This document discusses precipitation profiles of sprinkler irrigation systems. It covers several key topics in 3 sentences or less: Sprinkler irrigation distribution is affected by many factors like nozzle pressure, size and shape, sprinkler head design, rotation speed, trajectory angle, riser height, and wind. Different sprinkler head designs like fixed spray, pop-up, rotary, and shrub types are used for various landscape areas. The moisture distribution characteristics depend on sprinkler spacing, nozzle size, operating pressure, and depth of water application, with operating pressure having a significant effect on the wetting pattern.

1. A.KESHAV KUMAR,(ME12-007)
R.LAVANYA,(ME12-008)

2. PRECIPITATION PROFILES OF
SPRINKLER SYSTEM

3. Precipitation profiles of sprinkler irrigation
Meaning of precipitation:
The quantity of water falling to earth at specific
place within a specified period of time; “the
storm brought several inches of precipitation”

4. PRECIPITATION PROFILES OF
SPRINKLER SYSTEM
 Lateral movement of moisture is
more in clay soils.
 Linear and lateral movement of
moisture is present to some extent
in loamy soils.
 Sandy soils having high linear
movement when compared to
loamy soils.

6. Precipitation profile is a function of many factors:
Nozzle pressure.
Nozzle shape & size.
Sprinkler head design.
Sprinkler rotation speed.
Trajectory angle.
Riser height.
Wind.

8. Head Design Description Usage
Fixed Spray • Produce a tight, constant fan of
water
• Fan out in a radius of 5'-15'
• Small lawns
• Shrubs
• Ground cover
Pop-Up • Pop up above grass when activated
and disappear below
ground when not in use
• Provide even water distribution and
low spray angle
• Small lawns
• Medium lawns
• Large lawns
• Side lawns
• Gardens
Rotary • Deliver a single stream of water
that rotates in a circle
• Apply water more slowly than spray
designs
• Medium lawns
• Large lawns
• Side lawns
Shrub • Mounted above foliage on risers, or
extensions
• Special pattern nozzles provide
flexibility
• Ground cover
• Planters
• Shrubs
• Gardens

9. Fixed Spray Pop-Up
Shrub Rotary

10. Rotational speed
• The rotational speed is about 2.5m/s
• Rotational speed of sprinkler head significantly
affects the water distribution

11. Trajectory angle.

12. Risers
 Risers are an important component of any irrigation system.
 Since the main lines of irrigation systems do not always
connect directly to the sprinkler heads themselves, risers fill
the gap in between by providing the right connection
 Risers are available in 1/2" and 3/4" diameters
 Basic risers are rigid and best used for short distances
 Basic risers offer more economical options
 Cut-off risers allow you to make on-the-spot adjustments
 Flexible-tubing risers provide flexibility for installing
sprinkler heads in difficult spots

13. .
Riser Type Materials Points to Consider
Basic • Metal
• PVC
• Best for short distances
Cut-Off • Polyethylene • Provide installation
flexibility
• Can be trimmed in 1/2"
sections
Flexible • Polyethylene • Allow movement to reduce
stress on sprinkler heads
• Provide greater length

14. How to calculate a precipitation rate
 Physically measuring using cups is a very simple
method.
 You can purchase water-auditing cups
(sometimes called a catchcan), a rain gauge, or use
any non-tapered cup or can.
 Set the cup in the zone. Run that zone for several
minutes- we recommend 5, 10, or 15 minutes.
After the time is up, retrieve the can and check
the water level.
A rain gauge or catchcan will have measurements
indicating the amount of water caught.

16. MOISTURE DISTRIBUTION
CHARACTERISTICS

17. Moisture distribution characteristics:
1) Sprinkler spacing
2) Nozzle size
3) Operating pressure
4) Depth of water application

18.  Operating pressure affects more to the wetting pattern of sprinkler
irrigation.
 Operating pressure of pressure head ranging from
3.5m to 70m.

19. Moisture distribution characteristics:
Spray distribution characteristics of sprinklers and
their spacing will regulate the uniformity of water
application .
The spray distribution characteristics of sprinkler
heads are typical change with nozzle size and
operating pressure .
In this distribution pattern , the depth of water
applied surrounding the sprinkler, decreas as the
distance from the sprinkler increases .

21. Wetting pattern
Normally the area wetted is circular . The heaviest
wetting is close to the sprinkler .
 For good uniformity several sprinklers must be
operated close together so that their patterns
overlap .
 For good uniformity the overlap should be at least
65% of the wetted diameter.
If the pressure is above or below this then the
distribution will be affected. The most common
problem is when the pressure is too low. This
happens when pumps and pipes wear.

22. If the pressure is too high then the distribution will
also be poor.A fine spray develop which falls close
to the sprinkler.

23. EFFECT OF WIND SPEED ON SPRINKLER
SYSTEM

24. Effect of wind velocity on sprinkler system
 The wind velocity and wetting pattern of the soil
are closely related to each other .
 The wind distorts the circular pattern of wetting
in the shape of irregular ellipse .
 Wind velocity more than 16kmph ,the wetting
pattern , uniformity of application is adversely
affected , as result sprinkler irrigation is not
recommended at this velocity level.

25. Wind velocity from 0-8kmph , the application
uniformity is not affected.
Wind velocity up to 13kmph is acceptable but
beyond it the application uniformity gets
significantly affected.

26. No wind
Overlapped Sprinklers
Elongated parallel pattern
Dry zone

27. effect of wind on sprinklers
s.no Wind velocity kmph Sprinkler spacing across the wind direction(m)
1. 0 65
2. 0 to 6 55
3. 7 to 13 40
4. More than 13 30