Rivers and
Groundwater
SURFICIAL PROCESSES
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Erosion, Transportation, Deposition on the Earth’s
Surface
Landscapes created and destroyed
Involves atmosphere, water, gravity
Agents:
– Mass wasting (gravity), Running water
(streams), glaciers (ice), wind, water waves,
ground water
MASS WASTING
Masses of debris (mud, sand, gravel) or
bedrock moving downhill
 Landslides and slower movements
 Driven by GRAVITY
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Controlling Factors
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Slope angle- gentle vs steep
Local relief- low vs high
Thickness of debris over bedrock- slight vs great
Planes of weakness ( in bedrock)
– bedding planes; foliation; joints
– planes at right angle to slope vs parallel to
slope most dangerous
The Hydrologic Cycle
Powered by the Sun
 Evaporation primarily from tropical oceans
 Evapotranspiration- from surface water & plants
 Condensation- clouds
 Precipitation
 Runoff- from the land
 Infiltration/Percolation into soil and rocks
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Water Reservoirs
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Oceans- 97%
Ice caps and Glaciers- 2.15%
Groundwater- 0.62%
Lakes- 0.017%
Soil Moisture- 0.005%
Streams- 0.0001%
Atmosphere- 0.001%
Drainage Basins
Tributary
 Divide
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Drainage Patterns
Dendritic
 Radial
 Rectangular
 Trellis
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Factors Affecting Stream Erosion
and Deposition
Velocity
 Gradient
 Channel Shape and Roughness
 Discharge
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Factors Affecting Stream Erosion
and Deposition
Velocity
 Gradient
 Channel Shape and Roughness
 Discharge
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Meandering Streams and Point
Bars
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Meanders
Point Bar
Meander Cutoff
– Oxbow Lake
Flood Plains
– Natural Levees
Meandering Streams and Point
Bars
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Meanders
Point Bar
Meander Cutoff
– Oxbow Lake
Flood Plains
– Natural Levees
Meandering Streams and Point
Bars
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Meanders
Point Bar
Meander Cutoff
– Oxbow Lake
Flood Plains
– Natural Levees
DELTAS
Flooding
Flooding
 Urban Flooding
 Flash Floods
 Controlling Floods
 The Great Flood of 1993
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Flooding
Controlling Floods
 The Great Flood of 1993
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The Great Flood of 1993
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Excessive rain in upper midwest
6.6 million acres in 9 states flooded
Discharge exceeded 100-year discharges on many
rivers
– At St. Louis Mississippi Q=1,000,000 cfs
– River Stage 20 ft above flood stage
38 deaths
$17 billion in losses
Groundwater
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What happens to precipitation once it reaches the
ground
– infiltration
– percolation
Water filling pore space, cracks & crevices in rocksPorosity
Aquifer- Geologic unit that can store, transmit and
yield appreciable amounts of water
Porosity and Permeability
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Porosity
– % of rock or sediment that is open (void
spaces)
– ability to hold water
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Permeability- ability to transmit water
Movement of ground water
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Moves in response to differences in water
pressure & elevation
Velocity influenced by
– Slope of water table
– Permeability
Aquifers
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Geologic unit that can store, transmit and yield
appreciable amounts of water
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Highly permeable & saturated with water
– Good aquifers
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Aquitards- impermeable
Unconfined aquifer
– open to atmosphere
Confined aquifer
– under pressure
– artesian- flows w/o being pumped
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Wells
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Penetrate aquifer within the saturated zone
Water table rises and falls during seasons
– Recharge
Cone of depression
– Drawdown
Artesian well- no need to pump
– Artesian aquifer
Springs and Streams
Spring
– Water table intersecting hillside
 Gaining stream= Effluent Stream
 Losing stream= Influent Stream
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Springs and Streams
Spring
– Water table intersecting hillside
 Gaining stream= Effluent Stream
 Losing stream= Influent Stream
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WT
WT
Pollution of Ground Water
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Pollutants
– Chemicals
» Gasoline
» Pesticides & herbicides
» Fertilizers
» Heavy metals
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Bacteria, viruses, parasites- Sewage
Acid mine drainage
Radioactive waste
Natural pollution
Balancing Withdrawal &
Discharge
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Overpumping results in:
– Falling water table
– Ground subsidence
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Artificial recharge
Subsidence of land
caused by extraction
of groundwater in the
San Juaquin Valley, CA
The land sank 9m or
30 ft in 52 years
Effects of Groundwater Action
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Karst topography-Caves
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Rock usually limestone
Dissolves by weakly acidic water
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Dripstone- Speleothem
»
»
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rainwater pH 5.5 and carbonic acid from humus
stalagtite
stalagmite
Flowstone
– Sinkholes
Hot Water Underground
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Hot springs
– Near magma or cooling igneous rocks
– Deep-circulating groundwater or
Geyser
Precipitation of dissolved ions
– Travertine- calcite
– Sinter- silica
Mudpot
Geothermal Energy
Hot Water Underground
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Hot springs
– Near magma or cooling igneous rocks
– Deep-circulating groundwater or
Geyser
Precipitation of dissolved ions
– Travertine- calcite
– Sinter- silica
Mudpot
Geothermal Energy