Forests and Water: A State of the Art Review for Colorado

• Year: 2003
• Title: Forests and Water: A State-of-the-Art Review for Colorado
• Author: Colorado State University
• Description: Colorado State University 2003
• Publications - Doc Type: Other

Chapter 2
Effects of Forest Management on Runoff
2.1. Introduction
Colorado is relatively fortunate with respect to the
amount of scientific research that has been conducted on
the relationships between forest management and runoff.
The first paired- watershed experiment in the world was
conducted at Wagon Wheel Gap in southern Colorado in
the early 1900s, and this was followed by a long series of
studies designed to more rigorously document the effects
of forest harvest on annual water yields, the size of peak
flows, low flows, and, to a lesser extent, water quality.
Many of the most relevant studies have been conducted
on the Fraser Experimental Forest (FEF) northwest of
Winter Park, Colorado (Figure 2.1) (Alexander et al.,
1985; Alexander, 1987). This was established in 1937,
and for the last 60 years the FEF has been the pre -emi-
nent center for forest hydrology research in the central
Rocky Mountains. Similarly, the Manitou Experimental
Forest has been the site of numerous plot and water-
shed -scale studies in the ponderosa pine and mixed
conifer zone (Figure 2) (e.g., Berndt, 1960; Gary, 1975).
Information relevant to Colorado can also be drawn
from watershed studies in states with similar conditions
(e.g., Arizona, Idaho, Wyoming, and Utah), and a much
broader pool of forest hydrology research conducted in
other areas. Information from all of these sources is used
in this report. The first three sections of this chapter sum-
marize existing knowledge on the effects of vegetation
management on annual water yields, the size of peak
flows, and the size of low flows. The next two sections of
this chapter respectively review the effects of roads and
fires on runoff. The final section in this chapter discusses
the extent to which results from plot or small watershed
studies can be extrapolated to larger areas, and the mag-
nitude of changes in runoff that might be expected in
large watersheds. Since forest harvest is the primary
technique used to investigate the relationship between
forests and water, this necessarily is the primary focus
of this chapter. The removal of forest cover by insects,
disease, or windthrow generally should have a similar
effect, but the difficulty of conducting controlled ex-
periments and the paucity of data precludes a detailed,
quantitative review of the effects of these other types of
disturbance on runoff and water quality. Similarly, there
Saratoga 0 CC V� yoming Nebraska
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Fort
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FEF Denver L
Glenwood 1 -70
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Colorado Springs
Pueblo
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Durango
: xperimental Sites
oon Creek (CC)
raser Experimental Forest (FEF)
7anitou Experimental Forest NEF)
Vagon Wheel Gap (WWG)
N
0 50
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100
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Figure 2.1. Location of experimental forests in Colorado and selected paired watershed experiments.