Ground Water Basics continued Soil Moisture Regimes Aridic

Ground Water Basics continued

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 Isotropic Anisotropic Homogeneous Heterogeneous

Hydraulic Conductivity Values Freeze and Cherry, 1979

Layered media (horizontal conductivity) Q 4 Q 3 Q 2 Q 1 Q = Q 1 + Q 2 + Q 3 + Q 4 Flow K 2 b 2 K 1 b 1

Layered media (vertical conductivity) Q 4 R 4 Q 3 R 3 Q 2 Q 1 Flow R 2 R 1 K 2 b 2 K 1 b 1 Controls flow Q = Q 1 = Q 2 = Q 3 = Q 4 The overall resistance is controlled by the largest resistance: R = R 1 + R 2 + R 3 + R 4 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, ft 2/d, m 2/d

Schematic T 2 (or K 2) b 2 (or h 2) i=2 k 2 d 2 T 1 b 1 k 1 d 1 i=1

Pumped Aquifer Heads T 2 (or K 2) b 2 (or h 2) i=2 k 2 d 2 T 1 b 1 k 1 d 1 i=1

Heads h 2 - h 1 T 2 (or K 2) b 2 (or h 2) i=2 h 1 k 2 d 2 T 1 b 1 k 1 d 1 i=1

Leakance Leakage coefficient, resistance (inverse) • Leakance • From below: • From above:

Flows h 2 i=2 h 2 - h 1 qv T 2 (or K 2) b 2 (or h 2) k 2 d 2 T 1 b 1 k 1 d 1 i=1

Poisson Equation