Head pressure in a water column depends on which factor?

• A. Height of water column
• B. Volume of water
• C. Temperature
• D. Pressure at base

Answer: (A)

Head pressure, or hydrostatic pressure, comes from the weight of the water above a point. The pressure at the base of a column is determined by how tall the water column is, not by how much water there is in total. This relationship is captured by P = ρ g h, where h is the height of the water column. So as the height increases, the pressure increases in direct proportion (assuming density stays roughly constant). Volume changes the amount of water but not the pressure at a given depth unless it changes the height. Temperature can tweak density slightly, but the height remains the primary factor.