title: ‘Important hydraulic concepts’ date: 2022-05-17 permalink: /posts/2022/05/blog-post-Important hydraulic concepts/

• Water level: is known as gauge height or stage, is the elevation of the free surface of a seam, stream, lake or reservoir relative to a specified vertical datum. (https://en.wikipedia.org/wiki/Water_level) ** In hydrology, stage refers to the water level in a river or stream with respect to a chosen reference height.

• water head: or hydraulic head= pressure head + elevation, is a specific measureent of liquid pressure above a vertical datum. It was usually measured as a liquid surface elevation, expressed in units of length. There are four types of head used to calculate the total head in and out of a pump:

  ** Velocity head is due to the bulk motion of a fluid (kinetic energy). Its pressure head correspondent is the dynamic pressure. ** Elevation head is due to the fluid’s weight, the gravitational force acting on a column of fluid. ** Pressure head is due to the static pressure, the internal molecular motion of a fluid that exerts a force on its container. ** Resistance head (or friction head or Head Loss) is due to the frictional forces acting against a fluid’s motion by the container. (https://en.wikipedia.org/wiki/Hydraulic_head)

• water table: is the upper surface of zone of saturation/ is the surface where the water pressure head is equal to the atmospheric pressure. (https://en.wikipedia.org/wiki/Water_table)
• The driving force for transport of water in the unsaturated zone is the gradient of the hydraulic head, h, which includes a gravitational component, z, and a pressure component, p. H=z+p ** z is the elevation of the point above the datum. h, the reference level for the pressure head componenet is the atmospheric pressure. (http://doc.mikepoweredbydhi.help/webhelp/2017/mikeshe/MIKE_SHE_online/UZ_TechnicalReference/Richards_Equation.htm)