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The potential runoff computation is supported by
the window shown in Figure 4. Results for potential
runoff are shown graphically and numerically for
two positions. By pressing the button Aplication –
infiltration rate the model presents a dialog box to
insert the number of hours needed for a complete
revolution.
When the model is used to evaluate a system
under operation, first the common data to all
evaluations are introduced (equipment´s
characteristics); second the water depths caught in
catch cans placed along two radius are used to
compute DU and UC. Results are presented in
numerical and graphical formats.
4 CONCLUSIONS
DEPIVOT model is oriented to find solutions for the
critical aspects that limit achieving good
performances in the farmer irrigation practice.
Particular attention has been given to: determining
the irrigation water requirements and the
corresponding system discharge; sizing of the lateral
in order to achieve an adequate variation of pressure;
producing the sprinklers charts; determining the
functioning conditions for every sprinkler;
estimating the runoff potential; and defining the
main information for system management in
practice. The model is presented in WINDOWS
environment, with a structure between windows and
with a set of databases that can be consulted and
altered from the model itself. Once developed, the
model has been tested with results of field
evaluations. These results show that the model is
able to respond to the objectives that led to its
development, which are to assist farmers and
technicians in selecting and designing new centre-
pivot systems and to identify operational
performance problems and respective solutions.
ACKNOWLEDGEMENTS
The support by CEER - Biosystems Engineering
(POCTI/U0245/2003) and the research project
PTDC/AGR-AAM/105432/2008 funded by
Portuguese Foundation for Science and Technology
are acknowledged.
REFERENCES
Allen, R. G., 1989. USUPIVOT: Center pivot nozzle
selection computer software user´s manual.
Department of Agriculture and Irrigation Engineering,
Utah State University, Logan, Utah, 15.
Al-Kufaishi, S. A.,·Blackmore, B. S., H. Sourell 2006.
The feasibility of using variable rate water application
under a central pivot irrigation system. Irrig Drainage
Syst 20:317–327.
Bittenger, M., W., Logenbraugh, R. A., 1962. Theoretical
distribution of water from a moving irrigation
sprinkler", Transactions of the ASAE 5(1): 26-30
Bremond B., Molle, B., 1995. Characterization of rainfall
under centre pivot. Influence of measuring procedure.
Journal of Irrigation and Drainage Engineering ASCE
121 (5): 347 – 353
Heermann, D. F., Hein, P. R., 1968. Performance
characteristics of self-proped center-pivot sprinkler
irrigation system. Transactions of the ASAE 11(1): 11-
15
Heermann, D. F., Wallender, W. W., Bos, G. M, 1990.
Irrigation eficiency and Uniformity. In: Hoffman, G.
J., Howell, T. A., Solomon, K. H. (Eds.), Management
of Farm Irrigation Systems. ASAE, St. Joseph, MI,
125 -149.
James, L. G., 1982. Modeling the performance of center
pivot irrigation systems operating on variable
topography. Transactions of the ASAE 38(1): 143-149.
Keller, J. y Bliesner, R. D., 1990. Sprinkle and Trickle
Irrigation Van Nostrand Reinhold. New York.
Montero, J., Tarjuelo, J. M., Carrión, P. 2001. Nueva
versión del modelo de simulación de riego por
aspersión SIRIAS. In: XIX Congreso Nacional de
Riegos, AERYD, Madrid, CD-ROM paper C-18.
Pereira, L. S., Trout T. J., 1999. Irrigation Methods. In:
HN van Lier, LS Pereira, FR Steiner (Eds.) CIGR
Handbook of Agricultural Engineering, Vol. I: Land
and Water Engineering, ASAE, St. Joseph, MI, pp.
297-379
Qassim, A., Dunin F., Bethume M. (2008). Water balance
of center pivot irrigated pasture in northern Victoria,
Australia. Agric. Water Manag. 95, 566-574
Scaloppi E. J., Allen R., 1993. Hydraulics of Center-Pivot
laterals. Journal of Irrigation and Drainage
Engineering ASCE 119 (3): 554-567
Silva, L. S. (2006) The effect of spray head sprinklers with
different deflector plates on irrigation uniformity,
runoff and sediment yield in a Mediterranean soil.
Agric. Water Manag. 85, 243-252
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