TM 5-803-13/AFM 126-8
selection since plants naturally grow in groups requiring
humid regions where many adapted non-native grasses
similar soil and climatic conditions. Other important
tend to become dormant during periods of drought.
b. Design factors. The following factors should be
plant selection factors are hardiness to temperature
extremes; soil fertility requirements; ability to survive in
evaluated when designing an irrigation system:
very wet or dry soil conditions; the degree of tolerance for
-- Availability and accessibility of existing water sup-
wind or salt air; ability to be transplanted; and resistance
plies, including non-potable sources.
to insects and diseases. Recommendations on the
-- Amount of water required, as determined by type of
selection of plants tolerant of specific site conditions can
turf to be irrigated, climate, terrain and soil con-
be obtained from the Agricultural Extension Service; Soil
ditions.
and Water Conservation District; or from federal, state,
-- Budget.
county and city park and forest agencies.
TM 5-630/NAVFAC MO-100.1/AFM 126-2 provides
a. Trees and shrubs. To achieve maximum visual and
further guidance for the design of irrigation systems.
c. Types of systems. The use of pop-up systems is
functional effectiveness with minimum maintenance,
emphasis should be placed on the use of trees instead of
justifiable in arid and semi-arid regions where frequent
the extensive use of shrubs. Properly selected trees will
irrigation is required. Quick-coupling sprinkler systems
be less expensive to maintain than shrubs and have
are mainly used for areas where only supplemental irri-
greater visual impact on the landscape. Simple and
gation is necessary. Where pop-up spray systems are
effective planting designs can be achieved with trees,
used, automatically controlled, clock-timed systems are
lawns and a limited use of shrubs.
recommended to save labor and facilitate non-peak water
b. Evergreen and deciduous. Deciduous trees offer a
use. Hose bibs on building exteriors may be used for
wide variety of effects because of seasonal changes,
limited irrigation and hand-watering. Any irrigation
flowers, berries, fruit, and color and texture of bark.
system, either hand-watering or automatic pop-up sys-
Evergreen trees and shrubs provide green color during
tems, should be based on a feasible irrigation schedule in
seasons when deciduous plants are leafless and adds
terms of hours per day or per week.
d. Project justification. Projects using either pop-up
permanent structural value to the landscape. The areas of
the country where evergreen plants are not readily
or quick-coupling sprinkler systems must be justified on
available, deciduous ones may be used for a greater part
the basis of amortization and operating costs. An analysis
of the planting, with evergreens used only at focal points
should include:
in conjunction with important features and structures.
-- Estimated precipitation deficiency on an annual
c. Vines. Vines must be carefully selected. Many vines
basis and for the summer season (June through
climb by means of tendrils, disks or root-like hold-fasts
August).
which can damage wood or masonry walls. Maintenance
-- Acres of installation grounds currently irrigated by
and repair work can be difficult and costly if vines must
underground systems and all other means (hose
first be removed. Generally, vines should be restricted to
bibs, flooding or portable systems).
fences, trellises and structures other than buildings.
-- An analysis of the system's impact on water usage
rates, especially during peak usage periods, in rela-
2-18. Irrigation Systems.
tion to current installation water resources.
a. Basis for requirement. Irrigation requirements
-- A discussion of any soil factors or turfgrass
depend on several factors. In selected areas, it may be
management conditions affecting the irrigation
necessary to use irrigation to promote the healthy and
requirement.
e. Sewage plant effluent. Sewage treatment plant
attractive growth of turf. The use of drought-tolerant
ground covers, gravel or rock mulch will minimize the
effluent may be used for irrigation wherever feasible. In
need for irrigation systems. However, in some cases, the
addition to the justifications and information considered
location, importance or use of an area makes the
in the proceeding paragraphs, answers to these questions
substitution of alternative ground covers undesirable.
should be provided:
Irrigation requirements depend on several factors:
-- Is there enough effluent available to support both
-- Precipitation deficiency.
short and long-term irrigation needs?
-- Soil's water holding capacity.
-- Is the proposed irrigation distribution system iso-
-- Seasonal distribution of rainfall.
lated from existing distribution systems for potable
-- Quality of turf to be maintained.
water supplies?
Irrigation should generally be provided in arid and semi-
-- Will site-users have direct contact with irrigation
arid regions to enhance the quality of turf, even though
water?
lawns or other grasses may survive without irrigation.
-- Will Federal, state and local health requirements be
Supplemental irrigation may be needed in subhumid and
met?
2-19
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