Hydrologic Cycle and Groundwater:
Groundwater:
Groundwater:
The Hydrologic (water) Cycle and Groundwater:
I.
Water moves from air to ground through phase changes. (we will
discuss this in depth later in the year).
II.
Water that falls on land may become runoff, which means that it
will flow on the surface as streams.
III.
Water that infiltrates the soil becomes groundwater.
A. These terms describe water in the soil:
Zone of aeration: pore spaces are primarily filled with air, not water.
_Capillary fringe: aerated soil directly above the water table, in which water climbs up
through adhesion and cohesion.
Water table_: point below soil surface at which aerated soil becomes saturated soil.
_ Zone of saturation: all pore spaces are filled in with water.
__infiltration : water moves down through the pore spaces in the soil.
__Ground Water : all water in soil/porous rock beneath the water table.
B. Groundwater occurs wherever water saturates the soil. If it reaches the
surface, it becomes a stream, lake or pond.
C. Impermeable material will not allow water to flow through it because;
It is already saturated with water (flooding)
The particles are very tiny (clay) or very tightly packed
The ground is frozen
The ground is paved
The ground is too steep
The rain falls too quickly to infiltrate (soak in)
Aquifer and artesian wells:
D. Capillarity: water’s ability to climb up through the soil.
IV.
Soil Water Movement:
(page 301-308 text)
A. Pore space: Volume of a material that is taken up by air.
Porosity: percent of a material that is air space
Porosity and pore space depend on:
Sorting of material by size:
Large sediments leave larger pore spaces.
Shape of material:
Round, sorted particles have the most pore space
Packing of materials:
loose sediments contain the most pore space.
B. Permeability: water can move in the soil.
Infiltration: ability of water to flow down through a material.
Permeability: rate at which water will flow down through a material.
Permeability and infiltration rate depend on:
Size of pore spaces: large, round particles sorted by size have the largest
pore spaces and best permeability.
Connectedness of pores:
If the holes and cracks are not connected, there is no flow.
C.Capillarity: ability of water to move up through a soil, against gravity.
Capillarity is best when particles are very small.
Summary:
Best porosity: particles are round and sorted by size, loosely packed.
Best permeability: particles are round, large, loosely packed.
Best capillarity: particles are small and not too tightly packed.