused to deltas by damming and diversion of water.
running water23
Running water
  • Features produced by deposition
    • Natural levees
      • form parallel to the stream channel
      • commonly form around lowland rivers and creeks without human intervention
    • Area behind levee is characteristically poorly drained (water can not flow up the levee and into the river)
      • Marshes called backswamps result.
      • Yazoo tributaries
        • Since tributary stream can not enter river, it has to flow parallel to the river until it can breach the levee
        • Name comes from the Yazoo River, which runs parallel to the Mississippi River for 280 km (170 mi) before converging
running water24
Running water
  • Features produced by deposition
    • Alluvial Fan - fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads, typically at the exit of a canyon onto a flatter plain
    • As stream\'s gradient decreases, it drops coarse-grained material
      • Reduces capacity of channel
      • Forces it to change direction and gradually build up a slightly mounded or shallow conical fan shape. 
running water25
Running water
  • Floods and flood control
    • Floods are the most common geologic hazard
    • Causes of floods
      • Floods are caused by many factors and can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that can absorb rainfall.
causes of floods
Causes of floods
  • Heavy rainfall
  • Highly accelerated snowmelt
  • Severe winds over water
  • Unusual high tides
  • Tsunamis
  • Failure of dams, levees, retention ponds, or other structures that retain water
running water26
Running water
  • Floods and flood control
    • Engineering efforts
      • Artificial levees
        • Steeper slope than natural levee
        • Sometimes made of concrete
      • Flood-control dams
        • Store water, then let it out slowly
        • Destroy farmland, etc.
        • Trap sediment leading to erosion downstream
running water27
Running water
  • Floods and flood control
    • Engineering efforts
      • Channelization – altering channel
        • Clearing obstructions, dredging
        • Artificial cutoffs – increase gradient and velocity, lower chance of flooding
    • Nonstructural approach through sound floodplain management
      • Zoning regulations that minimize development and promote more appropriate land use
inside hurricane katrina
Inside Hurricane Katrina
  • Part 1
  • Part 2
  • Part 3
  • Part 4
  • Part 5
water beneath the surface groundwater
Water beneath the surface (groundwater)
  • Largest freshwater reservoir for humans
  • Geological roles
    • As an erosional agent, dissolving by groundwater produces
      • Sinkholes
      • Caverns
    • An equalizer of stream flow
water beneath the surface groundwater1
Water beneath the surface (groundwater)
  • Distribution and movement of groundwater
    • Distribution of groundwater
      • Belt of soil moisture
      • Zone of aeration
        • Unsaturated zone
        • Pore spaces in the material are filled mainly with air
water beneath the surface groundwater2
Water beneath the surface (groundwater)
  • Distribution and movement of groundwater
    • Distribution of groundwater
      • Zone of saturation
        • All pore spaces in the material are filled with water
        • Water within the pores is groundwater
      • Water table – the upper limit of the zone of saturation
water beneath the surface groundwater3
Water beneath the surface (groundwater)
  • Distribution and movement of groundwater
    • Distribution of groundwater
      • Porosity
        • Percentage of pore spaces
        • Determines storage of groundwater
      • Permeability
        • Ability to transmit water through connected pore spaces
        • Aquitard – an impermeable layer of material
        • Aquifer – a permeable layer of material
water beneath the surface groundwater4
Water beneath the surface (groundwater)
  • Features associated with groundwater
    • Springs
      • Hot springs
        • Water is 6–9° C (10–15° F) warmer than the mean air temperature of the locality
        • Heated by cooling of igneous rock
      • Geysers
        • Intermittent hot springs
        • Water turns to steam and erupts
water beneath the surface groundwater5
Water beneath the surface (groundwater)
  • Features associated with groundwater
    • Wells
      • Pumping can cause a drawdown (lowering) of the water table
      • Pumping can form a cone of depression in the water table
    • Artesian wells
      • Water in the well rises higher than the initial groundwater level
water beneath the surface groundwater6
Water beneath the surface (groundwater)
  • Environmental problems associated with groundwater
    • Treating it as a nonrenewable resource
    • Land subsidence caused by its withdrawal
    • Contamination
water beneath the surface groundwater7
Water beneath the surface (groundwater)
  • Geologic work of groundwater
    • Groundwater is often mildly acidic
      • Contains weak carbonic acid
      • Dissolves calcite in limestone
    • Caverns
      • Formed by dissolving rock beneath Earth’s surface
      • Formed in the zone of saturation
water beneath the surface groundwater8
Water beneath the surface (groundwater)
  • Geologic work of groundwater
    • Caverns
      • Features found within caverns
        • Form in the zone of aeration
        • Composed of dripstone
        • Calcite deposited as dripping water evaporates
        • Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor)
water beneath the surface groundwater9
Water beneath the surface (groundwater)
  • Geologic work of groundwater
    • Karst topography
      • Formed by dissolving rock at, or near, Earth’s surface
      • Common features
        • Sinkholes – surface depressions
        • Sinkholes form by dissolving bedrock and cavern collapse
        • Caves and caverns
      • Area lacks good surface drainage
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