Water Distribution Uniformity of Traveling Gun Sprinklers: Day–Night Wind and Towpath Alignment

Wind is a primary driver of nonuniform water application in traveling gun sprinklers, yet design guidance often treats wind only as speed. This study quantifies how diurnal wind regimes (day vs. night) and wind incidence relative to the towpath (φ) affect application-rate patterns and the Christiansen uniformity coefficient (UC) as a function of towpath spacing expressed as a fraction of wetted diameter (WD). Class-specific sprinkler patterns were generated with the Simulation Model for Sprinkler Irrigation (SIA) and combined with local daytime and nighttime wind-frequency data to build composite application-rate fields; these drove traveler simulations that computed cross-track depth, lateral overlap across spacings, and UC for representative wind speeds (0–6 m s−1) and φ (0°, 45°, 90°). Nighttime operation yielded higher UC, with a day–night crossover near ~50% WD and an average UC gain of ~9.5 percentage points; typical gains were +6 to +9 points between 55% and 90% WD. Wind incidence was as influential as speed: at 65.6% WD, increasing wind from 0 to 6 m s−1 reduced UC from 84.4% to 28.6% for φ = 0°, to 52.0% for 45°, and to 76.1% for 90°. Findings support nighttime scheduling, towpaths avoiding wind-parallel operation, and tighter spacings under windy conditions.