River Systems
Earth Space Science
Mr. Coyle
The Hydrologic Cycle
• Infiltration = Groundwater System
• Runoff = Surface Water System
• Runoff = Precipitation - Evapotranspiration
Where is the Water ?
RIVERS & STREAMS
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•
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Water Reservoirs
The Hydrologic Cycle
Surface Water Systems
Meandering
Deltas/Alluvial Fans
Floods and flooding
Importance of rivers
• Rivers:
–
–
–
–
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Provide water and nutrients for agriculture
Provide habitat to diverse flora and fauna
Provide routes for commerce
Provide recreation
Provide electricity
www.aquatic.uoguelph.ca/rivers/chintro.htm
Natural Watercourses
• Discharge- volume of water
• Velocity- rate of water movement
• Gradient- slope of inclined surface
Variation in time and space
• The shape, size and content of a river are
constantly changing, forming a close and
mutual interdependence between the river
and the land it traverses.
What is a Watershed?
www.dec.state.ny.us/website/2000/watersheds.gif
www.aquatic.uoguelph.ca/rivers/chwater.htm
www.epa.gov/watertrain/ecology/ecology21.html
L a rg e s t R iv e rs o f th e W o rld
A p p r o x . le n g th
R iv e r
O u tflo w
N ile M e d ite r r a n e a n S e a
m i.
4 ,1 8 0
km
6 ,6 9 0
A m a z o n A tla n tic O c e a n
3 ,9 1 2
6 ,2 9 6
M is s is s ip p i-M is s o u r i G u lf o f M e x ic o
3 ,7 1 0
5 ,9 7 0
Y a n g tz e K ia n g C h in a S e a
3 ,6 0 2
5 ,7 9 7
O b G u lf o f O b
3 ,4 5 9
5 ,5 6 7
H u a n g H o (Y e llo w ) G u lf o f C h ih li
2 ,9 0 0
4 ,6 6 7
Y e n is e i A r c tic O c e a n
2 ,8 0 0
4 ,5 0 6
P a r a n á R ío d e la P la ta
2 ,7 9 5
4 ,4 9 8
2 ,7 5 8
4 ,4 3 8
2 ,7 1 6
4 ,3 7 1
2 ,7 0 4
4 ,3 5 2
2 ,6 5 2
4 ,2 6 8
2 ,6 3 5
4 ,2 4 1
N ig e r G u lf o f G u in e a
2 ,6 0 0
4 ,1 8 4
M e k o n g S o u th C h in a S e a
2 ,5 0 0
4 ,0 2 3
2 ,3 4 8
3 ,7 7 9
2 ,3 1 5
3 ,7 2 6
2 ,2 9 1
3 ,6 8 7
M a d e ir a A m a z o n R iv e r
2 ,0 1 2
3 ,2 3 8
P u r u s A m a z o n R iv e r
1 ,9 9 3
3 ,2 0 7
1 ,9 8 7
3 ,1 9 8
1 ,9 7 9
3 ,1 8 5
1 ,9 0 0
3 ,0 5 8
1 ,8 8 5
3 ,0 3 4
1 ,8 0 0
2 ,8 9 7
1 ,8 0 0
2 ,8 9 7
D a n u b e B la c k S e a
1 ,7 6 6
2 ,8 4 2
E u p h r a te s S h a tt-a l-A r a b
1 ,7 3 9
2 ,7 9 9
D a r lin g M u r r a y R iv e r
1 ,7 0 2
2 ,7 3 9
1 ,7 0 0
2 ,7 3 6
1 ,6 7 7
2 ,6 9 9
Ir tis h O b R iv e r
Z a ir e (C o n g o ) A tla n tic O c e a n
H e ilo n g (A m u r ) T a ta r S tr a it
L e n a A r c tic O c e a n
M a c k e n z ie B e a u fo r t S e a (A r c tic O c e a n )
M is s is s ip p i G u lf o f M e x ic o
M is s o u r i M is s is s ip p i R iv e r
V o lg a C a s p ia n S e a
S ã o F r a n c is c o A tla n tic O c e a n
Y u k o n B e r in g S e a
S t. L a w r e n c e G u lf o f S t. L a w r e n c e
R io G r a n d e G u lf o f M e x ic o
B r a h m a p u tr a G a n g e s R iv e r
In d u s A r a b ia n S e a
Z a m b e z i M o z a m b iq u e C h a n n e l
T o c a n tin s P a r á R iv e r
The
Worlds
Largest
Rivers
Discharge
River
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Amazon, Brazil
Congo, Zaire
Yangtse Kiang, China
Orinoco, Venezuela
Brahmaputra, Bangladesh
La Plata, Brazil
Yenissei, Russia
Mississippi, USA
Lena, Russia
Mekong, Vietnam
Ganges, India
Irrawaddy, Burma
Ob, Russia
Sikiang, China
Amur, Russia
St. Lawrence, Canada
m^3/sec
190,000
42,000
35,000
29,000
20,000
19,500
17,800
17,700
16,300
15,900
15,500
14,000
12,500
11,500
11,000
10,400
% of total
Runoff
mm/yr entering
Ratio
oceans
835
340
560
845
1070
235
215
175
210
630
455
1020
135
840
190
310
13.0
2.9
2.4
2.0
1.4
1.3
1.2
1.2
1.1
1.1
1.1
1.0
0.9
0.8
0.8
0.7
0.47
0.25
0.50
0.46
0.65
0.20
0.42
0.21
0.46
0.43
0.42
0.60
0.24
0.32
0.33
U.S. Precipitation Map
Notice the effect of
the Rocky Mountains
U.S. Runoff Map
Laminar vs. Turbulent Flow
Near-Laminar flow in the
center of a river channel
Turbulent flow in the
headwaters of a rushing
mountain stream
So Where Does The Stream
Move Fastest?
• Headwaters move
slowest
• Mouth of stream moves
fastest
• Laminar flow is more
efficient than turbulent
flow.
• Deeper stream move
faster than shallow
streams
Sediment Load
Movement of Bedload by Saltation
Sedimentation
Longitudinal Stream Profile
Can be divided into 3 main parts
Drainage (Tributary) Transport System Distributary
System
System
Drainage System
• Stream energy is spent eroding downward
into the basement rock and...
• Moving sediment
• Creates “V” shaped canyon and valleys
• When streams emerge from the mountain
front, they often deposit some of this
sediment forming alluvial fans.
Alluvial Fans
Transition from Tributary to Transport
Aging Rivers: How Old Is It?
• Young- rapid bed erosion, waterfalls,
rapids, v-shaped valleys, few tributaries,
low volume
• Mature- well established tributaries, larger
volume of water, erode banks and not the
bed (bottom), meanders, oxbow lakes
Flash Flooding & Sheetwash
Braided Pattern = high slope + high
stream power + coarse bed materials
Braided Streams & Rivers
• High sediment load
• Constantly changing course
• Floodplain is completely occupied by
channels
• Many small islands called mid-channel bars
• Usually coarse sand and gravel deposits.
Meandering Rivers
Meandering Rivers
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Constantly erode material - Cut bank
Constantly deposit material - Point bar
Change their channel course gradually
Create floodplains wider than the channel
– Very Fertile soil
– Subjected to seasonal flooding
Formation of Meanders
Point
bar
deposits
Point Bar Deposits
Point bar deposits grows laterally
through time
Cut bank erosion
Point
bar
deposits
}
Meander
loop
Formation of an Oxbow
Meandering stream
flowing from
top of screen
to bottom
Maximum
deposition
Maximum
erosion
Meander scars
Oxbow Lake
Oxbow
cuttoff
1993 Mississippi Flood
Flooding & Sedimentation
Deltas - Distribution Systems
If the
Mississippi
changes course
again, what
will happen to
the City of
New Orleans?
Things to Remember
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Rivers are part of a larger hydrologic system
The have three main components:
Drainage (Tributary) systems - collect water
Transport Systems - move water along
– Alluvial fans, braided streams, meandering streams
• Rivers exceed their capacity during floods
• Distributary systems - return water to the sea
– Deltas.