Stream Ecology: River
Structure and Hydrology
Unit 1: Module 4, Lectures 1
Objectives
 Students will able to:
 describe how evaporation and precipitation
influence river formation.
 diagram the distribution of water on Earth.
 define and provide examples of a watershed.
 diagram stream networks and drainages.
 explain how a meandering stream can form an
oxbow lake.
 predict riffle and pool formation in a stream
segment.
Developed by: Merrick, Richards
Updated: August 2003
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Module 4 introduces students to:
 Lecture1:
 Lecture 2:
 The Importance of
Rivers
 The Hydrologic Cycle
 Watersheds as a
concept
 Geomorphology
 Hydrology
 flow and discharge
 storm and annual
hydrographs
 flood probability
 sediment transport and
deposition
 watersheds and
drainage networks
 channel morphology
 habitat scales
Developed by: Merrick, Richards
Updated: August 2003
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Importance of rivers
 Rivers:
 Provide
 Provide
 Provide
 Provide
 Provide
water and nutrients for agriculture
habitat to diverse flora and fauna
routes for commerce
recreation
electricity
www.aquatic.uoguelph.ca/rivers/chintro.htm
Developed by: Merrick, Richards
Updated: August 2003
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Natural watercourses
 Existence depends on:
 Availability of surface water
 A channel in the ground
 An inclined surface
www.aquatic.uoguelph.ca/rivers/chintro.htm
Developed by: Merrick, Richards
Updated: August 2003
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Lotic systems
 Four dimensions:
 Longitudinal
 Lateral
 Vertical
 Time
www.aquatic.uoguelph.ca/rivers/chintro.htm
The four dimensions of a lotic system
Developed by: Merrick, Richards
Updated: August 2003
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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.
www.aquatic.uoguelph.ca/rivers/chintro.htm
Developed by: Merrick, Richards
Updated: August 2003
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Effect of climate
 Rivers are very dependent on climate and their
characteristics are closely related to the
precipitation and evaporation regimes in their
drainage areas.
 Three types:
 Perennial or permanent rivers
 Periodic rivers
 Episodic rivers
www.aquatic.uoguelph.ca/rivers/chintro.htm
Developed by: Merrick, Richards
Updated: August 2003
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The hydrologic cycle
ga.water.usgs.gov/edu/charts/waterdistribution.gif
Developed by: Merrick, Richards
Updated: August 2003
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Distribution of water on earth
ga.water.usgs.gov/edu/charts/waterdistribution.gif
Developed by: Merrick, Richards
Updated: August 2003
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What is a watershed?
www.dec.state.ny.us/website/2000/watersheds.gif
Developed by: Merrick, Richards
Updated: August 2003
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What is a watershed?
www.dec.state.ny.us/website/2000/watersheds.gif
www.aquatic.uoguelph.ca/rivers/chwater.htm
Developed by: Merrick, Richards
www.epa.gov/watertrain/ecology/ecology21.html
Updated: August 2003
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Spatial scale: Stream segments
www.usda.gov/stream_restoration/chap1.html
Developed by: Merrick, Richards
Updated: August 2003
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Stream networks or drainages
www.usda.gov/stream_restoration/chap1.html
www.aquatic.uoguelph.ca/rivers/chwater.htm
Developed by: Merrick, Richards
Updated: August 2003
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Stream order
 A method of classifying or ordering the
hierarchy of natural channels.
 Strahler (1957) is the most widely used system.
 Stream order correlates well with drainage
area, but is also regionally controlled by
topography & geology.
www.usda.gov/stream_restoration/chap1.html
Developed by: Merrick, Richards
Updated: August 2003
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Spatial scale: Segment system
www.usda.gov/stream_restoration/chap1.html
Developed by: Merrick, Richards
Updated: August 2003
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Stream corridor and channel morphology
http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg
Developed by: Merrick, Richards
Updated: August 2003
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Cross section of a channel
www.usda.gov/stream_restoration/chap1.html
Developed by: Merrick, Richards
Updated: August 2003
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Floodplain
www.usda.gov/stream_restoration/chap1.html
Figure 1.21
Developed by: Merrick, Richards
Updated: August 2003
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Meandering rivers
A meander becomes more pronounced as the
streamline shifts between the river banks.
Developed by: Merrick, Richards
Formation of an oxbow lake
http://www.aquatic.uoguelph.ca/rivers/chphys.htm
Updated: August 2003
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Sinuosity: Gradient and substrate
 Big meanders
 low gradient
 fine substrates
Developed by: Merrick, Richards
 Small meanders
 high gradient
 coarse substrates
Updated: August 2003
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Braided channel
 Braided Pattern = high slope + high stream
power + coarse bed materials
earthsci.org/teacher/basicgeol/stream/stream.html#Erosion%20by%20Streams
Developed by: Merrick, Richards
Updated: August 2003
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An oxbow lake
dnr.metrokc.gov/WTD/wetland79/images/oxbow-01-30.jpg
Developed by: Merrick, Richards
Updated: August 2003
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Spatial scale: Reach system
www.usda.gov/stream_restoration/chap1.html
Developed by: Merrick, Richards
Updated: August 2003
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Riffles, pools, and cascades
 Riffles and pools alternate in somewhat
predictable patterns
www.aquatic.uoguelph.ca/rivers/chphys.htm
Developed by: Merrick, Richards
Updated: August 2003
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Pool - riffle sequence
 Riffle to riffle = 5 - 7 channel widths
http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg
Developed by: Merrick, Richards
Updated: August 2003
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