Update on Wintertime Snowfall Augmentation
in the Western U. S.
NWRA Annual Meeting
Emerging Water Augmentation
Strategies
7 March 2012
Arlen Huggins
Associate Research Scientist
Division of Atmospheric Sciences
Desert Research Institute
Reno, Nevada
Winter Cloud Seeding for Snow/Water
Augmentation
• Conceptual model for winter cloud seeding
• Current research activities
– Randomized experiments
– Physical studies
– Hydrologic modeling
• Operational projects in the western U.S.
• Upper Colorado River Basin Projects
– Colorado, Utah, and Wyoming
– Upper and Lower Basin interaction
• Summary of snow augmentation status
Conceptual Diagram of Orographic Cloud Seeding
Ground-based seeding with silver iodide
-10C
-5C
Recent Research
• Australian Snowy Mountain Project
– Funded by Australian government and
conducted by Snowy Hydro
– 5-year study with randomized seeding of a
single target
– Published results showed a statistically
significant 14% increase in target precipitation
for “seeded” events
• U. of Wyoming airborne radar study
– Radar signal increase noted during seeding
periods
– Radar signal increase corresponds to a
significant precipitation rate increase
Recent Research
• WY Weather Modification Pilot Project
– Dual-target experiment: one target randomly seeded
when cloud conditions are similar over both targets – 4hour experimental units (EUs)
– 121 EUs to date; requesting funding for an additional
two years – funded by state of WY
– Statistical evaluation of paired seed vs. no-seed
precipitation values – 200+ EUs desired
– Targeting and environmental assessment using trace
chemistry techniques
– Unique use of atmospheric modeling for forecasting and
evaluation of seeding events
– Hydrologic modeling to assess impact of seeding on
streamflow in the North Platte RB
• U. of WY airborne radar study being repeated
– NSF funding (~$1M budget) with more ground based
instrumentation
– Attempting to verify earlier findings
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UW Cloud Radar
3 mm (95 GHz, W-band), dual-polarization
pulse width: 250-500 ns
max range: 3-10 km
volume resolution @ 3 km range: < 40 m
minimum detectable signal (@ 1 km): ~-30 dBZ
Cloud droplets are much smaller than ice crystals, thus in a
mixed-phase cloud, reflectivity is dominated by ice crystals.
UW Cloud Lidar
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non-coherent eyesafe backscatter lidar
up & down (down only for 4 out of 7 flights)
backscatter power & depolarization ratio
attenuated by cloud layers
lidar & radar can be combined to estimate cloud properties
WWMPP model
output of seeding
plume trajectories,
winds and cloud
water content
Plume of ice
crystals
Weather station
controls dispenser
Seeding materials & delivery methods
Research on Wintertime Cloud Seeding in
Mountainous Terrain
 Has verified all the links in the chain of the cloud seeding
conceptual model
 Has verified ice crystal and precipitation enhancement
through physical observations
 Has shown evidence of precipitation enhancement through
statistical evaluations
 Has revealed situations when cloud seeding is ineffective
 Does not have all the answers to every meteorological
situation where cloud seeding is applied
Operational Cloud Seeding Projects
Nevada Cloud Seeding Projects
 Tahoe funded by TMWA and
WRWC
 Walker Basin funded by BOR
(Desert Terminal Lakes Project)
 NE Nevada funded by SNWA
Utah Projects
Cost share
between state
and local
water groups
Cost ~ $370K
Est. snow
water increase
> 150 AF
Colorado Projects in WY2011 – Local Funding plus CWCB/LCRB grants
Areas with snowfall
augmentation
potential in the UCRB
1967-1968 Runoff
Augmentation Estimates
10% increase
1.3 – 1.9 MAF
Hunter (USBR, 2005)
2-year SNODAS w/+10%
0.6 – 1.1 MAF
Griffith/Solak (NAWC, 2006)
NWS Runoff Model
5-15% increase
0.6 – 1.6 MAF
Collaboration between Upper and Lower
CRB States in Snow Augmentation Projects
 Cooperative agreement between (CO, UT and WY) and (AZ,
CA and NV) – in place since 2006
 LCRB funding to:
 Extend operations in existing projects in UT & CO
 Add new equipment (seeding and observing) in UT & CO
 Add additional research equipment (WY)
 Apply modeling, physical evaluations, etc. to ongoing
projects
Summary of Water Augmentation by
Wintertime Cloud Seeding
 A reasonably healthy research component
 Steady number of operational projects
 Funded mainly by state, regional and local water agencies +
power companies
 Augmentation strategy used for over 50 years
 Project evaluations indicate benefits justify costs
 Operations being enhanced by interstate/basin cooperative
agreements
 Instrumentation and modeling advances have improved
operational efficiency – room for further improvement
 Hydrologic modeling used more to assess water augmentation
aspect and its economic, political and environmental benefits