Logging for Water
Kim Raby
GEOG 3511
What’s
happening:
Snow collects in
clearings
instead of being
intercepted and
evaporating
before it can
become
overland flow,
yielding more
runoff
Can it work? Is
it worth it?
C1 site, NWT Ridge
Molotch et al., 2007, Hydro Processes
posted on my web site
Forest canopy intercepts snow
Full canopy tower
with eddy flux
instrument to
measure latent
heat.
If we know LE, we
can conver to mm
of sublimation
Below canopy eddy flux
Way cool experiment
• We can measure sublimation above
the forest canopy
• We can measure sublimation below
the forest canopy
• We can partition sublimation into
• Canopy sublimation
• Below-canopy sublimation
• Never been done before
Soil temperature and
moisture
Sublimation and precip
Cumulative sublimation
Drought year 2002
• Above-and below-canopy eddy
covariance systems indicated
substantial losses of winter-season
snow accumulation by sublimation
• Snowpack = 0.41 mm d-1
• Canopy = 0.71 mm d-1
• Total = 1.11 mm d-1
 About 1.5’’ per month
• More than a 100% of precip was lost
to sublimation
Maximum sublimation
• 3.7 mm d-1
• Occurred immediately after snowfall
• Driven by canopy interception of snow
• High latent heat fluxes
• This value translates to about 5” per
month, or about 3’ of water during the
snow season.
• HUGE AMOUNT OF ET!
Below-canopy sublimation
• Driven by high sensible heat gradients
• Caused by warm canopy pumping heat
into a cold atmosphere
• High sensible heat gradient drives a
high specific humidity gradient
• RH is 100% at snow surface
• RH is much lower above snow surface
• High sublimation rates from snowpack
is the result
Interception
• Sublimation is greater from vegetation
than from ground
Higher temperature on leaf surface
Greater surface area
Trees radiate longwave radiation
Higher air temperature surrounding snow
Increase in SVP
• Cut trees to decrease interception
Increase snowpack volume
Increase water yield
Denver Post, 11/10/02
Coon Creek, WY
4,100 acre demonstration
project illustrates patch
cuts in lodgepole pine
forest
1990s research says
clearcut increased spring
runoff by 17 percent
Is this the right decision for Colorado?
Fraser Experimental Forest
Summary of 50 years
of clearcutting and
thinning experiments at
small scale Fraser
Experimental Forest
The more area
removed, the greater
the SWE increase
If 100 percent of basal
area is removed, ~35
percent increase in
water yield
Yields have been longlived but clearcuts must
be maintained
Source: Meiman 1987
Large-Scale Replication
Goal of the Coon Creek Water Yield Augmentation Pilot Project: to test whether
results demonstrated at small scale experimental basins (like Fraser
Experimental Forest) can be duplicated to operational/large watershed scale
Control: Upper East Fork
Treatment: Coon Creek
Maximum mean daily
discharge comparison
Daily mean flow
increased 11% with
treatment
Source: Troendle et al. 2001
Increased Water Yield
Control: North
Fork of Dry Creek
Treatment:
Brownie Creek
Slopes are
significantly
different
(p=0.0001)
Flow during the
two periods is
significantly
different
~70 percent
increase in water
yield relative to
control after
harvesting 25
percent of
Brownie Creek
91% increase
24% increase
Source: Troendle and Stednick 1999
Peak SWE Increases
Fraser
Experimental
Forest
Increased accumulation after plot cut averaged 5.8 inches of water
or 45 percent more than upwind plot
No significant difference between upwind and downwind forest plots
Source: Meiman 1987
Area of Clearcut
How large should the clearcut be?
•Very site-dependent
•This representation is for the Fraser Experimental Forest (maximum snow
depth at 5H (5x the canopy height))
•As the size of the opening increases, its efficiency in trapping snow decreases
to the point (approximately 15H) where there is a net loss
Loss is
associated
with
increased
wind scour
and
sublimation
losses
Source: Troendle and Meiman 1984
Influence of Wind
James River site,
Alberta, Canada
SWE is greatest on the
leeward side of a
clearing
wind direction
first peak
clearing
second peak
SWE is least on the
windward side of a
clearing
Second peak occurs
because right before
the snow hits the far
side of the forest,
decrease in wind speed
results in additional
snow accumulation
Source: Golding and Swanson 1986
SWE Increases
clearing
wind direction
Fraser Experimental Forest
Similar results
Increased snow accumulation and SWE at leeward edge of forest
Source: Gary 1974
Hydrograph
Fraser Experimental Forest, Fool Creek Watershed
Total seasonal flow increased by 40 percent (longer duration of high flows)
Peak flow increased by 20 percent
Most of the detectable change occurred in May
Source: Troendle and Olsen 1994
Hydrograph
Increases in peak
discharge mean more
erosion and flooding
Results in a need for
additional reservoirs
to store water for low
flows
Generally, flows
increased most
during wet years as
opposed to during
droughts
During drought (low
antecedent
moisture), snowmelt
infiltrates and
recharges
groundwater, does
not go to discharge 
NEED RESERVOIRS
Source: Troendle and Stednick 1999
Sedimentation
Appalachian catchment
Logging-related activities
(including road construction
activities) increase erosion and
sedimentation
Sediment yield increased
considerably as a result of road
building and logging activities
Source: Swank et al. 2001
Nutrient Loading
Appalachian catchment
Logging activities increase nutrient loading, DOC, conductivity (ion concentrations)
Sustained increases in nitrate concentrations after clearing and logging due to:
•Reduction in nutrient uptake due to vegetation mortality
•Nutrient release from decomposition of trees and logging residue
•Increased soil N transformations
Source: Swank et al. 2001
Wildfire mitigation?
• Proponents herald logging to increase
water yield as a “forest health effort”
• Say it will serve a dual purpose
• Increase water yield
• Reduce fire risk
• However, logging trees at high
elevation catchments will not reduce
fire in high risk areas (at lower
elevations)
• Logging in high elevation areas could
mean less money to spend on thinning
fire-prone areas
Other considerations for CO
• Cutting lodgepole pine stands would remove habitat for
federally threatened lynx and other interior forest
species
• High cost, maintenance required to maintain yields
• Difficult to replicate Fraser results in other parts of
Colorado
• Study of runoff changes as a result of cutting ski runs at Eldora
(Gaudagno)



deep snow collected in spruce-fir stands
open runs scoured almost bare by high winds
didn’t produce same results as Fraser experiments
• Other environmental costs
• Erosion and sedimentation can stifle habitat for fish and aquatic
insects
• Amount of water flowing off trees increases as they
mature
• Colorado’s middle-aged forests will soon become old-growth and
capture more snowfall
• Shift focus from increasing supply  reducing demand?
Less ET with Higher
Elevations
• Trees intercept
snow
• Less snow reaches
ground
• High ET loses in
both winter and
summer for
forested areas
• Less tress with
higher elevations
• Colder air temps
with higher