flow in aquifers groundwater hydraulics daene c. mckinney
TRANSCRIPT
Summary
• Confined Aquifer Flow– Continuity Equation– Steady Horizontal Flow– Transmissivity
• Unconfined Aquifer Flow– Continuity Equation– Steady Horizontal Flow– Steady Horizontal Flow with Infiltration– Drains
Flow in an Unconfined Aquifer• Dupuit approximations
– Slope of the water table is small– Velocities are horizontal
Ground surface
Bedrock
Unconfined aquifer
Water table
Dx
Qx
K
h
x
yz
Steady Flow in an Unconfined Aquifer
• 1-D flow
• Steady State
• K = constant
h
FlowhA
hB
Water Table
Ground Surface
Bedrock Lx
Steady Flow in an Unconfined Aquifer With Infiltration
hhMax
FlowhA
hB
Water Table
Ground Surface
Bedrock
N, Infiltration
Lx
Steady Flow Constant K
Steady Flow in an Unconfined Aquifer With Infiltration
hhMax
FlowhA
hB
Water Table
Ground Surface
Bedrock
N, Infiltration
Lx
hhMax
FlowhA
hB
Water TableGround Surface
Bedrock
N, Infiltration
Lx
Steady flow in an unconfined aquifer with infiltration
Example (Embankment)
• GivenL = 3000 mK = 20 m/dayhA = 30 m
hB = 20 m
N = 500 mm/yr
• Find: Flow to the streams and shape of water table
hhMax
FlowhA
hB
Water Table
Ground Surface
Bedrock
N, Infiltration
Lx
Example (Drains)• Subsurface drains are often used to prevent the water table elevation from
increasing to an elevation where it would waterlog the roots of crops or bring unwanted salts and other chemicals in to the root zone.
• Steady, 1-D flow , homogeneous, isotropic aquifer, w/infiltration
hd
hMax
Water Table
Ground Surface
Lower Confining Layer
N, Infiltration
Lx