Lecture 4a - Soil Water Fundamentals Flashcards
What is each soil layer callde?
horizon
What are the major horizons?
topsoil (A), subsoil (B), parent material (C), consolidated berock (R)
Describe topsoil.
majority of biological activity, loss of secondary minerals
Describe subsoil.
zone of accumulated materials
Decribe parent material.
base mineral substrate
What differs between each soil horizon?
color, particle size, density, hydraulic conductivity
What is primary soil structure?
size distribution of individual particles (sand, silt, clay)
What is secondary soil strucutre?
arrangement of particles into larger aggregates, can have a large influence on water movement
Why might darcy’s law be invalid for unstatured flow?
strong soil-water bonding, macropores
What is volumetric water content (theta)?
vol water/vol total soil
What is gravimetric water content (u)?
mass of water/mass of dry soil
What is degree of saturation?
fraction of pore space filled with water (0-1)
What are matric potential, soil suction and soil tension (pitchfork)?
paressure required to remove water from soil, cohesive attractive force between water and soil particle
Explain hydraulic gradient.
in saturated zone flow driven by gradient in +ve pore pressure whereas in unsatured zone flow driven by gradient in -ve matric potentials
What is infilatration capacity (fp)?
theoretical maximum rate of water transmission into soil as influence by soil factors
How are matric potential and hydraulic gradients in the unsaturated zone measured?
tensiometers
What is infiltration rate (f)?
rate of water transmission into soil as influenced by soil factors and water availability at soil surface
