20041022Application.pdf

IDAttO IDAHO POWER COMPANI
POWER O. BOX 70-.;: BOISE, IDAHO 83707
An IDACORP Company
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BARTON L. KLINE
Senior Attorney
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October 21 2004
Jean D. Jewell , Secretary
Idaho Public Utilities Commission
472 West Washington Street
P. O. Box 83720
Boise, Idaho 83720-0074
Re:Case No. IPC-04-~lf
Application To Recover Expenses Associated
With Cloud Seeding Program for the Winter
of 2004-2005
Dear Ms. Jewell:
Please find enclosed for filing an original and seven (7) copies of Idaho
Power Company s Application to recover expenses associated with the Company
Cloud Seeding Program for the winter of 2004-2005. Also enclosed are nine (9) copies
of the testimony of Idaho Power Company witnesses Gregory W, Said and Gary Riley.
One copy is designated as the Reporter s Copy. A computer disk containing the
testimony is also enclosed.
I would appreciate it if you would return a stamped copy of this transmittal
letter in the enclosed self-addressed, stamped envelope.
ve~ro~
Barton L. Kline
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Enclosures
Telephone [phone] Fax [phone] E-mail BKlinefWidahopower.com
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BARTON L. KLINE, ISB # 1526
MONICA B. MOEN , ISB # 5734
Idaho Power Company
1221 West Idaho Street
O. Box 70
Boise , Idaho 83707
Telephone: [phone]
FAX Telephone: [phone]
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Attorneys for Idaho Power Company
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
IN THE MATTER OF THE APPLICATION OF
IDAHO POWER COMPANY TO DEFER
EXPENSES ASSOCIATED WITH ITS
CLOUD SEEDING PROGRAM FOR THE
WINTER OF 2004-2005. CASE NO. IPC-04-;t'f
APPLICATION FOR
ACCOUNTING ORDER
In accordance with RP 052 , application is hereby made to the Idaho Public
Utilities Commission ("Commission ) by Idaho Power Company ("Idaho Power" or
Company ) for an accounting order authorizing the Company to defer 900/0 of the Idaho
jurisdictional expenses the Company incurs during the winter of 2004-2005
(approximately October 15, 2004 through April 30, 2005) to operate its ongoing program
for cloud seeding to increase precipitation in the Payette River Basin.
In support of this Application Idaho Power represents as follows:
Idaho Power is an Idaho corporation , whose principal place of business is
1221 West Idaho Street, Boise, Idaho 83702.
APPLICATION FOR ACCOUNTING ORDER, Page
II.
Idaho Power operates a public utility supplying retail electric service in
southern Idaho and eastern Oregon. Idaho Power is subject to the jurisdiction of this
Commission in Idaho and to the jurisdiction of the Oregon Public Utility Commission in
Oregon. Idaho Power is also subject to the jurisdiction of the Federal Energy
Regulatory Commission ("FERC"
III.
Simultaneous with the filing of this Application , Idaho Power has filed its
direct case consisting of the testimony and exhibits of witnesses Gregory W. Said and
Gary Riley. While Idaho Power believes that this case should be processed under
modified procedure (RP 201 et. seq.
),
Idaho Power stands ready for immediate
consideration of this Application if it is the Commission s determination that a hearing
should be held.
IV.
Idaho Power has operated a cloud seeding program on a limited basis for
a number of years. In Order No. 29505 issued in Case No. IPC-03-13, the
Commission found that the operating expenses and capital costs associated with the
cloud seeding program that the Company included in its general rate case filing would
not be recoverable because of the short duration of the cloud seeding program during
the test year and the lack of data demonstrating the effectiveness of the cloud seeding
program. By this Application the Company is requesting that the Commission review
new information that demonstrates the scientifically-measured benefits of the
Company s cloud seeding program undertaken during the winter of 2003-2004. This
APPLICATION FOR ACCOUNTING ORDER , Page 2
information was not available and could not be presented to the Commission in Case
No. IPC-03-13. As demonstrated in the testimony and exhibits described above , it is
now possible to provide scientifically valid measurements of the benefits of cloud
seeding. As the above referenced testimony and exhibits also show, the measured
benefits of the 2003-2004 cloud seeding program indicate that even in an extremely dry
winter, Idaho Power s cloud seeding program resulted in material amounts of additional
precipitation , which translated into additional streamflows and cost savings for Idaho
Power s customers.
Idaho Power believes that these measured benefits would continue into
the future if the cloud seeding program is continued. The Company has already funded
two years of cloud seeding without any cost recovery. The Company would like to be
able to recover its costs associated with the continuation of the cloud seeding program
during the winter of 2004-2005. Operating the program during the winter of 2004-2005
would allow the Company to obtain 'one more year of benefit quantification to confirm
that cloud seeding is an appropriate long-term program for future inclusion in Idaho
Power s base rates.
In this Application Idaho Power is not asking the Commission to defer
expenditures associated with the Company s cloud seeding program on a long-term
basis. By this Application Idaho Power is requesting that the Commission only
authorize the Company to defer the expense associated with operating the cloud
seeding program during the winter of 2004-2005 for subsequent recovery at the time the
Company implements its 2005/2006 PCA rates. This one additional year of cloud
APPLICATION FOR ACCOUNTING ORDER , Page 3
seeding program expenses would be approximately $950 000. Idaho Power proposes
that the Idaho jurisdictional portion of these expenses be shared on the same ninety
percent-ten percent (900 /100/0) ratio by which other power supply expenses are shared
between customers and shareholders in the PCA.
VI.
The accounting that Idaho Power is proposing for the 2004-2005 cloud
seeding O&M expense is more particularly described as follows:
During the deferral period , the Company will record the deferred
regulatory assets with the following monthly entry:
Record the regulatory asset:
DEBIT:Account 182.3 - Regulatory Assets
CREDIT:
and
Account 407.4 - Requlatory Credits
Account 421. - Interest Income
Beginning June 1 , 2005, the Company will reverse the regulatory assets
with the following monthly entry:
Record reversal of regulatory assets:
DEBIT:Account 407.3 - Requlatory Debits
CREDIT:Account 182.3 - Regulatory Assets
VII.
Communications with respect to this Application should be sent to the
following:
APPLICATION FOR ACCOUNTING ORDER, Page 4
Barton L. Kline, Senior Attorney
Monica B. Moen, Attorney
Idaho Power Company
O. Box 70
Boise, Idaho 83707 -0070
bkline ~ idahopower.com
mmoen ~ idahopower.com
Gregory W. Said
Director of Revenue Requirement
Idaho Power Company
O. Box 70
Boise , Idaho 83707-0070
gsaid ~ idahopower.com
NOW , THEREFORE , Idaho Power respectfully requests that the
Commission issue its order authorizing Idaho Power to record the 2004-2005 expenses
associated with the cloud seeding program in the manner described in Paragraph IV
above. Alternatively, this deferral could be reflected as a line item in the PCA.
DATED at Boise, Idaho, this 2.1 day of October, 2004.
DJci
BARTON L. KLINE
Attorney for Idaho Power Company
APPLICATION FOR ACCOUNTING ORDER, Page 5
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UTJLlnE:3 CD ISSiOH
BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
IN THE MATTER OF THE
APPLICATION OF IDAHO POWER
COMPANY TO DEFER EXPENSES
ASSOCIATED WITH ITS CLOUD
SEEDING PROGRAM FOR THE
WINTER OF 2004-2005
CASE NO. IPC-04- ~'i
IDAHO POWER COMPANY
DIRECT TESTIMONY
GREGORY W. SAID
October 2004
Please state your name and business address.
My name is Gregory W. Said and my business
address is 1221 West Idaho Street, Boise, Idaho.
By whom are you employed and in what
capaci ty?
I am employed by Idaho Power Company as the
Manager of Revenue Requirement in the pricing and Regulatory
Services Department.
Please describe your educational background.
In May of 1975, I received a Bachelor of
Science Degree in Mathematics with honors from Boise State
Uni versi ty.In 1999, I attended the Public Utility
Executives Course at the University of Idaho.
Please describe your work experience wi
Idaho Power Company.
I became employed by Idaho Power Company in
1980 as an analyst in the Resource Planning Department.
1985, the Company applied for a general revenue requirement
lncrease.I was the Company witness addressing power supply
expenses.
In August of 1989, after nine years in the
Resource Planning Department, I was offered and I accepted a
position in the Company s Rate Department.Wi th the
Company s application for a temporary rate increase in 1992,
my responsibilities as a witness were expanded.Whi Ie
SAID, Di
Idaho Power Company
continued to be the Company witness concerning power supply
expenses, I also sponsored the Company s rate computations
and proposed tari f f schedules in that case.
In 1994, I was asked to become the Meridian
District Manager for a one-year cross-training opportuni ty.
In 1995, I returned to my position in the Rate Department.
In October 1996, I was promoted to lead a team of analysts
In the newly reorganized Pricing & Regulatory Services
Department, formerly known as the Rate Department.As the
Manager of Revenue Requirement, I coordinate the Company
efforts to recover prudently incurred expenses and
investments via the rates and charges of the Company.
What is the Company requesting in this
application?
The Company is requesting that the Commission
take a' new look at the appropriateness of an Idaho Power
cloud seeding program.This new look would be based on
additional information not available when the Commission
considered cloud seeding in the IPC-03-13 case.New
information includes the measured benefits of cloud seeding
during the winter of 2003-2004.Idaho Power believes that
there will be similar measurable benefi ts in the future that
the Company and its customers can obtain if the cloud
seeding program is continued.Recogni zing that, in the
past, the Commission has expressed reservations concerning
SAID, Di
Idaho Power Company
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the efficacy of cloud seeding, the Company is requesting
approved funding for just one addi tional year of cloud
seeding.Wi th the data from this addi tional year, the
Company believes that the two years quantification of
benefi ts will convince the Commission that ongoing rate
recovery for a cloud seeding program would be appropriate.
On-going recovery would be accomplished by inclusion in base
rates as part of the Company s next general rate case or
through a request for inclusion in the PCA.At this time,
the Company requests an accounting order that allows the
Company to defer expenses incurred for cloud seeding efforts
during the 2004-2005 winter period of time.Cloud seeding
expenses would first be incurred around October 15, 2004 and
the season would continue until approximately April 30,
2005.At a point in time after the cloud seeding season,
the Company will request a review of the costs for inclusion
in rates and simultaneous amortization.
Please provide a brief history of the
Company s recent activities with cloud seeding.
The Company has had some experlence with
cloud seeding dating back to 1995.However, my invo vemen t
with the current efforts in cloud seeding began in 2001.
Wi th the extremely high market prices that were then being
experienced, the Company was desirous of finding any and all
measures to assist in the reduction of overall power supply
SAID, Di
Idaho Power Company
16,
expenses.Stream flow enhancement via cloud seeding was one
of the options avai lable to the Company.
Prior to the winter of 2001-2002, Company
personnel met wi th members of the Commission Staff to
discuss the possibility of a cloud seeding pilot program.
three-year pilot program was envisioned.Staff was
reluctant to support such a program because they were not
confident that the Company would be able to demonstrate
cloud seeding benefi ts.Wi thout Staff support, the Company
declined to make an application for a pilot program to the
Commission.The Company did not fund cloud seeding during
the winter of 2001-2002.Prior to the following winter,
2002-2003, the Company again met with the Staff, providing
addi tional information of cloud seeding efforts and measured
benefi ts in other areas of the country.Staff was still
reluctant to support a pilot program, but the Company was
willing to fund the ini tial efforts in cloud seeding wi thout
an accounting order with the hope that sufficient data would
be available to demonstrate the efficacy of the program
during the general rate case review.Mr. Riley will discuss
the cloud seeding efforts and measured resul ts of cloud
seeding in his testimony.
The first year of cloud seeding efforts
primarily involved installation of equipment with limited
cloud seeding and limi ted measurement of cloud seeding
SAID, Di
Idaho Power Company
benefi ts.The second winter of cloud seeding, 2003-2004,
provided the first real opportunity to quantify the benefits
of cloud seeding on the Company s system.The Company
test year for the general rate case was 2003, prior to the
point in time that the quantification of benefi ts was
determined.The Commission, in Order No. 29505, denied the
inclusion of cloud seeding costs in the Company s revenue
requirement stating "results are at this time speculative.
The Commission also stated it would be unfair to ratepayers
to include all cloud seeding program cost in the test year
as if it were continuing each year into the future.
Given the Commission findings with regard to
cloud seeding, why is the Company again asking for cloud
seeding program cos t recovery?
The Company continues to believe that there
are measurable benefi ts associated wi th cloud seeding that
can be obtained for the Company and its customers.Mr.
Riley has now quantified the costs and benefits of cloud
seeding during the winter of 2003-2004.This quantification
was not available for review during the IPC-03-13 case.
The Company would like to continue the cloud seeding program
this winter, 2004-2005, to provide one more year of benefit
quantification to demonstrate to the Commission that cloud
seeding is an appropriate program for future inclusion in
ra tes .The Company has already funded two years of cloud
SAID, Di
Idaho Power Company
seeding wi thout any cost recovery.Benefi ts of cloud
seeding, however, have been received by customers of Idaho
Power through the Company s PCA.
How have the Company s cus tomers benef i ted
from cloud seeding efforts?
To the extent that the Company s cloud
seeding program created addi tional snow pack that
subsequently reached the river and flowed through the
Company s hydro resources, additional zero cost generation
was available for consumption by the Company s customers.
The cost was not truly zero, but cloud seeding costs are not
recorded in tradi tional PCA accounts.As a resul t , the
Company s Idaho jurisdictional customers received the
majority of cloud seeding benefits while the Company
shareholders received all of the cloud seeding program
costs.
What FERC accounts are used to record cloud
seeding related expenses?
Capi tal expendi tures for cloud seeking are
ini tially recorded in FERC account 107 Construction Work In
Progress and subsequently moved to FERC account 101 Electric
Plant In Service when operational.Winter 2003-2004 cloud
seeding expenses were recorded in FERC account 536.
Did the Company "wri te-off" its capi tal
investment in cloud seeding as a result of Order no. 29505?
SAID, Di
Idaho Power Company
As I have stated, the Company continuesNo.
to believe that there are benefits for the Company and its
customers to be derived from cloud seeding.Al though the
Company cannot currently earn a return on cloud seeding
investment, the Company continues to believe it can justify
inclusion of its cloud seeding investment in rate base in
the future.
What level of cloud seeding investment
remains on the books at this time?
The Company has $269,567 of cloud seeding
investment in Account 101 Electric Plant In Service that is
not included in the Company s rate base.
Will the Company add to its cloud seeding
investment during the winter 2004-2005 period?
Yes, the Company envisions adding
approximately $21,000 of cloud seeding investment during the
winter 2004-2005 period.This investment, as well as the
$269,567 of current investment, will need to be justified
for inclusion in rate base during a future rate case.The
Company is not asking the Commission to make any
determinations regarding cloud seeding investment at this
time.
Does the Company envision current period
expensing of cloud seeding cost during the winter 2004-2005
time period?
SAID, Di
Idaho Power Company
Yes, the Company believes it will spend in
the neighborhood of $900,000 to $1,000,000 on cloud seeding
O&M expenses if the Commission approves deferrals for the
winter 2004-2005 period.
What is the Company requesting that the
Commission approve for deferral purposes in this case?
Similar to PCA logic, the Company is
requesting that the Commission approve the deferral of 90%
of its Idaho jurisdictional percentage of cloud seeding O&M
expenses during the winter 2004-2005 time frame.Idaho
Power will continue to have its investment in cloud seeding
remain at risk while not included in rate base.Idaho Power
will also expense 10% of its Idaho jurisdictional cloud
seeding O&M expenses.This could be reflected as a line
i tern in the PCA or tracked separately.Cus tomers in Idaho
have already seen 90% of the benefits derived from cloud
seeding over the last two winters while bearing none of the
costs.Commission approval of winter 2004-2005 cloud
seeding efforts would match expenses and benefits such that
customers would continue to see 90% of the benefits, but
would also be responsible for 90% of the expenses which
would be deferred for recovery next year.
When would the Company envision a change in
rates and amortization of deferred cloud seeding expenses to
occur?
SAID, Di
Idaho Power Company
The Company envisions filing a request for a
rate change and amortization of deferred cloud seeding
expenses by May 1, 2005 for rates to be put in place for the
June 1, 2005 through May 31 , 2006 period of time.I f the
Commission prefers that cloud seeding deferrals be included
as a line i tern in the PCA, the Company would include the
cloud seeding deferrals in its April 15, 2004 PCA
application.
Does this conclude your testimony?
Yes, it does.
SAID, Di
Idaho Power Company
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BEFORE THE IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-04-
IN THE MATTER OF THE
APPLICATION OF IDAHO POWER
COMPANY TO DEFER EXPENSES
ASSOCIATED WITH ITS CLOUD
SEEDING PROGRAM FOR THE
WINTER OF 2004-2005
IDAHO POWER COMPANY
DIRECT TESTIMONY
GARY RILEY
October 2004
Please state your name and business address.
My name is Gary Riley and my business address
is 1221 West Idaho Street, Boise, Idaho.
By whom are you employed and in what
capaci ty?
I am employed by Idaho Power Company as
Senior Meteorologist in the Water Management department.
Please describe your educational background.
I attended the USAF Weather Observers School
in 1965 and the Weather Forecasters School in 1970-71,
gradua ting from both wi th honors.I received a Bachelor of
Science Degree from Longwood College (now Longwood
University) in 1981 , graduating Summa Cum Laude with a maJor
in physics and a minor in mathematics.I received a Mas ter
of Science degree in Atmospheric Science from the State
University of New York at Albany in 1984.
Please describe your work experience wi
Idaho Power Company.
I was hired by Idaho Power Company in June
2002 to implement and run the Company s cloud seeding
project on the Payette River Basin and to provide weather
forecasting support tailored to the Company s needs and
interests.
The cloud seeding proj ect is designed to augment the
wintertime snowpack in the Payette River Basin and thereby
RILEY, Di
Idaho Power Company
increase sprlng and summer runoff through the Company
Hells Canyon Complex.The proj ect became operational in
late January of 2003, with the first seeding on February
2003.Operations ended for the season on April 15, 2003 and
resumed between November 1, 2003 and April 21, 2004.
Please describe your experience in the field
of weather modification.
Prior to joining Idaho Power, I was Vice
President and Chief Scientist for Atmospherics Incorporated
in Fresno, CA.Founded in the mid 1960s, Atmospherics is
one of the oldest and most respected weather modification
companies in the world.I first began working for
Atmospherics in December 1991, and while there I supported,
operated, and/or managed weather modification projects in
Cali fornia, Nevada, Colorado, and Texas.Internationally,
proj ects were conducted in Spain, India, Indonesia, and
Costa Rica.
From 1987 through early 1991, I was employed by
Intera Technologies of Calgary, Alberta, Canada as a Senior
Meteorologist and I was the Assistant Manager of the Greek
National Hail Suppression Project.
Please briefly describe the theory behind
cloud seeding as it applies to Idaho Power s proj ect to
augment snowfall.
The natural precipitation processes
RILEY, Di
Idaho Power Company
fundamentally inefficient in the majority of cases.That is
to say that more water is available for precipi tation than
actually falls as precipitation.The air in a storm system
usually contains plenty of water, but it does not contain
enough of the types of particles capable of acting as ice
nuclei.These particles start the process of converting the
available water into ice and finally, into snowfall.Cloud
seeding to augment wintertime snowfall works by partially
reducing the defici t by introducing more of these particles
in to the storm sys tem.
What factors are necessary for cloud seeding
to be effective and provide the benefit of additional
snowfall?
To be effective, three fundamental and
necessary condi tions need to exist in the airmass passlng
over the target area - in our case, the Payette River Basin.
First, the air must already be producing, or be
abou t to produce, precipi ta tion (thi s is snow enhancemen
not snow making) Such a winter storm can produce a
thermodynamic environment favorable for activation and
transport of the seeding material into the part of the storm
where the precipi tation forms.
Second, the air must contain an appreciable amount
of supercooled liquid water.Supercooled liquid water is
simply water suspended in the air at temperatures below
RILEY, Di
Idaho Power Company
freezing, that is below 32 OF or 0 oC.Pure water can exist
in the liquid state to temperatures as cold as -40 oc (or of
- they are the same at that temperature)This liquid water
is converted, first to ice, and then to snow, by contact
wi th a nucleating particle by a process called ice
nucleation.
Third, and as is usually the case, there must be an
insufficient number of naturally occurring ice nucleating
particles to efficiently convert the available supercooled
liquid water first into ice crystals and ultimately, into
snowfall.Naturally occurring ice nucleants typically
consist of tiny clay particles, pollutants, and bacteria
that have been picked up and transported into the cloud by
the wind.
Given an environment where snow is falling
and surplus supercooled liquid water exists, but there are
insufficient ice nucleating particles, what can be done to
effect additional snowfall?
When there is more supercooled liquid water
present than can be converted to ice by the available ice
nuclea ting particles, the introduction of addi tional
nucleating particles can convert some of the surplus
moisture into ice crystals.These subsequently grow into
snowflakes and fall to the ground.
Does cloud seeding in one area reduce the
RILEY, Di
Idaho Power Company
precipi tation falling downwind?
This was one of the first areas of
investigation when cloud seeding technology began to be
applied, and it continues to be examined.Numerous
investigations have found no evidence of any "Rob Peter to
Pay Paul" effects.Several recent studies have found
beneficial increases in areas downwind of cloud seeding
proj ects as far away as 125 miles or more.
What does Idaho Power Company utilize as ice
nucleating material?
The primary seeding material used by Idaho
Power Company is silver iodide.It has been known since the
later part of the 1940s that silver iodide acts as a very
effective ice-nucleating particle at temperatures between
about -4 oC and -15 oC.One gram of the material creates
from 10 10 to 10 15 ice nuclei, depending on the temperature.
Our network of seven ground-based generators can each
release 20 grams per hour.Depending on the configuration
and other constraints, the proj ect aircraft can release from
151 to as much as 1500 grams per hour.To put those numbers
into perspective, cloud physics data collected during a
storm on 25 March 2004 indicates the yield from the aircraft
alone was more than 600 acre-ft per seeding hour with a
release rate of 234 grams per hour.
Are you able to target where the addi tional
RILEY, Di
Idaho Power Company
snow will fall?
To place this addi tional snowfall in the
proper place, the target area, requires an understanding of
how, and how fast, the process works.For effective cloud
seeding, accurate information about the temperature and
moisture structure and about the wind flow into and across
the target area is needed.The seeding material must be
released so that there is the correct amount of time
available for it to be transported into the portion of the
storm having the proper temperature and humidity structure
and where the factors mentioned earlier exist.
How long does it take to form snow once the
silver iodide has been introduced into the storm?
The typical timeframe required for the
addi tional particles to be transported into a sui table
environment, induce freezing and grow into snowflakes is on
the order of twenty minutes.I t can take another twenty
minutes for the snowflakes to fall to the surface. Hence,
the silver iodide needs to be introduced into the storm
system in a wind regime that will carry it into a zone
favorable temperatures and moisture and then transport
into and across the target area in a time "window " of 15 to
40 minutes.
How do you know tha t the snow on the ground
is the result of cloud seeding efforts rather than snow that
RILEY, Di
Idaho Power Company
would have been present wi thout cloud seeding?
Cloud seeding proj ects have, until recently,
relied on statistical analysis of Target - Control, or
seeded area vs. non-seeded area, data sets.Because the
yield from any particular cloud seeding season lies well
within the natural range of variability of precipitation, it
can take many years to obtain statistically significant
results and determine a reliable measure of success or
failure.For that reason, many scientists and statisticians
were reluctant to accept the results indicative of success.
Nevertheless, this procedure is still commonly used.
In the last 10 to 15 years however, significant
advances have been made in both our unders tanding of the
physics involved and in our ability to confirm and evaluate
resul ts through trace chemistry investigations.
Because the materials used for cloud seeding are
known, as is the time of their release, analysis of the
snowpack itself provides information about where the seeding
material fell, how much of the material went towards
addi tional snowfall, and how much was simply scavenged, or
swept out of the air, by precipi tation already occurring.
The presence of enhanced silver in the target area
snowpack indicates accurate targeting, but it says nothing
about whether it was deposi ted in the form of addi tional
snow or scavenged.Releasing an inert, non-nucleating
RILEY, Di
Idaho Power Company
16 '
tracer simul taneously wi th the active seeding agent makes it
possible to determine if the source was additional
precipi tation or scavenglng.
Did Idaho Power Company take steps to measure
the effect of its cloud seeding program using this new,
sophisticated approach?
Idaho Power contracted Desert ResearchYes.
Insti tute, an extension of the Uni versi ty of Nevada, to
perform an analysis of snowpack samples from the Payette
River Basin this past winter.The tracer used was indium
sesquioxide (In
) ,
whose particles are similar in size and
dispersion characteristics to the nucleating silver iodide
(AgI) .However, unlike the active material, the tracer is
non-nucleating and is removed from the air only by
scavenglng.Therefore, any change in the ratio of silver to
, indium from what it was at the point and time of release
gives a measure of how many of the silver particles went
into making addi tional snow and how many were scavenged.
Did Idaho Power measure the success of its
cloud seeding efforts in the winter of 2002-2003?
Yes.The original proj ect plan did not
include an evaluation of benefit for the first season.The
combination of start-up operations and a short operational
season, only 2 ~ months, severely limited the amount of data
available.However, two direct, and one indirect, analyses
RILEY, Di
Idaho Power Company
were conducted, and all produced similar resul ts.All three
of the analyses were independent.No Idaho Power Company
personnel involved in seeding decisions took part in the
evaluation.
Please describe the two direct analyses
the cloud seeding effort during the winter of 2002 - 03.
The first was by an Idaho Power employee not
otherwise involved in the project.The second evaluation
was done by an independent consul tant.A tradi tional Target
- Control analysis, consisting of a linear regression of
precipitation at sites inside and outside of the target area
indicated a 16% increase in precipi tation during the 2 ~
month period between February 1 and April 15, 2003.That
translates to 2.2 inches of addi tional water when averaged
over the Payette River Basin.Given a target area of
approximately 938 square miles, that works out to 110,000
acre-ft of water.
The precipitation data was also provided to an
independen t consul tan t who determined that along wi th the
16% increase during the operational period, the project
would likely have produced a 9% increase had it been
operational for the entire winter. The reason the seasonal
value is lower is because over the course of a full winter,
weak events and storms not meeting seeding cri teria would
combine to produce appreciable precipitation. These one,
RILEY, Di
Idaho Power Company
two, and three inch snowfalls contribute significantly to
the seasonal total and reduce the percentage of the
augmented snowfall, although the augmentation in inches of
addi tional water remains the same.
Please describe the indirect evaluation of
the cloud seeding effort during the winter of 2003 - 03.
An indirect evaluation was provided by North
American Weather Consultants of Sandy, UT.North American
operates a snow enhancement proj ect on the adj acent Boise
River Basin for the Boise Project Board of Control.Their
ini tial analysis of the Boise Basin 2002 - 03 season data
indicated a "no effect" result until it was realized that
the non-seeded Control si tes being used for the Boise
proj ect were seeded Target si tes for Idaho Powers ' payet te
proj ect After developing a new set of unseeded Control
sites, North American arrived at a 13% increase for the
Boise proj ect, and by inference, for Idaho Power s proj ect
as well.
Did Idaho Power measure the success its
cloud seeding efforts the winter of 2003-2004?
Yes.Similar the analysis done on the
2002 - 03 season, a Target - Control analysis indicated a 5%
increase in precipitation in the Payette River Basin for
this past season.This reduced yield - 5%, down from 13 to
16% - was expected because it was a dryer than normal ,year
RILEY, Di
Idaho Power Company
and the inclusion of the trace chemistry analysis mentioned
earlier placed several constraints on operations.Still,
even with only 80% of normal precipitation, the yield
represents an addi tional 68,000 acre-ft of water.
Snow samples collected by Desert Research Insti tute
and analyzed in their ul tra-clean laboratory in Reno showed
very high levels of silver present and very little indium.
Further, comparison of the depth at which the silver was
found with data from nearby SNOTEL sites shows it to be
consistent wi th seeded events.Degradation of the snowpack
prior to sample collection prevented the laboratory from
quantifying the yield in augmented precipitation, but the
data indicate scavenging was not a significant factor and
Idaho Power has an effective project.
Can you provide the Commission wi th an
example from this analysis to help understand how the silver
and indium relate to each other in seeded snowfall?
As an example, I would like to offerYes.
Exhibi t This is a figure provided by Dr. Ross Edwards of
Desert Research Insti tute showing the concentrations of
silver and indium detected in a snow sample from the east
side of the Payette River Basin target area.The sample was
collected on Mount Zumwalt at an elevation of 8,225 feet.
Note the different scales for silver (left side) and Indium
(right side)Three seeding events are depicted and the
RILEY, Di
Idaho Power Company
silver to indium ratios show that for every silver iodide
particle scavenged, between 6 and 19 other silver iodide
particles contributed to additional snowfall.
Were the results of your measurement of cloud
seeding success consistent wi th those for other proj ects and
enti ties?
Yes.The yields I have indicated, 5 to 16%,
are within the range of expectations from wintertime
orographic cloud seeding contained in statements from the
World Meteorological Organization, the American
Meteorological Society, the American Society of Civil
Engineers, the Weather Modification Association, and even
Idaho s Department of Water Resources.All of these
indicate cloud seeding to augment wintertime snowpack can
produce increases of from 5 to 20% when done correctly.
Desert Research Insti tute has said the resul ts of the trace
chemistry evaluation are consistent with and similar to
those from investigations of this type in California and
Nevada.Two of the comparable projects in California are
operated by power companies (Pacific Gas and Electric and
Southern California Edison) for the same purpose as Idaho
Power s program.The results of trace chemistry evaluations
of the Lake Almanor proj ect run by Pacific Gas and Electric
and those from Southern California Edison s proj ect on the
San Joaquin River have appeared in peer revi,ewed
RILEY, Di
Idaho Power Company
publications of the American Meteorology Society and the
North American Hydroelectric Industry.
Can you provide one of these articles that is
written in language someone not familiar with weather and
cloud seeding might understand?
Yes.I have here a copy of an article by
Brian McGurty reporting on the results of the study on the
San Joaquin River project that appeared in Hydro Review.
think the Commission will find it very readable, and I offer
it as Exhibit
Given a quantification of additional snow
resul ting from the Company s cloud seeding efforts, did you
quantify how the additional snow translated into additional
stream flows at the Company s hydro facilities?
Yes.The data from the 2002 - 03 Target -
Control evaluation was fed into the CHEOPS hydrological
model to determine the generation potential of the augmented
water when it passed through the Hells Canyon Complex.That
allowed the determination of the benefi t gained from the
augmented water to be evaluated under several scenarios of
seeding effectiveness and varying losses of the augmented
water prior to reaching the Hells Canyon Complex.The mode
indicated increased generation capaci ties ranging from
approximately 14,000 MWh if only 25% of the addi tional water
reached the power plants to as much as 56,000 MWh if all of
RILEY , Di
Idaho Power Company
the water passed through the complex.
The data from the 2003 - 04 season was entered into
the National Weather Service River Forecas t Sys tern Model,
and the inflow into the reservoirs on the Payette River was
calculated for Seed and No-seed scenarios.The computer
simulation determined that an additional 67,700 acre-ft of
water flowed through the Payette drainage in the seeded
scenarlO.Tha t is in very good agreement wi th the 68, 000
acre-ft determined from the Target - Control regression.
This difference is easily accounted for in that the model
takes losses to soil moisture and evaporation into effect
and these factors are not included in the simpler regression
analysis.
Did you quantify the financial benefi t of the
additional stream flow at the Company s hydro facilities?
Yes.Along wi th the calculation of
additional generation capacity, the CHEOPS data for the 2002
- 03 season places the dollar value of the water at $ 1.
million if only 50% of the augmented water reaches Hells
Canyon Complex.However, the Payette River Basin was chosen
for the cloud seeding project in part, because the river
reservoirs have a high probabili ty of refill.Hence, the
actual value would be closer to the 100% expectation with a
value of $2.1 million.
Using the Target - Control yield of 110,000 acre-
RILEY, Di
Idaho Power Company
of water and the in-house rule that for every hour one acre
foot of water passes through Hells Canyon Complex, 0.5 MW
can be generated, the value can be readily estimated.
Taking the average high ($32.13 /MWh) , the average low
($29.47/MWh) , and the average average ($30.47/MWh) price of
power for the period May through August 2003 gives a
comparable value between $1.6 and $1.8 million.For
example, using the average price: 110,000 acre-ft times 0.
MWh/acre-ft times $30.47 /MWh indicates the water to be worth
$1.7 million for hydropower generation alone.Thi s number
does not consider any monetary value of ancillary benefits
to the region in the form of improved water condi tions for
fish and wildlife, recreation and navigation, irrigation, or
additional drinking water, although these benefits also
exist.
The value of the 2003 - 04 yield was estimated by
taking the yield, 68,000 acre-ft, and using the same
approach.The generation potential from last season would
be $1.4 million at an average price of $41.76/MWh.(68,000
acre-ft times 0.5 MWh/acre-ft times $41.76/MWh = $1.
million. That value is obtained by using the average of
the On Peak and Off Peak Mid-C prices for the period from
May through 31 August 2004.The value is closer to $ 1.
million if the higher Border prices are used.
Both of the computer simulations reveal one
RILEY, Di
Idaho Power Company
addi tional benefi t from cloud seeding.The flow in the
payet te River
shifted later
longer.This
is not only increased, the peak flow
into the year and higher flows are maintained
means that more water will be available to the
Hells Canyon Complex as heavier summertime loads begin to
become a significant factor for operations.
Can you provide an example of the computer
model output that illustrates this later peak in streamflow
and the enhanced flow duration?
Yes.Exhibit 3 was prepared using the model
output and shows the peak flow is shifted from late May into
June and that higher flow levels are maintained into early
July.Note that the figure does not include data for all of
July and Augus t .
How did the financial benefits of cloud
seeding compare to the costs of cloud seeding?
The answer to thi s ques tion wi 11 depend to
some extent on the accounting period chosen.Because most
of the activity associated with the project is based on the
water year rather than the calendar year, the accounting
period was defined as July 1 through June 30.
The project expenses between July 1, 2002 and June
30, 2003 were:
Capi tal:23, 723 and
0 & M:$ 802,348
RILEY, Di
Idaho Power Company
Total:$ 826,071.
The proj ect yield, based on the average resul
already discussed was $1.7 million.Tha t gives a benef i t
cost ratio slightly greater than 2 to
For the year of July I, 2003 through June 30, 2004,
the proj ect incurred significant addi tional expenses in
association wi th the trace chemistry evaluation.These
included not only the direct costs of the evaluation in
payments to Desert Research Insti tute, but the added burden
of building and maintaining seven addi tional ground-based
genera tor uni ts to release the tracer.Consequently, the
expenses during this timeframe were:
Capi tal:237 ,067 and
0 & M:$1,066,408
$1,303,475.Total:
Using the Mid-C power costs and the estimated yield
value, $ 1.4 million stated earlier, the benefi t to cost
ratio for this past season, even with the high costs and
reduced efficiency associated with the trace chemistry
evaluation, is slightly better than 1 to Once the tracer
work is done and drops out of the expenses, a benefi t to
cost ratio of better than 4 to 1 is expected.
What additional information does Idaho Power
expect to gain by measuring snow augmentation again this
winter?
RILEY, Di 1 7
Idaho Power Company
One primary objective is determining if using
aircraft to seed storms is cost effective.A second
objective relates to the trace chemical used. From last
season s samples, Desert Research Insti tute discovered that
local dust contains fairly high levels of cesium.Cesium
was used last season to tag the seeding material released by
the aircraft in an attempt to measure cost effectiveness.
different material, bismuth iodide (BiI
) ,
will be used this
winter to better quantify benefits.
Third, this year data will be collected in a more
timely manner from more locations wi th better accessibili ty.
Desert Research Insti tute will be collecting samples as soon
as possible after seeding events, and four new sampling
si tes accessible by snowmobile have been found.These will
allow collection of at least some data, even if helicopter
flights to the more remote si tes are not possible due to
wea ther More frequent and more timely collection of the
samples will provide data on the densi ty of the snowpack
tha t can be used along wi th the tracer data to quanti fy the
amount of augmented snow so that we do not have to rely as
heavily on the Target - Control statistics.
The results will be used to refine the project
design and configuration and make it even more effective.
Were the financial benefi ts of cloud seeding
retained by the Company?
RILEY, Di
Idaho Power Company
As a meteorologist I am not in a posi tion to
answer that question other than to say that Mr. Said informs
me that the financial benefi ts of cloud seeding are captured
in the Company s PCA.As a resul t the Company s Idaho
customers receive the maj ori ty of cloud seeding benefi ts.
Does this conclude your testimony?
Yes f it does.
RILEY Di
Idaho Power Company
BEFORE THE
IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-O4-
IDAHO POWER COMPANY
EXHIBIT NO.
G. RILEY
.....
T"'"
:.;::(.)
Exhibi
Site MZ Silver and Indium
Ag/ln =19 Ag/ln =11
Ag/ln =6
Snow Depth (em)Indium
Silver
T"'"
:.;::
CtJ
(.)
:::J
This diagram shows the concentrations of silver and
indium detected in a snow sample from the east side of the
Payette River Basin target area.The sample was collected on
Mount Zumwalt at an elevation of 8,225 feet during March , 2004.
Note the different scales for silver (left side) and Indium
(right side) the scales differ by a factor of 12.Three seeding
events are depicted and the silver to indium ratios show that for
every silver iodide particle scavenged, between 6 and 19 other
silver iodide particles contributed to addi tional snow.The
figure was prepared by Dr. Ross Edwards of Desert Research
Insti tute, Reno, NV.
Exhibit No.
Case No. IPC-O4-
Riley, IPca
Page 1 of 1
BEFORE THE
IDAHO PUBLIC UTILITIES COMMISSION
CASE NO. IPC-O4-
IDAHO POWER COMPANY
EXHIBIT NO.
G. RILEY
Exhibi t 2.
Exhibit 2 is a copy of an article appearing in the April
1999 issue of Hydro-Review entitled Turning Silver into Gold:
Measuring the Benefi ts of Cloud Seeding.The article has been
peer reviewed, and was wri t ten by Brian McGurty.
Mr. McGurty is Chief Hydrographer and Technical
Specialist/Scientist for Southern California Edison.In that
capaci ty, he oversees that company s year round cloud seeding
program to augment water supplies for hydropower generation on
the San Joaquin River in the central Sierra Nevada of California.
This project, along with five others sponsored by Pacific
Gas and Electric and the Los Angeles Department of Water and
Power , are all in place to augment water for hydropower
generation and are rate based by the California Public Services
Commission.Other proj ects exist for both hydropower generation
and for public water supplies.Some of the California proj ects
have been active for 50 years or longer.
The Exhibit consists of seven (7) pages, including this
one.
Exhibit No.
Case No. IPC-O4-
Riley. IPca
Page 1 of 7
, Reprinted from
HYDRO.
REVIEW
The Magazine of the
North American Hydroelectric Industry
Volume 18, Number April 1999
Turning Silver into Gold:
Measuring the Benefits of Cloud Seeding
By BrianM. McGurty
(QCopyright HCI Publications , 1999. 410 Archibald Street, Kansas City, MO 64111.816-931-1311
Exhibit No.
Case No. IPC-O4-
Riley, IPca
Page 2 of 7
101' ~: 4\ T iii, J;;,
: ~"
1VJ 0, Dci I F' I~ C AT, l 0 1\1:
.. '.. .,,' ,' ",.. ,' ", ,
Exhibit No.
Case No. IPC-O4-
Riley, IPca
Page 3 of 7
Turning Silver to Gold:
Measuring the Benefits of Cloud Seeding
Although it is a widely used technology, cloud seeding still is
regarded with ,skepticism by many who are unfamiliar with its
application. A recent research program in California is helping
the practice gain the respect it deserves.
By Brian M. McGurty
eteorologists estimate that
about six times more water
passes over the u.s. each year
as vapor and cloud droplets than runs
down all of its streams and rivers com-
bined. Only a small portion of the avail-
able water in the clouds actually falls to
the ground as precipitation. In a water-
starved, populous region such as Cali-
fornia, any improvement in the effi-
ciency of the precipitation process
would yield widespread benefits. These
benefits would include an increase in
clean, renewable electricity from hydro-
power; increased reservoir storage for
recreation; increased water supplies for
domestic and agricultural consumption;
groundwater recharge; and various envi-
ronmental enhancements for fish
wildlife, and botanical resources.
Many California water managers
seeking to extract additional water from
Brian McGurty is chief hydrographer
and technical specialist/scientist in the
hydropower generation division
Southern California Edison. He has
been responsible for Edison s cloud
seeding program for more than ten
years.
lZlPeer Review~d "
, "" ,
, Thi$ortide has been eval~pteda~d~ditediHacc6rddnii:! "
." "
h~~~ r:~~:~~:~~d~ ~t~~~~~r:~:4~~!:r~8~ s'i~~~ni,
.. .
$ctipt$fpr lechni~qIQct~tq9';o5~fvl(\~K'alld j)ve('itnpOr'i 0
tancewilhil"lth~hi~I'~ltktric:'ihdijst1)r~:.
" ":, , ", ,
2 HYDRO REVIEW / APRIL 199()
the atmosphere, use cloud seeding to
enhance mountain snowpacks. Num-
erous comparisons of seeded and un-
seeded watersheds, dating back to the
1950s , have indicated that the technique
does produce a significant increase in
watershed runoff. A 1997 study by
Atmospherics, Inc., of Fresno, Califor-
nia, highlighted the economic impor-
tance of even moderate increases in
runoff. 1 Using data from ten cloud seed-
ing programs and site-specific watershed
and hydro project , information, the
study s author showed that a reported 2
to 9 percent increase in supplemental
runoff from the seeding programs had an
annual value of between $25 million and
$115 million. This value resulted from
increased hydroelectric generation and
increased water supply for agricultural
municipal, and environmental uses.
In 1992, Southern California Edison
commissioned the Desert Research Insti-
tute of Reno, Nevada, and Atmospherics
Inc. to conduct a five-year field and lab-
oratory research program to verify and
document the effects of cloud seeding
over Edison s 1 000-MW Big Creek
project. The study, the most comprehen-
sive research of its kind yet conducted,
corroborated previous indirect estimates
of gains in snowpack caused by cloud
seeding. It also indicated that, from the
perspective of benefit-cost ratio, the pro-
gram is remarkably successful.
Gaging Success through
Comparisons
In the past, Edison and others have in-
directly inferred the success of cloud
seeding efforts through "target versus
control" statistical comparisons of
streamflow data snow survey data,
rain gages, and radar data in seeded
and unseeded watersheds. For example
, since the 1950s comparisons of runoff
in the San Joaquin River (seeded by
Edison) to the nearby Merced River
(not seeded) have consistently sug-
gested that Edison s cloud seeding pro-
gram increases the water supply of the
San Joaquin River by about 9 percent
on average. Other industry estimates of
the increase in other watersheds, based
on the same analytical methods, range
from about 5 to 15 percent.
Unfortunately, the large range of nat-
ural variability associated with these
methods can limit the statistical signifi-
cance of the results. In addition, tradi-
tional streamflow measurements often
are only accurate to within about 10 per-
cent and are particularly uncertain in
wet years, and an unknown amount of
water is lost to evaporation and percola-
tion. Also, it is becoming increasingly
difficult to obtain "control" data because
virtually every available watershed is
either directly or indirectly seeded.
Unlike many previous indirect esti-
mates of seeding s effects, the Big
Creek research was based on field and
laboratory studies of seeded snow. The
research team was able to use physical
and chemical methods to make direct
measurements of the snowpack affected
by seeding and to compare the water
content of the seeded snowpack to nat-
ural snow.
Understanding Cloud Seeding
Water vapor is continuously present to
some degree throughout the atmosphere.
If some mechanism, such as an advanc-
ing front, causes air to cool sufficiently,
the water in the air is condensed from
vapor to cloud droplets that form around
microscopic particles called cloud con-
densation nuclei. On average, about one
million cloud droplets are needed to
produce a single raindrop, and a typical
cloud condensation nucleus is only
about one-one-hundredth the size of a
cloud droplet.
Among the various ,condensation par-
ticles present in the atmosphere, a few
have just the right size and shape to
become ice nuclei. The water vapor
phase is converted to a solid precipita-
tion phase when cloud droplets freeze
around ice nuclei and become ice crys-
tals. However, the vast majority of the
available water in the clouds remains in
a vapor and cloud droplet phase. This
creates an opportunity to artificially
assist the precipitation process by
adding more ice-forming nuclei (such as
silver iodide) to the atmosphere.
In addition to providing additional
nuclei, cloud seeding increases updrafts
in the cloud through a secondary latent
heat of fusion effect. This makes the
cloud larger, more buoyant, and able to
process a greater amount of water over a
longer period of time. Radar images of
seeded clouds indicate increased cloud
top height, increased precipitation area
and longer precipitation times than in
adjacent unseeded clouds.
From the Laboratory to the Watershed
In 1946, Dr. Vincent Schaefer of the
General Electric Research Laboratory in
Schenectady, New York, was conduct-
ing experiments on supercooled clouds
in a refrigerated "cold box." Anxious to
quickly cool the box to the temperature
needed for his experiments, he placed
some pieces of dry ice in the box. Much
to his surprise, in the presence of the
extremely cold dry ice, aerosol particles
began to act as condensation nuclei, and
the vapor around the nuclei froze into
crystals. Some ice crystals grew large
enough to fall and coat the inside of the
box, fortuitously pointing to a new wayto artificially glaciate super-cooled
clouds. Dr. Schaefer then repeated the
effect in the free atmosphere by dispens-
ing crushed dry ice from an airplane. In
this way he was able to create snow
crystals in a cloud, verifying the earlier
cold box laboratory experiments and
calculations.
Once the ice-forming properties of
dry ice were demonstrated, researchers
recognized that other solid substances
with crystalline structures similar to that
of ice could function much the same. In
1947, Drs. Bernard Vonnegut and Irving
Langmuir (also of the G.E. Lab) found
that the atoms in silver iodide in a
hexagonal crystal form assume an
arrangement identical to the positioning
of the oxygen atoms in ice. Silver iodide
crystals act as ideal ice nuclei at temper-
. atures below -5 degrees Centigrade.
After Vonnegut s findings, enthusi-
asm ran so high among the experi-
menters that they initially talked about
the possibility of modifying the weather
over the entire U.S. using only a small
amount of silver iodide. By 1950, about
10 percent of the land surface of the
S. was being seeded by farmers,
ranchers, utilities, lumber companies,
irrigation districts, and municipalities.
In the past, as many as 20 programs
have been in operation at the same time
in California alone. In an average year
there are 13 seeding programs in Cali-
fornia, targeting virtually every major
watershed in the state.
Edison s Cloud Seeding Program
For nearly 50 years, Edison has seeded
the clouds over its Big Creek hydroelec-
tric project in order to increase the water
supply to the reservoirs of the project.
The Big' Creek program is the oldest
continuously operated cloud-seeding
program in the world. The hydroelectric
project, located on the San 10aquin
River in central California, includes six
major reservoirs with a combined stor-
age capacity of over 500,000 acre-feet
and nine hydroelectric powerhouses
with a total generation capacity of
approximately 1,000 MW. The water-
t=xnlDlt NO. Z
Case No. IPC-O4-
Riley, IPca
Page 4 of 7
shed above the Big Creek hydroelectric
facilities consists of about 1 600 square
miles of rugged mountainous terrain,
with elevations ranging from less than
000 feet to over 13 000 feet.
Edison s program is currently run by
Atmospherics, Inc. The program is
staffed by experienced pilots , meteorol-
ogist-forecasters, and various support
personnel. Major equipment includes a
computerized ground-based radar sur-
veillance system with digitized outputs
specially equipped turbocharged twin
engine aircraft, a network of aircraft
and ground-based silver iodide dispens-
ing systems , a computerized satellite
weather data acquisition system, a com-
bined dual-channel radio and satellite
communication system, and a computer-
ized targeting model. The personnel
and equipment are available 24 hours
per day, seven days a week, year-round.
Edison s use of both ground and air-
borne dispense mechanisms is unique;
other programs typically use only one of
the two methods.
Seventeen fixed-location manual and
remote-controlled ice nuclei generators
are located on the ground throughout the
watershed. Mobile dispensing systems
include the aircraft-mounted nuclei gen-
erators and a mobile ground-based gen-
erator. The fixed ground generators are
strategically placed throughout the
watershed at elevations from about
800 feet to nearly 10 000 feet to allow
seeding of cloud systems moving from
Southern California Edison operates a cloud seeding program to enhance snowpacks in the
Sierra Nevada headwaters of the San Joaquin River. There is much evidence that the program
does produce an increase in runoff, with benefits for hydroelectric generation, agriculture. and
domestic water supplies.
HYDRO REVIEW / APRIL 1999
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0" "~J!"0'
" .... .-'
, lL" , ,
':-.....~, ,. .-.-...-' ....
tf:~.
1fflI.... ~...:.:.
. :,
;:-:A,
,;;' :.~~:.~:. '::':...:,;~....
",1
~'.,
:.:1-:"
"":.
:'t:.
southerly to northwesterly directions,
The locations of the fixed ground gen-
erators are based on. a variety of factors
including the effects of low-level bound-
ary layer windflows over complex terrain.
Activation of the generators is based upon
a theoretical 17 -minute interval from ice
nucleation to crystal fall-out along a path
perpendicular to the prevailing wind
direction. The generators produce silver
iodide smoke particles by burning a 2
percent solution of silver iodide in ace-
tone, injected into a propane flame,
Through the years there has been sub-
stantial indirect evidence that the seed-
ing program enhances the snowpack and
results in increased water supply to the
project reservoirs, However, until recen-
tly the technology to make direct mea-
surements of seeding s contribution to
the snowpack did not exist.
Sampling, Testing Seeded Snow
The Big Creek research team was able
to take advantage of several recently-
developed techniques, which included:
- State-of-the-art vertical snow profil-
ing to measure the concentration of sil-
ver (the seeding agent) in the snowpack;
Innovative trace (source-receptor)
chemistry tagging techniques;
Measurement of supercooled liquid
water using dual channel microwave
radiometers;
Upper air sounding measurements;
Mountaintop icing and other meteor-
ological measurements; and
- New seeding solution formulations
for improved ice nucleating perfor-
mance.
Cesium and indium, inert trace chem-
icals, were used as source-receptor tags
on the seeding agent, silver iodide.
Cesium was used with the ground gen-
erators and indium with the aircraft gen-
erators. This was the first research effort
in which trace chemistry was used to
determine the relative contributions of
seeding using both ground-based and
airborne sources,
After seeding with the tagged nuclei
the investigators sampled the snow in
vertical profiles to detect the presence of
silver iodide and the tracer chemicals,
Eleven sites were sampled following
stonn events from January to April 1994,
The snow profiles were set up to
determine the chemical and water con-
tent of the snowpack as a function of
depth and time. Precipitation data were
concurrently collected to establish the
timing of the snow profile samples,
To collect the samples, the investiga-
Exhibit No.
Case No. IPC~O4-
Riley, IPCO
Page 5 of 7
1E'
:!Ii
Figure 1: These micro-photographic images of ice crystals before, during, and after a pulse
of cloud seeding show the effects of introducing silver iodide nuclei to the cloud, The silver
iodide promotes the formation of the smaller, more densely packed crystals shown in the
middle periods of the time sequence. (From Volume 29 of the Journal of Weather Modifica-
tion-see Note 5)
tors pushed the vertical snow profiler
downward into the snowpack, then dug
a pit next to the profiler so that partition
plates could be inserted into the profiler.
Each partitioned layer, 2 centimeters
high and with a 200-square-centimeter
cross section, became one sample for
chemical and water content analysis
yielding well over 600 samples, The
samples were rapidly carried by heli-
copter to a staging area and transported
in a refrigerated truck to the lab, After
each sampling visit, the investigators
moved a snow board and a snow pole
onto the surface of the snow to establish
the level at which the next round of
sampling would begin,
Accurate detection of the tracers
depended on careful handling of the
samples during and after extraction.
Prior to use, each profiler was cleaned
with detergent, rinsed, with distilled
deionized water, and 'then sealed in
polyethylene bags, The samples were
collected with gloves and baggies to
prevent contamination and were kept
frozen to prevent adsorption by the con-
tainer walls while in route to the lab,
In the laboratory, the project team used
flameless atomic absorption spectropho-
tometer techniques to detect the tracers in
the snow samples, Metal concentrations
were determined from the absorption
peak height measurements by compari-
Table 1 : Concentrations of Silver Iodide (Agl) at Sample Sites in 1994
Seeding
Target
Area
Sampling
Location
Percent ofAll Samples Concentration
Elevation Number of Containing Agl of Agl(feet) Samples Above Background (ppt)
Primary 10,400 117,
22,
66,
21,
13.
100 121,
29,
60,
14,
14.
11,
12.4
Pioneer Basin
Rosemarie
Meadow
Colby Meadow
Mammoth Pass
Dutch lake
Edison lake
Florence lake
Mean
000
700
500
100
800
200
Secondary Strawberry Mine
Huntington lake
Cow Meadow
Shaver lake
Mean
800
000
200
370
HYDRO REVIEW / APRIL 1999
Table 2: Calculated Increase in Precipitation Due to Cloud Seeding, in 1994
Density Calculated Increase in
Sampling Ratio Precipitation
Location (Seeded/Unseeded)Percent Inches
Pioneer Basin 21.
Rosemarie
Meadow
Colby Meadow 22.
Mammoth Pass
Dutch lake
Florence lake
Mean
Strawberry Mine
Huntington lake 1.47
Cow Meadow 1.05 1.46
Shaver lake 1.15
Mean
Seeding
Target Area
Primary
Secondary
son with a second degree polynomial
regression fitted to standard peak height
data for the tracers and silver iodide.
Modified analysis of variance techniques
were used to determine the sample
elTors, which included component contri-
butions from both standard calibration
and from individual sample runs.
Measuring the Presence of
Seeded Silver
The 11 sample sites included seven
inside the primary target area for seed-
ing and four representing a secondary
target area. Table 1 lists the results of
vertical snow profiling for the presence
of silver at each of the 11 sites.
In the primary target area, seeded sil-
ver was detected above the background
level of 6 parts per trillion (ppt) in more
than 70 percent of the samples. The
measured concentrations of 13.
121.0 ppt, 2.3 to 20 times the back-
ground level, indicated very effective
seeding results. By comparison, in other
programs silver has been found in only
10 to 20 percent of the samples and at
concentrations of only 10 to 40 ppt 3 As
expected and h9ped, both the frequency
and concentration of silver detected in
the samples were greater in the primary
target area than in the secondary area. In
addition, seeding from ground genera-
tors was most effective for target sites
such as Pioneer Basin, that are located
in canyons where stable southwesterly
flow is frequently channeled. It was
least effective for sites, such as Rose-
marie Meadow, that are sheltered by
ridges from the predominant southwest-
erly flow.
Detecting the Source of Seeded Silver
The project team used two of the sam-
5 HYDRO REVIEW / APRIL 1999
piing sites, Pioneer Basin and Rose-
marie Meadow, to study the sources of
the seeded silver in detail. The useof different tracers for the aircraft
and ground-based seeding solutions-
cesium for the ground generators and
indium for the aircraft-made this
analysis possible. Although Pioneer
Basin and Rosemarie Meadow are at
similarly high elevations, Pioneer Basin
is exposed to southwesterly windflows
while Rosemarie Meadow is not
At Pioneer Basin, both tracers were
present in the snowpack, but indium
showed the lowest frequency and con-
centration, indicating that the majority
of the silver at Pioneer Basin originated
from ground-based generators. Based on
loading estimates and the composition
of the ground-based tracer solution, 72
percent of the silver detected at Pioneer
Basin was released from the ground
generators. In contrast, no cesium was
detected at Rosemarie Meadow, indicat-
ing that all of the silver detected at that
site originated from the aircraft These
results showed the value of trace chem-
istry as a way to differentiate between
seeded snow from different sources, and
thus to study the relationship between
the prevailing windflow patterns at a
site and seeding effectiveness;
Analyzing the Density
Seeded Snow
Ice particles produced by seeding are
smaller than those that would occur
naturally. Therefore, measurements of
snow density can be used to infer
whether the snow crystals were formed
naturally or by seeding with silver
iodide. In particular, when seeding is
conducted from the ground, a substan-
tial portion of the seeded ice crystals
would be expected to be smaller than
natural snow crystals, which form and
fall from greater heights and colder tem-
peratures. Additionally, crystals falling
from a seeding plume would be ex-
pected to be more uniform than natural
crystals and primarily of needle, col-
umn, and plate forms.
. Researchers working in the Wasatch
Mountains of Utah in 1993 and 1994
documented ice crystal images before
during, and after a pulsed seeding
experiment.4 (See Figure 1.) During the
seeding portion of the experiment, the
ice crystals increased in number and
uniformity compared to the unseeded
crystals, which were much more vari-
able in size and habit In addition, dur-
ing the seeding pulse ice crystal concen-
tration, ice nuclei concentration, and
precipitable water increased, and the
percent of ice crystals of larger size
dropped significantly. These experimen-
tal measurements suggest a conceptual
model , which is that seeding would pro-
duce an increase in snowpack density
due to the increased packing of smaller
denser seeded crystals among the larger
natural crystals.
From this conceptual model, seed!
no-seed density ratios can be compared
to silver concentrations. Previous ex-
periments, in which the relative fre-
quency distributions of silver were
related to snow density, have docu-
mented that higher-density snow is cor-
related with higher concentrations of
seeded silver. Therefore , an equation
can be developed that relates the esti-
mated increase in precipitation due to
seeding to the total amount of precipita-
tion containing silver (above the back-
ground level) and the average seed!no-
seed sample density ratio. The Big
Creek investigators applied such an
equation to snow samples taken in
March and April 1994 at the 11 sample
sites , with results as shown in Table 2.
Snow samples unaffected by seeding
would be expected to have density
ratios, on average, around 1.0. The data
in Tables 1 and 2 show that, as more sil-
ver is contained in a sample, the density
ratio rises higher above the threshold of
0. This increase indicates that the
seeding process is directly associated
with changes in sample density.
Adding Up the Benefits
The Big Creek researchers, using direct
measurements of snowpack density, cal-
culated that the seeding program pro-
duced a minimum ;",ror~~c~ n nr~ciD-Exhibit NO. L
Case No. IPC-O4-
Riley, IPca
PaOA n of 7
T;:
BEFORE THE
IDAHO PUBLIC UTiliTIES COMMISSION
CASE NO. IPC-O4-
IDAHO POWER COMPANY
EXHIBIT NO.
G. RILEY
Exhib i t
NWSRFS Model - Observed Flows and Simulated Flows with Reduced SWE
Payette River at Payette, ID
9000
; .," ,, ,, ,, ",",
';"i'
" "' ,, '; ",.:,'" ;;; ";" ,:;: "" "
;i, "
" ', "; "..,, ,, ,, "
unseeded Case ; I
' ;:~V-seeded Case
" ," "" "\ ,'~ ", ,
fv' "
, ""' "
I"':.c".
1\\"/1 '" I
j "
ii: 4000
, ,,
',.; fift:
':',,
;,N,,I' ~,?I "
", i'
III LI, ,
"""; ..' (~!
;i
,.. ";.,j ",' ",,
i.' , "
' "" ",'" "" "~ '
i: ";
",, "
3000 /"!if
\' ' "
It"
"! " "..'~ "",,
' le
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2000 "
':: , "
\Z'
~.. :' ,, ";'.:;.."
0"'
:"" , .
1000
" '' '," ", ,:': " ""'" "
lii.D':..
a m "
, , '' '/ ,. "\/,'
3/10 3/30 4/19 5/9 5/29 6/18 7/8
8000
' '
7000
6000
, "
J!! 5000
-Observed Natural Flows -Simulated Flows, Reduced SWE Augmented Fish Water
Hydrograph produced from the National Weather
Service River Forecast System Model output showing the
effect on flow in the Payette River with and without snow
augmentation by cloud seeding.Note that not only is the
total flow increased,but also that the peak flow occurs
later and higher flows are maintained longer into the year
in the seeded case.
Exhibit No.
Case No. IPC-O4-
Riley, IPca
Page 1 of 1