hydrology
Hydrology
Contents
of Entire Course
Hydrologic
Cycle
Groundwater
Terminology
adapted to HTML from lecture
notes of Prof. Stephen A. Nelson Tulane University
Hydrologic
Cycle
| |
Total Water |
Fresh Water |
Unfrozen Water
(Fresh) |
| Ocean |
97 % |
- |
- |
| Ice |
2 % |
87 % |
- |
| Ground |
0.6 % |
13 % |
97 % |
| Lakes and Streams |
- |
0.3 % |
3 % |
| - Fresh Water |
0.009 % |
- |
- |
| - Salty Water |
0.008 |
- |
- |
Groundwater
Terminology
Zone
of Saturation
The area where all
the pore space in the ground is filled with water.
Zone
of Aeration
The area of where the
pore space is mostly empty, or full of air.
Water
Table
The level below which
the ground is saturated.
Groundwater
Aquifer
A large volume of the
subsurface that is thoroughly saturated with water, and through which
water
travels freely. It contains a large volume of water which can be
accessed
for use.
Aquiclude
A layer of impermeable
material, for example clay, that prevents water from passing through.
Perched
water table
Subsurface area saturated
with water above an aquiclude, forming a local water table above the
regional
water table..
Hydraulic
Conductivity
A measure of permeability.
( How fast does the water travel through the substance?).
Hydraulic
Gradient
The difference in
the elevation of the water table over a given length.
The rate of groundwater
flow is dependent on the hydraulic conductivity and hydraulic gradient.
The greater the conductivity or the
greater the gradient the more rapid
groundwater flows.
Transpiration
The process by which
water sorbed by plants is returned to the atmosphere as a gas.
Evapotranspiration
The combined processes
of Evaporation and Transpiration.
- Porosity
- The percentage of void
space in a rock.
*Well sorted sand
may have a porosity of 30% to 40%.
*Poorly sorted sand
will have a lower porosity because the finer grained sediment fills the
spaces between the larger grains.
*Most igneous rocks
have very low to no porosity.
*Limestones may
have a low or high porosity. If it has undergone erosion or
dissolution,
it may even have large caverns.
- Permeability
- The ease with which
water can pass through a substance.
A substance through
which water cannot pass is said to be Impermeable.
The permiability of
various sediment types, ranging from most permeable to least permeable,
is:
Gravel Most permeable
Sand
Silt
Till
Clay Least permeable
Hydraulic
Head
The term applied
to water pressure due to the difference in the height of water in a
closed
system. Water tends to reach its own level. This phenomena may result
in
artesian wells and springs, and is used in providing water to
municipalities
via a water tower.
