HYDRAULICS_5 Design of Irrigation Systems by László Ormos

DESIGN OF MANIFOLD The manifold is a pipe with multiple outlets to the inlets of lateral pipes. The size of plot, the flow rate and the number of shifts in a complete irrigation cycle should be taken into consideration. An orchard is designed for irrigation with a solid set system. The manifold is laid in the center of the field. The whole plot is irrigated simultaneously. The flow rate of selected sprinklers is q s =0.11m 3 /h at a pressure h s =2bars. The space between the sprinklers along the laterals is e s =6m. Space between laterals is e L =8m. What are the diameters of pipes if the local head loss in the manifold and laterals is 10%?

DESIGN OF MANIFOLD The topography of field is the following: B=96m manifold lateral H=96m

DESIGN OF MANIFOLD Design of lateral 1.The maximum allowable pressure head variation is: 2.The number of sprinklers on every laterals is as follows: 3.The length of lateral is: 4.The total outlet of a lateral is:

DESIGN OF MANIFOLD For 16mm PE lateral pipe 5.The hydraulic gradient when Q=0.88m 3 /h and J 16 =22% 6.The head loss in the lateral pipe (including 10% local head loss) and coefficient F 6 =0.38, is: Since h f >  h the pipe diameter has to be increased. 7.The hydraulic gradient if diameter is 20mm of PE which has J 20 =6.5% by Q=0.88m 3 /h. is:

DESIGN OF MANIFOLD 8.The head loss in the lateral pipe (including 10% local head loss) and coefficient F 8 =0.38, is: Since h f <  h the pipe diameter is good. 9.The inlet pressure in the lateral is: 10.The water pressure by the last sprinkler on the lateral is:

DESIGN OF MANIFOLD Design of manifold 11.The number of laterals is as follows: 12.The length of manifold is: 13.The total flow rate is as follows:

DESIGN OF MANIFOLD For 63mm PE manifold pipe 14. The hydraulic gradient when Q=21.12m 3 /h and J 63 =7.2% 15. The head loss in the manifold (including 10% local head loss) and coefficient F 24 =0.371, is: 16. The pressure by the manifold inlet is: 17. The pressure by the inlet of last lateral is:

DESIGN OF MANIFOLD 18.The minimum pressure in the entire system at the last sprinkler on the last lateral is as follows: 19.The pressure difference between the first and last sprinkler is: Since the pressure difference  h f-l is lower than the allowable pressure head variation  h max, the system is good.

References Azenkot, A.(1998):”Design Irrigation System”. Ministry of Agricul- ture Extension Service (Irrigation Field service), MASHAV Israel Dr. Avidan, A.(1995):”Soil-Water-Plant Relationship”. Ministry of Agriculture Extension Service (Irrigation Field service), CINADCO, Ministry of Foreign Affairs, MASHAV, Israel Sapir, E.-Dr. E. Yagev (1995):”Drip Irrigation”. Ministry of Agricul- ture and Rural Development, CINADCO, Ministry of Foreign Affairs, MASHAV, Israel Sapir, E.-Dr. E. Yagev (2001):”Sprinkler Irrigation”. Ministry of - culture and Rural Development, CINADCO,Ministry of Foreign Affairs, MASHAV, Israel Eng. Nathan, R. (2002):”Fertilization Combined with Irrigation (Fertigation)”. Ministry of Agriculture and Rural Development, CINADCO,Ministry of Foreign Affairs, MASHAV, Israel