Watersheds. A river is the report card for its watershed. Alan Levere. Arizona Water Issues 2010 The University of Arizona HWR203 1

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1 Watersheds A river is the report card for its watershed. Alan Levere 1

2 What separates watersheds? How do you identify watershed boundaries? Drainage Divides River Networks boto.ocean.washington.edu/gifs/purus.gif Contour Lines Reynolds and Johnson 2

Drainage Basin Drainage Divide A region or area bounded by a drainage divide and occupied by a drainage system; specifically, the tract of country that gathers water originating as precipitation and

3 Drainage Basin Drainage Divide A region or area bounded by a drainage divide and occupied by a drainage system; specifically, the tract of country that gathers water originating as precipitation and contributes it to a particular stream channel or system of channels, or to a lake, reservoir or other body of water. The original meaning of the term signifies a water parting or the line, ridge, or summit of high ground separating two drainage basins. Source: Glossary of Geology, 3rd Ed.,1987, AGI 2010 The University of Arizona HWR203 3

Watershed Definitions A region draining into a river or lake (American Heritage Dictionary) The area that produces runoff to a downstream point (Handbook of Hydrology) The area contained within a

4 Watershed Definitions A region draining into a river or lake (American Heritage Dictionary) The area that produces runoff to a downstream point (Handbook of Hydrology) The area contained within a drainage divide above a specified point on a stream (Dictionary Of Geologic Terms) The upstream area that can contribute runoff to a point below. A drainage basin that divides the landscape into hydrologically defined areas. (Environment Canada) 4

It runs north-south along the crest of the Rocky Mountains (in Mexico and Canada too) and is sometimes called the Great Divide.

5 The Continental Divide is a line separating waters that flow into the Atlantic Ocean or Gulf of Mexico from those that flow into the Pacific Ocean. It runs north-south along the crest of the Rocky Mountains (in Mexico and Canada too) and is sometimes called the Great Divide. This map layer was compiled by the U.S. Geological Survey by extracting the appropriate lines from the Hydrologic Unit Boundaries layer of the National Atlas condivm.html

6 Watershed - Importance 1. Understand what a watershed is both literally and conceptually (including the mapped representation of a watershed and the issue of scale). 2. Understand the components and processes of a watershed including runoff, soil, geology, geography, permeability, storage, land cover, land use, vegetation, precipitation, stream flow, flooding, drought (climate), fire, drainage patterns, erosion, deposition and population. 3. Understand a watershed as a system (e.g. a change in one area will affect the dynamics of the entire system) and how that system functions. 4. Understand that watershed management is complex because of culture, economics, politics, social constructs, scientific studies and aesthetics. Some water users include urban, rural, agricultural, business & industry, energy, recreation, fish and wildlife and earth systems. 5. Understand that watersheds change over time both naturally (e.g. flooding, fire) and due to anthropogenic causes (e.g. damming a river, water rights, water withdrawals). 6. Know some of the issues facing the watershed managers of the Colorado River Watershed as well as other Southwestern Watersheds. 6

7 The drainage pattern allows you to understand the watershed boundaries and directions of stream flow even without topography 7

8 although a shaded DEM helps! 8

9 Seeing Watersheds Activity 1: trace the main channel of the river from its mouth to the headwaters. 2: trace the major tributaries (start at the coast/gulf). 3a: Find the drainage divides by marking a dot above the top of each river, midway to the adjacent watershed. 3b: Connect the dots (start at the mouth) to form the watershed boundary. 4:Identify sub-watersheds of major tributaries 9

10 Synonyms: Basin Catchment Catchment Area Catchment Basin Drainage Area Drainage Basin Feeding Ground Gathering Ground Hydrographic Basin Watershed Source: Glossary of Geology, 3rd Ed.,1987, American Geophysical Institute 10

11 Watershed Sub-watershed HUC: HUC:

12 Colorado source of 4 WS s = 8,131,000 af 12

13 Major Western Rivers Strahler:

14 Major Western Rivers ag.arizona.edu/watershed/ Columbia Klamath Yellowstone Snake Sacramento Platte San Joaquin Gila Rio Grande 14

15 Colorado River Watershed before 1921 Green River Grand River Colorado River Musser,

16 Colorado River Watershed after 1921 How to determine headwaters? Green River Hydrology larger drainage area Green River drains larger area Politics who wants it more CO Legislature wanted river to begin in CO Musser, Colorado River Grand Colorado River River 16

Outline. Watershed Basics. Bottom line: one page summary. Watershed Definitions

Outline. Watershed Basics. Bottom line: one page summary. Watershed Definitions A river is the report card for its watershed. Alan Levere Watershed Basics ADEQ SW Short Course June 13, 2013 Phoenix, AZ Outline Definition and examples of watersheds Why watersheds are important; Fundamental/Enduring