United States
Environmental Protection
Agency
Environmental Research
Laboratory
Athens, GA30613
Research and Development
EPA-600/S3-82-069 May 1984
Project Summary
Trends in U.S. Irrigation:
Three Regional Studies
Kenneth D. Frederick, James Hanson, James Pagano, Robert N. Shulstad,
Ralph D. May, Billy E. Herrington, and Jon M. Erstine
Three separate reports, each dealing
with irrigation in a different region of
the United States, are brought
together in this volume. Although they
are disparate in approach and level of
effort, combined they provide a
comprehensive view of the prospects
for irrigated agriculture in the United
States over the next several decades.
The three studies are "Western
Irrigation: Its Past and Future
Growth" by Kenneth D. Frederick,
"Growth and Prospects for Irrigation
in the Eastern United States" by
James Hanson and James Pagano,
and "The Economic Potential for the
Expansion of Irrigation in the
Mississipi Delta Region" by Robert N.
Shulstad, Ralph D. May, Billy E.
Herrington, and Jon M. Erstine.
This Project Summary was dev-
eloped by EPA's Environmental
Research Laboratory, Athens. GA, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Western Irrigation
This study is a systematic attempt to
assess both the current and the future
role of western irrigation in producing
the nation's farm output and the
resource and environmental pressures
affecting and stemming from western
irrigation. Past trends, water supply
conditions, water institutions,
economic forces, and environmental
factors are examined for their impacts
on the course of western irrigation over
the next two to three decades. The
influence of these institutions and
economic forces on resource use
efficiency and environmental consid-
erations also are considered along with
the broad policy implications of the
analysis.
Past Trends
The addition of about 25 million
irrigated acres in the West was an
important factor in the ability of
American farmers to increase crop pro-
duction by 70 percent from 1950 to
1977 without any net increase in total
harvested acreage. A very rough
estimate of the impact of irrigation of
four principal crops on agricultural land
use suggests that the higher average
yields obtained on these irrigated lands
reduced the harvested land required to
produce the 1977 national output of
corn, sorghum, wheat, and cotton by 7
million acres. Furthermore, by making
high productivity farming possible in
arid areas, irrigation has expanded the
acreage suitable for agriculture by
about 10 to 13 million acres.
Analysis of four principal crops—corn,
sorghum, wheat, and cotton—suggests
that, while western irrigation had a
significant impact, it was not the
principal factor underlying the impress-
ive increases in national average crop
yields from 1950 to 1977. The
combination of the improved yields on
irrigated farms and the increase in the
relative acreage devoted to irrigation
accounted for 13 percent of the national
rise in corn yields, 16 percent for
-------
sorghum, 7 percent for wheat, and 44
percent for cotton. Irrigation's contribu-
tion to production increases was even
greater; 28 percent of the national
increase in corn production over this
period was on irrigated lands, 20
percent for sorghum, 12 percent for
wheat, and 175 percent for cotton.
Examination of changes in the rate
and location of the growth of western
irrigated acreage indicates two broad
trends that are likely to continue in the
future. The rate of growth of irrigated
acreage has declined steadily over the
last three decades, and the locus of the
growth has moved from the south to the
north. From 1945 to 1954,79 percent of
the growth of irrigated acreage was in a
southern belt extending from Texas and
Oklahoma to California. In subsequent
decades, this region contributed 31
percent and then only 1 percent of the
overall growth of western irrigation. In
contrast, the central and northern High
Plains contribution to the expansion of
western irrigation rose from about 10
percent from 1945 to 1954 to over 90
percent from 1964 to 1974.
Water Supplies
Total surface water withdrawals for
irrigation have fluctuated around a level
trend since the 1950's, and the
combined impact of several factors
suggests this situation may continue for
several more decades. First of all, total
water requirements exceed average
year streamflows within the West's
principal irrigated areas and there is
little water available for expansion in
most of the other areas. Where there is
water for expansion, the increases will
go primarily to nonagricultural users
who can afford to pay higher water
costs. The comparative stability of
surface water use for irrigation in the
face of increasing water scarcity
reflects in part the insulation of most
surface water costs from both market
considerations and rising energy costs.
Undoubtedly, there will be transfers of
water from agricultural to other uses,
particularly within the water-scarce
areas, as farmers are presented with
increasing opportunities to sell their
water rights. However, since large
percentage increases in other water
uses can be accomodated with small
changes in irrigation water use, at least
over the next several decades, the
impacts of such transfers on irrigation
will be gradual and relatively minor from
the perspective of the entire West.
Moreover, transfers of water rights from
irrigation to other uses in the water-
scarce areas are likely to be offset in part
by modest increases in irrigation within
the regions where surface water is still
available for appropriation. Federal
irrigation projects, which are
encountering increasing resistance to
their high investment costs and the high
opportunity costs of diverting more
scarce water to irrigation, will not make
any further significant contribution to
the expansion of western irrigation.
For several decades, the growth of
western irrigation has been based on
groundwater withdrawals which rose
threefold between 1950 and 1975.
Currently groundwater withdrawals,
which account for about 39 percent of
all western irrigation water, result in
the mining of more than 22 million
acre-feet per year from western
aquifers. Even though groundwater
stocks are still large in relation to
current use and mining is not a threat to
exhaust physically the water stored in
any of the water resource regions or
subregions in the foreseeable future,
the combination of the overdrafts and
rising energy costs threaten the
economic supply of water for many
irrigators. In some regions, especially
the High Plains, the combination of
increasing pumping depths, declining
well yields, and rising energy costs
already has started to curtail pumping
and irrigated acreage. In the absence of
sharp increases in real crop prices,
future expansion likely will be limited to
areas with relatively low pumping
depths or access to energy supplies
under relatively favorable terms. But
combining one or both of these condi-
tions with favorable growing conditions
will become increasingly rare.
The water available for irrigation is
not likely to be augmented significantly
in the next several decades through
development of unconventional
sources of supply. Although some
forms of weather modification, particu-
larly winter cloud seeding, appear
technologically and economically
promising, institutional obstacles are
apt 19 inhibit its widespread adoption.
Cost factors associated in part with
their high energy intensity suggest that
water importation and desalinization of
seawater will not be profitable for use in
irrigation. And a combination of cost,
technical, and institutional uncertain-
ties make icebergs an unlikely source of
western water for the foreseeable
future.
Institutional Factors
Western water law and management
institutions were developed when
water was plentiful in relation to
demand. Important objectives of early
water law and policy were to give
investors clear and unambiguous title to
water rights, to encourage the
development of water resources, and to
minimize uncertainty and conflict
among users.
Today, the West faces a situation
where the water is scarce in relation to
demand and the costs of developing
new supplies are high in relation to its
value in irrigation. Urban, industrial,
recreational, and wildlife needs for
fresh water are becoming increasingly
competitive with irrigation. Yet, there
has not been a corresponding
adjustment in the laws and institutions
that control and manage the resource.
All too often the laws and institutions
governing water use limit rather than
facilitate the transfer of water to higher-
valued uses and stifle rather than
encourage conservation measures.
Such deficiencies are common with
most state water institutions, but they
are especially severe in the case of
federal projects that provide irrigators
enormous subsidies but little to no
opportunity or incentive to benefit from
conservation.
Groundwater users do not have the
security of long-term access to low cost
water enjoyed by the owners of senior
surface water rights. Groundwater
supplies often are depletable resources
threatened by the addition of new wells,
and the costs of pumping are closely
linked to energy costs. Individually,
pumpers have improved the efficiency
of their water use; collectively they have
sought government help in limiting
depletion and curbing water cost
increases. Many states have enacted or
are considering legislation to limit
pumping in order to extend the life of the
aquifers. In terms of achieving a long-
term efficient use of the resource, one
problem with the current groundwater
situation is that farmers' costs do not
include the loss to neighboring farmers
and future users of depleting an aquifer.
Theoretically, taxes on pumping could
internalize these costs, but practically, it
would be difficult to approximate the
ideal level for such a tax, and any tax
would be strongly resisted by pumpers.
-------
Economic Factors
In general groundwater irrigators pay
the most for their water and are the most
susceptible to further cost increases
stemming from both rising energy costs
and declining water levels. Groundwater
costs vary widely depending on the
pumping depth and the type and cost of
the fuel. For a typical farmer pumping
from 200 ft. with electicity, water at the
wellhead costs about $24/acre-foot;
distributing this water through a center
pivot system adds another $20 to
$30/acre-foot to irrigation costs
(assuming 1980 energy prices and
deflating all costs to 1977 constant
dollars). A doubling of electricity prices
would add another $32 to the costs of
irrigation if no adjustments were made
to the higher energy costs. Such cost
levels would make it difficult to irrigate
profitably grains, cotton, many other
crops in the absence of significant
increases in crop prices. Farmers
confronted with even higher pumping
depths and declining aquifers will be
even harder pressed to compete in the
absence of crop price increases.
Surface water costs also vary widely
depending on the distance and height
the water must be transported to arrive
at the farm, the availability of subsidies,
and the need for on-farm pumping to get
it to the field. Surface water costs,
however, tend to be considerably lower
than and not as subject to change as
groundwater costs. Farmers with senior
rights to surface waters that can be
distributed through gravity have the
lowest costs and are the least suscept-
ible to future changes. For these fortun-
ate farmers, water is virtually a free
resource, and it is probably treated as
such unless the farmer has an oppor-
tunity to sell or put to alternative uses
any water saving. Another fortunate
group of irrigators comprises the farmers
receiving water from federal water
projects. This highly subsidized water is
used on nearly 20 percent of the West's
irrigated acreage.
Most irrigators have a wide range of
opportunities for responding to high
energy and water costs short of
abandoning irrigation. Measures such
as improving pump efficiency, tailwater
re-use systems, and irrigation
scheduling already are profitable under
a variety of conditions. Future
innovations undoubtedly will provide
further opportunities for increasing the
yields per unit of irrigation water and
reducing the cost of water. But since
technological developments will not be
limited to irrigated agriculture alone,
they are not likely to alter the adverse
impacts rising energy costs and water
scarcity are having on the profitability of
irrigated relative to dryland farming. On
the other hand, if real crop prices rise as
some analysts predict, irrigators with
their higher than average yields will
tend to benefit more than dryland
farmers.
Environmental Factors
There are a variety of environmental
problems associated with irrigation but
the only ones likely to have any
significant effect on the role of
irrigation are groundwater depletion,
low streamflows, and salinity.
Current water requirements defined
to include mstream uses exceed
average streamflows in the most
favorable areas for irrigation. Analysis
undertaken by the U.S Department of
Agriculture suggests irrigated acreage
might have to be reduced by about 20
percent to ensure sufficient water is left
in the streams for optimum fish, wildlife,
and other environmental values.
An estimated 25 to 35 percent of the
West's irrigated lands have salinity
problems. But the lands where salinity
is likely to significantly curtail product-
ion comprise a much smaller percentage.
The productivity of several mill ion acres,
primarily in the lower Colorado River
Basin and California's San Joaqum
Valley, are threatened by high salt
levels. The annual damages to
agricultural plus municipal and
industrial users of the salt-laden waters
already probably exceed $100 million,
and they undoubtedly will rise unless
preventive measures are taken.
Improved basin-wide and on-farm water
management have great potential for
reducing salinity levels and mitigating
the damages from high salt levels.
However, institutional obstacles to
adopting basin-wide management
schemes and the high costs of some of
the structural measures that might
achieve the same result suggest an
increasing number of farmers will be
confronted with serious salt problems
Nevertheless, although the impacts will
be serious within the affected areas, the
overall impact on the productive
potential of western irrigation is not
likely to exceed 2 to 3 percent over the
next several decades.
Another environmental problem that
could affect the growth of irrigation over
the next several decades is
groundwater pollution from the
infiltration of agricultural chemicals
The most likely area to experience a
significant expansion of irrigation is the
Nebraska Sandhills, where agricultural
chemicals, especially nitrogen, are
readily leached into the groundwater
Good on-farm water management can
keep nitrate levels within tolerable
levels, but failure to adopt such
practices could lead to state
intervention to enforce better
management practices, possibly
limiting the growth of irrigation in the
area
Projections of Irrigated
Acreage
Over the next several decades
changes in total irrigated acreage will
depend in a large part on what happens
to agricultural prices. Although irri-
gation in many areas of the West is
constrained by physical and
institutional limits on developing new
water supplies, there are additional
lands with access to water for irrigation.
Within these areas, the important
constraints on irrigation are economic.
Significant increases in product prices
would offset the negative impacts of
high energy prices and increasing
pumping depths; the development of
new irrigated lands would be
stimulated, and the decline in irrigated
farming in areas with significant
groundwater mining would be slowed.
Even in the absence of significant
change in crop prices, some net
expansion of western irrigation seems
likely. Most of the expansion will be in
the Northern Plains states, and more
specifically within the Nebraska
Sandhills This area has considerable
potential for expansion, and based on
recent investments in wells and center
pivots, irrigation investment in the area
is profitable at current price levels.
Modest increases in irrigation within
the Dakotas is also likely although
irrigation will remain relatively unimprt-
ant in these states. The increases within
the Northern Plains will be partly offset
by some reduction in irrigation in the
Kansas and Nebraska High Plains.
The impacts of high energy costs and
declining groundwater tables will force
a significant decline in irrigation by the
turn of the century within the High
Plains of Texas and Oklahoma.
Increases in irrigated acreage within
the eastern areas of these states will be
-------
modest in comparison to the declines in
the western areas. Thus, with no
change in crop prices, a 2 million acre
decline in irrigation is likely for the
Southern Plains.
The Mountain region will experience
little net change in irrigated acreage but
within this large, heterogeneous area
comprising eight states, significant
changes in the location of irrigation are
likely. The southern areas and eastern
Colorado, where current levels of
irrigation are dependent on
nonrenewable water sources, will
experience some decline in irrigated
acreage. In the absence of high crop
prices, these declines will be offset only
in part by some modest increases in
irrigation within the rest of the
Mountain region.
In the Pacific region, a modest overall
expansion of irrigation is likely even
with no increase in crop prices.
California's irrigated acreage might rise
about 5 to 10 percent to roughly 10
million acres by 2000. While the Pacific
Northwest is the area least affected by
water shortages, the region's water is
becoming increasingly valuable for
alternative uses. Furthermore, very
inexpensive electricity is no longer
available for expanding pumping.
Consequently, additions to irrigated
acreage in the Northwest over the next
several decades are not likely to push
the totals for Washington and Oregon
much beyond 5 million acres without
significant crop price increases.
Overall, irrigated acreage in the West
will increase only about 6 to 7 percent
over the next two to three decades or
from about 50.2 million in 1977 to 53.5
million in 2000 to 2010. A 25 percent
increase in real farm prices might add
another 4.5 million irrigated acres in the
West, more than doubling the growth of
irrigated acreage over the next two to
three decades. This relatively low
anticipated sensitivity to real price
levels is primarily a reflection of two
factors-the fact that no foreseeable
crop price levels will make irrigation
competitive with most municipal and
industrial water uses and the
importance of institutional and resource
factors in determining the level of
irrigation.
Qualitative Changes in
Western Irrigation
The nature as well as the rate of growth
of irrigation will be very different from
the past when irrigated farming was
stimulated by the availability of
inexpensive water and energy. Water
withdrawals will be reduced as it
becomes more profitable both to make
water saving investments and to reduce
the water delivered to the plant, even if
it means some reduction in crop yields.
While total irrigated acreage may not
peak until the first decade of the next
century, total withdrawals for irrigation
probably will peak much sooner,
perhaps within the next decade.
Improved yields to water inputs and
shifts to higher-value crops will enable
the value of production from irrigated
farms to rise even after the quantities of
land and water in irrigation have peaked
and started to decline. Thus, both water
withdrawals and acreage are likely to
become increasingly poor indicators of
changes in the contribution of irrigated
output to national agricultural
production.
Policy Implications and
Conclusions
The policies, laws, and institutions
governing the use of western waters
were developed largely during a period
when water supplies were abundant
relative to demand. An important
objective of the 1902 Reclamation Act
was to stimulate settlement of the arid
West, and the subsidies built into
federal irrigation projects undoubtedly
encouraged western rural settlement
during the first five or sixdecades of this
century. Moreover, by providing
assurances of continued access to
water, state water laws helped attract
investment to the West.
Water is now a principal constraint on
further development, and the subsidies
and laws insulating many water users
from the increasing value of the
resource have become a deterrent
rather than a stimulant to development.
State laws and policies not only allow an
inefficient use of western water, they
ensure it by reducing or eliminating the
incentive and opportunities for trans-
ferring water to higher value uses.
Improving the efficiency of western
water use does not require forcing the
owners of water rights to pay for what
has been legally given to them. Indeed,
any attempt to abrogate these rights
would be futile and potentially
damaging to the region since it would
threaten the entire legal and institution-
al structure that has brought order to
the allocation of western water. A more
acceptable alternative for providing
incentives to conserve water in areas
where it is scarce is to allow and
facilitate the sale of water that is not
used by the owners of the water rights.
Then, even if a farmer does not have to
pay for the water, there would be an
opportunity cost to putting the water to
any particular use.
Since irrigation is a relatively low-
value user, a more market-oriented
allocation system is likely to transfer
water from irrigation to municipal,
industrial, and other uses. However,
these negative impacts on irrigation
might be more than offset by the added
incentive that would be provided to
increase the returns to the water used
in irrigation. A reduction in the
environmental damages from irrigation
practices would be a further benefit of
policies designed to make water costs
more nearly reflect the scarcity value of
the resource.
If the transition from water
abundance to scarcity allows for an
efficient use of the resources over time,
irrigation will contribute to agricultural
production and growth for many more
decades. Future potential lies primarily
in increasing the returns to water, not in
the development of new water supplies.
Realization of this potential requires
providing incentives to conserve water
and encourage the development of
more effective ways for farmers to
respond to higher water and energy
costs and salinity levels.
Eastern Irrigation
The study of eastern irrigation
represents a very modest research
effort to describe the past growth of
eastern irrigation and to assess the
prospects for increased irrigation in two
farm production regions, the Lake
States and the Southeast.
As of 1939, the 559,000 acres of
irrigated rice in the Delta region
accounted for about three-fourths of
acreage irrigated in the East; fruits and
vegetables in Florida accounted for
most of the remaining irrigation. By
1950 the Eastern States still only had
about 1.5 million acres under irrigation
or 6 percent of the national total. From
1950 to 1974, however, eastern
irrigation grew at an annual rate of 4.6
percent, nearly three times the rate of
growth of western irrigation. By 1977,
17 percent of the nation's irrigation was
in the East. Yet, irrigation still repre-
-------
sented only 3.5 percent of total eastern
cropland and pasture.
Several factors played a major role in
the expansion of eastern irrigation in
recent decades. Improvements in
irrigation technology have made
irrigation cheaper and more versatile.
The modern self-propelled sprinkler
systems have drastically reduced the
labor cost of irrigation, they are less
capital-intensive than the hand-moved
systems, and center pivots can operate
on sandier, hillier terrain with slopes up
to 9 to 10 percent. Furthermore, the
complementary inputs to irrigation
water—fertilizers, pesticides, herbi-
cides, machinery, and land itself-have
grown both more expensive and more
productive. This means that the "penalty"
paid in lower yields and unrecovered
costs of chemical inputs during drought
years is higher than before while,
conversely, the reward for having the
right amount of water at the right time is
greater.
Although rainfall in the East is
adequate in most years to provide good
yields to most crops, there are several
types of situations where irrigation is
likely to be feasible. Historically,
irrigation of rice varieties that require
flooding has been important in the Delta
region. Although the statistics on
eastern irrigation are no longer
dominated by rice, this crop still
accounted for 23 percent of eastern
irrigated acreage in 1969. Since
irrigation reduces the risk of crop loss
during dry periods, drought has
provided an important impetus to the
expansion of irrigation. Indeed, this has
been the major factor for the growth of
irrigation in the Corn Belt. More
generally, however, irrigation of high-
value crops often is justified because
the difference between average
irrigated and dryland yields is sufficient
to cover the costs of irrigation. Thus, the
high-value crops, peanuts, tobacco,
orchards, potatoes, and vegetables,
accounted for 32 percent of eastern
irrigation in 1969. And finally irrigation
may be profitable in areas of abundant
rainfall if the soils do not retain moisture
well. This factor explains the expansion
of irrigation of crops such as corn and
soybeans on sandy soils.
The areas with the greatest potential
for expansion of irrigation are the
Mississippi Delta, the Southeast, and
the Lake States. The Delta region was
not considered in this analysis since it
was studied separately by a group at the
University of Arkansas. The prospects
for expanded irrigation in the Northeast,
Appalachian, and Corn Belt regions are
considered to be small. In the sandy
areas of the Southeast and Lake States,
however, irrigation grew rapidly during
the 1970's and further rapid growth is
likely. Capital, not energy, costs are the
major obstacle to profitable irrigation in
the East. Energy costs are not as crucial
as in the West primarily because
eastern farmers apply much less water.
Double-cropping, switching to high-
value crops, and use of portable
irrigation systems that can be used on
several fields are common ways of
offsetting the high Investment costs of
eastern irrigation.
Corn and soybeans are likely to be the
major irrigated crops in the Southeast
and Lake States. Irrigated wheat will
grow in importance, especially where it
can be double cropped with soybeans.
Cotton will not be a major irrigated crop
in the East because of pest problems.
Several environmental problems will
be associated with the expansion of
eastern irrigation. In some parts of the
Southeast pumping may bring some
long-term decline in groundwater
levels resulting in a reduction in surface
flows. Land clearing to accomodate
sprinkler systems is likely to aggravate
erosion. The Southeast and several
areas in the Lake States already have
water quality problems stemming from
agricultural runoff, and deliveries of
sediment and agricultural chemicals to
water bodies may rise with the
expansion of irrigation. In particular, the
spread of irrigation on sandy soils poses
a danger of excessive nitrate concentra-
tions in the groundwater.
Irrigation in the Mississippi
Delta Region
This study employs a cost-benefit
analysis to determine the potential for
irrigation in the Mississippi Delta
region. Cost-benefit ratios are
compared to determine the crop rotation
providing the highest rate of return on a
given soil group under alternative
situations. These situations take into
account two different levels of crop
prices, nine soil groups, two levels of
crop yields, three irrigation methods
(flood, furrow with gated pipe, and
center pivot) using two different fuels
(diesel and electric), six possible
rotations, two levels of variable
production costs, and two levels of
opportunity costs. The opportunity cost
of irrigated cropland is represented by
the yearly net returns from dryland
crop production that would be foregone.
The study of the cost/benefit ratio
analysis entails 24 situations in all
which are compared at a 10 percent
discount rate. The analysis is based on
and data have been gathered for a six-
county area, which comprises a highly
representative sample of the Delta
region in terms of soil types, slopes,
drainage, cropping patterns, farm
organization, and climate.
A total of 17,641,546 acres within the
Mississippi Delta Region possess the
physical characteristics that permit
irrigation. A total of 15,493,278 acres
can be irrigated through the use of any
of the three techniques examined,
furrow, flood, or center pivot irrigation.
An additional 2,148,268 acres have
potential for center pivot irrigation only
due to excessive or uneven slope.
Furrow irrigation is the most econ-
omical alternative for all soils where the
technique is physically possible. Under
the assumptions examined, for 16 of the
24 situations it is economically feasible
to irrigate all of the potential 15,493,278
acres of cropland with furrow irrigation.
The feasibility for increasing irrigation
within the Delta region is decreased
only under the most unfavorable situa-
tion examined; 1985 baseline crop
prices, 33 percent increase in variable
production costs, and average yields. If
these conditions prevail, it is
economical to irrigate only 60 percent of
the potential furrow irrigated acres, or
9,428,190 acres.
There are 2,148,268 acres of Delta
cropland that are either too steep or
undulating to permit furrow irrigation.
Center pivot irrigation is the only choice
for this acreage unless land forming is
used to create the proper slope. The
potential for center pivot irrigation
ranges from 2,148,268 acres, or 100
percent of the potential center pivot
irrigated acreage, to 465,030 acres
across the various situations examined.
The estimated potential regional
increase in soybean production
resulting from irrigation ranges from an
increase of 198,020,989 bushels, a 71
percent increase, to 74,931,516
bushels, a 26.8 percent increase. In 20
of the 24 situations examined, the
increase in regional soybean production
ranges between 35 and 55 percent.
Much of the difference in these figures
results from whether average or high
level management is assumed.
In 22 of the 24 situations examined, at
least 90.5 percent of the region's
-------
cropland could be profitably irrigated.
For the six-county sample area this
percentage would constitute
approximately 1,866,318 acres.
However, the Federal census indicates
only 180,762 acres, 9.7 percent of
sample area cropland, was irrigated in
1978.
While irrigation is expanding,
growth is limited in the short run by
several factors. The first factor is the
availability of capital. This project has
assumed that adequate capital is
available for irrigation expansion.
However, to install irrigation systems on
all profitable soil groups in the Delta
region would require from 1.86 to 2.16
billion dollars at present costs,
depending on fuel type used. Also,
farmers would need capital to operate
the systems plus their normal crop
production capital requirements. This
amount of capital will become available
only over an extended period of time.
Another factor may be a lack of
knowledge among farmers concerning
irrigation investment costs, operating
costs, and yield response. Until very
recently, little research tying these
factors together had been done for the
Delta region. Because of this lack of
research, producers have not had a firm
foundation upon which to assess the
profitability of irrigation.
Insufficient labor may also inhibit
irrigation growth. Many farmers may
have labor busy with other activities or
may have difficulty in securing extra
labor on a short-term basis.
The study did not consider the
following aspects of the irrigation
expansion issues: 1) the availability of
labor necessary to furrow irrigation
systems, 2) the tax advantages that
serve to decrease the real cost of
irrigation systems, particularly capital
intensive center pivot systems, 3) the
possibility of land forming those soils
that cannot be furrow irrigated now and
installing surface irrigation rather than
center pivot irrigation, and (4) the
quality and quantity of water available
for expanding irrigation.
The most visible environmental
effects due to irrigation are damages
from soil erosion and run-off water
containing pesticides and fertilizers.
Excessive sediment loads due to erosion
could increase water treatment costs
for municipalities, damage domestic
and industrial water supplies and water
recreation, damage wildlife and fish
populations, and lower aesthetic
values. Mechanical removal of
sediment from streams and lakes would
be costly.
Erosion would also carry pesticides
and fertilizers with the sediment.
Irrigation of some crops might require
greater amounts of these materials than
would be used in dryland agriculture.
Pesticides and fertilizers carried from
the fields would enter the aquatic
environment and might disrupt fish and
other organisms crucial in the food
chain. The greatest effects of these
materials would be nitrate pollution of
groundwater, decreased supplies of
dissolved oxygen in water and resultant
growth of aquatic plants, and increased
concentrations of salt in the water.
Proper management of irrigation could
reduce all these environmental
problems.
Kenneth D. Frederick, James Hanson, James Pagano, Robert N. Shulstad, Ralph
D. May, Billy E. Harrington, and Jon M. Erstine are with Resources for the
Future, Washington, DC 20036.
G. W. Bailey is the EPA Project Officer (see below).
The complete report, entitled "Trends in U.S. Irrigation: Three Regional Studies,"
(Order No. PB 84-159 409; Cost: $35.50, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 7O3-487-465O
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
College Station Road
Athens, GA 30613
. S. GOVERNMENT PRINTING OFFICE: 1984/759-102/0936
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
! ;M 564 I,''-.- \
\ />^!3:~>
••• / ''- : - .'
PS 0000.5(29
------- |