week4 Flashcards
what is the saturated zone
where pores are water filled
what is the vadose zone
above saturated zone, where pores are generally unsaturated and filled partly by air and water. important for plants/earth living zone
what is capillary fringe
transition zone with high moisture content at the base of the vadose zone just above the water table. depends on grain size.
what is field capacity
moisture content after free gravity drainage, 2-3 after rain/run on creates soil saturation
what are the 4 type sof soil water
chemically bonded, adhesion, gravitational, capillary
what are some of the forces on soil water and drainage
gravity (pulls water down), adhesion (attraction of water to silica) and cohesion (water to water attraction)
macropores are how big
> 60um water drains freely
micropores are how big
<60um small enough to adhesive and cohesive forces holding water to poer wall are stronger than gravitiy trying to drain soil
what is capillarity
brings solutes to the soil surface due to upwards and horizontal travelling of water and efflorescence can occur.
how can capillary rise be altered
finer pore spaces allows more water to rise, the capillary fringe is not a flat surface.
what is soil water potential
its negative (like a suction), when soil becomes dry, water is held tightly to pores and minerals.
who uses the most groundwater in aus
NT
porosity of sediments is determined by what
how tightly packed the grains are (porosity = 20-40%
why is groundwater usage so high
because its the largest freshwater ecosystem
what sediment has the best permeability
gravel, sand, silt then clay
