WSP02037

• File Number: 8200.700
• Description: Colorado River Basin - General Publications
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1979
• Author: US Forest Service
• Title: Managing Vegetation to Increase Flow in the Colorado River Basin - US Forest Service
• Water Supply Pro - Doc Type: Report/Study

OOOSge

Managing Vegetation to Increase Flow
in the Colorado River Basin

Alden R. Hibbert

Managemenllmplicalions

The combined surface and ground water
supplies in the Colorado River Basin are generally
adequate for current needs. However. growing
demands and use of water in the Colorado River
Basin could result in a widespread water shortage
as early as 1995.' Local shortages exist already.
One method of augmenting the water supply is
management of forest and brush lands to increase
streamflow.
Theoretically, the surface water supply in the
Colorado River Basin could be increased by as
much as one-third (6 million acre-feet annually) if
vegetation and snow on 16% (26 million acres) of
the basin were manipulated solely to increase
water yield. However, other forest resources.
economics. and social and environmental con~
cerns must also be considered, which tend to
greatly reduce both treatment area and effective-
nesS.
Water yield increases are greatest where large
reductions can be made in water transpired by
plants andlor evaporated from snow. Clearcutling
and Iype conversion usually increase water yield
the most. These practices may be appropriate in
several vegetation types, such as chaparral and
mountain brushlands. where the commercial value
of the vegetation is low. However, where c1earcuts
and type conversions are not acceptable manage-
menl practices, the potential for increasing water
yield is less, although it may still be substantial in
many cases.

au. S. Depanment of Interior, Bureau of Reclamation. Executive
Summary of critical water problems facing rhe 11 western states.
Westwide Study. 85 p.

Where much snow falls in windswept, treeless
areas, evaporation of blowing snow can be reduced
by trapping snow in large drifts behind snow
fences, where it more effectively contributes to
streamflow. Opportunities exist to increase water
yield by this technique on selected sites in alpine,
high elevation sagebrush, and mountain grassland
areas. However, the high cost of snow fences and
their visual impact on the open landscape musl be
taken inlo account.
In the examples used in this report. Upper Basin
yield could be increased by 500,000 acre-feet per
year, or 3.5%, by treating up to 22% of each vegeta-
tion type, except aspen, in which 40% would be
trealed. About one-half of the increase would come
from the subalpine forests, including Douglas-fir.
In the Lower Basin, more extensive treatments
would be necessary 10 get an additional 250,000
acre-feet annually, an B% increase in water yield.
About 92% of the lotal increase would be generated
by treatment of about 20% of the chaparral and '33%
of the ponderasa pine.
While information on cost of producing extra
water is incomplete, it is believed that the least
expensive water would come from cQmmeTdal
forests, where timber yields would pay for part of
the treatment costs. Water would be more ex pen-
si ve fram type con versions, because most of the
treatmenl costs would be levied against water pro-
duction. However, most of the water is expected to
cost less than imported water, and Some of the
water from commercial forests would supplemenl
and be in the price range of water produced by
weather modification.

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