Drip Irrigation Design, Installation and Operation
Design logic for drip
This domain tests how to turn crop water demand into emitter number, run time, zone flow, pipe size and pressure requirement. Design starts with peak ETc, crop spacing, wetted area, soil intake, application efficiency and emitter selection, then checks emission uniformity and hydraulic losses.
Core rules
- Crop demand per plant = ETc (mm/day) × area per plant (m²), because 1 mm over 1 m² = 1 L.
- Application rate per plant = number of emitters × emitter discharge; run time = demand ÷ application rate.
- Use net demand and divide by application efficiency (often 85–90% for well-designed drip) to get gross run time.
- Keep pressure variation within the manufacturer’s limit, commonly ±10–20%; use pressure regulators and balanced zones.
- Install filters, flush valves, and a schedule for chlorination/acidification where water quality requires it.
Worked example
Tomato plants are spaced 0.6 m² per plant. Peak ETc = 6 mm/day. Two 2 L/h emitters per plant give 4 L/h. Crop demand = 6 × 0.6 = 3.6 L/plant/day. Run time = 3.6 ÷ 4 = 0.9 h/day. At 90% application efficiency, gross run time = 0.9 ÷ 0.90 = 1.0 h/day. If there are 2,000 plants, zone flow = 2,000 × 4 = 8,000 L/h = 8 m³/h; the submain and valve must be sized for that flow at acceptable friction loss.
Traps
Do not use ET0 without Kc; do not design on average ET instead of peak; do not forget efficiency, leaching requirement, or rain; do not assume emitter flow stays 2 L/h if pressure is low; do not omit flushing after installation.