Quantitative Elements of Physical Hydrology - DEEPS€¦ · 4 Watershed: The area that delivers water to a distributed collection zone. Application: Extent of recharge zone of a local

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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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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 delivering water to a collection (outflow) point.

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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.


Consider a drop of water . . .


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The “drop” rolls down gradient.


And down gradient . . .


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Leaving the watershed.



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Delineating a watershed begins at the outflow point.


Trace the boundary up-gradient.© John F. Hermance

February 04, 2007

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Continue to the farthest point from the outflow zone.


Return to the starting point, and go the other way.


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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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Mississippi Catchment (Sub-Basins: Hydro1k)

Mississippi River Catchment

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Rio Grande River Catchment

Colorado River Catchment

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The Continental Divide in terms of several principal basins.

Mississippi R.Colorado R.

Rio Grande R.


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Watershed: The area delivering water to a distributed collection zone.



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A more complicated example (from the Thames River Watershed).

To summarize:


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Exercise: Trace the watershed.


A note of caution: The conventional paradigm may not apply.

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The geologic watershed may differ from the topographic wayershed.


And what do you do about "pods", "dimples" or depressions?

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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]

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Quantitative Elements of Physical Hydrology - DEEPS€¦ · 4 Watershed: The area that delivers water to a distributed collection zone. Application: Extent of recharge zone of a local