Irrigation and Water Management
Irrigation questions test system components, hydraulics, and water efficiency. Know the anatomy: water source, backflow prevention, mainline, valves, lateral lines, heads (spray, rotor, drip), controllers, and sensors (rain, soil moisture). Understand zones by plant water need, sun exposure, and head type - never mix spray and drip on one zone. Traps include omitting backflow prevention, mismatching precipitation rates, and ignoring head-to-head coverage.
Hydraulics: know pressure (psi), flow (gpm), and that friction loss and elevation change reduce pressure at heads. Understand that matched precipitation rate heads apply water evenly across a zone. Know distribution uniformity and why head-to-head spacing (heads spaced at their throw distance) prevents dry spots. Distinguish drip (low flow, high efficiency, longer run times) from spray (high flow, short runs) and rotors (gear-driven, larger areas).
Water management: evapotranspiration (ET) drives scheduling; smart controllers adjust run times to ET and weather. Understand cycle-and-soak for slopes and tight soils to prevent runoff. Know that overwatering causes runoff, disease, and shallow roots, while deep infrequent watering builds drought tolerance. Review rain harvesting, greywater basics, and the role of mulch in reducing water demand.
Worked rule of thumb: to estimate run time, divide the plant water need (inches per week) by the zone's precipitation rate (inches per hour) to get hours per week, then split into cycles. Example: 1 in/week needed, 0.5 in/hr precipitation rate = 2 hours/week, split into two 1-hour runs or cycle-and-soak on a slope.
Review backflow type selection (e.g., reduced pressure vs. double check) and local code requirements; questions often test the safety device, not the schedule.