Project Skywater December 1968

I

I

A PROGRESS REPORT

ON PROJECT SKYWATER

THE BUREAU OF RECLAMATION'S

ATMOSPHERIC WATER RESOURCES

PROGRAM

by

Archie M. Kahan

Office of Atmospheric Water Resources Office of Chief Engineer

Bureau of Reclamation

United States Department of the Interior Denver, Colorado

For presentation to the An·

nual Meeting at tbe

Colorado

River Water Users

Associa-ABSTRACT

This paper

reports the present

status

of Project Skywater, the

Bureau of

Reclamation's

Atmospheric Water

Resources Program,

discuss

es

recent progress

and

provides same details of the planned

Colorado

River Pilot Project.

Thirty-seven

research

groups with

an annual total support level

of $4,700,000 are engaged in studies

designed to develop the

technology

for precipitation management.

Recent experimental

evidence i

ndi

cates

t

hat cloud seeding

results can range from

inc

reases

to

dec

reases

depending on the

meteorological

circum-stances attendant t

o individual seedings.

Mathematical models

of cloud

behavior are

available to

guide

field experimentation.

Instrumentation for t

racing nuclei plumes is

coming

into

wide-spread

use.

An

operationally-oriented,

randomized pilot project

is being

pla

nned

for

t

he Upper Colorado

River

Basin.

DESCRIPTORS--

weather

modification/ cloud seeding/ artificial

precipitation/

water

resources

development

A Progress Report on

Project Skywater - The Bureau of Reclamation's Atmospheric Water Resources Program I. Introduction

1-bst of you have already been exposed to a great deal of al.k about weather modification.

Many

of you have seen, at a previous meeting

of this association, 11

Rivers in the Sky," the motion picture tha

describes how and why the Bureau of Reclamat ion undertook i s comp re-hensive program of research aimed at learning how better to tap the water resources of the atmosphere. There is, therefore, probably

very l ittle need to spend time today laying the background for the

now widely accepted concept that, under some meteorological circtnn -stances, man can change the amount and/or location of precipita ion.

Few knowledgeable people today would differ wit h the assertion that

del ivery of the right kind and the right amount of cloud seeding chemicals to the right place in the atmosphere at the right t ime will result in changes in the behavior of the seeded clouds and in t he result ing precipitation.

This unanimity turns out t o be somewhat fragile, however, when one attempts to find acceptably precise definitions of what constitutes this right kind, amount, plac·e, and time to produce desirable changes. A host of important questions remainS to be answered before anything approaching a consensus on what is "right" is reached. Between recognition of the exciting scientific fact that precipitation can sometimes be artificially changed and the existence of a widely

applicable, rel iable technology for accomplis.hing such changes in an economically sound and socially acceptable manner, lies a con-siderable gap in available knowledge. This gap is being narrowed. It is my purpose today to bring you up to date on the effort that has been mounted, ment ion something of what has been recently learned, and tell you what is being planned for the near future toward further narrowing of the knowledge gap with some special emphasis in the Colorado River Basin.

II. Current Project Skywater Effort

In the current fiscal year, approximately $4,700,000 will be expended by Project Skywater in pursuance of its goal of acquiring the tech-nology for adding to the useful water supply. The effort supported by this expenditure now extends across the nat ion. In response to the increasing recognition that water supply probl ems are not the exclusive property of the West, from the Stat es of Washington to Florida, from Cal ifornia to the New England States, the best avail-able minds have been put to work on problems of precipitation

management . We have under contract

3

7

research groups drawn from

private industry, universities, st ate governments, and Federal agencies. Figure 1 lists these groups and t he 11 categories of

effort which they are currently pursuing. Each group is playing a role contributary to the eventual development of operational systems. When developed, these operating systems will include the basis for making sound decisions about whether or not to apply cloud seeding

technology, the means of recognizing seeding opportunities, the means of proper treatment, and the basis for evaluation of accomplishment.

III. What has been Learned Recently

The results of several carefully designed, randomized experiments have been published in the last 2 or

3

years. In his country and abroad, from programs sponsored by he Bureau of Reclamation and by others, a picture is emerging which shows tha cloud seeding can produce results ranging from significant increases in precipitation, through no detectable effect to actual decreases. Which of these occur appears to depend quite heavily on the temperature and wind structure of he atmosphere at the time of seeding, the ype of storm seeded and manner in which the seeding is carried out.

Of special pertinence to the Colorado River Basin are the recently published results of an excellent experiment near Climax, Colorado, conducted by Professors Lewis 0. Grant and Paul Mielke of Colorado State University under sponsorship of the National Science Foundation. Grant and Mielke analyzed 283 cases occurring from the winter of

1959-1960 through the spring of 1965. They found that the increase in snowf'all of' seeded clouds over unseeded ones averaged 54.5 percent for those cases where the 500 millibar surface temperatures (cloud top approxi..m.!ftely) ranged between -12 and -20 degrees centigrade.

The amount of increase dropped to 12. 3 percent for temperatures between -21 °C and -23°C. A decrease of' -14.8 percent resulted

when temperatures fell between -24°C and -39°C. The warmer cases were associated with a deficit of ice nuclei, while the cold cases

had plenty from natural sources.

A further analysis of the same data by Charles Chappell, also of Colorado State University, brought out the importance of wind velo-city during seeding. Precipitation increases were shown to be greatest when the wind velocity ranged between 22 and 28 meters per second. The decreases observed were associated with winds of 10 meters per second or less. The cold cases tended to be the ones having light winds .

The power of relatively simple mathematical models of cloud behavior in guiding field experimentation has been demonstrated quite recently. A one-dimensional model developed by Professor L. G. Davis and

Mr.

Alan Weinstein at Pennsylvania State University has been applied by them in the field at Flagstaff, Arizona, in connection with the Bureau of Reclamation sponsored program conducted by Meteorology Re~earch, Incorporated. With the help of the mathematically derived prediction of how clouds should develop if seeded or if left unseeded,

it has been possible to conduct more meaningful seeding experimentation.

Increases in cloud height and precipitation amount due to seeding have been clearly demonstrated. A similar model employed by

Dr. Joanne Simpson of ESSA in guiding the seeding of cumulus clouds in the vicinity of Miami, Florida, resulted in precipitation from

individually seeded cumulus clouds averaging 1 0 acre-feet more per

cloud than unseeded cases. Fourteen randomly selected seeded clouds produced an average of

237

acre-feet per cloud as measured by a

cal ibrated radar. Five unseeded cases averaged

97

acre-fee . This represent s an increase of

144

percen due to seeding. These models also give warning of what clouds should go unseeded if you would

avoid precipitation decreases. Some past seeding effor s would have

benefited had present models been available.

A third area of important recent progress worthy of special mention

has to do with an increasing abil ity o pin down what happens to silver iodide once it has been released by the generating device. Detection of plumes of seeding nuclei is now possible in three dimensions, thanks to a cont inuous nuclei counter developed at the

National Center for Atmospheric Research and manufactured by E. Bollay

Associates. A number of these are in use in aircraft and at ground

installat ions throughout Project Skywa ter. Using one of these counters,

the University of Wyoming has been able to show the relationship between plume width and the stability of the atmosphere. In Figure 2, one can

see bow narrow a seeding plume

(8°

to

9°)

is observed when lapse rates

attain values associated with unstable conditions. The broad plumes

(30 degrees for example) that were frequently formerly assumed to

exist generally appear to be confined to the more stable conditions .

This relation provides guidance in the design of seeding experiments

Another facet of progress is the detection of seeding material in

samples of precipitation. A method developed by Professor

J.

A.

Warburton at the University of Nevada employs neutron activation

analysis to determine the concentration of silver present in

care-fully taken snow and rain samples. Silver concentrations in samples

taken from several unseeded storms were about 20 x lo-12 grams of

silver per milliliter of precipitation. In seeded storms, silver

concentrations ranged from 20 to 200 x 10-12 grams of silver per

milliliter. This is a concentration of from 0.02 to 0.2 parts per

billion. This sensitive method permits determination of where silver

iodide was present while precipitation was in progress. While the

presence of silver in precipitation does not prove that silver

iodide played a role in producing the precipitation, it does provide

a means of differentiating between parts of a storm that were seeded

and parts that were not. Preliminary indications from an experiment

in the Park Range Mountains of Colorado suggest that there is

associ-ation between the larger silver concentrations and the larger

pre?ipitation amounts.

One of the frequently voiced concerns about cloud seeding has to do

with downwind effects. Many people are prone to draw on the analogy

of upstream appropriation of streamflow to conclude that upstream

cloud seeding must produce downwind decreases to compensate for

upstream increases. A study by Keith Brown and Robert Elliott of

results of looking at precipitation records for stations downwind

from seeding projects indicated centers of precipitation increase

extending approximately 100 miles downwind.

An analysis by E. E. Adderley of rainfall experience downwind from

cloud seeding projects in Australia shows similar extensive areas

of increase. Professor Braham's results in Project Whitetop in

Missouri show radar echo increases, then decreases, then increases

downwind. While none of these studies can be said to answer the question of downwind effects for all circumstances, they certainly

suggest that the frequent assumption of extensive downwind decreases

is not well supported by experimental data collected to date.

In addition to the topics discussed above in some detail, there has

been progress in other areas such as cloud seeding generator

develop-ment, instrumentation systems for acquiring and processing

meteor-ological data in real-time and in increased understanding of the

precipitation processes. Time limitations preclude giving detailed

recognition to all the recent progress. Suffice it to say that this

increased understanding has brought increased appreciation of the

complexity of precipitation management and of the need for carefully

designed seeding programs if the results are to be the ones desired.

To insure that the best knowledge available is applied to the

decisions being made, we have held a series of 110rking conferences which we call the Skywater Conferences. These bring together our

co

ntractors

a

nd

other

invited experts in the

.

field

to focus on some

major fac

e

t

of our

tot

a

l

problem.

The four conferences held to date

have

been

concerned

with: (1) The chemistry and physics of cloud

nucleation, (2) the

design and evaluation of weather modification

experiments, (

3)

the

production and delivery of seeding materials,

and

(4)

th

e

optimization

of operational weather modification. Each

co

nference

has

in effect asked

the

questions:

''

What is

known

about the subject at band?"

''what

do

we need

to

know

that

we don't know?"

"What

is

t

he

best attack

on the problem?"

Proceedings

of th

e

conferences

have been published and are being

ci

rcula

t

ed. We have

been gratified by

their

reception as a

contri-bution to progr

ess

in the

field.

IV. What

is

Planned for the

Future

In

1966

we

issu

ed

a

report entitled "Plan

to

Develop Technology for

Increasing Water

Yield

from Atmospheric

Sources." This plan provided

for

the

development

of a region-by-region capability for enhancement

of the

nation's water

resources by increasing or redistributing

precipitation.

An

orderly progression from experimental projects

to

pilot projects

was proposed as the means of achieving an

opera-tional capability.

Although

the

funding made available to us

has

not

reached

the level contemplated in the plan, we have been attempting

to go forward as

best ve can. Recent legislation bas put added emphasis

The

Colorado

River Bas

in Pro

j

ec

t

Ac

t (

ca

ll

e

d t

he Centra

l

Arizona

Project

Bill) directs the Secre

t

ary of the Interior to cond

u

c

t

a

"full and

complete

reconnaissance

"

to d

eve

lop

a

"

general plan to

meet

future water

needs

of the Wes

t

ern Uni

t

ed Sta

t

es"

(

wes

t

of the

Continental Divide).

Important

to

this p

l

an is means of augmenting

the

Colorado

River by 2-1/2 million acre-fee

t

.

A final report is

due in

1977

with

progress reports every

2

years

b

eginning in

1

971.

No importation

can

be

considered

in

these repor

t

s until after

1978.

The

Statement of

the

House

specifies tha

t

"all possible sources of

water must be

considered, including water conserva

t

ion

and

salvage,

weather modification, desalination, and

importation from areas of

surplus. The first evaluations

of the pilo

t

pro

j

ec

t

are planned to

be

included

in

the

1973

progress report, giving

4

additional years

to integrate weather modification into

the water planning for the

Colorado River Basin and

to confirm

applica

t

ion

in

other parts of

the

Western States.

At

t~e

Skywater IV Conference,

"Optimization of

Operational

Weather

Modification," held .May 21-22,

1968,

it was

the

general consensus

of those attending that present knowledge was suffici

.

ent for a

large-scale feasibility test or pilot project

in

the Upper

Colorado

River

Basin

to augment snowfall. We

mve

contracted with

Colorado

State University for the design

and

planning of

a

Colordo

River

The pilot project will be operationally oriented. With a yearly

randomization between the two project areas, all storms favorable

for seeding will be seeded for maximum precipitation increase

and

unfavorable storms will not be seeded. Seeding criteria will

essen-tially be those found at Climax to be favorable for increasing

precipitation. Main favorable criterion is a 500-mb temperature,

considered to be generally representative of winter cloud top tem-peratures, of -l3°C to -23°C with -l6°C to -20°C the highly favorable

range. Winds at 500mb should exceed 10 mps for favorable seeding

with most productive speeds at 22 mps to 28 mps and should be blowing

more perpendicular against the orographic barrier.

The two project areas are 140 miles apart, separated by the central Colorado mountain massif where Climax is located. The northern

project area is approximately 1,000 square miles and the southern

area is about 3,000 square miles. The two areas are quite

dissim-ilar, yet together are representative of the main water production

or seeding areas in the Colorado River Basin. The northern area is cup· shaped and somewhat sheltered by upwind mountains, while the

southern area is exposed to stor.ms from the northwest through

southwest. More favorable seeding events are expected in the

southern area because of generally warmer temperatures. With the

exception of the northwestern part of the northern area, runoff

Evaluation will primarily be directed toward determ1 ning the snowfall

increase due to seeding. Given a normal occurrence of favorable

seeding situations in the 4-year period (the 'Winters

1969-1970

through

1972-1973),

an indicated increase of about

10

percent or more should

be statistically significant . Seasonal streamflow increases based

on gage records are not expected to be statistically significant

within a 4-year period but streamflow increase evaluations, including

precipitation-runoff relations, will be an important part of the

evaluations.

Approximately

40

instrumented sites recording hourly precipitation,

surface wind, and temperature will be installed during the summer

and early fall of

1969.

These will. be located at approximately

1,000

feet el.evation differences in

10

or 12 watersheds that are

representative of the project areas. Remote acquisition of data

will be provided where necessary and feasible although the project

budget should limit communication facilities to only a few of these

sites. Each of the representative watersheds will be gaged by an

existing or additional stream gage. This fall, three new gages have

been installed by the USGS in likely watersheds (at the western

bottom of Berthoud Pass, western bottom of Wolf Creek, and southern

bottom of Red lt:>untain Pass ) •

Samples of falling snow will be collected at four points and stored

A

data

network

for recognition of favorable seeding situations and

tactical

seedi

ng

control

will

be

included. At least one project

sounding statio

n,

possibly

mobile between the areas, and several

remote instr

umen

t

ed sites with radio communication in and around

t

he project

areas

will be installed.

According to

present plans,

seeding will mostly be done from 22

ground-based,

remo

t

e

controlled

silver iodide generator sites located

around

t

he

p

rojec

t

areas,

6

for

the

northern area and

16

for the

southe

rn

area

.

Some

air seeding is planned.

The operating

period

will generally be October 15 through May 15.

Seeding t

he

firs

t

s

eas

o

n,

1969-1970,

will be in the northern area.

A

random schedule

will

b

e

set in

advance for a 4-year and longer

pe

riod

.

To

balance

t

he installa

t

ion cost of

the

seeding and

recog-nition

sys

tems between

FY

1970

and

FY 1971,

the

northern area

equipment

will

be

installed in

FY

1970

and the southern area the

next fiscal

year.

A

contract to

be put out for bids in March 1969

will

b

e

for

t

he

installation

and operation of the seeding and

recognition systems.

Estimated costs

over the 5-year period should exceed

$2

million,

mainly

including

the design contract at Colorado State University,

t

he

evaluation

network contract, the seeding contract,

and

In addition

to the

Colorado River

Pilot Project,

we are

planning a

pilo

t

project in

the

nor

th

ern Grea

t

Plains

i

n

North

Dakota.

Others

will be undertaken as

circumstances

permi

t

.

The

fact

t

hat

pilot

projects are being planned

should

no

t b

e

misread

as a

ju

s

t

ification

for curtailment of

other

nee

ded

research

and

experimentation.

Although

present budget limitations have

f

orced

same reduction

in

o

t

her activi

t

ies, the need

is cl

ear for

greatly expanded

re

s

ear

ch

and

development if

the

crude

t

echnology

presently available is

to

be replaced

in

the

future

by

truly

optimum

proc

edures.

We have a

lot

let't

to

learn but we are

on

our

way

to

tap the

ATMOSPHERIC WATER RESOURCES PROGRAM

FY. 1969

JOB NUMBER - PERCENT OF EFFORT Figure l

19-00-oBol-76-XX-YY

Number

Cloud Seeding Engr of Jzydro Instr Legal, Ope1·ate Precip Plan & Ne eo

(YY) Contractor No. Pcyaics Material Systems & Econ System Effects Social, tc. Adapt Eval Develop Support.

01 02 0~ o4 02 06 07 08 09 10 11

01 Bureau of Reclamation - General Prog Admin 10 90

02 Bureau of Reclamation - Special Investiga~s: 100

03 Bureau of Reclamation - Contract Admin 100

o4 Bureau of Retlamation - Consultants 100

South Dakota School of Mines & Technology 0 20 20 10

versity o 'tlyaming 7 20 10

University of Nevada 20 10 30 10 10 2

Colorado State University - Hydrology 50 50

Colorado State University - Equipment 70 30

Colorado State Universit - Wind Tunnel Stu 1

1Jt State Univers ty 20 20 20

12 Fresno State College 10 20 10 10 10 30 10

13 Nev Mexico State University 10 90

14 Montana State University 40 50 )0

1 Ulliversi of California Los eles 1.00

1 Uhiversity of Arizona 100

17 University of Denver - Evaluation 1'<>

18 University of Wisconsin 100

19 Nev York university 20 8o

20 Penn State Uhiversi~ 50 50

21 CSU - Operational Adaptation 100

22 Texas A&M University 100

23 University of Miebigan 100

24 Univ of Illinois - Water Survey Evaluation 100

25 Univ of Denver - Cloud Pcysics 100

26 Univ of Denver - Co~uter Modeling 100

27

40 Naval Weapons Center

41 Geological Survey 100

42 Soil Conservation Service - Colorado 100

43 Soil Conservation Service - New Mexico 100

44 Soil Conservation Service - Wasbin~on 100

45 u.s. Army 100

46 U.S. Air Force

50 ESSA - Weather Bureau 100

51 Forest Service 50 50

8 Bonneville Power Administration - Hun~ HJrse:

53

6o State of Washington 70 20 10

61

70 E. Bollay Associates, Inc. 10 70 20

71 Meteorolo~ Research₁ Inc. 90 10

72 T. G. Owe Berg, Inc. 100 73

74 Aerometric Research, Inc. 100

75 Travelers Research Center 50 50

11 10 9 8

7

14

14

14

-

14

15 •

i5

eli

14

• 6

10

Figure 2 Relationship between the temperature lapse rate

(°C Km-1) in the transporting layer and the

hori-zontal angl of dispersion of the silver iodide

plume from the generator. Each data point for

the UW exp riment shows the ratio of the travel-ing speed (m

sec-1~

of the nuclei to the mean wind speed (m sec· ) in the transporting layer.

0

University of Wyoming

0

Smith and Heffernan (1956)

0

0

0

FIGURE 3

NORTHERN PRO

J

ECT AREA

• EXISTING STREAM GAGE

.

~ z - "

_,-.r

r--,-r _ _ r - J ,__...r-'""";

1

..

r ,~ ... ;;..-· r -I I : : .r J ._ ~ r -1

I

.

~ _J <( 1-L _- - L I;

-; ' ~ ;

.

:

.

z

-·

•''

-,_

I

I

, I

_.

I

.

!

1,

I

.

·I

r-'-_I

I

~

I

...

I

.

.

.

1

-r

_.

-I