What does precipitation rate specify in sprinkler design?

• A. The annual rainfall total
• B. The rate of soil infiltration per hour
• C. The depth of water applied per unit area per hour
• D. The nozzle discharge rate

Answer: (C)

Precipitation rate is the rate at which water is applied to the ground over a defined area, measured as a depth of water per unit area per unit time (typically inches per hour or millimeters per hour). In sprinkler design this tells you how quickly the zone delivers water to the soil footprint, which is essential for matching irrigation to how fast the soil can infiltrate water and how much water the plants need. If the rate is too high for the soil’s infiltration capacity, water can pond or runoff instead of soaking in; if it’s too low, you’ll need longer runtimes or more cycles to meet demand. It also guides sprinkler spacing and overlap to achieve uniform coverage. The idea isn’t the total rainfall in a year or the soil’s infiltration rate itself, and it isn’t just the discharge of a single nozzle—the precipitation rate combines the flow from all active heads over the area to express how much water depth is applied per hour.