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An Example of Clay Mineral Formation
Clay minerals are the most abundant product of weathering and
they are formed when Silicate minerals decompose by hydrolysis
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2KAlSi3O8 + 2H+ + 9H2O >> Al2Si2O5(OH)4 + 2K+ + 4H4SiO4
Orthoclase feldspar+ acid + water>> clay + potassium + soluble silica
The ions released from silicate minerals in the weathering process aresodium, potassium, calcium, iron, and magnesium ions. They are carriedaway by rain and river waters or become important soil nutrients.
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Mineral Stability
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Water, Hydrology, Streams, and Rivers
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Learning Objectives
1. Hydrologic cycle2. Residence time of water in a system3. Streams and rivers
4. Stream’s functions; hydraulic parameters and load5. Particle Transport and Stokes Law6. Base level and graded steam concepts7. Floods and flood control
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Annual Water Balance
• Stream Runoff = Input – Losses
– Input = rain and snow
– Losses =evapotranspiration
• Storage
– changes in volume of soil water
or lake or river water
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Why is residence time important?
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Annual Water Balance
• What is the average discharge of the Ottawa
River at the Carillon Dam (~Montreal)?
– Flow = 1940 m3 sec-1
– Drainage Area = 146,300 km 2
– Unit Discharge = Flow / Drain area= 0.42 m a-1
• How does the annual discharge compare with
the Mackenzie? The Fraser? The Amazon?
• How does the unit discharge compare?
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Residence Time of Water in Pink
Lake, Gatineau Park?
• Catchment Area = 2km2
• Precipitation = 800 mm/a
•
Evaporation = 500 mm/a• Lake Volume = 1*107m3
• Residence time = Volume /Input
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Residence Time of Water in Pink
Lake, Gatineau Park
• Catchment Area = 2km2 = 2*106 m2
• Precipitation = 800 mm/a =0.8 m/a
•
Evaporation = 500 mm/a= 0.5 m/a• Lake Volume (V) = 1*107m3
ALWAYS CHECK YOUR UNITS!
Do a dimensional analysis
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Residence Time of Water in Pink
Lake, Gatineau Park
• Catchment Area = 2km2 = 2*106 m2
• Precipitation = 800 mm/a =0.8 m/a
•
Evaporation = 500 mm/a= 0.5 m/a• Lake Volume (V) = 1*107m3
• Residence time = Volume /Input
• Input (I) = (Precip-Evap)*Catchmt Area• Input = (0.8m-0.5m)*2*106 m2 =0.6*106 m3
• Residence time = V/I = (10/0.6)=16.6 a
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What happens when ….
• Water input greater than output?
– Water level in river / lake rises
• Flooding
• Ships can hold more cargo and do not ground in channels
• Water loss greater than precipitation input?
– Water levels drop, salinity rises,
– Soil dries up and wind-born soil transport increases• Agricultural crop failure
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A Drought Example
• Average Precipitation is 80 cm/a & Evaporation
is 60 cm/a
• What is the runoff?
• The soil water contains 20 cm water equivalent
• How many years will the water in the soil last if
the temperature rises 5oC and P is 80 and E is 85
cm/a?
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Streams and Rivers• Streams are any flowing body of water
• Rivers are major branches of a stream system
Fraser River, BC Stoney Creek, Texas
• Stream distribution→ f (plate tectonics, climate system)
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Hydrologic Cycle
Distribution of Earth’s water
1. Oceans:
2. Freshwater:
2a.
2b.
2c.
97.2%
2.8%
glaciers:
groundwater:
other lakes:
streams:atmosphere:soil moisture:
2.15%
0.62%
0.009%0.005%
0.0001%0.001%
So, why do we care?
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Streams are major geological agents of
change in landscapes (transfer materialfrom the highs to the lows – plane outrelief)
Importance
Most cities are built onfloodplains of riversSource of drinking water
Streams provide pathways for
inland colonization of continentse.g. Jacques Cartier
Lewis and Clark
Agriculture
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Stream system components
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Drainage basins
Drainage basin: total area drained bya stream and its tributaries
Drainage divide: ridge of high grounddividing one drainage basin from another
(red line – imaginary!)
Tributary: small stream flowing into a
larger one (contribut es)
Some terminology:
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Drainage basins
Largest drainage
basin of N. Am.?
Ottawa River drainage basin
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Stream system components Headwaters
Mouth
Longitudinal profile: cross-sectionalview of the stream bed (red line)
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1. valleys: sloping area aroundthe stream
Stream system components
2. channels: bottom of valley,where water flows
3. floodplains: flat area in valley
level with top of channel. Portionof the valley that can be flooded
Headwaters
MouthThe three basic parts of a stream:
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From upstream to downstream
discharge m3/s
v e l o c i t y m / s
d e p t h m
w i d t h m
Hydraulics and channel geometry
b) discharge (Q): Q (m3/s) = U (m/s) x A (m2)
Q ↑ downstr . - from collection of tributaries
a) gradient (L): height/distance (cm-m/km)↓ in L downstream.
d) velocity (U): average U ↑ downstr .; less bedroughness, higher Q, larger channels(overcome the lower L)
c) depth (d) & width (w): channel size ↑ downstr .;also, ↑ A = ↓ friction; larger streams have higher U
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Stream Processes
1. erosion
2. transport
3. Deposition …
Stream’s “job” = plane out relief
Accomplished through:
via channelized flow (most efficient)
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What controls erosion vs. transport vs. deposition?
a) hydraulic parameters
b) stream morphology
c) material (eroding intoand/or transporting)
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What keeps a particle suspended?Stokes Law describes the forces
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Force of (1) buoyancy and (2) frictional and form drag due to flow
Force of gravity
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Particles settle when FG>(FB+FD)
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Force of Buoyancy and Force of drag due to flow
Force of gravity
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Forces on a Particle in Flowing Water
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Force Difference betweengravity and buoyancy
Force of Gravity on Particle ‘p’
Gravity Force = mpg = Vp Dpg
Fluid Buoyancy Force = VpDf g
Force G-B = Vp(Dp-Df )g
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Particle settling in Flowing Water
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Force of Frictional drag due to flow
Fluid Drag Force
Drag = 0.5 C Df Rp2 W2
Df is fluid density
Rp is particle radius
W is water velocity
C Drag coefficient
Particle is dragged along by
flow so drag force is in the
direction of flow velocity
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Water Velocity and Particle Transport
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Particles settle when FG>(FB+FD)
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Base level and graded streams
Distance from headwaters of river (km)
A l t i t u d e a b o v e
s e a l e v e l ( m )
MouthSource
Longitudinalprofile
Base level: level below which astream cannot erodee.g. sea level, lake level, dam
Graded stream: equilibrium statewhere channel geometry andhydraulic parameter enable thestream to transport its load withneither deposition nor erosion.
Interplay between erosion, transport, and deposition → f(base level)
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Base level and graded streams
Changes in base level result in an
adjustment in the longitudinal profile
1) Increase in base level
longitudinal prof. adjusts by:
2) Decrease in base level
longitudinal prof. adjusts by:
↑ deposition
↑ erosion↑ transport
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Channel pattern
Braided rivers
rapid and irregular dischargehigher slopeserodible banks
rapid channel migrationabundant coarse sedimentin-channel bars (lense of sediment)
Braided if interlacing network of channels
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http://gsc.nrcan.gc.ca/landscapes/photos/photographs/alberta/jaspernationalpark/img11_03_02.jpghttp://gsc.nrcan.gc.ca/landscapes/photos/photographs/alberta/jaspernationalpark/img11_03_02.jpg
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Channel pattern
Meandering rivers
lower and more regular dischargelower slopescohesive banksslower more regular channel migration
abundant fine sediment
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Channel pattern
well developed levees
build-up of river banks →floods
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Channel pattern
Flow in meanderingchannels
Downstream flow
Helicoidal flow pattern
Cross-channel flow(secondary flow)
+
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point bar depositsalong inner bank
Channel pattern
Flow in meanderingchannels
Downstream flow
Helicoidal flow pattern
Cross-channel flow(secondary flow)
+
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Floods when streams leave their beds
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Flood – when discharge > stream capacity
→ stream overflows its banksNATURAL process
Floods - when streams leave their beds
Causes -
Contributing factors:• low infiltration rate
• topography
• ice-jam• rapid snow melt
• ...
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Floods - when streams leave their beds
Ice-jam Artificial levee breach – New Orleans(Hurricane Katrina, August 2005)
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Impacts – One of the mostdeadly and destructive geologichazards; Why?
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Floods
Flood consequences –
• life loss, disease, water contamination
HUMAN impact
MATERIAL impact
• destruction or damage ofproperty and infrastructures
LANDSCAPE modification
• erosion (high discharge)
• sedimentation (reduced velocity →
channel invades floodplain)
• channel avulsion
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Alberta FloodsJune 19-22 2013
• >200mm rain in two days• Snow cover & Saturated ground• Steep watershed – no storage• 4 deaths, 100k evacuees• $>1B flood damage
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Flood Control Techniques
Controls -
Winnipeg, Manitoba –floodplain of Red River
• artificial levees
• dams
• channelization
• Natural Storage Areas• Live elsewhere
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Video Reviewing Hydrologic Cycle
• https://www.youtube.com/watch?v=ts19O41k
wDA
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Summary of Key Concepts
https://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDA
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Summary of Key Concepts
1. Streams / Rivers transport water, solutes and sediment
2. Water runoff (Flow) is the difference between water inputs andevapotranspiration (if at steady state)
3. Unit runoff allows discharge to be calculated and flows to be
scaled in different catchments
4. Water Residence time is average time a water molecule is in the
lake, river, stream, atmosphere etc
5. Stokes Law describes the settling of particles in streams and
other moving fluids. (gravity vs buoyancy and drag)
6. Flooding is the most damaging and dangerous direct impact of
excess flow• Streams are loci of human habitation.
• Extreme events are difficult to predict and control.
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N L
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Next Lecture
• Groundwater
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