ground water basics continued. soil moisture regimes aridic arid climate, usually dry, irrigation...
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Ground Water Basicscontinued
Soil Moisture Regimes• Aridic arid climate, usually dry, irrigation required for crop
production.• Ustic—semiarid climate, rainfall during a growing season. • Xeric—semiarid climate, Mediterranean climate, cool, moist winters,
dry summers,• dryland crop possible from stored soil water. • Udic—humid climate, usually moist, generally irrigation not required
for crop• production. • Perudic—precipitation exceeds evapotranspiration in all months, but
soil is not• saturated for long periods.• Aquic—soil saturated long enough to cause anaerobic conditions
Soil Moisture Regimes
Types of Porous Media
Homogeneous Heterogeneous
Isotropic
Anisotropic
Hydraulic Conductivity Values
Freeze and Cherry, 1979
Layered media (horizontal conductivity)
M
ii
M
ihii
h
b
KbK
1
1
Q1
Q2
Q3
Q4
Q = Q1 + Q2 + Q3 + Q4
K1
K2
b1
b2
Flow
Layered media(vertical conductivity)
M
ihii
M
ii
v
Kb
bK
1
1
/Controls flow
Q1
Q2
Q3
Q4
Q = Q1 = Q2 = Q3 = Q4
R1
R2
R3
R4
R = R1 + R2 + R3 + R4
K1
K2
b1
b2
Flow
The overall resistance is controlled by the largest resistance: The hydraulic resistance is b/K
Aquifers
• Lithologic unit or collection of units capable of yielding water to wells
• Confined aquifer bounded by confining beds
• Unconfined or water table aquifer bounded by water table
• Perched aquifers
Transmissivity
• T = Kb
gpd/ft, ft2/d, m2/d
Schematic
i = 1
i = 2
d1
b1
d2
b2 (or h2)
k1
T1
k2
T2 (or K2)
Pumped Aquifer Heads
i = 1
i = 2
d1
b1
d2
b2 (or h2)
k1
T1
k2
T2 (or K2)
Heads
i = 1
i = 2
d1
b1
d2
b2 (or h2)
k1
T1
k2
T2 (or K2)
h1
h2
h2 - h1
LeakanceLeakage coefficient, resistance (inverse)
• Leakance
• From below:
• From above:
d
k
1
11
i
iiiv d
khhq
1
11
i
iiiv d
khhq
Flows
i = 1
i = 2
d1
b1
d2
b2 (or h2)
k1
T1
k2
T2 (or K2)h1
h2 h2 - h1
qv
Poisson Equation
2
2
,TqR
xhhh
vxxxx
yx
T
qR
x
h v
2
2
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