Environmental Engineering Reference
In-Depth Information
U
Unconfined aquifer:
An aquifer whose upper surface is a water table free to
fluctuate under atmospheric pressure.
Unsaturated zone:
A subsurface zone above the water table in which the
pore spaces may contain a combination of air and water.
V
Vehicle of disease transmission:
Any nonliving object or substance con-
taminated with pathogens.
Vernal pool:
A small lake or pond that is filled with water for only a short
time during the spring.
W
Wastewater:
The spent or used water from individual homes, a community,
a farm, or an industry that contains dissolved or suspended matter.
Water budget:
An accounting of the inflow to, outflow from, and storage
changes of water in a hydrologic unit.
Water column:
An imaginary column extending through a water body from
its floor to its surface.
Water demand:
Water requirements for a particular purpose, such as irriga-
tion, power, municipal supply, plant transpiration, or storage.
Water softening:
A chemical treatment method that uses either chemicals
to precipitate or a zeolite to remove those metal ions (typically Ca
2+
,
Mg
2+
, Fe
3+
) responsible for hard water.
Water table:
The top water surface of an unconfined aquifer at atmospheric
pressure.
Waterborne disease:
Water is a potential vehicle of disease transmission,
and waterborne disease is possibly one of the most preventable types
of communicable illness. The application of basic sanitary principles
and technology has virtually eliminated serious outbreaks of water-
borne diseases in developed countries. The most prevalent water-
borne diseases include typhoid fever, dysentery, cholera, infectious
hepatitis, and gastroenteritis.
Watershed:
The land area that drains into a river, river system, or other body
of water.
Wellhead protection:
The protection of the surface and subsurface areas
surrounding a water well or well field supplying a public water sys-
tem from contamination by human activity.
Y
Yield:
The mass of material or constituent transported by a river in a speci-
fied period of time divided by the drainage area of the river basin.