How does elevation affect pressure requirements in an irrigation system?

• A. Elevation has no impact on pressure in irrigation systems.
• B. Pressure regulators negate elevation effects.
• C. Higher elevation zones require more head to deliver water, increasing TDH and potentially reducing pressure elsewhere.
• D. Lower elevations require more head than higher elevations.

Answer: (C)

Elevation creates a hydrostatic head: water must be lifted to reach higher zones, so more pressure (head) is needed to deliver water there. In an irrigation system, the pump has to supply enough total dynamic head (TDH) to overcome gravity (the elevation difference) and friction in the pipes. If a zone sits higher than the water source, you need extra head to push water uphill; for every foot of rise, you gain about 0.43 psi (since 1 psi ≈ 2.31 feet of water). For example, 20 feet of rise requires roughly 8–9 psi of additional pressure just to reach that height. When the pump adds this extra head, the pressure available at lower parts of the system can drop if the source can’t meet the total demand, which is why higher elevation zones can have lower pressure if the system isn’t sized for that head. Pressure regulators don’t eliminate this need for elevation head, and lower elevations don’t require more head than higher ones.