DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH CENTER-PIVOT SPRINKLER

SYSTEMSValín Sanjiao M.I.; Santos Pereira L. Agricultural Engineering Research Center, Institute of Agronomy, Technical University of Lisbon.

WATER SAVING IN MEDITERRANEAN AGRICULTURE & FUTURE RESEARCH NEEDSCIHEAM, Mediterranean Agronomic

Institute of Bari, Italy

Design new systems

Hydraulic simulation

Occurrence of runoff

EndY

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Evaluation of operating systems

Input data field

Computation of performance indicators

Computation of emitters chart

Acceptable runoff?

Gross irrigation

requirements

SpansEmittersSystems

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STHE MODEL

Conceptual structure

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THE MODEL

Gross irrigation requirements

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THE MODEL

Hydraulic simulation

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THE MODEL

Selection the emitter chart

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THE MODEL

Calculation of the application rate

Run off

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THE MODEL

Performance indicators

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SMODEL APPLICATION

Performance indicators in field evaluations

HidranteL (m)

U (m/s)Pp (kPa)

Qh (m3h-1) 50,8 130.9273,8 281,1 272,9 50,6

0.72 3,5476 518 497 555

3,1428-Jun-00 13-Jul-00 28-Jun-00Fecha 13-Jun-00 14-Jun-00 16-Jun-00

445 168 310

Vigia

H233/234/235 H-116

Lucefécit Lucefécit

Resultados R A R B R A R B R A R B R A R B R A R B R BZav (mm) 9,4 8,8 10 7,5 8,5 8.8 6,4 5,7 7.9 6,2 11,7 11,8

Zlq (mm) 7,5 7,7 8,1 5,8 6,5 7,7 5,1 4,3 6,2 4,9 9,8 10,3

UD (%) 79,4 87,7 80,4 76,8 77,6 80,4 79,3 74,6 78,2 78,8 83,8 87,2CU (%) 88 91,4 83,7 85,6 85,6 88,8 81,3 85,7 85,5 88,4 88,15

9,58,9

PELQ (%) 58,8

79,1

y (mm) 10,7 11 10,6

71,2 52,8

9,5

58,8

The results analyzed herein refer to field evaluations of center-pivot systems in operation in Alentejo (Portugal)

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Main problems were:

i) high working pressure, ranging from 476 kPa to 555 kPa, much above recommended pressure for systems with FSPS emitters;

ii) high wind drift and evaporation losses due to small diameter of droplets as a result of high functioning pressure of emitters; and

iii) 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.

MODEL APPLICATION

Performance indicators in field evaluations

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SMODEL APPLICATION

Performance indicators obtained in DEPIVOT

The model DEPIVOT was used to simulate alternatives to the existing systems

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CONCLUSIONS

Field evaluations of center-pivot systems have shown that these systems are often poorly designed and the selection of emitters is often inappropriate

The operation pressure is excessive

Friction losses observed were often greater than 20% of the operation pressure

Runoff was also often produced due to high application rates

Small drops that easily evaporate or are drawn by the wind

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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

The beneficial water use.