Optimizing Pipe Diameters in Drip Irrigation Systems through Spatial Grouping of Subplots into Irrigation Shifts

Efficient hydraulic design of drip irrigation systems requires pipe sizing to account for the spatial distribution of irrigation demand and the sequence of system operation. When pump capacity limits the area irrigated simultaneously, different combinations of active subplots can produce different hydraulic conditions despite maintaining the same total discharge. This study develops a method that integrates spatial subplot grouping into operating shifts with hydraulic network analysis to support pipe diameter selection. The method combines equal-area field subdivision, max–min pairing based on centroid distances, pump discharge constraints, and hydraulic calculations for each operating shift. An irregular field of approximately 19.02 ha was divided into 12 subplots and organized into six paired shifts. Each planned shift covered approximately 3.17 ha at a discharge of 111.24 m³ h⁻¹, with a scheduled irrigation sequence lasting 18.81 h. Centroid distances between paired subplots ranged from 287.20 to 349.24 m. Preliminary hydraulic calculations covering 11 connected subplots showed that the five complete paired shifts required pumping heads of 22.71–25.00 m at approximately equal inlet discharge. The maximum mainline velocity was 0.98 m s⁻¹, below the adopted limit of 2.2 m s⁻¹. These results demonstrate that equal discharge does not eliminate differences in hydraulic loading and that pipe sizing must consider the governing operating shift. The proposed approach can support preliminary design and operational assessment of drip irrigation networks on irregular fields where pump capacity requires rotational irrigation, providing a basis for comparing subplot groupings and evaluating commercial pipe diameters.