UNDERSTANDING THE BASICS
DRIP IRRIGATION SYSTEM OVERVIEW
A drip irrigation system comprises many components, each one of them playing an important part in the
operation of the system.
The aim of this chapter is to provide an overview of the drip irrigation system components, their functions
OTHER IRRIGATION SYSTEMS:
DRIP IRRIGATION SYSTEM LAYOUT
There are basically two main types of water sources: groundwater and surface water:
Many existing and potential water supply sources for irrigation systems are derived from surface water,
which does not tend to have high levels of salts (with the exception of some coastal areas), and thus
systems are usually less prone to the formation of precipitates in drippers when using a surface water source.
Surface water, however, tends to introduce biological hazards. If wastewater is being considered as a
source, quality and clogging potential will vary depending upon the extent of treatment.
Groundwater is generally of higher quality than surface water. However, iron and manganese levels should
be measured, as high levels may lead to dripper clogging, and treatment may be required.
Pumps & pumping stations
Unless the water at the source is supplied at an adequate flow rate and pressure (by municipal or other
entity supply, a pre-existing pump upstream from the irrigation system or gravitational pressure*), a pump
will be needed to push water from the source through the pipes and drippers.
*Gravitational pressure (also known as hydrostatic pressure) is the pressure at a point in a fluid at rest
due to the weight of the fluid above it. If the water source is at a higher elevation than the drippers in the
field, the elevation difference between them will determine the gravitational pressure in the system
(e.g. the water level in a tank is 5 meters above the elevation of the pump's axis, the gravitational pressure
is 5 meters = 0.5 bar = 7.25 PSI).
Selecting a pump for an irrigation system requires an understanding of the water conditions and local
Poor pump selection can lead to high operating costs and shortened pump life; this in turn impacts on the
performance and reliability of the whole irrigation system.
When a pump site is selected it is necessary to consider a range of factors, including availability of power,
proximity to the development site and water quality issues.
Power source for the pump
The power source for the pump will depend on the availability and accessibility of the energy resource in
the local area.
In most instances, electricity is preferred because of reduced labor requirements and higher efficiency,
resulting in lower energy cost. Three-phase power is usually required to operate over 10 horsepower (hp)
If electricity is not available, alternative power sources such as diesel, gasoline, or solar may be used. The
most common alternatives are gasoline engines for small pumps and diesel engines for larger pumps.
PUMP MACHINERY SYSTEM
Filtration is critical in any drip irrigation system. Effective filtration is essential for proper irrigation system
operation and long-term performance, as it prevents the irrigation water from clogging the drippers.
The concept "water quality" relates to the variety and concentration of the dissolved and suspended
components in the water.
Water requirements for drip irrigation
The quality of water for irrigation relates to the parameters required to maintain the crop's health and the
integrity of the irrigation system. Every type of pressurized irrigation system requires attention to the
water quality to avoid clogging of the irrigation components in order to enable orderly long-term irrigation
according to the irrigation program.
Water quality will dictate filtration requirements, chemical injection requirements, and management of the
irrigation systems to prevent dripper clogging.
Causes of dripper clogging in systems may be chemical (precipitates or scale), physical (grit or particulates
such as sand and sediment) or biological (such as algae or bacteria).
The water’s chemical characteristics are influenced by the variety and concentration of the substances
dissolved in it. These dissolved substances include ions of dissolved salts such as chloride, sodium and
nutrients (nitrogen, phosphorous, potassium and others). Calcium and magnesium influence the hardness
of the water, iron and manganese are liable to be found either dissolved or as a residue, along with other
dissolved organic compounds and even poisonous substances.
The biological characteristics of the water quality include a variety of living organisms such as microorganisms, including bacteria, viruses, single celled entities, algae and zooplankton, which develop in open
water along with creatures developing within the water transport system itself.
The water quality is expressed by the physical conditions and the variety and concentration of its
The quality of the water is determined by a wide variety of parameters (measured or calculated)
affecting the crop, the soil and the irrigation system. Some of them are listed below:
• EC (electrical conductivity)
• pH (level of acidity or alkalinity)
• Ca (calcium - hardness of the water)
• Mg (magnesium)
• Na (sodium)
• K (potassium)
• HCO3 (bicarbonate)
• CO3 (carbonate)
• Alk (alkalinity)
• Cl (chloride)
• SO4 (sulfate)
• PO4 (phosphate)
• N-NH4 (nitrogen-ammonium)
• N-NO3 (nitrogen-nitrate)
• B (boron)
• Fe (iron)
• Mn (manganese)
• TSS (total suspended solids)
• TDS (totally dissolved solids)
• Algae and Chlorophyll
• BOD (biochemical oxygen demand*)
• COD (chemical oxygen demand*)
• VSS (volatile suspended solids)
*When waste, industrial effluent and/or recycled waters are used.