REPORT ON WATLK EEMANDS, QUALITY CONSIDERATIONS
AND PUBLIC HEALTH ASPECTj OF THE PR0PCS3D LYMAN PROJECT
IN SOUTHWESTERN WYOMING
Prepared at the Requesc of and
in Cooperation with the Bureau of Reclamation
Region 4, U. S. Department of Interior, Salt Lake City, Utah
P* ojcc; 1
N E V
L i P
a IXKO
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFAKE
Public Heal, h Service
Bureau of State Services
Division of Water Supply and Pollution Control
ilegion VIII
Denver, Colorado
Colorado River Basin Kater Qua^ir.y Control Project
September 1962
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REPORT ON WATER DEMANDS, QUALITY CONSIDERATIONS
AND PUBLIC HEALTH ASPECTS OF THE PROPOSED LYMAN PROJECT
IN SOUTHWESTERN WYOMING
Prepared at the Request of and
in Cooperation with the Bureau of Reclamation
Region 4, U. S. Department of Interior, Salt Lake City, Utah
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Bureau of State Services
Division of Water Supply and Pollution Control
Region VIII
Denver, Colorado
Colorado River Basin Water Quality Control Project
September 1962
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CONTENTS
Page
SECTION A. BASIS FOR THE REPORT AND SUMMARY OF FINDINGS A-1
Introduction A-1
Summary A-1
Recommendations A 3
SECTION B. PHYSICAL DESCRIPTION OF THE PROJECT AREA B-1
Location and Size B-l
Physiography B-l
Project Features B-l
Land Use and Ownership B-2
Soils B-2
Climate B-4
Hydrology B-4
Transportation Facilities B-6
SECTION C. PRELIMINARY ECONOMIC SURVEY C-l
Introduction C-l
Identification of the Study Area C-l
Resource Utilization in the Local Economy C- 1
Summary of Current and Expected Future Economic Activity C-5
SECTION D. WATER REQUIREMENTS AND USE D-1
Present Water Use D-1
Expected Future Water Use D-2
SECTION E. WATER QUALITY CONSIDERATIONS E-l
Present Status E-1
Probable Future Situation E-4
Stream Flow Regulation for Water Quality Control E-5
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SECTION F. VECTOR-BORNE DISEASE AND RELATED PROBLEMS F-1
Nature and Extent of Mosquito and Other Vector Problems F-1
Anticipated Effects of the Project on Vector Problems F-5
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SECTION A. BASIS FOR THE REPORT AND SUMMARY OF FINDINGS
INTRODUCTION
Consideration has been given in this report to present and estimated
future water demands, water quality considerations and general public health
aspects of the Bureau of Reclamation's proposed Lyman Project in southwestern
Wyoming. This study was initiated in accordance with the memorandum of under-
standing of September 28, 1956, between the Bureau of Reclamation Region 4,
Department of Interior, and the Public Health Service, Region IX, Department of
Health, Education, and Welfare. After a meeting of the two agencies at the
Region 4 office of the Bureau of Reclamation on August 2, 1962 and subsequent
discussions, the study was expanded to cover all areas of Public Health Service
interest, and Public Health Service responsibility as set forth in section 2(b)
of the Federal Water Pollution Control Act (Public Law 660, 84th Congress as
amended by Public Law 87-88, approved July 20, 1961).
The Lyman Project Area is an integral part of the Colorado River Basin
now under study by the Colorado River Basin Water Quality Control Project.
One of the objectives of this basinwide effort is to develop a plan and program
of comprehensive water quality management. The first phase of this study, a
report for the Green River sub-Basin, which includes the Lyman Project area,
is scheduled for completion during Fiscal Year 1964. Since the preliminary
investigations covered in this report were made in advance of detailed field
investigations to be carried out in support of the development of a comprehen-
sive water supply and pollution control program for the Colorado River Basin,
certain materials, conclusions, and recommendations contained in this report
may require later revision.
Three areas are studied in this report: 1) The Lyman Project area, 2)
Blacks Fork Basin, and 3) Bridger Valley. The Lyman Project area consists of
the area to receive project irrigation water around Lyman, Wyoming. The
Blacks Fork Basin was used for the evaluation of the water quality aspects.
The Bridger Valley division was used for the economic analysis since this area
includes the major portion of economic activity and is the smallest geographic
subdivision of published census data.
SUMMARY
The Lyman Project, located in Uinta County, Wyoming, is one of the
authorized projects of the Colorado River Storage Project. It is proposed
as a means of improving the Irrigation water supply of the area and thus im-
proving its agricultural economy. No additional lands will be brought under
irrigation as a result of the proposed project.
Construction features include the Meeks Cabin Dam and Reservoir on the
Blacks Fork above Fort Bridger, the China Meadows Dam and Reservoir on the
East Fork of Smiths Fork above Mountain View, and some Pitching and lateral
structures for more efficient distribution of irrigation water. Recreational
facilities are planned for both of the reservoirs.
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A-2
Under present conditions almost all of the 49,630 acres under irriga-
tion suffer from inadequate water supplies during the latter part of the
irrigation season. Under project operation, supplemental supplies would be
made available for some 36,000 acres of the presently irrigated lands. A
minimum flow of 10 and 8 cubic feet per second is to be provided below the
storage reservoirs on Blacks Fork and East Fork of Smiths Fork respectively.
In addition, the project is expected to result in an additional 49,000 acre-
feet of water for irrigation diversion, including 13,100 acre-feet of
irrigation return flow for use in the lower reaches of the project area.
Calcium carbonate is found at various depths in all virgin soils of
the area but has disintegrated in most of the soils under irrigation. The
surface layer of the residual soils, has a high concentration of lime.
The economy of the study area is almost entirely dependent upon agricul-
ture at the present time and is not expected to change within the foreseeable
future. Beyond 1980, however, as industrialization beoo mes more important
to the economy of southwestern Wyoming, some increase in local non-agricul-
tural activity is anticipated.
Irrigation is by far the dominant water use in the area. At the present
time no water is being used for manufacturing or other industrial purposes.
The Blacks Fork and its tributaries, except for Hams Fork, are not utilized
for domestic water supplies at this time. Water for future municipal and
industrial purposes will be available from Fontenelle Reservoir which is
now under construction on the Green River. Storage of water for municipal
and industrial purposes, therefore, does not appear warranted in this
project. Individual ground water supplies obtained from deep wells are not
expected to be affected by the project development. Future irrigation
demands are expected to exceed available supplies, even with the project in
operation.
The quality of the water of Blacks Fork and its tributaries, including
Smiths Fork, above the presently irrigated area is satisfactory for municipal
and industrial purposes. Above the irrigation return flow points, the total
dissolved solids ranged from 50 to 135 parts per million; below the irrigation
return flow points in the vicinity of Urie, the water is generally of poor
quality as total dissolved solids ranged from 1,700 to 3,200 ppm. Below the
confluence of Smiths Fork and Blacks Fork total dissolved solids range from
700 to 5,000 ppm. The effect of improved regulation of irrigation water as a
result of project operation on total dissolved solid content in the stream
below the irrigation return flow points cannot be determined without additional
field investigation and evaluation.
Temporary construction camps will probably be required to serve employees
during the construction phase of the project. Water supplies and sanitary
facilities developed for this purpose should meet the standards required by
the Wyoming State Department of Public Health.
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A-3
On the basis of a preliminary evaluation of the probable future economy
of the Lyman area, there appears to be little likelihood that downstream
beneficiaries of water quality control will locate immediately downstream
of the project area. Storage of water for flow regulation for quality
control therefore does not appear warranted. Some 13,100 acre-feet of
irrigation return flow water is expected to be reused for irrigation downstream
from its return point and according to the Bureau of Reclamation, it is ex-
pected to be of suitable quality for reuse for this purpose.
Encephalitis, commonly known as sleeping sickness or brain fever, is now
the most important mosquito-borne disease in the United States and in the area
in which the proposed project will be located. Records of the U. S. Depart-
ment of Agriculture show that equine encephalitis cases have occurred in Uinta
County, Wyoming, statural breeding places occur in most irrigated areas, but
usually the man-made mosquito sources are frequently caused by the same faulty
irrigation and drainage practices that cause serious soil and water problems
such as excessive water losses, water logging, erosion, salt and alkali ac-
cumulations, damage to soil structure, leaching of plant nutrients and
reduced crop yields. Every effort should be made to encourage farmers to use
improved irrigation and drainage methods to prevent and minimize mosquito
sources.
RECOMMENDATIONS
Quality and quantity aspects cannot be artificially separated when
planning for optimum development of an area's water resources. Since many
diverse interests in the project area are involved, it is essential that
we'ier resource development aspects that pertain to the general health and
welfare of the project impact area are coordinated with Federal, state and
local health department requirements. To minimize the potential damage to
the health and welfare of the project impact area that may be associated with
the development of the Lyman Project, it is recommended that the following
be given due consideration:
1. The water users organization operating as the general administrative
and contracting agency for the proposed project should be advised
of the services and information available from local and state health
authorities in order that these services may be utilized by their
project residents.
2. All construction camps should be provided with at least minimum
water and sanitary facilities in accordance with State and local
health department requirements.
•\
3. All recreational areas should be provided with at least minimum
water and sanitary facilities in accordance with State and local
health department requirements. Wherever possible precautionary
measures should be taken to prevent formation of recreational
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A-4
areas without provisions being made for a safe water supply and
adequate sanitary facilities.
4. All effort should be extended during construction stages, includ-
ing land leveling and clearing, to exclude excess silt and debris
from surface waters.
5. The Wyoming and Utah State Departments of Health should be kept
currently informed regarding changes in plans and proposed con-
struction schedules so that guidance and consultation may be
provided on public health problems that may be encountered.
6. At this time, no storage be planned in project reservoirs for purposes
of water quality control because there are no apparent future users
that require higher quality water.
7. Recommendations relating to vector control:
In order to minimize public health hazards, every possible effort should
be made to avoid creating conditions which will increase populations of
mosquitoes and other arthropods and rodents of public health importance. It
is recommended that the following principles and practices be adhered to in
the design, construction, operation, and maintenance of the proposed project.
Responsibility for Vector Control
Responsibility for vector prevention and control is normally associated
with land ownership or operating rights. Therefore, the agency, group, or
individuals responsible for various aspects of the proposed project should
be prepared to accept full responsibility for the prevention and control of
vector problems resulting from the design, construction, operation or
maintenance of the project.
Prevention and Source Reduction Measures
Mosquitoes and Other Aquatic Insects
A. Reservoirs
1. Prior to impoundage, the reservoir basins should be prepared as
follows:
a. The normal summer fluctuation zone of the permanent pool should
be completely cleared except for isolated trees and sparse
vegetation along abrupt shorelines or in the deeper portions of
the pool which will be exposed to wave action.
b. All depressions, marshes, borrow pits, and sloughs which will be
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A-5
flooded by the reservoir at maximum pool level and which will
retain water at lower pool levels should be provided with drains
to insure complete drainage or fluctuation of water within them.
2. After impoundage, the following maintenance measures should be
carried out - in all potential mosquito-producing areas located within
flight range of human population groups or recreational areas
frequented by significant numbers of persons:
a. All dense vegetation should be removed periodically from flat,
protected areas within the normal summer fluctuation zone of
the permanent pool.
b. Vegetation, debris, and flotage should be removed periodically
from all drains to insure free flows.
3. Water level management to minimize conditions favorable for mosquito
production should be used to the maximum degree permitted by the pri-
mary purposes of the reservoirs. This will minimize the need for
repetitive measures for controlling vegetation and mosquito production.
4. As a general principle, waterside recreational areas, particularly
those which have facilities for overnight occupancy, should be located
along sections of reservoirs which have a low production potential
for mosquitoes and other aquatic insects.
B. Project Irrigation Conveyance and Distribution System
1. Lining or other satisfactory seepage control measures should be pro-
vided for all sections of canals and laterals located in porous
material where excessive leakage would result in waterlogged areas,
seeps, and ponds.
2. Drains should be installed to prevent ponding of excess irrigation
water and natural runoff along the upper side of canals and laterals.
All drainage crossing or inlet structures should be placed on grade
to avoid ponding.
3. All borrow areas should be self-draining to keep them from retaining
ponded water.
4. Where possible, provision should be made to prevent turnouts and
other hydraulic structures from retaining residual water when they
are not being used.
5. Effective measures should be provided to prevent ponding of leakage
from water control structures.
6. Vegetation and debris which retard normal flows should be periodically
removed from all conveyance channels, water control structures, and
drains.
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A-6
C. Project Drainage Systems
1. Trunk drainage systems should be installed to insure complete removal
and proper disposal of excess irrigation water, natural runoff, and
seepage from both irrigable and nonirrigable lands affected by the
distribution and use of irrigation water on the project.
2. Drainage ditches should be designed, constructed, and maintained so
as to minimize ponding in the channels and to insure free flows at
all times.
3. Provision should be made to prevent water from ponding behind spoil
banks.
4. Underdrains, culverts, inlets, etc., should be placed on grade to
prevent ponding.
D. Irrigated Farms
1. The farm supply system, drainage system and field layout should be
properly fitted to the topography, soil, water supply, crops to be
grown, and irrigation methods to be used.
2. All surface irrigated fields should be properly leveled or graded
to provide for efficient water application and removal of excess
water without ponding.
3. An adequate drainage system should be provided for removal of excess
water from all portions of the farm.
4. Irrigation methods should be used which will provide optimum irri-
gation efficiencies
I
5. Application of irrigation water should be limited to that required
to fill the crop root zone plus unavoidable losses and excess water
to prevent upward movement of salts.
6. Cultural and soil management practices that will develop and maintain
good soil structure and infiltration rates should be utilized to the
fullest extent possible.
Terrestrial Arthropods and Rodents at Recreational Areas Associated with
Reservoirs
1. Proper storage, collection, and disposal of refuse should be practiced
in order to prevent and control flies, wasps, other noxious insects,
rats, wild rodents, and other small mammals.
2. All buildings should be rodentproofed at recreational areas where
rodents are prevalent which may create public health hazards.
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A-7
3. Debris, rubbish, and other materials which may serve as harborage for
rodents and other small mammals should be removed periodically.
4. Brush and weeds along paths, trails, roadways, and other areas of
frequent use by visitors should be removed in order to reduce the
likelihood of tick infestation.
Supplemental Chemical Control Measures
In situationsvhere adequate vector control is not obtained through the
prevention and source reduction measures outlined above, provision should
be made for supplemental use of insecticides and rodenticides to achieve
the desired level of control.
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SECTION B. - PHYSICAL DESCRIPTION OF THE PROJECT AREA
LOCATION AND SIZE
The potential Lyman project, located entirely in Uinta County in
southwestern Wyoming, is authorized as one of the participating projects
of the Colorado River storage project. The project area is located within
the upper part of the Green River Sub-Basin of the Colorado River Basin and-
is centered about 40 miles east of Evanston, Wyoming. The Lyman area, gen-
erally known as Bridger Valley, extends from the foothills of the Uinta Moun-
tains northward for about 25 miles,
PHYSIOGRAPHY
Blacks Fork and its tributaries, which would provide the project water
supply, are bordered on the west by the Bear River drainage basin and on the
east by the Henrys Fork watershed. Blacks Fork and its tributaries originate
high in the Uinta Mountains in Utah and drain the central portion of the
mountains' northern slope. From their headwaters the streams flow in a
northerly and easterly direction for about 75 miles, thence east and south
for about 40 miles to the Green River.
PROJECT FEATURES
The Lyman project is contemplated primarily as a means of improving
the study area's irrigation water supply and thus bettering agriculture
production on lands near the town of-Lyman, Wyoming, in Bridger Valley.
The project plan proposes two reservoirs for storing and regulating the
flows of Blacks Fork and Smiths Fork to provide supplemental water supplies
to 36,000 acres of the 49,630 acres of presently irrigated land. Inadequate
water supplies and soil deficiencies do not permit service to all presently
irrigated land.
Meeks Cabin Dam and Reservoir on Blacks Fork of 33,000 acre-feet
capacity would be located in Wyoming about 36 road miles southwest of Fort
Bridger, Wyoming. With an active capacity of 30,000 acre-feet, this
reservoir would increase usable water supplies by an average of about 37,400
acre-feet, about 10,400 acre-feet of which would come from reuse of return
flows.
China Meadows Dam and Reservoir on East Fork of Smiths Fork of 13,000
acre-feet capacity would be located in Utah about 25 road miles south of
Mountain View, Wyoming. With an active capacity of 11,000 acre-feet, of
which 10,000 acre-feet would-be utilized for irrigation, this reservoir
would increase usable water supplies by an average of about 11,600 acre-feet,
about 2,700 acre-feet of which would be from the reuse of return flows.
Approximately 1,000 acre-feet of the active storage in China Meadows Reservoir
will be used to replace existing storage rights in Marsh and China Lakes and
to maintain minimum flows in East Fork of Smiths Fork and thus improve fish-
ing values in these areas of the watershed.
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B-2
Recreation facilites are planned for all reservoirs. Consideration
is also being given to providing small fish ponds, about five feet deep,
at about one-half mile intervals in the first 10 miles of the Blacks
Fork -River below the Meeks Cabin Dam and Reservoir.
Project water will be distributed through existing ditches and laterals.
It is not expected that water users will undertake extensive land leveling
or ditch improvement work, but some improvements in farm application effi-
ciency is expected from the additions of some ditch and lateral structures
and from close control in the distribution of water. The project, however,
does not plan to provide any drainage facilities.
The Upper Colorado River Basin Compact of 1948 sets forth the basis
for ultimate division of that portion of the water supply covered in the
Colorado River Compact of 1922. The project plan contemplates a more effir
cient use of available irrigation water. Development of the Lyman project
will result in a reduction in flow of the Blacks Fork by an estimated annual
depletion of 9,800 acre-feet due to increased consumptive use on project
land, but this is still within Wyoming's alloted share under Upper Colorado
River Basin Compact. The project will not interfere with other potential
projects utilizing the water resources of the Colorado River Basin.
LAND USE AND OWNERSHIP
The project development area lies entirely within Uinta County, Wyoming.
A summary of land ownership for the county and the project area is shown in
Table B-l. Approximately 58 percent of the county and 31 percent of the
project area is in private ownership. Federal lands account for only 38.4
percent of the county but 64.5 percent of the project area. State and
local ownership was estimated to be 3.9 percent of the county and 4.6 per-
cent of the project area.
Approximately 86 percent of the 1,200 square mile land area in Uinta
County is devoted to grazing and mineral reservations. Approximately 8 per-
cent is presently used for irrigated crop production. Almost 6 percent of
the county land area is included in the Wasatch and Ashley National Forests.
SOILS
Soils of the Lyman project area are not deeply weathered since they
were developed under the influence of a semiarid climate. Three major groups
of soils are found: 1) Alluvial soils in narrow bands along the major
stream; 2) terrace soils on benches adjacent to the alluvial soils; and
3) residual soils formed on ridges of the higher elevations. Calcium carbon-
ate is found at various depths in all virgin soils but has disintegrated in
soils under irrigation.
The alluvial soils include the Havre and Logan Series and are moderately
calcareous in their native state. These are found primarily along Blacks
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B-3
Table B-l. Land Ownership in Uinta County, Wyoming and in the Lyman Project
Area, 1958.
Type of Ownership Uinta County Lyman Project area JL/
acres
percent
acres
percent
Private
764,968
57. 7
189,120
30. 9
State and Local 2/
50,899
3.9
28,160
4.6
Federal
508,933
38.4
394,300
64. 5
Bureau of Land Management
463,974
35.0
348,460
57.0
National Forest
36,880
2.8
45,840
7.5
Other
8,079
. 6
_ — _
_ _
Total
1,324,800
100.0
611,580
100.0
1/ Includes Wyoming's portion of the Lonetree area, Henrys. Fork drainage.
Estimate of this acreage not available.
2/ Includes county, municipal, highway rights-of-way, etc.
Source: Land Ownership in Wyoming Counties, 1958, Information Circular #3,
Division of Business and Economic Research, College of Commerce and Industry,
University of Wyoming, Laramie, Wyoming. Revised 1960 and unpublished data
obtained from Mr. Richard Bakalar, Work Unit Conservationist, Soil Conserva-
tion Service, U.S.D.A., Mountain View, Uinta County, Wyoming.
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B-4
Fork arid Smiths Fork. Textures vary from sandy loam to clays. Gravel and
cobble stones are common on the surface and at varying depths. In general,
these soils are permeable and possess a fairly good water-holding capacity.
Benchlands consisting of terrace soils classified in the Ashuelot and
Avon Series, are found between Blacks Fork and Smith Forks and in limited
amounts east of Smiths Fork. The surface horizon consists of a capping
of gravel and cobble ranging in depth from a few inches to 15 feet. Under-
lying the surface layer are various formations including shale, mudstones
and sandstones.
Areas of residual soils, primarily the Cut Bank and Shavano Series,
occur to the west of Blacks Fork, north of Millborne and at several
locations in Bridger Valley. The surface layer, commonly 8 to 12 inches in
depth and of a sandy loam texture, has a high concentration of lime which
leaches readily under irrigation. The substratum contains considerable lime.
CLIMATE
The Lyman area has a cool semiarid climate with freezing temperatures
having been recorded in every month of the year. The average period between
frosts is commonly about 92 days. Although the mean annual temperature is
41 degrees F, extremes ranging from 37° F below zero to a high of 102° F
have been recorded. Precipitation normally averages about 10 inches and is
more or less equally distributed throughout the year. High winds are common
which accounts for high evaporation rates in spite of the temperatures. A
summary of average climatological data for the Lyman study area is shown in
Table B-2.
HYDROLOGY
The discharge of Blacks Fork and tributaries, which would provide
project water, has wide annual and season fluctuations. Runoff from rapidly
melting snow exceeds the capacity of existing diversion canals during the
early irrigation season, while irrigation requirements exceed the available
streamflow later in the season. Table B-3 shows the period of record and
maximum, minimum and average stream flows at selected stations during the period.
The basic plan of development of the Lyman project consists of con-
struction of facilities to store non-irrigation flows and the excess spring
runoff. Regulated release of stored water will provide a supplemental
water supply during the latter part of the irrigation season for about 36,000
acres of project lands.
Under the proposed projecjt plan a minimum flow of 10 cfs would be main-
tained in the Blacks Fork below Meeks Cabin Dam and a minimum of 8 cfs would
be maintained in the East Fork of Smiths Fork below China Meadows Dam.
Other gaging stations are included in Table B-3 in order that comparisons
in the -area may be made. Note the dilutional effect of the Green River on flows
from Blacks Fork.
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B-5
Table B-2. Summary of Average Climatological Data for the Lyman Project
Area in Southwestern Wyoming. 1/
Annual precipitation (inches)
10.0
Growing season precipitation (inches)
5. 7
Effective growing season precipitation (inches)
2.0
July mean temperature (degrees Farenheit)
66.2
January mean temperature (degrees Farenheit)
o
00
r-^
Average annual temperature (degrees Farenheit)
41. 0
Coldest temperature recorded (degrees Farenheit)
-37.0
Hottest temperature recorded (degrees Farenheit)
102. 0
Frost-free period (June 10 to September 10) (days)
92
JL/ Averages computed on the basis of data gathered at the Lyman and Fort
Bridger weather stations.
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B-6
Table B-3. Summary of Streamflow Data near the Lyman Project Area in
Southwestern Wyoming.
Period
Flows
U.S.G.S.
of
Maximum
Minimum
Avg.over
Pd. of Record
Gaging Stations
Record
cfs
cfs
(cfs)(ac.
-ft. per yr.)
Green River near Green
River, Wyo. 1/
1951-60
14,600
170
1,614
1,168,000
Blacks Fork near
Millburne, Wyo. 2f
1939-60
2,530
20
155
112,200
East Fork of Smiths Fork
near Robertson, Wyo.
1939-60
1,200
7/
44.4
32,140
West Fork of Smiths Fork
near Robertson, Wyo. 4/
1939-60
920
0.2
19.8
14,330
Blacks Fork near Green
River, Wyo. _5/
1947-60
5,500
0
313
226,600
Green River near Green-
dale, Utah 6>/
1950-60
19,600
208
2,133
1,544,000
1/ One mile southeast of town of Green River. Flow affected by trans-
mountain diversions, storage reservoirs, power development, irrigation
diversions, irrigation return flows.
2/ Fifteen miles southwest of Millburne. Diversions above station for
irrigation.
3/ Nine miles southeast of Robertson. No diversions above station.
4/ Twelve miles southwest of Robertson. No diversions above station.
_5/ Twelve and one-half miles southwest of town of Green River and about
14 miles above mouth. Diversions above station to irrigate about 114,000
acres. 18small reservoirs above station.
6/ Half mile downstream from Flaming Gorge Dam. Diversions above
station for irrigation and raw water supplies for municipal and industrial
uses.
Tj Not determined.
TRANSPORTATION FACILITIES
The Lyman area is favorably located in regard to major transportation
facilities. U.S. Highway 30 traverses the area and serves as the major
transportation outlet. A branch of the Union Pacific Railroad skirts the
western edge of the project area. In addition, an 8 inch oil pipeline of
the Pioneer Products Company and a 13 inch gas pipeline of the Mountain
Fuel Cdmpany pass through the area. Local secondary road facilities tend
to be somewhat limited and many of them are still unimproved.
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SECTION C. PRELIMINARY ECONOMIC SURVEY
INTRODUCTION
This section of the report contains an initial analysis of the present
and probable future economy of the Lyman Project area in Uinta County,
Wyoming. The study area is included in an overall economic base survey of
the Green River sub-Basin now underway as a part of the comprehensive water
quality management study by the CoLorado River Basin Water Quality Control
Project. The findings of this study, scheduled for completion during fiscal
year 1964 may require revisions in the preliminary economic evaluations pre-
sented below.
IDENTIFICATION OF THE STUDY AREA
The economic study area is primarily limited to the Bridger Valley Divi-
sion of Uinta County, Wyoming as delineated by the Bureau of Census, U. S.
Department of Commerce and because this area includes the major portion of
economic activity. The geographic extent of this area is too small to allow
for adequate consideration of external factors affecting its probable future
growth. These preliminary findings, therefore, can serve only as a general
guide to local development possibilities.
RESOURCE UTILIZATION IN THE LOCAL ECONOMY
The resource base of the Lyman project area provides limited opportu-
nities for future development. Past development as well was hampered by a
shortage of available resources. Irrigation, for example, is dependent upon
spring runoff and therefore suffers from a shortage during the late season
irr iga t ion per iod.
Resource-oriented activity in the study area is limited almost solely to
agriculture. No mining or manufacturing firms are In operation at the present
time. Recreational activity is present to a limited degree and some activity
attributable to through-travelers is in evidence.
POPULATION CHARACTERISTICS
The last population increase in the study area occurred during the 1930-
1940 decade. A moderate decline in population has continued from 1940 to
date (Table C-l). Under the definition in use by the Bureau of the Census,
all of the area's population is classified as rural >»' According to available
population projections, almost no increase in population is expected to the
year 1980.2,/
—^Includes all towns of less than 2,500 population.
2 /
—'Population projections prepared for Wyoming counties, 1950-1980, by the
Division of Business and Economic Research, College of Commerce and
Industry, University of Wyoming, Laramie.
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C-2
Table C-l. Population Distribution by Census Enumeration Units, Lyman Project
and Uinta County, Wyoming, 1940-1960lL'
County Divisions and
Sub-divisions
Lyman Project Area
Uinta
County
1930
1940
1950
1960
1930
1940
1950
1960
Bridger Valley
Division
Lyman town
All other rural
377
1,818
378
2,002
483
1,566
425
1,533
377
1,818
378
2,002
483
1,566
425
1,533
Total
2,195
2,380
2,049
1,958
2,195
2,380
2,049
1,958
Evanston Division
Evanston town
All other rural
--
--
--
--
3,075
1,302
3,605
1,238
3,863
1,419
4,901
625
Total
4,377
4,843
5,282
5,526
Grand Totals 2 ,195^21 1,958 6 ,5 72^7,223^7,33ll11,484
1/ Refer to U. S. Department of Commerce, Bureau of Census, United States
Census of Population: Wyoming, 1960, "Number of Inhabitants," PC(1) 52A, page
52-4 for a map of the Census county divisions.
2/ County census divisions were changed in the 1960 Census of Population,
therefore for 1930, 1940 and 1950 Census division districts 1,2,3,4 and 5 were
combined to form the Evanston Division and Census division districts 6,7,8,9,
10, 11 and 12 were combined to form the Bridger Valley Division.
Source: U. S. Census of Population
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C-3
LABOR FORCE CHARACTERISTICS
It was estimated that the labor force experienced a decline of 14 percent
from 1950 to 1960. The unemployment rate of 3.4 percent recorded in 1960 shows
almost no change from that experienced in 1950, Out of an average employed labor
force of 650 persons in I960, approximately 35.4 percent were engaged In agriculture,
3.1 percent in manufacturing, and 61.5 percent in other miscellaneous commercial
activities. _1/ The employment distribution is expected to remain relatively un-
changed through 1980. Agricultural employment is expected to level off at about
one-third of the labor force and slight increases are anticipated in services and
trades catering to tourists and other thru-travelers.
AGRICULTURE AND FORESTRY
Irrigated agriculture, dating from about 1862, is the most important economic
activity in the study area. Feed production in support of livestock, primarily
forage crops, has predominated through the years (Table C-2). This type of
cropping pattern has been developed due to the limitations of a short, relatively
cool growing season, and the remoteness to markets for cash crops. On-farm pas-
tures are supplemented by summer grazing on National Forest and Bureau of Land
Management lands. Part-time farming is prevalent in the area; during 1960,
approximately 50 percent of the farm operators supplemented their income with
off-farm employment.
Agriculture Is expected to remain the dominant industry in the study area
and the farm population is expected to remain more or less stable at the present
level. A slight decline in irrigated acreage is anticipated in 1980. The crop-
ping pattern is expected to remain unchanged. Some expansion in the use of
National Forest lands is anticipated. This will likely involve increased recrea-
tional activity and timber production. Granger, Wyoming, located downstream from
the project area, has been considered as a likely site for a pulp mill but this
development is not expected to occur before 1980.
MINERALS
The Lyman Project is practically devoid of mineral deposits. Oil and gas
deposits have been discovered but have not been utilized to date. Some deposits
of coal and sulphur are known to occur but these are not considered of major
economic significance.^/. Mineral production is therefore not expected to have
any impact on the future economy of the study area.
MANUFACTURING
Manufacturing has never been an important segment of the local economy nor is
it expected to increase significantly in the near future. Westvaco's trona plant
a few miles northeast of the town of Lyman currently draws some of its labor force
from the project area and some expansion of production is anticipated. In addi-
tion, there may be some increased activity if a pulp mill is located in the area
in the distant future as mentioned above. It is assumed that any future water
demands for industrial development downstream of the project area will be met from
State purchased water stored in Fontenelle Reservoir now under ^construction on
the Green River, north of the project area.
_1/ U. S. Census of Population.
2/ R. E. Lund» A Study of the Resource. PeopleT and Economy of Southwestern
Wyoming, 1(Draft for Criticism and Review) Division of Business and Kconomic
Research, College of Commerce and Industry, Univ. of Wyo., Laramie, Wyo.,Jan.1962.
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C-4
Table C-2. Irrigated Land Use, Lyman
Project,
Wyoming, 1950
and 1958. 1/
Crop
1950
1958
acres
percent
acres
percent
Alfalfa
2,402
6.0
1,983
6.2
Wheat
701
1.8
none
Barley
2,361
5.9
81
.3
Oats
2,765
7.0
301
.9
Sunflower silage
none
107
.3
Rotation pasture
6,398
16. 1
306
.9
Meadow hay land
5,430
12.7
12,992
40.3
Permanent pasture
18,900
47.6
15,984
49.6
Potatoes
262
0.7
none
Farmstead & Others
481
1.2
464
1. 5
Totals
39,700
100.0
32,218
100.0
JL/ Does not account for all irrigated land in the project area. Accord-
ing to the Bureau of Reclamation, the total irrigated acreage approximates
50,000 acres.
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C-5
OUTDOOR RECREATION
Present recreational activity in the Lyman project area is limited
primarily to fishing and hunting in and near the Uinta Mountain range.
Tourists and other travelers moving through the study area on U.S. High-
way 30 add significantly to the area's source of basic income. Their
impact is concentrated primarily in service station sales and motel
receipts. Future development in activities oriented to recreation is
likely. 1/ The area has not kept pace with the rest of southwestern
Wyoming in developing tourist facilites and it is therefore anticipated
that an effort will be made to expand this source of basic income.
SUMMARY OF CURRENT AND EXPECTED FUTURE ECONOMIC ACTIVITY
The study area's economy is dependent almost entirely upon agricultural
production at the present time and this is expected to continue to 1980.
Approximately 50 percent of the farm operators supplement their income from
off-farm employment. A slight decrease in irrigated acreage is expected
to occur by 1980 but the farm population level is expected to remain more
or less unchanged. Overall population is likewise to remain more or less
constant at the present level.
Present employment opportunities in and near the study area are limited
--a tourist service center at Little America, Wyoming, Westvaco's trona
plant, a few sawmills, road construction and some local business. No major
increase in the various sectors of the local economy appear feasible to the
year 1980. Beyond 1980, as industrialization becomes more important to the
economy of southwestern Wyoming, some increase in local economic activity
can be anticipated, but water demands that may develop beyond 1980 are
expected to be met from Fontenelle Reservoir. This activity will likely
include a pulp mill at Granger, some manufacturing, and continued expansions
of those businesses dependent upon tourists and other travelers.
\J Personal interview with staff members of the Division of Business and
Economic Research, University of Wyoming, Laramie, August 29, 1962.
-------
SECTION p. WATER REQUIREMENTS AND USE
PRESENT WATER USE
Irrigation is by far the predominant water use in the project area.
Public water supplies constitute a small use due to a relatively low
population density. At the present time no water is being used for manu-
facturing or other industrial purposes.
PUBLIC WATER SUPPLIES
No towns in or adjacent to the project area utilize the Blacks Fork or
Smiths Fork as a source of domestic water supply. Water supplies within
the general vicinity of the potential project are summarized in Table D-l.
Table D-l. Public Water Supplies in the Blacks Fork Basin near the Lyman
Project Area, Wyoming
Community
Source
Est. Popula-
tion Served
Treatment
Remarks
Ft. Bridger
Indv. wells
_ -
None
—
Granger
Well
120
Chlorination
Kemmerer
Hams Fork
2900
Chlorination,
Also serves
filtration
Diamondville
& Frontier
Lyman
Springs
483
Chlorination
--
Mt. View
Well
400
None
In general, individual water supplies are obtained from wells that are
developed at a depth of approximately 50 feet. A few deeper wells have been
developed resulting in artesian flows. There are several springs in the
area. Shallow wells, producing water of poorer quality, may be developed
at depths of about 15 feet.
IRRIGATION WATER USE
One of the first water rights in Wyoming was a territorial permit for
an irrigation diversion from Blacks Fork which was issued in 1862. Over
time, rights to use water in Blacks Fork and Smiths Fork and their tribut-
aries have been adjudicated for the irrigation of 82,380 acres, approximate-
ly 82,000 acres of which are located in the Lyman Project area. The
adjudication permits diversions at the rate of approximately 1 second-foot
of water for each 70 acres of land under irrigation. The period of use, how-
ever, was not defined. The Bureau of Reclamation estimates that about 50,000
acres are actively under irrigation. 1/
1/ Approximately 34,100 acres are irrigated from the Blacks Fork and minor
tributaries and 15,530 acres are irrigated along the valley formed by the
Smiths Fork.
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D-2
No records have been maintained of past water uses in the project area.
Data are available, however, on total depletions occurring in the project area
and these may be used to give a rough approximation of average annual irri-
gation use. On the basis of the difference recorded at gaging stations below
the mouth of Smiths Fork on Blacks Fork near Lyman and records available for
above the head of these irrigation lands, a present depletion of 64,200 acre-
feet is indicated. Since irrigation currently practiced is dependent upon
natural stream runoff, most of this diversion occurs during the period of
spring runoff. This results in overirrigation during the early part of the
irrigation season and extreme shortages during the later season irrigation
period. Present water supplies would average only 50 percent of a full
supply, based on an ideal demand. Only about 3,000 acres presently under
irrigation would receive a full supply.
EXPECTED FUTURE WATER USE
Expected future water use from supplies developed by the Lyman Project
will be limited primarily to irrigation. Future municipal and any industrial
water supplies are not expected to be taken from Smiths Fork or Blacks Fork
below the project area, but are expected to be supplied by Fontinelle Reservoir.
Irrigation demands are expected to exceed supplies, even after the Lyman Project
is put into operation. The project is expected to supply almost 50,000 acre-
feet of additional irrigation water for some 36,000 acres of potential project
lands, (Table D-2). Non-project lands would continue to receive direct diver-
sions. Based on the Blaney-Criddle method of analysis, the Bureau of Reclamation
has estimated that an annual diversion of 4.7 acre-feet will be needed per acre
of crop production in the Blacks Fork area and 4.4 acre-feet per irrigated
acre will be required in the Smiths Fork &rea.
Table D-2. Summary of Project Water Supply, Proposed Lyman Project
Average Annual Increase in
Irrigation Diversions
Active (Acre-Feet)
Reservoir
Irrigation
Capacity
Storage
Releases
Increased
Return Flow
Total
Meeks Cabin
on Blacks Fork
30,000
27,000
10,400
37,400
China Meadows
on Smiths Fork
10,000
8,900
2,700
11,600
Project Totals 40,000 35,900 13,100 49,000
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SECTION E. WATER QUALITY CONSIDERATIONS
PRESENT STATUS
SURFACE WATER SITUATION
The quality of the water of Blacks Fork and its tributaries above the
presently Irrigated area is considered satisfactory for municipal and
industrial purposes. Chemical quality data pertaining to the surface waters
appear in Table E-l and E-2. Data from the Bureau of Reclamation indicate
that the total dissolved solids of Blacks Fork water ranges from about 50-
135 ppm 15 miles southwest of Millburne above irrigation return flows, whereas
near Urie, about 10 miles below Millburne and below irrigation return flows, the
water is generally of poor quality as total dissolved solids range from about
700 to 3,200 ppm. Below the confluence with Smiths Fork the total dissolved
solids In the Blacks Fork range from about 700 to 5,000 ppm. The maximum
determined total dissolved solids in Smiths Fork Creek water above Robertson
was 159 ppm. In general, water of good chemical quality is available in the
Blacks Fork above Millburne and in Smiths Fork above Mountain View,
Some small areas in the bottom lands contain large salt concentrations
on the surface. Lands northeast and southeast of Lyman are high in soluble
salts which are believed to result from the shale strata that underlies the
soil. Proper application of irrigation water and drainage measures would tend
to remove some of these salts. Return flows from presently irrigated lands in
these areas are reflected in the total dissolved solids ranging from 671 to
4,912 ppm on samples collected from Blacks Fork Creek near Lyman.
GROUND WATER SITUATION
The potential project development is not expected to be detrimental to
ground water supplies now utilized for domestic purposes in the project area.
SEWAGE DISPOSAL
In general the individual open country and town homes are equipped with
modern plumbing and utilize septic tanks and subsurface disposal of waste
waters where the public sewers are not available. It is estimated that about
25 percent of the homes do not have satisfactory waste disposal systems. Good
subsoil drainage is encountered in the area, with the exception of some bottom
land areas and on low benches where the impervious shale strata is close to
the surface and natural drainage channels do not exist.
Municipal waste disposal facilities for the communities in and adjacent
to the project area having public waste collection systems are summarized in
Table E-3.
-------
Table E-l. Chemical quality of surface waters* in the Lyman Project Area
Smiths Fork
Blacks Fork
East Fork
West Fork
Blacks
i Fork
near .
Millburnei/
near .
Robertsonf/
near .
Robertson^/
Near
Robertson
Near
Mt. View
Near
Urie
Near
Lyman
Concentration
V59-10/61
V59-2/6l
5/59-10/61
V59-5/59
5/59-3/61
V59-3/6l
V59-3/62
(ppm)
(22)
(20)
(19)
(2)
(21)
(25)
(33)
Dissolved solids
135
85
159
116
472
3,150
it, 912
2k
20
25
99
152
716
671
Hardness
127
67
120
92
216
1,5^5
1,709
(Computed)
20
13
18
82
87
35^
269
Calcium
36
25
36
27
63
395
386
5
5
6
25
22
82
72
Magnesium
9
k-
7
6
14
136
182
1
0.1
0.6
4
7
36
21
Sodium
k
3
5
7
81
327
773
1
1
1
5
15
90
96
Chlorides
2
1
28
4
73
102
183
0
0
0
3
10
30
k6
Sulfates
20
16
15
19
153
1,760
2,961
(Computed)
2
0
1
11
16
276
232
* Data from Bureau of Reclamation, Region U. Number in parenthesis represents number
of samples. Maximum and minimum values shown.
1/ 15 miles southwest.
2/ 9 miles southeast.
3/ 12 miles southvest.
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E-3
Chemical quality and river flows—select stations* near
the Lyman Project Area
Green River near
Concentration;/ Green River, Wyo.^/
Blacks Fork near
Marston, Wyo.3/
Green River
near
Greendale,
Utah—/
740
855
2,360
4,U8o
730
Dissolved solids
164
159
3^5
278
237
279
-
519
-
359
383
420
950
1,980
4oo
Hardness
118
ll4
156
48
143
170
-
262
-
203
90
213
100
Calcium
28
57
4o
^5
72
-
4o
106
33
Magnesium
9
l4
11
lb
20
-
97
397
Ill
Sodium
12
4o
20
27
74
-
14
133
56
Chlorides
2.4
21
8
5
35
-
328
1,430
335
Sulfates
33
87
63
89
193
-
10,290 2,766 15,200
Discharge (cfs) 357 9 1+00
2,048 379 2,677
* U.S.G.S. water supply paper 1523-
1/ Multiple entries represent maximum, minimum, and weighted values.
2/ 1 mile southeast of town of Green River.
3/ 12 miles upstream from 1/ above.
5/ 1/2 mile below Flaming Gorge Dam.
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E-4
Table E-3. Waste Disposal Facilities in Blacks Fork Basin
Community
Estimated
Population
Served
Treatment
Discharged
to
Diamondville
Ft. Bridger
Individual facilities
Individual facilities
Individual facilities
Frontier
Granger
Kemmerer
160 Septic tank
2030 None but oxidation pond
planned
100 Oxidation pond
400 Oxidation pond
Blacks Fork
Lyman
Mt. View
Hams Fork
Blacks Fork
Smiths Fork
CONSTRUCTION PHASE OF PROJECT
Limited housing accommodations are available within a 50-mile radius
of the construction area to serve the contractors' employees during the
construction phase of the project. Under these conditions a temporary
construction camp may be necessary. A sanitary survey of all proposed
construction camp sites by the State Department of Public Health would be
desirable to assist in solving of problems that may have a public health
significance.
Adequate sanitary facilities to serve temporary camps as well as
permanent housing should be included with construction plans so as to
eliminate pollution of surface waters. The establishment of a trailer
park or temporary construction camp in a National Forest requires a
special use permit from the Forest Service to cover the sites and plan
approval by the Wyoming State Department of Public Health to insure the
installation of proper sanitary facilities.
Project development will help to improve the local economy and increase
the opportunity for residents to enjoy a higher standard of living. Some
of the more important factors in creating a healthful environment include
the development of safe and ample water supplies, proper waste disposal
facilities, and insect and rodent control measures. District Health Unit
No.„ 2 of the Wyoming State Department of Health with headquarters in Rock
Springs is available to assist the inhabitants of the project area on
environmental health problems. The Wyoming State Department of Health
headquarters staff provides supplementary public health services in Uinta
County.
Recreation facilities are planned for all reservoirs. In addition to
recreational activities on the reservoirs, fishing will be enhanced by the
series of fish ponds proposed in the 8-mile stretch of the Blacks Fork
below the potential Meeks Cabin Dam and reservoir. Existing resorts in the
project area provide limited recreational activities. In addition to the
FUTURE SITUATION
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E-5
planned development of recreational activities in the overall water resource
development plan, the spontaneous occurrence of recreational areas following
the filling of reservoirs necessitates the need for adequate sanitary facilities
and safety measures as protection against health hazards.
Water supplies and sanitary facilities at all recreational areas should be
constructed and maintained in accordance with the Wyoming State Department of
Public Health standards.
The dissolved solids concentration in Blacks Fork downstream of the pro-
posed project is expected to increase over present levels, primarily due to
the contemplated reuse of irrigation return flows which already have high
concentrations. However, no water uses are expected to develop that would be
affected by this level of dissolved solids. Blacks Fork will flow into the
reservoir on Green River formed by Flaming Gorge Dam. Considering the relative
flows and relative water quality of Blacks Fork and Green River, the effect of
the future water quality of Blacks Fork on the Green River is expected to be
slight.
STREAM FLOW REGULATION FOR WATER QUALITY CONTROL
On the basis of a preliminary evaluation of the probable future economy
of the Lyman area, there appears to be little likelihood that downstream bene-
ficiaries of water quality control will locate below the project area. Approxi-
mately 13,100 acre-feet of irrigation return flow will be developed by the
operation of the proposed project and this supply will be used for irrigation in
the lower portion of the Basin. The quality of these return flows is expected
by the Bureau of Reclamation to be suitable for the downstream irrigation.
The water needs of the future economic development downstream of the project
area are expected to be met by the storage in Fontenelle Reservoir on the Green
River. Between the area of expected limited municipal and industrial growth
near Granger and Westvaco and the mouth of Blacks Fork, there does not appear to
be any need for higher quality water. The wastes from these developments are
not expected to affect any other uses of the stream. Therefore, the need for
storage of water in either Meeks Cabin or China Meadows Reservoirs for the pur-
pose of stream flow regulation for water quality control is not apparent at this
time.
-------
SECTION F. VECTOR EVALUATION OF THE PROPOSED BUREAU OF RECLAMATION
LYMAN PROJECT. UINTA COUNTY, WYOMING
NATURE AND EXTENT OF MOSQUITO AND OTHER VECTOR PROBLEMS
In September 1959 and May and July 1960, field reconnaissances of the
Lyman Project area were conducted to determine (1) the kinds and abundance
of mosquitoes and other vectors in the area; (2) existing sources of these
vectors; (3) effect of the proposed project on vector problems; and (4)
measures which might be incorporated into the design, construction, and
operation of the project to minimize vector production. Based on field
observations, mosquitoes appeared to be the vectors of major public health
importance in the area. At several locations in the project area deer flies
and horse flies were prevalent and annoying and biting specimens were col-
lected for identification.
PUBLIC HEALTH AND SOCIO-ECONOMIC IMPORTANCE
Encephalitis, commonly known as sleeping sickness or brain fever, is
now the most important mosquito-borne disease in the United States and in
the area in which the proposed project will be located. Mosquitoes transmit
the encephalitis viruses among birds and from them to humans and horses.
There are no effective chemotherapeutic measures for preventing or treating
human cases, and some individuals, particularly children, who recover from
encephalitis often suffer permanent mental disability.
Records of the U. S. Department of Agriculture show that equine encepha-
litis cases occurred in Uinta County, Wyoming and/or neighboring counties
during 11 years of the 17-year period, 1939 through 1955, for which records
are available. During several years, Uinta County had an incidence in
excess of 5 encephalitis cases per 1,000 horses.
Although no human outbreaks of encephalitis have been reported in Uinta
County, the records of equine encephalitis indicate that the viruses of this
disease are present in the area. Since encephalitis virus is active in the
area and Culex tarsalis, the primary vector, is present, future outbreaks of
the disease may occur among horses and humans.
The vicious-biting Aedes mosquitoes may create public health problems
by interfering with the healthful outdoor activities of both children and
adults during the summer months. Individuals, particularly children, fre-
quently require medical attention and sometimes hospitalization for treatment
of secondary infections and allergic reactions resulting from mosquito bites.
In addition to their public health importance, large numbers of biting
mosquitoes also cause severe economic losses by lowering meat and milk pro-
duction, by reducing the efficiency of agricultural and industrial workers,
by interfering with recreational enterprises, and by lowering the value of
real estate.
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F-2
Several other groups of aquatic insects may be produced in sufficient
numbers in habitats associated with water resource projects to create public
health and economic problems. Deer flies and horse flies are often produced
along the margins of impoundments and in seeps and marshes in irrigated areas.
These insects are vicious biters of both man and livestock and are sometimes
involved in the transmission of disease such as tularemia and anthrax. Several
species of small gnats of the family Heleidae are vicious biters and often
produce severe reactions and vesicular lesions. These gnats are produced in
damp acreas of many irrigated valleys as well as alkaline marshes and other
wetland areas. Black flies plague both man and livestock with their irritat-
ing and painful bites. They normally breed in streams, but are sometimes
produced in large numbers in irrigation conveyance systems, particularly drop
structures and other water control devices where the flow is relatively fast.
Vectors of terrestrial origin, including arthropods such as ticks, mites,
fleas, and flies, and rodents such as ground squirrels, chipmunks, and mice
may be important at recreational sites along the shores of reservoirs. In
addition to the irritation, discomfort, and annoyance caused by the arthropod
bites, the public health importance of these vectors involves a number of
human diseases including Rocky Mountain spotted fever, Colorado tick fever,
relapsing fever, tick paralysis, dysentery, typhoid, tularemia, typhus, and
plague.
VECTOR SPECIES COLLECTED IN THE AREA
Mosquitoes.--Aedes increpitus, Aedes vexans, and Aedes dorsalis were the
predominant mosquito species collected during the surveys. Prolific produc-
tion of these vicious-biting mosquitoes was observed in flooded meadows and
marshy roadside ditches in the vicinity of Millburne and Robertson in May
1960. In July 1960, prolific production of A. vexans was found also in over-
flow pools and other undrained surface depressions along Black Fork in the
vicinity of Millburne. Larvae of Culex tarsalis, the primary vector of
encephalitis in the West, were found in considerable numbers during July, in
association with larvae of Culiseta inornata, a suspect enzootic vector of
encephalitis. The major sources of C. tarsalis and C. inornata appeared to
be seepage area, marshy roadside ditches, and flooded borrow pits along
secondary roads where drainage is blocked by unculverted turnins which pro-
vide acess to farmsteads and fields.
Deer Flies and Horse Flies.--Adults of Chrysops discalis, a vicious-bit-
ing deer fly, and Tabanus Lineola, a highly annoying horse fly, were collected
at various localities in the project area. In addition to the annoyance re-
sulting from the bites of these flies, C. discalis is considered an important
vector of tularemia in western North America. Marshes and seepage areas
prevalent in the project area appear to be favorable for the production of
deer flies and horse flies.
GENERAL RELATIONSHIPS BETWEEN IRRIGATION AND VECTOR PROBLEMS
The production of mosquitoes and other aquatic insects of public health
importance is widespread in many irrigation areas. Natural breeding places
occur in mofit irrigated areas, but usually the man-made mosquito sources are
-------
F-3
frequently caused by the same faulty irrigation and drainage practices that
cause serious soils and water problems such as excessive water losses, water-
logging, erosion, salt and alkali accumulations, damage to soil structure,
leaching of plant nutrients, and reduced crop yeilds. Mosquito sources
commonly associated with irrigation may be grouped into three principal
categories: (1) those related to storage reservoirs; (2) those related to
irrigation conveyance systems; and (3) those related to use of irrigation
water on the farm and the disposal of excess water.
The condi .tions associated with storage reservoirs which are conducive
to mosquito production include emergent vegetation and/or flotage and
debris in shallow water areas and embayments that are protected from wave
action; undrained depressions, borrow pits, sloghs, and swamps within the
fluctuation zone; rising or constant pool levels which cause the water to
remain in the marginal vegetation for more than four or five consecutive
days during the mosquito breeding season; and marshy seeps below dams. It
is often difficult to control mosquito production on a reservoir that has
not been properly prepared prior to impounding. The principal preimpoundage
preparation measures for mosquito control include: clearing of the r.eservoir
basin; final removal of vegetation from the fl^uGifruateion zone prior to im-
pounding; and drainage for depressions, sloughs., -tarid.-swamps within the
fluctuation zone. Of paramount importance is>the fact that the maximum
benefits from water level management for mosquito-'C-onfrro 1 can be realized
only when the reservoir has been properly prepared. ; Several phases of
water level control, particularly flood surcharge,''constant level pool,
and cyclical fluctuation and/or seasonal recessions can-< sametimes be adapted
to irrigation storage reservoirs in order to minimize* -conditions favorable
for mosquito production. A particular phase may '-bemused primarily to destroy
mosquito larvae, or it may be directedat vegetatromoor flotage favorable for
mosquito production. A flood surcharge above the upper normal pool level for
a few days in the spring prior to the mosquito breeding season followed by
a sharp drawdown is effective in stranding objectionable flotage. The in-
vasion of marginal vegetation can be limited by holding*the reservoir at a
constant level during the early spring growth period. 'This phase is especially
important since it will increase the effectiveness of sajtsequent fluctuation
or recession. Seasonal water level recession used alone
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F-4
valuable agricultural lands Mosquitoes are also produced in various other
types of water areas associated with irrigation conveyance systems. Typical
examples are ponded areas where canals block natural drainageways, residual
water in turnout structures, stilling basins and other hydraulic structures,
and pools caused by leakage from turnouts and other water control structures.
Although such habitats are generally of minor importance in comparison with
those caused by seepage and the numberous other breeding places that occur
in irrigated areas, they also contribute to the overall mosquito problem.
In many irrigated areas, the .nost important mosquito sources are those
associated with the use of water on the farm and the disposal of excess water.
Studies on several operating irrigation projects have shown that mosquito
sources in this category are usually caused by poor irrigation and drainage
practices that also result in serious agricultural problems, including re-
duced crop yields. These practices include inadequate land preparations;
use of field layouts and irrigation methods that do not fit land, crops, and
water supply; application of water in excess of crop requirements; inadequate
drainage systems for disposal of excess water, and poor maintence of distri-
bution and drainage systems. All of these practices contribute to the develop-
ment of both "on-field" and "off-field" aquatic habitats which are favorable
for prolific mosquito production. Permanent and semipermanent aquatic habitats
produce large number of C. tarsalis, and intermittently flooded areas produce
tremendous numbers of Aedes mosquitoes.
Mosquito sources on irrigated fields have been found to occur iaost often
on those used for pastures, hay meadows, and other close-growing crops® In
order for the aquatic stages to mature and produce adult mosquitoes, ponded
water must be present for at least four or five days. Observations in several
irrigated areas have shown that when water is ponded on fields long enough
to produce mosquitoes, the better forage grasses and legumes are frequently
killed and replaced by undesirable wetland plants.
Heavy mosquito production also occurs in numberous "off-field" aquatic
habitats. Many of the mosquito sources located outside irrigated fields are
caused by improper disposal of excess water. Roadside ditches, borrow pits,
depressions on wasteland, and numerous other undrained areas are flooded
by excess irrigation water when farm and trunk drainage systems are inadequate.
Such habitats produce large numbers of C. tarsalis and other mosquitoes of
public health importance.
FACTORS RESPONSIBLE FOR MOSQUITO-PRODUCING HABITATS IN THE PROJECT AREA
It was observed that mosquito-producing habitats in the project area
are largely associated with poor irrigation and drainage practices. In many
cases, the meadows and pastures have not been leveled or graded. Many of
these unleveled, hu.nmocky meadows are irrigated by wild flooding and are
inadequately drained, resulting in prolonged ponding which provides favorable
conditions for the production of mosquitoes. Due to the inadequacy or lack
of drainage facilities, excess runoff from the meadows collects in roadside
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ditches, sloughs, marshes, and other undrained depressions creating numerous
"off-field" aquatic habitats that produce tremendous numbers of mosquitoes.
Seepage from unlined canals and the high water table resulting from excessive
application of irrigation water also results in numerous aquatic habitats
highly favorable for production of C. tarsalis and other irrigation mosquitoes.
During the period of high flows in the spring, low-lying areas adjacent
to the streams and distribution canals are flooded. This condition also
results in the production of large numbers of mosquitoes, particularly A.
vexans, a highly annoying floodwater species. It was noted that many of the
aquatic habitats producing tremendous numbers of mosquitoes in the project area
could be eliminated by installation of culverts to provide drainage of road-
side ditches and borrow areas and by other minor drainage work.
ANTICIPATED EFFECTS OF THE PROJECT ON VECTOR PROBLEMS
The reduction in flooding of lowland areas located downstream from the
proposed reservoirs should result in a reduction in natural aquatic habitats
which are favorable for the production of mosquitoes and other aquatic insects
of public health importance. Portions of the reservoirs that have steep shores
with little or no vegetation and are exposed to strong wave action will be un-
favorable for the production of nosquitoes and other aquatic insects of public
health importance. Mosquitoes and other aquatic insects of public health
importance may be produced in tributary embayments and other marginal areas
of the reservoirs where the topography is flat and the water is shallow, pro-
tected from wave action, and contains emergent vegetation or flotage. In such
areas appropriate .ueasures for prevention and control of aquatic vectors
should be provided. The development of recreational and other puhlic use areas
at various locations along the shores of the reservoirs may result in the
exposure of hu.ians to vectors of terrestrial origin including arthropods such
as ticks, fleas, flies, and rodents such as ground squirrels, chipmunks, and
mice. In order to minimize public health hazards at waterside recreational
areas, appropriate prevention and control measures for both aquatic and
terrestrial vectors should be carried out.
The proposed lining of canals should minimize seepage areas which are
favorable for mosquito production. Likewise, the proposed drainage should
eliminate and prevent numerous mosquito sources. Additional measures of
these types may be needed after the project is in operation. Since many of
the more serious existing mosquito sources in the area are associated with
poor irrigation and drainage practices employed by the water users, every
effort should be made to encourage farmers to use improved irrigation and
drainage methods to prevent and minimize mosquito sources.
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