[hī′drȯ·lik ′grād·ē·ənt]
(fluid mechanics)
With regard to an aquifer, the rate of change of pressure head per unit of distance of flow at a given point and in a given direction.
(hydrology)
The slope of the hydraulic grade line of a stream.

1. The loss of head per unit distance of flow.
2. In a drainage system, the slope of a drainage line between the trap outlet and vent connection.
References in periodicals archive ?
Pressure drop at the rated flow rate can vary, depending on where the cooling coil is located in the system hydraulic gradient curve.
It can be seen from these studies that Darcy's flow law, which assumes a linear correlation between the flow and hydraulic gradient, has been commonly used for its simplicity.
WhereQ is the water discharge, K is the hydraulic conductivity of the soil (soil permeability), A isthe cross sectional flow area and i is the hydraulic gradient which is given by the following equation:
It was determined that in the course filtration at higher hydraulic gradients, clay mineral particles re-orientate parallel to the water flow lines, and, with the hydraulic gradient dropping down, clay particles do not return to the initial position.
v--velocity of flow in the sample [m/s], i--hydraulic gradient [m/m] where hydraulic gradient is:
The orientation of the septic plumes was estimated by use of an OhmMapper TR1 electrical resistivity mapper and the direction of groundwater flow was estimated on the basis of the hydraulic gradient as determined from a three-point problem solution at each site (Heath, 1998; Humphrey, Deal, O'Driscoll, & Lindbo, 2010).
From soil--water studies, it is known that there are conditions under which the linear relation of flux and hydraulic gradient of Darcy's law of water movement is disturbed (Hubbert 1956).
Transmmissivity is widely employed in groundwater hydraulics; it is known to be the rate at which water of a prevailing kinematics viscosity is transmitted through a unit width of aquifer under a unit hydraulic gradient.
Groundwater flowing though soil exerts a destabilizing force on the soil that is proportional to the hydraulic gradient, which can lead to what has been termed "pop-out" streambank failures.
Bank filtration is a natural water treatment process that induces surface water to flow in response to a hydraulic gradient through sediment and into a vertical or horizontal well.
Among the topics are risk analysis of individual landslides in the Three Gorges Reservoir, the simultaneous modeling of internal erosion and deformation of soil structures, geotechnical properties of zinc and lead mine tailings from Tara Mines in Ireland, pH changes in solidified dredged materials, the rapid drawdown of the water table in layered soil column, and a mathematical model for determining the critical hydraulic gradient in soil piping.

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