EV 403 Ground Water Hydrology
Porosity
Porosity, =
Also, porosity, =
@1
And! Porosity, = +
@
1
Specific Yield and Specific Retention
Specific yield (Sy) is the volume of water that drains from a
saturated rock or sediment by gravity, relative to the t

EV 403 Ground Water Hydrology
Darcys Law and Hydraulic
Conductivity
Darcys Law
The quantity dh represents the change in head with distance,
dl.
The negative sign is a convention such that the direction of
flow is toward lower hydraulic head.
The essence o

EV 403 Ground Water Hydrology
Storage Properties of Aquifers 1
Moisture Content
Recall that the porosity (n) of earth materials is the ratio of
the volume of the voids (Vv) to the total volume (VT) of the
sample. The volume of the voids may be further di

EV 403 Ground Water Hydrology
Content:
The Hydrologic Equation
Water
The Hydrologic Cycle
Distribution of Water
Elements of the Hydrologic Cycle
The Hydrologic Equation
Conservation of water mass in the hydrologic system
is expressed as follows:
Inflow O

EV 403 Ground Water Hydrology
Hydraulic Head, Fluid Potential
Storage Properties of Aquifers 1
To discuss hydraulic gradient, one must introduce the concept
of hydraulic head.
The hydraulic head is a means of expressing the potential
energy of a unit we

EV 403 Ground Water Hydrology
Equations of Groundwater Flow
Equations of Groundwater Flow
Groundwater flow can be described by partial differential
equations where the spatial coordinates, x, y, z, and time, t,
are the independent variables.
Let us cons

EV 403 Ground Water Hydrology
Darcys Law
In 1856 in France, Henry Darcy conducted his now
famous experiment of pouring water through sedimentpacked pipes to see how much would flow through them
in a given amount of time [volume of flow per unit time].
F

EV 403 Ground Water Hydrology
Specific Discharge, Average Linear
Velocity and Flow Nets
Specific Discharge and Average Linear Velocity
Recall Darcys law:
(eq.9-1)
It states that the flow (discharge) will be proportional to the
hydraulic gradient (dh/dl)

EV 403 Ground Water Hydrology
Aquifer and Aquifer Characteristics
Heterogeneity and Anisotropy
Hydrologic properties (hydraulic conductivity,
specific storage, etc.) may vary through space within
a geological formation.
The spatial variation of hydrauli

EV 403 Ground Water Hydrology
Storage Properties of Aquifers 2
Compressibility of a Porous Medium
The compressibility of a porous medium, , is defined as
(eq.7-9)
where VT is the total volume of the porous medium, dVT is the
change in the volume of the

EV 403 Ground Water Hydrology
Unsaturated Zone, Vadose Zone, Soil Moisture Zone, Zone of
Aeration rock, water and air
Capillary Fringe region above water table where water rises
due to capillary forces in the porous medium.
Saturated Zone, Phreatic Zone