Watershed Delineation

Transcription

1 Foundations of Physical Hydrology Watershed Delineation Contact information: Jack Hermance Environmental Geophysics/Hydrology Department of Geological Sciences Brown University, Providence, RI Tel: (Information for the Presenter) Conventions for Prompting Slide Changes. This is the toggle symbol to prompt presenter to return to previous slide for quick comparisons with the current slide. The following traffic light signals appear in lower right corner of the slide to prompt presenter accordingly. Move forward quickly, probably the next slide has the essential information (e.g. labels). Move forward after a slight pause to assess whether content deserves brief comment. Move forward after a longer pause, perhaps a few brief comments are required. This is a pausing point at which motivating comments can be made, or the contents thoroughly discussed. 1

2 Foundations of Physical Hydrology Topics for Watershed Delineation What is a watershed? How are they delineated? (An aside on creating DEMs.) 2

3 Watershed: The area delivering water to a collection (outflow) point. 3

4 Application: Extent of recharge zone of a local reservoir. Watershed: The area that delivers water to a distributed collection zone. 4

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6 3D Wireframe Surface Overlaying a Colored Contour Base. Plane view (2D) contoured map with colored image map. 6

7 Consider a drop of water... The drop rolls down gradient. 7

8 And down gradient... Leaving the watershed. 8

9 Delineating a watershed begins at the outflow point. 9

10 Trace the boundary up-gradient. Continue to the farthest point from the outflow zone. 10

11 Return to the starting point, and go the other way. Hopefully, the two traces meet. 11

12 The watershed. The surface topography. 12

13 The watershed. Topographic "Divide" 13

14 Continental Divide Stream hydrography from North American Atlas. Elevation from NA Hydro1k Gtopo30 DEM. 14

15 Continental Divide Regional Watersheds Landcover classes (from remote sensing data) 15

16 Mississippi River Catchment Rio Grande River Catchment 16

17 Colorado River Catchment Guadalupe River (Texas) Catchment 17

18 Guadalupe River (Texas) Catchment Guadalupe River (Texas) Catchment 18

19 (A more detailed characterization of stream hydrography.) Guadalupe River (Texas) Catchment (Hydrography: National Atlas) (Example of "nested" catchments.) Guadalupe River (Texas) Catchment (Sub-Basins: Hydro1k) 19

20 Mississippi Catchment (Sub-Basins: Hydro1k) The Continental Divide in terms of several principal basins. Colorado R. Mississippi R. Rio Grande R. 20

21 Watershed: The area delivering water to a distributed collection zone. 21

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24 To summarize: A more complicated example (from the Thames River Watershed). Exercise: Trace the watershed. 24

25 A note of caution: The conventional paradigm may not apply. The geologic watershed may differ from the topographic wayershed. 25

26 And what do you do about "pods", "dimples" or depressions? 26

27 Watersheds: The fundamental unit of hydrology Analogous to basic physics and chemistry, where the fundamental unit is the atom, in hydrology the fundamental unit is the watershed. Just as atoms are comprised of electrons, protons and neutrons, so are watersheds comprised of landforms, biota, streams, lakes and aquifers. However, unlike atoms, where electrons, protons and neutrons can be pulled off and take on an activity of their own, in watersheds, a stream or an aquifer cannot be isolated from the other components. 27

28 Foundations of Physical Hydrology End of Presentation (Watershed Delineation) Contact information: Jack Hermance Environmental Geophysics/Hydrology Department of Geological Sciences Brown University, Providence, RI Tel: