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 4
Historic and Projected Changes in Runoff
4 1 Natural and Anthropogenic Effects on Forests and
Water Yields
As discussed in Chapter 2, a change in the type or den-
sity of forest vegetation can alter the amount of runoff.
Changes in forest type and density can result from natu-
ral causes, such as succession; from climate variations;
from natural disturbances such as wildfires, windthrow,
and insect infestations; and from anthropogenic distur-
bances, such as logging, grazing, or prescribed fire. In
some cases it is difficult to separate anthropogenic and
natural disturbances, as fire suppression will facilitate
succession, and climatic changes may be due to both
anthropogenic factors and natural fluctuations. The goal
of this chapter is to discuss the effects of timber harvest,
fire, climate change, grazing, insect infestations and
other disturbances on forest cover and water yield.
The analysis of past, current, and projected effects of
forest management on water yield will focus on national
forest lands, as there is more information on past and
current management activities for these lands than for
private forestlands. From a water yield perspective, na-
tional forest lands are of primary concern because these
account for 49% of forest lands in Colorado (Figure
4.1) (DNR, 2002), and the majority of these lands are
in the higher elevation areas that generate most of the
state's runoff (Benson and Green, 1987). Another 19%
of the forests in Colorado are managed by the Bureau
of Land Management, but most of these forests are in
lower elevation areas with limited potential for altering
water yields.
Only 28% of the forested areas in Colorado are in private
ownership, with no major holdings by private timber
companies (DNR, 2002). The number of private land-
owners who have at least one acre of forested land has
increased from 46,300 in 1990 to an estimated 200,000
in 2000 (DNR, 2002). This fragmentation of private
forest lands indicates that the majority of these parcels
Figure 4.1. Map of national forest lands in Colorado.
30
Roosevelt
Routt
National
National
Forest
Forest
Arapaho
National
Forest
.White. River
National Forest
Grand Mesa
National Forest.. -
Pike:
National
Forest
Gunnison
National
Uncompahgre
Forest
National
Forest
San Isabel ^'
National
0 50 100 km
Forest
San Juan
Rio Grande
1 1
National
National
0 25 50 miles
Forest
Forest
Figure 4.1. Map of national forest lands in Colorado.
30