How is hydraulic head defined?

Hydraulic head is a crucial concept in hydrogeology that represents the total potential energy available to groundwater. It is defined as the height of the free surface of water above a specific point, which accounts for both the pressure and elevation of the water at a given location. In essence, the hydraulic head reflects the energy status of groundwater and is often measured in terms of meters or feet above a reference point, typically sea level or the bottom of a well.

This definition captures the relationship between gravity, pressure, and the elevation of water, which influences groundwater flow. As water rises in a well due to its hydraulic head position relative to a reference level, it indicates how groundwater will move through an aquifer system in response to varying conditions, such as extraction or recharge.

Other choices do not align with the principles of hydraulic head. The pressure exerted by water below the surface pertains to fluid pressure rather than the elevation aspect that defines hydraulic head. The total volume of water stored underground relates to aquifer storage, while the temperature of the groundwater table does not pertain to hydraulic head at all, as hydraulic head specifically concerns the height of the water and its energy potential rather than temperature characteristics.