|
Sprinkler/overhead irrigation applies water
to the irrigated area via a network of pressurised pipe with sprinkler
heads.
Set irrigation systems are using as an emitter,
various type of agricultural sprinklers (also called overhead irrigation).
Based on the technical specifications they can be low capacity, medium
size and heavy duty/large area sprinklers with one or two nozzle outlets.
The sprinklers shoot jets of
water into the air and spread it to the field in the form of rain drops in
a circular pattern.
|
Sprinkler Type |
Q |
H |
Nozzle |
Wetted Diameter |
|
L/hr |
bar |
mm |
m |
| Low capacity |
400-2180 |
1-5 |
2.5-8 |
15-29 |
| Medium |
620-4080 |
1.5-5.5 |
3.2-7 |
23-41 |
| Full and Part circle |
286-1310 |
2.5-7 |
2.8-16 |
18-74 |
| Heavy duty/Large area |
8500-110000 |
2-10 |
3.2-32 |
39-130 |
Based on the height of the water jet above
the nozzle, they are divided into low angle (4-11º), or high angle
(20-30º). They are made of brass or high engineering plastics with
internal or external threaded connections. They are installed vertically
on small diameter riser pipes fitted on the laterals.
The sprinkler spacing in the field is
rectangular or triangular at distances not exceeding 60% or their diameter
coverage (see pictures).
The manufacturer/supplier brochures usually are
showing the sprinkler's: nozzle size (mm), operation pressure (bar or
kPa), discharge/flow (L/hr or m3/hr), the radius or the
diameter of the coverage (m) and the precipitation/application rate
(mm/hr) at different spacing (triangle or rectangular). Also the
recommended/optimum values are highlighted.
Filtration requirements are necessary and
should be about 20 mesh.
It is a flexible system that can be used to
supply adequate moisture for plant growth as well as for frost control or
crop cooling during heat waves.
In historical order, the Hand Move Systems
were the first sprinkler systems (usually portable aluminium pipes).
To minimise the labour, when shifting the pipes, and for better
management, the aluminium pipes were attached to wheels or skids and moved
across as one long pipeline on wheels. These were then called Side Roll
Systems. Because they were still labour intensive and
hard to manage the movement of the pipes after irrigation, the permanent
or solid sets/fixed sprinkler systems came along. In these systems the
main lines and the submains have been buried and only the sprinklers with
the risers were visible.
Set systems have their
advantages and
disadvantages. |