Which unit is used to express precipitation rate in irrigation design?

Which unit is used to express precipitation rate in irrigation design?

• A. Inches per hour
• B. GPM
• C. PSI
• D. Liters per second

Answer: (A)

Precipitation rate is about how much water depth is delivered to the soil per unit of time across the area being irrigated. In irrigation design, the standard way to express that rate is inches per hour (or millimeters per hour in metric). Using a depth-per-time unit lets you directly relate the applied water to soil infiltration, plant needs, and potential runoff. If water is applied too fast, infiltration can't keep up and you lose efficiency; if too slow, you may under-water. The other options measure flow or pressure rather than the depth of water applied per area per hour: gallons per minute and liters per second are volume-per-time, and PSI is pressure. Those are important for sizing pumps, pipes, and nozzles, but they don’t describe how much water depth is being added to the ground each hour.

Precipitation rate is about how much water depth is delivered to the soil per unit of time across the area being irrigated. In irrigation design, the standard way to express that rate is inches per hour (or millimeters per hour in metric). Using a depth-per-time unit lets you directly relate the applied water to soil infiltration, plant needs, and potential runoff. If water is applied too fast, infiltration can't keep up and you lose efficiency; if too slow, you may under-water. The other options measure flow or pressure rather than the depth of water applied per area per hour: gallons per minute and liters per second are volume-per-time, and PSI is pressure. Those are important for sizing pumps, pipes, and nozzles, but they don’t describe how much water depth is being added to the ground each hour.