From 1955 to 1988 peak discharge data were collected from two watersheds (one logged, one un-logged) at the HJ Andrews Experimental Forest in Blue River, Oregon.  Both watersheds have similar elevation and lie on the western slopes of the Oregon Cascades in the Willamette National Forest.  The logged (i.e. treated) watershed in the study was 100% clearcut -- presumably at the beginning of the research.  It is not clear whether additional clear cutting was performed during the period of study.  The un-logged watershed (i.e. the "control") had vegetation consisting mainly of "100- to 500-year-old Douglas fir, western hemlock, and western red cedar in closed canopy stands, with increasing amounts of Pacific silver fir above 800 m."  One goal of the research was to "quantify long-term changes in storm hydrograph behavior associated with clear-cutting and road construction".

Peak discharge from both watersheds was collected for 352 storm events.  Discharge (sometimes called flow) is measured in units of volume per time. Examples of units of measure for discharge include "gallons per second" and "cubic feet per minute"; in this data set, discharge is recorded in "cubic meters per second", or m3/s.   The logged watershed in this study has an area of about 45 square kilometers (km2) while the un-logged watershed has an area of 21 km2.  To eliminate the effects of area on discharge, the data must be adjusted or "normalized".  This is done by dividing discharge by basin area to give what is referred to as "Unit Discharge", with measurement units in "cubic meters per second per square kilometer" (m3/s/km2).  Unit discharge tells us how much flow comes off a standard sized piece of land in the watershed, on average.

Vegetation in forests, especially large trees, acts like a sponge, soaking up water and slowly releasing it.  On the flip side, a lack of vegetation allows precipitation to flow more quickly through the soil and into the groundwater, where it may exit the watershed in a stream or river.  This data set is in agreement with these facts:  we observe that for most storm events, peak unit discharge is always higher in the logged watershed.  On the graph, we observe that most data points lie above the imaginary 45 degree or y = x line, indicating that the x coordinate (un-logged) is smaller that the y coordinate (logged).  Students may want to examine the distribution of differences of unit discharge between the two watersheds. How significant are the differences in peak unit discharge?  Is the distribution nearly normal?  Students may also conjecture as to why the data "spreads out" as unit discharge increases.

Data presented at this website is modified from that found at the HJA site, and the graph displayed above was created by QELP.  Data sets [available at the HJA website] were provided by the Forest Science Data Bank, a partnership between the Department of Forest Science, Oregon State University, and the U.S. Forest Service Pacific Northwest Research Station, Corvallis, Oregon. Significant funding for these data was provided by the National Science Foundation Long-Term Ecological Research program (NSF Grant numbers BSR-90-11663 andDEB-96-32921).

For more information on the US Long Term Ecological Research Network (LTER), visit http://lternet.edu/sites/
Information about the HJ Andrews Experimental Forest can be found at http://www.fsl.orst.edu/lter/


date of peak discharge*

Peak discharge, un-logged (m3/s/km2)

Peak discharge, logged (m3/s/km2


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Information and dataset were obtained from the following link: https://seattlecentral.edu/qelp/sets/061/061.html

The Quantitative Environmental Learning Project (QELP) was developed by Greg Langkamp (mathematics) and Joe Hull (geology and environmental science) at Seattle Central Community College.

The central goal of QELP is to promote quantitative science literacy and applied mathematics through curricular revision at the college level by linking and integrating mathematics and environmental science. One of our main goals is to promote interdisciplinary education between science and mathematics at the beginning college level (first or second year). One reason for the absence of integrated science-math programs in colleges is that few appropriate classroom-ready resources are available, particularly in environmental mathematics. The National Science Foundation (NSF) has awarded us a 2-year grant to help address this problem and make the results available to educators.

QELP is funded through the Division of Undergraduate Education (DUE) at the NSF. Our project number is 9980740, which runs from July 2000 to July 2002. For NSF hosted information about this and other NSF projects, search the PIRS database at: http://www.ehr.nsf.gov/PIRStart

R Dataset Upload:

Use the following R code to directly access this dataset in R.

d <- read.csv("https://www.key2stats.com/Logging_and_Stream_Discharge_1692.csv")

R Coding Interface:

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