Design of Agricultural Irrigation Systems in Florida

standards are included in the list of references in this
publication (1, 12, 13, 36). Copies of these standards
are available from the developing agency.

 Computer software has been developed by the
University of Florida to help with the design and
management of Florida irrigation systems. Water
management utilities were published by Zazueta et al.
(69) and continue to be developed. A complete list
of available software is published in the IFAS
Microcomputer Software Catalog (64).

 Major components of irrigation systems must
often be designed in groups for compatibility and
efficiency. This publication discusses the major
component groups of 1) control equipment; 2) water
conveyance system; 3) water distribution system; and
4) pumping system. Selection of operating conditions
(flow rates and pressures) is also discussed. This
publication references many other publications which
provide more information on specific aspects of
irrigation system design in Florida.

 SYSTEM COMPONENT GROUPS

 Control Equipment

 The objective of control equipment design is to
 specify components that will enable the irrigation
 system to be efficiently and safely managed and
 monitored in order to optimize crop production,
 conserve water and preserve water quality. Control
 equipment consists of the components required to
 regulate and monitor water and chemical applications
 to an irrigation system, and safety equipment required
 to protect the water supply from contamination.
 These include valves, pressure regulators, flow
 meters, backflow prevention systems, filters, pressure
 gauges, chemical injection equipment, and irrigation
 controllers.

 Valves

 Valves are required to control the filling of
 irrigation systems at pump startup, to control flows to
 the desired subunits of a system, and to allow flushing
 of irrigation pipes. Only properly pressure-rated
 irrigation valves must be used to avoid failures due to
 system pressure and hydraulic shock (water hammer)
 problems. Valve materials and components must be
 resistent to corrosion by the irrigation water and any
 chemicals injected during irrigation. I o I


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 Valves must be properly sized to avoid excessive
pressure losses. Normally, valves should be the same
size as the pipeline in which they are installed.
Installing smaller valves to save initial costs will result
in higher operating costs for the life of the system due
to friction losses.

 Automatically-controlled irrigation systems will
require the use of automatic valves. These may be
controlled by electric solenoids or hydraulic pressures,
depending upon the type of timer/controller used.
Like manual valves, automatic valves should be
selected based on friction loss and water hammer
considerations.

 For more information on valve types and
selection, see IFAS Ext. Cir. 824, Valves in Irrigation
Systems (19). For information on estimating and
controlling hydraulic shock, see IFAS Ext. Cir. 828,
Water Hammer in Irigation Systems (7).

Pressure Regulators
 Pressure regulators may be required to maintain
 the desired operating pressure in pipe flow systems.
 These valves are required when it is necessary to
 manage changing pumping conditions such as those
 due to changes in the water source or flow
 requirements to subunits of the irrigation system.
 Regulators are also required if some subsections of a
 system operate at different pressures than others.

 Pressure regulators are often installed at either
 the irrigation pump outlet, the entrances to subunits,
 or at both locations. Pressure regulators may include
 slow opening and check valve features. The slow
 opening feature will allow an irrigation system to fill
 slowly upon pump startup, thus avoiding water
 hammer problems. The check valve feature will help
 to prevent backflow to the water source, thus helping
 to protect the water supply from contamination.

 Because of their cost and the pressure losses
 which occur through them, pressure regulators should
 be used only when absolutely necessary. The system
 subunits should be designed to have as nearly the
 same pressure and flow rate requirements as possible
 to minimize the number of regulators. In some cases,
 field sizes, layouts, or slopes will not permit the same
 flow rate and pressure to be used for all subunits.
 Then, pressure regulators will be necessary. For
 more information on pressure regulating valves, see
 IFAS Ext. Cir. 824, Valves in Irigation Systems (19).