Sprinkler Irrigation Design, Installation and Operation
Sprinkler design basics
This domain tests sprinkler selection, spacing, precipitation rate, uniformity, operating pressure, wind effects and scheduling. Unlike drip, sprinklers wet a broad area, so overlap and evaporation losses matter.
Core rules
- Precipitation rate (mm/h) = sprinkler discharge (L/h) ÷ area served (m²); with spacing S1 × S2, area = S1 × S2.
- Sprinkler spacing should follow the manufacturer’s recommendation and wind conditions; wider spacing lowers cost but reduces uniformity.
- Nozzle flow rises with pressure; operate near the design pressure, not far above or below.
- Net irrigation = gross × application efficiency; wind, evaporation and runoff reduce efficiency.
- Audit pressure at the last sprinkler and check for clogged or worn nozzles.
Worked example
A sprinkler discharges 1,000 L/h and is spaced 12 m × 12 m. Area = 144 m². Precipitation rate = 1,000 ÷ 144 = 6.94 mm/h. To apply 30 mm net at 75% efficiency, gross depth = 30 ÷ 0.75 = 40 mm. Run time = 40 ÷ 6.94 = 5.8 h. If the system is shifted between sets, the set time and number of sets determine the total irrigation time.
Traps
Do not confuse gross and net application; do not ignore wind drift and evaporation; do not use spacing larger than the wetted overlap allows; do not size pipe for average flow when several sprinklers operate together; do not forget pressure loss along the lateral.