1. DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS
Valín Sanjiao M.I.; Santos Pereira L.
Agricultural Engineering Research Center, Institute of Agronomy, Technical University of Lisbon.
WATER SAVING IN MEDITERRANEAN AGRICULTURE & FUTURE RESEARCH NEEDS
CIHEAM, Mediterranean Agronomic
Institute of Bari, Italy

2. THE MODEL Conceptual structure
Start
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS
Design new systems
Evaluation of operating systems
Gross irrigation requirements
Input data field
Hydraulic simulation
Spans
Emitters
Systems
Computation of emitters chart
Computation of performance indicators
Occurrence of runoff N
Acceptable runoff?
End Y

3. THE MODEL Gross irrigation requirements
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

4. THE MODEL Hydraulic simulation
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

5. THE MODEL Selection the emitter chart
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

6. THE MODEL Calculation of the application rate
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS
Compare
Run off

7. THE MODEL Performance indicators
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

8. MODEL APPLICATION Performance indicators in field evaluations
The results analyzed herein refer to field evaluations of center-pivot systems in operation in Alentejo (Portugal)
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

9. MODEL APPLICATION Performance indicators in field evaluations
Main problems were:
high working pressure, ranging from 476 kPa to 555 kPa, much above recommended pressure for systems with FSPS emitters;
high wind drift and evaporation losses due to small diameter of droplets as a result of high functioning pressure of emitters; and
application rates excessive relative to soil infiltration rates.
These problems result of poor design, mainly relative to the selection of spray heads which were not in agreement with the existing characteristics of the pressurized distribution network and the characteristics of the soils and relief in the area.
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

10. MODEL APPLICATION Performance indicators obtained in DEPIVOT
The model DEPIVOT was used to simulate alternatives to the existing systems
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS

11. CONCLUSIONS The operation pressure is excessive
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS
The operation pressure is excessive
Runoff was also often produced due to high application rates
Small drops that easily evaporate or are drawn by the wind
Field evaluations of center-pivot systems have shown that these systems are often poorly designed and the selection of emitters is often inappropriate
Friction losses observed were often greater than 20% of the operation pressure

12. DEPIVOT shows that it is possible to:
CONCLUSIONS
The model DEPIVOT was conceived to support farmers in selecting new systems and improving the existing ones.
DEPIVOT shows that it is possible to:
achieve much better performances;
reduce the operating pressure and save energy;
control wind drift and evaporation losses,
control runoff
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER SYSTEMS
The beneficial water use.