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Quantitative Elements of Physical Hydrology
© John F. HermanceFebruary 04, 2007
Watershed & Catchment DelineationWatershed & Catchment Delineation
Contact information:Jack HermanceEnvironmental Geophysics/HydrologyDepartment of Geological SciencesBrown University, Providence, RI 02912-1846Tel: 401-863-3830e-mail: [email protected]
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Quantitative Elements of Physical Hydrology
© John F. HermanceFebruary 04, 2007
Topics for Watershed Delineation
What is a watershed?
How are they delineated?
Catchments and Reaches in GIS
(An aside on creating DEMs.)
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Watershed: The area that delivers water to a distributed collection zone.
Application: Extent of recharge zone of a local reservoir.
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Plane view (2D) contoured map with colored “image” map.
© John F. HermanceFebruary 04, 2007
Consider a drop of water . . .
© John F. HermanceFebruary 04, 2007
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The “drop” rolls down gradient.
© John F. HermanceFebruary 04, 2007
And down gradient . . .
© John F. HermanceFebruary 04, 2007
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Delineating a watershed begins at the outflow point.
© John F. HermanceFebruary 04, 2007
Trace the boundary up-gradient.© John F. Hermance
February 04, 2007
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Continue to the farthest point from the outflow zone.
© John F. HermanceFebruary 04, 2007
Return to the starting point, and go the other way.
© John F. HermanceFebruary 04, 2007
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Hopefully, the two traces meet.© John F. Hermance
February 04, 2007
The watershed.© John F. Hermance
February 04, 2007
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Topographic "Divide"
(Catchments are often definedby topographic "divides".)
Stream hydrography from North American Atlas.
Continental Divide
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Continental Divide
Elevation from NA Hydro1k Gtopo30 DEM.
Landcover classes (from remote sensing data)
Regional Watersheds
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The Continental Divide in terms of several principal basins.
Mississippi R.Colorado R.
Rio Grande R.
© John F. HermanceFebruary 04, 2007
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Watershed: The area delivering water to a distributed collection zone.
© John F. HermanceFebruary 04, 2007
© John F. HermanceFebruary 04, 2007
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© John F. HermanceFebruary 04, 2007
A more complicated example (from the Thames River Watershed).
To summarize:
© John F. HermanceFebruary 04, 2007
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© John F. HermanceFebruary 04, 2007
Exercise: Trace the watershed.
© John F. HermanceFebruary 04, 2007
A note of caution: The conventional paradigm may not apply.
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© John F. HermanceFebruary 04, 2007
The geologic watershed may differ from the topographic wayershed.
© John F. HermanceFebruary 04, 2007
And what do you do about "pods", "dimples" or depressions?
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Quantitative Elements of Physical Hydrology
© John F. HermanceFebruary 04, 2007
End of Presentation(Watershed Delineation)
End of Presentation(Watershed Delineation)
Contact information:Jack HermanceEnvironmental Geophysics/HydrologyDepartment of Geological SciencesBrown University, Providence, RI 02912-1846Tel: 401-863-3830e-mail: [email protected]