stream ecology: river structure and hydrology unit 1: module 4, lectures 1

Stream Ecology: River Structure and Hydrology

Unit 1: Module 4, Lectures 1

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2

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.


Module 4 introduces students to:

Lecture1: The Importance of

Rivers The Hydrologic Cycle Watersheds as a

concept Geomorphology

watersheds and drainage networks

channel morphology habitat scales

Lecture 2: Hydrology

flow and discharge storm and annual

hydrographs flood probability sediment transport and

deposition


Rivers: 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

Importance of rivers


Existence depends on: Availability of surface water A channel in the ground An inclined surface


Natural watercourses


Four dimensions: Longitudinal Lateral Vertical Time

Lotic systems


The four dimensions of a lotic system


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.


Variation in time and space


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



The hydrologic cycle

ga.water.usgs.gov/edu/charts/waterdistribution.gif


ga.water.usgs.gov/edu/charts/waterdistribution.gif

Distribution of water on earth


www.dec.state.ny.us/website/2000/watersheds.gif

What is a watershed?


What is a watershed?

www.aquatic.uoguelph.ca/rivers/chwater.htm

www.dec.state.ny.us/website/2000/watersheds.gif

www.epa.gov/watertrain/ecology/ecology21.html


Spatial scale: Stream segments

www.usda.gov/stream_restoration/chap1.html


www.aquatic.uoguelph.ca/rivers/chwater.htm


Stream networks or drainages


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.



Spatial scale: Segment system



http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg

Stream corridor and channel morphology



Cross section of a channel


Floodplain

www.usda.gov/stream_restoration/chap1.htmlFigure 1.21


Meandering rivers

http://www.aquatic.uoguelph.ca/rivers/chphys.htm

A meander becomes more pronounced as the streamline shifts between the river banks.

Formation of an oxbow lake


Small meanders high gradient coarse substrates

Sinuosity: Gradient and substrate

Big meanders low gradient fine substrates


Braided Pattern = high slope + high stream power + coarse bed materials

Braided channel

earthsci.org/teacher/basicgeol/stream/stream.html#Erosion%20by%20Streams


dnr.metrokc.gov/WTD/wetland79/images/oxbow-01-30.jpg

An oxbow lake


Spatial scale: Reach system



Riffles, pools, and cascades

Riffles and pools alternate in somewhat predictable patterns

www.aquatic.uoguelph.ca/rivers/chphys.htm


Pool - riffle sequence

Riffle to riffle = 5 - 7 channel widths

http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg

stream ecology: river structure and hydrology unit 1: module 4, lectures 1

Documents

meandering stream

stream corridor

stream segmentsdeveloped

stream ecology

diagram stream networks

stream order correlates

stream ordera method

distribution of water