Update on Wintertime Snowfall Augmentation in the Western U. S.

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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


Ground
-
based seeding with silver iodide

-
10C

-
5C

Conceptual Diagram of Orographic Cloud Seeding

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


4
-
hour 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


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


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