Hydraulic Head

Abstract The hydraulic head (or total head) is an indicator of fluid energy expressed in units of length, such as meters or feet. Hydraulic head combines all forces (e.g. gravity, pressure, inertia, surface tension, solute concentration, fluid density) that cause water movement in many hydrologic systems, including surface water, soil water, and groundwater. The hydraulic gradient (i.e. the slope or spatial change in hydraulic head) is used to find the magnitude and direction of fluid flow, where water flows from high‐to‐low head. The temporal change in the hydraulic head is used to estimate changes in water storage. While the water surface elevation in streams and wells can be used to approximate the hydraulic head, water levels must be corrected for water velocity, dissolved‐ and suspended‐solid concentrations, barometric pressure, and other factors.