Skip Navigation
Button that takes you to back to the home page. Button that takes you to the teacher pages. Button that takes you to the modules and activities page. Button that takes you to the related links page. Button that takes you to the references page. Button that takes you to the Problem Based Learning model page. Button that takes you to the glossary page.Image map of some Water Quality puzzle pieces.  Please have someone assist you with this.

Button that takes you to the Overview page.
Button that takes you to the Biological Assessment page.
Button that takes you to the Chemical Assessment page.
  Image that says Rock Size. Button that takes you to the Physical Assessment page. Button that takes you to the Elevation and Catchment Area page. Button that takes you to the Stream Order page. Button that takes you to the Forest Canopy page. Button that takes you to the Width, Depth, and Velocity page. Button that takes you to the Turbidity page. Button that takes you to the Total Solids page. Button that takes you to the Temperature page.

Water Quality Assessment: Physical: Rock Size
The size of rocks on the bottom of a stream is very important. It affects the flow of water through a channel. Streams with a mixture of large and small stones tend to have increased turbulence. This leads to increased oxygenation of the water. Rock size may also affect the species of organisms that inhabit a stream.

Image showing a sample of rocks collected from Wheeling Creek.Typically, scientists measure the size of the rocks removed from the benthic sampler during the biological assessment. Scientists assume that the rocks are round and estimate their area as " ", where "r" is ½ the longest distance across the rock. Another method is to photograph the rocks on a white pan and use video image analysis to calculate the exact area of each rock (see photo). Photo: Sample of rocks collected from Wheeling Creek. Photo courtesy of Dr. Ben Stout.

A lack of variability in rock size may indicate that a stream has been dredged at some point in the past.

 

Overview ..|.. Biological Assessment ..|.. Chemical Assessment ..|.. Physical Assessment.

Elevation and Catchment Area / Stream Order / Forest Canopy / Width, Depth, and Velocity / Rock Size / Turbidity / Total Solids / Temperature
Glossary  .|
Related Links  .|.. References ..|.. PBL Model  .|

  Home ..|.. Teacher Pages ..|.. Modules & Activities  

Button that takes you back to the Water Quality main page.

HTML code by Chris Kreger
Maintained by ETE Team
Last updated November 10, 2004

Some images © 2004 www.clipart.com

Privacy Statement and Copyright © 1997-2004 by Wheeling Jesuit University/NASA-supported Classroom of the Future. All rights reserved.

Center for Educational Technologies, Circuit Board/Apple graphic logo, and COTF Classroom of the Future logo are registered trademarks of Wheeling Jesuit University.