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 HomogeneousHeterogeneous Isotropic Anisotropic

Hydraulic Conductivity Values Freeze and Cherry, 1979

Layered media (horizontal conductivity) Q1Q1 Q2Q2 Q3Q3 Q4Q4 Q = Q 1 + Q 2 + Q 3 + Q 4 K1K1 K2K2 b1b1 b2b2 Flow

Layered media (vertical conductivity) Controls flow Q1Q1 Q2Q2 Q3Q3 Q4Q4 Q = Q 1 = Q 2 = Q 3 = Q 4 R1R1 R2R2 R3R3 R4R4 R = R 1 + R 2 + R 3 + R 4 K1K1 K2K2 b1b1 b2b2 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, ft 2 /d, m 2 /d

Schematic i = 1 i = 2 d1d1 b1b1 d2d2 b 2 (or h 2 ) k1k1 T1T1 k2k2 T 2 (or K 2 )

Pumped Aquifer Heads i = 1 i = 2 d1d1 b1b1 d2d2 b 2 (or h 2 )k1k1 T1T1 k2k2 T 2 (or K 2 )

Heads i = 1 i = 2 d1d1 b1b1 d2d2 b 2 (or h 2 )k1k1 T1T1 k2k2 T 2 (or K 2 ) h1h1 h2h2 h 2 - h 1

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

Flows i = 1 i = 2 d1d1 b1b1 d2d2 b 2 (or h 2 )k1k1 T1T1 k2k2 T 2 (or K 2 ) h1h1 h2h2 h 2 - h 1 qvqv

Poisson Equation