Basic Hydrogeology
Or –
“How do I get water from rocks?”
How Does Groundwater
Form?
Source: Heath, 1980
Source: Heath, 1980
Occurrence of Groundwater
Source: Heath, 1980
Source: Heath, 1980
Porosity
Source: Heath, 1980
Specific Yield
Darcy’s Law
Q=
Discharge
(volume/time)
dh
K*A*( /
Hydraulic
Conductivity
(distance/time)
)
dl
Cross-sectional
Area
Hydraulic Gradient
(change in head/
Change in distance)
Hydraulic Conductivity
Q=
dh
K*A*( /dl)
Q = K*i*A
K = Qi/A
Hydraulic Conductivity
K = Qi/A
“The volume of water that will move
in a porous medium in unit time
under a unit hydraulic gradient
through a unit area measured at
right angles to the flow direction.”
Source: Heath, 1980
Transmissivity
T = Kb
where
K= hydraulic conductivity (ft/day)
b = aquifer thickness (ft)
Generalized Cross-Section
of NC Coastal Plain
Source: Heath, 1980
Typical NC Coastal Plain X-Section with Flow Lines
Source: Heath, 1980
From Driscoll, 1986, Groundwater & Wells
Hydrogeology of the
Piedmont and
Mountains
The Rosetta Stone
Source: Heath, 1980
Deeper
Soil/ Saprolite
Transition Zone
Bedrock
Transition Zone
Flow Through Transition Zone
Riparian Buffer
Saprolite
Alluvium
Transition Zone
Granite bedrock
Neuse
River
Lookie Here!
Source: Cunningham and Daniel, 2001
Well in Diabase Dike
Bottom of
Casing =
84 feet
Static
Water
Level =
27.5 feet
Source: Heath, 1980
Response of
fractured rocks to
withdrawals
Cone of
Depression
Cary, NC
Recommended Reference:
“Basic Ground-Water Hydrology”
USGS Water Supply Paper 2220
By Ralph Heath, 1983