Observing the water balance in the
Sierra Nevada: SNAMP
1. Introduction: Montane water
balances
2. SNAMP: headwater, fireshed,
future projections, water quality
3. Conclusions
Collaborators: R Bales, UC Merced, S. Glaser,
UC Berkeley & many others
Phil Saksa, Sarah
Martin, Martha
Conklin & Roger
Bales
Sierra Nevada
Research Institute,
UC Merced
Basic montane water balance
Precipitation = Evapotranspiration + Runoff
=
+
Assumption: runoff is from both streams and
shallow groundwater
2. Sierra Adaptive Management Project
(SNAMP: USFS, DWR, USFW & UC)
Study Sites
Last Chance, Tahoe
National Forest
Sugar Pine, Sierra
National Forest
Sierra Nevada Adaptive Management Project
snamp.cnr.berkeley.edu
Field Measurements – Water Quantity
Management Question (headwater basins):
Will forest treatments (SPLATs) increase water yield in response to
reduced water demand by vegetation?
Approach:
Measure water budget components (stream discharge, snow and soil
moisture) and meteorological variables capturing the spatial
heterogeneity of the landscape in a headwater basin.
Monitor headwater basins for 3 yrs before treatment and 1 yr after
Results:
The climate variability and low precipitation following treatments
masked any measurable changes in water yield directly related to
SPLATs.
During the study period, because of the highly variable conditions, the
correlation between our control and treated catchments changed
annually.
Sierra
Nevada Adaptive Management Project
snamp.cnr.berkeley.edu
Forest Treatments
Last Chance
Strategically Placed Landscape
Treatments (SPLATs) in Deep Creek and
Grouse Creek
8 % of biomass (4% basal area)
removed in the catchment (i.e. 18% of
catchment was treated midway up the
catchment; up to 33% biomass was
removed in treated areas)
Study design: before, after, control,
impact (BACI)
Treatment
Underburn
Tractor Thin
Cable Thin
Sierra Nevada Adaptive Management Project
Mastication
snamp.cnr.berkeley.edu
Water Yield Results
Flux, cm
precipitation, cm
250
200
150
100
50
0
Flux, cm
200
treatment discharge, cm
Treatments
Last Chance
2010
250
control discharge, cm
2011
2012
2013
2011
2012
2013
Sugar Pine
150
100
50
0
2010
Sierra Nevada Adaptive Management Project
Water Year
snamp.cnr.berkeley.edu
Last Chance Streamflow Results
Log Transformed Daily Streamflow
1
2010 Normal
0.5
2011 Wet
Treatment
0
2012 Dry
-0.5
2013 Dry
-1
-1.5
Stream water sources
different all years;
Need multiple years to
capture variability
-2
-2.5
-3
-2.5
-2
Sierra Nevada Adaptive Management Project
-1.5
-1
Control
-0.5
0
0.5
snamp.cnr.berkeley.edu
RHESSys Hydro-Ecologic Modeling
Mountain hydrology – water fluxes
precipitation
evapotranspiration
infiltration
sublimation
snowmelt
runoff
ground & surface
water exchange
Sierra Nevada Adaptive Management Project
snamp.cnr.berkeley.edu
Headwater Calibration (Bear Trap Creek)
Average
Wet
Dry
Dry
SWE
(cm)
140
Treatments
0
Soil Storage
(cm)
40
Discharge
(cm)
0
4
0
Oct
Apr
Oct
Apr
Sierra Nevada Adaptive Management Project
WY 2010
WY 2011
Oct
Apr
WY 2012
Oct
Apr
Sep
snamp.cnr.berkeley.edu
WY 2013
Fireshed-scale modeling
Management Questions:
Can the calibration for the headwater version of the hydrologic
model be transferred to the larger firesheds?
How does the fireshed respond to SPLATs and wildfires?
Approach:
Compare the geology and hydrologic responses of the headwater
basin to the larger scale basin.
Run the hydrologic model and look at the responses of the
fireshed to SPLATS and wildfire.
Results:
The calibrations for the headwater model were successful in
setting up the fireshed model.
The water yield increased in response to forest treatments and
wildfires, but the low increase from the implemented
Sierra Nevada Adaptive Management Project
snamp.cnr.berkeley.edu
treatments may be difficult to observe.
soil storage
evapotranspiration
streamflow
Sierra Nevada Adaptive Management Project
Modeled Changes following SPLATs
Modeled Changes following SPLATs
snow
snamp.cnr.berkeley.edu
Water Quality
Management Question:
Will forest treatments (SPLATs) decrease water quality in
response to increased flow?
Approach:
Measure water chemistry.
Results:
Groundwater storage helps to
maintain some baseflow
during dry years.
Sierra Nevada Adaptive Management Project
snamp.cnr.berkeley.edu
Baseflow season stream water conductivity
Day of Year
Sierra Nevada Adaptive Management Project
Blue/Cyan = wet years
Red/Pink = dry years
snamp.cnr.berkeley.edu
Fireshed Modeling Results
• SPLATs at Last Chance resulted in a vegetation decrease of 8%
leading to runoff increases of at least 12% for the initial 20
years, falling to 9.8% by year 30.
• Where thinning occurs matters: No increase in runoff was
predicted for a uniform 8% reduction LAI .
• Precipitation matters: SPLATs at Sugar Pine resulted in a 7.5%
decrease in vegetation, but increases in runoff were less than
3%.
• Timing matters: Gains occur at times that dam operation is
concerned with flooding risk & timing of peak snowmelt.
• Maintenance matters: Increases in water yield decrease as
vegetation grows back over a 30-yr period.
Sierra Nevada Adaptive Management Project
snamp.cnr.berkeley.edu