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Ecosphere: Total of all
the ecosystems on the planet, along with their interactions; the sphere of air,
water, and land in which all life is found.
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Ecosystem: A system formed
by the interaction of a group of organisms and their environment.
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Edwards
aquifer: An arch-shaped
belt of porous, water bearing limestone composed of the Comanche Peak, Edwards,
and Georgetown formations trending from west to east to northeast through Kinney,
Uvalde, Medina, Bexar, Comal, Hays, Travis, and Williamson counties.
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Edwards
outcrop: Where
the Edwards and associated limestone formations are found at the surface. This
area is also referred to as the Recharge Zone.
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Effective
porosity: The
portion of pore space in saturated permeable material where the movement of
water takes place.
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Effective
precipitation:
The part of precipitation
which produces runoff; a weighted average of current and antecedent precipitation
"effective" in correlating with runoff. It is also that part of the precipitation
falling on an irrigated area which is effective in meeting the requirements
of consumptive use.
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Effluent: The sewage or
industrial liquid waste that is released into natural water by sewage treatment
plants, industry, or septic tanks.
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Ejector: A device used
to inject a chemical solution into wastewater during water treatment.
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Electrical
charge: The charge
on an ion, declared by its number of electrons. A Cl- ion is in fact a Cl atom
which has acquired an electron, and a Ca++ ion is a Ca atom, which has lost
two electrons.
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Electrodialysis: A process which
uses an electrical current and an arrangement of permeable membranes to separate
soluble minerals from water. It is often used to desalinate salt or brackish
water.
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Electrolyte: Substance that
dissociates into ions when it dissolves in water.
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Elutriation: Freeing sludge
of its mother liquor by washing it with water.
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Emulsifier: A chemical that
helps suspending one liquid in another.
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Emulsion: Dispersion of
one liquid in another liquid, occurs when a liquid in insoluble.
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Endangered
species: One
having so few individual survivors that the species could soon become extinct
in all or part of its region.
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End-of-pipe
techniques: Techniques
for water purification that serve the reduction pollutants after they have formed.
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Enrichment: When the addition
of nutrients, such as nitrogen and phosphorus, from sewage effluent or agricultural
runoff to surface water, greatly increases algal growth.
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Enteric
viruses: A category
of viruses related to human excreta found in waterways.
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Environment: All of the external
factors, conditions, and influences that affect an organism or a community.
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Environmental
assessment: The
critical appraisal of the likely effects of a proposed project, activity, or
policy on the environment, both positive and negative.
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Environmental
monitoring: The
process of checking, observing, or keeping track of something for a specified
period of time or at specified intervals.
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EPA: Environmental
protection agency.
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Epilimnion: Warm, less dense
top layer in a stratified lake. Compare hypolimnion.
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Erosion: The wearing down
or washing away of the soil and land surface by the action of water, wind, or
ice.
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Escarpment: The topographic
expression of a fault.
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Eschericha
coli (E. coli):
Coliform bacterium that
is often associated with human and animal waste and is found in the intestinal
court. It is used by health departments and private laboratories t measure the
purity of water.
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Estuarine
waters: Deepwater
tidal habitats and tidal wetlands that are usually enclosed by land but have
access to the ocean and are at least occasionally diluted by freshwater runoff
from the land (such as bays, mouths of rivers, salt marshes, lagoons).
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Estuarine
zone: Area near
the coastline that consists of estuaries and coastal saltwater wetlands.
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Estuary: Regions of interaction
between rivers and nearshore ocean waters, where tidal action and river flow
create a mixing of fresh water and saltwater. These areas may include bays,
mouths of rivers, salt marshes, and lagoons. These brackish water ecosystems
shelter and feed marine life, birds, and wildlife.
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Euphotic
zone: Surface
layer of an ocean, lake, or other body of water through which light can penetrate.
Also known as the zone of photosynthesis.
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Eutrophic: Having a large
or excessive supply of plant nutrients (nitrates and phosphates). Compare oligotrophic.
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Eutrophic
lake: Shallow,
murky bodies of water that have excessive concentrations of plant nutrients
causing excessive algal production.
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Eutrophication: The natural process
by which lakes and ponds become enriched with dissolved nutrients, resulting
in increased growth of algae and other microscopic plants.
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Evaporation: Process by which
water is changed from a liquid into a vapor. See also evapotranspiration and
transpiration.
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Evaporation
ponds: Areas
where sewage sludge is dumped and dried.
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Evapotranspiration: A collective
term that includes water discharged to the atmosphere as a result of evaporation
from the soil and surface-water bodies and as a result of plant transpiration.
See also evaporation and transpiration.
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External
cost: Cost of
production or consumption that must be borne by society; not by the producer.
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Extinction: Complete disappearance
of a species because of failure to adapt to environmental change.
