Glossary of Water Resource Terms
- abandoned water right
- a water right which was not put to beneficial use for a number of years, generally five to seven years.
- abandoned well
- a well which is no longer used. In many places, abandoned wells must be filled with cement or concrete grout to prevent pollution of ground water bodies.
- the uptake of water, other
fluids, or dissolved chemicals by a cell or an organism (as tree roots
absorb dissolved nutrients in soil).
- a gradual increase in land area adjacent to a river.
- acid rain
- the acidic rainfall which results when rain combines with sulfur oxides emissions from combustion of fossil fuels.
- the condition of water or soil that contains a sufficient amount of acid substances to lower the pH below 7.0.
- the amount of water required to cover one acre to a depth of one foot. An acre-foot equals 325,851 gallons, or 43,560 cubic feet. A flow of 1 cubic feet per second produces 1.98 acre-feet per day.
- activated carbon adsorption
- the process of pollutants moving out of water and attaching on to activated carbon.
- the molecular attraction asserted between the surfaces of bodies in contact. Compare cohesion.
- a court proceeding to determine all rights to the use of water on a particular stream system or ground water basin.
- abandoned well
- a well which is no longer used. In many places, abandoned wells must be filled with cement or concrete grout to prevent pollution of ground water bodies.
- administrative order
- a legal document signed by
U.S. EPA directing an individual, business, or other entity to take
corrective action or refrain from an activity. It describes the violations
and actions to be taken, and can be enforced in court. Such orders may be
issued, for example, as a result of an administrative complaint ordering the
respondent to pay a penalty for violations of the Clean Water Act.
- administrative order on
- a legal agreement signed
by U.S. EPA and an individual, business, or other entity through which the
violator agrees to pay for correction of Clean Water Act violations, take
the required corrective or cleanup actions, or refrain from an activity. It
describes the actions to be taken, may be subject to a comment period,
applies to civil actions, and can be enforced in court.
- the adhesion of a substance to the
surface of a solid or liquid. Adsorption is often used to
extract pollutants by causing them to be attached to such
adsorbents as activated carbon or silica gel.
Hydrophobic, or water-repulsing adsorbents, are used to
extract oil from waterways in oil spills.
- advanced wastewater
- any treatment of sewage
that goes beyond the secondary or biological water treatment stage and
includes the removal of nutrients such as phosphorus and nitrogen and a high
percentage of suspended solids.
- aerated lagoon
- a holding and/or treatment
pond that speeds up the natural process of biological decomposition of
organic waste by stimulating the growth and activity of bacteria that
degrade organic waste.
- the mixing or turbulent exposure of
water to air and oxygen to dissipate volatile contaminants
and other pollutants into the air.
- aeration tank
- a chamber used to inject
air into water.
- aerobic treatment
- process by which microbes
decompose complex organic compounds in the presence of oxygen and use the
liberated energy for reproduction and growth. Such processes include
extended aeration, trickling filtration, and rotating biological contactors.
- life or processes that
require, or are not destroyed by, the presence of oxygen.
- a progressive build up of a channel bed with sediment over several years due to a normal sequence of scour and deposition, as distinguished from the rise and fall of the channel bed during a single flood.
- aggressive water
- water which is soft and acidic and can
corrode plumbing, piping, and appliances.
- simple rootless plants
that grow in sunlit waters in proportion to the amount of available
nutrients. They can affect water quality adversely by lowering the dissolved
oxygen in the water. They are food for fish and small aquatic animals.
- algal bloom
- a phenomenon whereby excessive nutrients within a river, stream or lake cause an explosion of plant life which results in the depletion of the oxygen in the water needed by fish and other aquatic life. Algae bloom is usually the result of urban runoff (of lawn fertilizers, etc.). The potential tragedy is that of a "fish kill," where the stream life dies in one mass extinction.
- substance or chemical used
specifically to kill or control algae.
- the condition of water or
soil that contains a sufficient amount of alkali substance to raise the pH
- the measurement of constituents in a
water supply which determine alkaline conditions. The
alkalinity of water is a measure of its capacity to
neutralize acids. See pH.
- allogenic recharge
- recharge that occurs in a sinking stream, entering an aquifer through sinkholes or fault planes. Contrast autogenic recharge.
- relating to, composed of,
or found in alluvium.
- sediments deposited by erosional
processes, usually by streams.
- a sudden or perceptible change in a river's margin, such as a change in course or loss of banks due to flooding.
- ambient background
- a representative
concentration of the water quality in a receiving water body, determined
from monitoring. The statistic or data used to determine the value from the
range of data is dependent on the purpose of the monitoring and the
application of the data.
- ambient medium
- material surrounding or
contacting an organism (e.g., outdoor air, indoor air, water, or soil
through which chemicals or pollutants can reach the organism.
- amprometric titration
- a way of measuring
concentrations of certain substances in water using the electric current
that flows during a chemical reaction.
- a secondary channel of a stream which leaves and then rejoins the main channel. The two channels are separated by stable, vegetated lands.
- a life or process that
occurs in, or is not destroyed by, the absence of oxygen.
- anistropic aquifer
- an aquifer in which permeability varies with direction of flow. The Edwards is a highly anistropic aquifer. Modeling flow in such aquifers is very problematic.
- annular space
- the space between two concentric
cylindrical objects, one of which surrounds the other,
such as the space between the walls of a drilled hole and
- anti-degradation clause
- part of federal and water
quality requirements prohibiting deterioration where pollution levels are
above the legal limit.
- appropriative rights
- "first in time, first in
right” principle of allocating water rights based. Usually involves a user
being allowed to take water from a particular source without regard to the
contiguity of the land to the source.
- growing in, living in, or frequenting water.
- aquatic life use
- a beneficial use designation in which the water body provides suitable habitat for survival and reproduction of desirable fish, shellfish, and other aquatic organisms.
- a formation which, although porous and
capable of absorbing water slowly, will not transmit
water fast enough to furnish an appreciable supply for a
well or a spring.
- something made up of
- aqueous solubility
- the maximum concentration
of a chemical that will dissolve in pure water at a reference temperature.
- the raising or fattening of fish in
enclosed ponds. Compare mariculture.
- a geologic formation that will yield
water to a well in sufficient quantities to make the
production of water from this formation feasible for
beneficial use; permeable layers of underground rock or
sand that hold or transmit groundwater below the water
- geological formation that
may contain groundwater but is not capable of transmitting significant
quantities of it under normal hydraulic gradients. May function as confining
- the formation of an erosion-resistant layer of relatively large particles on a streambed or bank resulting from removal of finer particles by erosion.
- artesian aquifer
- a geologic formation in which water is under sufficient hydrostatic pressure to rise above the top of the aquifer in the subsurface. Artesian aquifers are confined aquifers. Also see unconfined aquifer.
- artesian well
- a water well drilled into a confined aquifer where enough hydraulic pressure exists for water rise in the well to a height above the top of the aquifer in the subsurface. Also see flowing artesian well.
- artesian zone
- a zone where water is confined in an
aquifer under pressure so that the water will rise in the
well casing or drilled hole above the bottom of the
confining layer overlying the aquifer.
- a test for a specific
chemical, microbe, or effect.
- an organism group of interacting species in a given ecosystem, for example, a fish assemblage or a benthic macroinvertebrate assemblage.
- the ability of a water
body to purify itself of pollutants.
- assimilative capacity
- the capacity of a natural
body of water to receive and dilute wastewaters or toxic materials without
damage to aquatic life or humans who consume the water.
- the process whereby the magnitude of a flood event is reduced by slowing, modifying, or diverting the flow of water.
- autogenic recharge
- recharge that occurs by falling directly on an aquifer's outcrop at the surface. Contrast allogenic recharge.
- average annual recharge
- amount of water entering the aquifer
on an average annual basis. Averages mean very little for
the Edwards because the climate of the region and
structure of the aquifer produce a situation in which the
area is usually water rich or water poor.
- background level
- the concentration of a
substance in an environmental media (water or soil) that occurs naturally or
is not the result of human activities.
- a pressure that can cause
water to backflow into the water supply when a user's wastewater system is
at a higher pressure than the public system.
- reverse seepage of water in a
- reversing the flow of water through a
home treatment device filter or membrane to clean and
- the sloping land bordering a stream channel that forms the usual boundaries of a channel. The bank has a steeper slope than the bottom of the channel and is usually steeper than the land surrounding the channel. Right and left banks are named facing downstream.
- bank-full capacity
- the rate of water flow
that completely fills a channel; the flow rate at which the water surface is
level with the flood plain.
- bank stability
- occurs when the channel bank configuration does not change significantly over time.
- bar screen
- in wastewater treatment, a
device used to remove large solids from the incoming wastewater stream.
- any artificial obstruction placed in
water to increase water level or divert it. Usually the
idea is to control peak flow for later release.
- base flows
- the component of a flow regime that represents normal flow conditions between precipitation events. Base flows provide a range of suitable habitat conditions that support the natural biological community of a specific river sub-basin.
- related to the measurement of water depth within a water body.
- bed forms
- three-dimensional configurations of bed material, which are formed in streambeds by the action of flowing water.
- bed load
- the particles in a stream
channel that mainly move by bouncing, sliding, or rolling on or near the
bottom of the stream.
- bed stability
- occurs when the average elevation of the streambed does not change significantly over time. Aggradation and degradation are the two forms of bed instability.
- beneficial use
- the amount of water necessary when
reasonable intelligence and diligence are used for a
stated purpose; Texas law recognizes the following uses
as beneficial: (1) domestic and municipal uses, (2)
industrial uses, (3) irrigation, (4) mining, (5)
hydroelectric power, (6) navigation, (7) recreation, (8)
stock raising, (9) public parks, and (10) game preserves.
- pertaining to the bottom of a body of water, on or within the bottom substrate material.
- Best Management Practice (BMP)
- methods or measures
designed and selected to reduce or eliminate the discharge of pollutants
from point and nonpoint source discharges. As used in the stormwater
context, BMPs are a schedule of activities, prohibitions of practices,
maintains procedures and other management practices to prevent or reduce the
pollution of waters of the state. BMPs include treatment requirements,
operating procedures and practices to control plant site runoff, spills or
leaks, sludge or waste disposal, or drainage from raw material storage.
- uptake and retention of substances by
an organism from its surrounding medium (usually water)
and from food.
- a test to determine the
relative strength of a substance by comparing its effect on a test organism
with that of a standard preparation.
- monitoring the aquatic
environment to determine the health of a stream.
- the variety of plant, animal, and microorganism species present in the ecosystem and the community structures the form.
- biogeochemical cycling
- the flow of chemical substances to and from the major environmental reservoirs (atmosphere, hydrosphere, lithosphere, and biosphere).
- biological integrity
- the ability to support and
maintain balanced, integrated functionality in the natural habitat of a
given region. The concept is applied primarily in drinking water management.
- decomposition of complex
organic materials by microorganisms. Occurs in self-purification of water
bodies and in activated sludge wastewater treatment.
- a test used to evaluate the relative
potency of a chemical by comparing its effect on a living
organism with the effect of a standard population on the
same type of organism.
- a process that uses living organisms to remove pollutants.
- a nutrient-rich organic material
resulting from the treatment of wastewater. Biosolids
contain nitrogen and phosphorus along with other
supplementary nutrients in smaller doses, such as
potassium, sulfur, magnesium, calcium, copper and zinc.
Soil that is lacking in these substances can be reclaimed
with biosolids use. The application of biosolids to land
improves soil properties and plant productivity, and
reduces dependence on inorganic fertilizers.
- the earth and all its ecosystems.
- the plant (flora) and animal life (fauna) of a region or ecosystem.
- wastewater from toilet, latrine, and
agua privy flushing and sinks used for food preparation
or disposal of chemical or chemical-biological
- water samples containing a chemical of
known concentration given a fictitious company name and
slipped into the sample flow of the lab to test the
impartiality of the lab staff.
- a proliferation of algae
and/or higher aquatic plants in a body of water; often related to pollution
or excessive nutrients, especially when they accelerate growth.
- the water drawn from boiler systems
and cold water basins of cooling towers to prevent the
buildup of solids.
- a type of wetland that accumulates
appreciable peat deposits. They depend primarily on
precipitation for their water source, and are usually
acidic and rich in plant matter with a conspicuous mat or
living green moss.
- boiling point
- the temperature at which a liquid
boils. It is the temperature at which the vapor pressure
of a liquid equals the pressure on its surface. If the
pressure of the liquid varies, the actual boiling point
varies. For water it is 212 degrees Fahrenheit or 100
- Biochemical Oxygen Demand. A measure
of the amount of oxygen required to neutralize organic
wastes. The BOD of a wastewater is a characteristic reflecting
treatability or stage of decomposition. Compare COD and CBOD.
- boundary conditions
- definition or statement of conditions or phenomena at the boundaries of a model; water levels, flows, and concentrations that are specified at the boundaries of the area being modeled.
- mixed fresh and salt water.
- breakpoint chlorination
- addition of chlorine to
the point where all organic matter and ammonia compounds have been destroyed
and any additional chlorine becomes a free chlorine residual available for
- highly salty and heavily mineralized
water containing heavy metal and organic contaminants.
- the tendency of a body to float or
rise when immersed in a fluid; the power of a fluid to
exert an upward force on a body placed in it.
- calcium carbonate
- CACO3 - a white precipitate that forms
in water lines, water heaters and boilers in hard water
areas; also known as scale.
- amount of energy required to raise the
temperature of 1 gram of water 1 degree Celsius.
- to check, adjust, or determine by comparison that a computer model will produce results that meet or exceed some defined criteria within a specified degree of confidence.
- the overhanging cover formed by branches and foliage.
- capillary action
- movement of water through
very small spaces due to molecular forces called capillary forces.
- capillary forces
- forces that cause ground
water to rise above the surface of the saturated zone into the spaces
between soil particles in the unsaturated zone.
- capillary zone
- soil area above the water table where
water can rise up slightly through the cohesive force of
capillary action. See phreatophytes.
- a class of new-age pesticides that
attack the nervous system of organisms.
- carbon adsorption
- a treatment system that
removes contaminants from ground water or surface water by forcing it
through tanks containing activated carbon treated to attract the
- the collective term for the natural
inorganic chemical compounds related to carbon dioxide
that exist in natural waterways.
- a tubular structure intended to be
watertight installed in the excavated or drilled hole to
maintain the well opening and, along with cementing, to
confine the ground waters to their zones of origin and
prevent the entrance of surface pollutants.
- a large underground opening in rock
(usually limestone) which occurred when some of the rock
was dissolved by water. In some igneous rocks, caverns
can be formed by large gas bubbles.
- Carbonaceous Biochemical
Oxygen Demand. A BOD test in which a nitrification inhibitor is added,
so that only the carbonaceous oxygen demanding compounds are measured.
- cement grout
- a mixture of water and cement in the
ratio of not more than 5-6 gallons of water to a 94 pound
sack of portland cement which is fluid enough to be
pumped through a small diameter pipe.
- Comprehensive Environment Response,
Compensation and Liability Act. Also known as SUPERFUND.
The Act gave EPA the authority to clean up abandoned,
leaky hazardous waste sites.
- certificate of water right
- an official document which serves as
court evidence of a perfected water right.
- colony forming units.
Concentrations of water quality indicator organisms such as fecal coliform
bacteria are measured in cfu/100 ml.
- a natural or artificial watercourse that continuously or intermittently contains water, with definite bed and banks that confine all but overbanking streamflows.
- natural or intentional
straightening and/or deepening of streams so water moves faster and causes
less flooding. Channelization can sometimes exacerbate flooding in
other downstream areas.
- check dam
- a small dam constructed in a gully or
other small water course to decrease the streamflow
velocity, minimize channel erosion, promote deposition of
sediment and to divert water from a channel.
- chemical weathering
- attack and dissolving of parent rock
by exposure to rainwater, surface water, oxygen, and
other gases in the atmosphere, and compounds secreted by
organisms. Contrast physical weathering.
- Chezy's equation
- the empirical equation used to estimate the hydraulic conditions of flow within a channel cross section. Alternative to Manning's equation.
- Chezy's roughness
- a coefficient in Chezy's equation that accounts for energy loss due to the friction between the channel and the water.
- the adding of chlorine to water or
sewage for the purpose of disinfection or other
biological or chemical results.
- chlorine contact chamber
- the part of a wastewater
treatment plant where treated water is disinfected by chlorine.
- the difference between the amount of
chlorine added to water, sewage, or industrial wastes and
the amount of residual chlorine remaining at the end of a
specific contact period. Compare residual
- chute spillway
- the overall structure which allows
water to drop rapidly through an open channel without
causing erosion. Usually constructed near the edge of
- to move in a circle, circuit or orbit;
to flow without obstruction; to follow a course that
returns to the starting point.
- a tank used to collect rainwater
runoff from the roof of a house or building.
- the clearing action that
occurs during wastewater treatment when solids settle out. Clarification is
often aided by centrifugal action or chemically induced coagulation.
- a tank in which solids
settle to the bottom and are subsequently removed as sludge.
- Clean Water Act
- federal legislation
enacted in 1972 to restore and maintain the chemical, physical and
biological integrity of the surface waters of the United States. The stated
goals of the Act are that all waters be fishable and swimmable.
- climatic cycle
- the periodic changes climate displays,
such as a series of dry years following a series of years
with heavy rainfall.
- climatic year
- a period used in meteorological
measurements. The climatic year in the U.S. begins on
- generalized weather at a given place
on earth over a fairly long period; a long term average
of weather. Compare weather.
- a torrential downpour of rain, which
by it spottiness and relatively high intensity suggests
the bursting and discharge of water from a cloud all at
- in water treatment, the use of
chemicals to make suspended solids gather or group
together into small flocs.
- Chemical Oxygen Demand.
A measure of the oxygen equivalent of the organic matter content of a sample
that is susceptible to oxidation by a strong chemical oxidation.
Differs from the BOD test in that COD uses oxygen derived from chemicals,
while BOD uses oxygen derived from air dissolved in water.
- a molecular attraction by which the
particles of a body are united throughout the mass
whether like or unlike. Compare adhesion.
- cold vapor
- method to test water for the presence
- coliform bacteria
- non-pathogenic microorganisms used in
testing water to indicate the presence of pathogenic
- collector well
- a well located near a surface water
supply used to lower the water table and thereby induce
infiltration of surface water through the bed of the
water body to the well.
- finely divided solids which will not
settle but which may be removed by coagulation or
- combined sewer
- a sewer system that carries both
sanitary sewage and stormwater runoff. When sewers are
constructed this way, wastewater treatment plants have to
be sized to deal with stormwater flows and oftentimes
some of the water receives little or no treatment.
Compare separate sewer.
- Combined Sewer Overflow (CSO)
- the discharge of a mixture
of storm water and domestic waste when the flow capacity of a sewer system
is exceeded during rainstorms.
- community water system
- In Texas, a public water
system which has a potential to serve at least 15 residential service
connections on a year-round basis or serves at least 25 residents on a
- sealing off access of undesireable
water to the well bore by proper casing and/or cementing
- composite sample, weighted
- a sample composed of two or more
portions collected at specific times and added together
in volumes related to the flow at time of collection.
- amount of a chemical or pollutant in a
particular volume or weight of air, water, soil, or other
- the change of state from a gas to a
liquid. Compare evaporation, sublimation.
- a natural or artificial channel
through which fluids may be conveyed.
- cone of depression
- natural depression in the water table
around a well during pumping.
- confined aquifer
- an aquifer that lies between two rock layers of very low permeability. Most confined aquifers also are artesian aquifers. Compare unconfined aquifer.
- confining bed or unit
- a body of impermeable or distinctly
less permeable material stratigraphically adjacent to one
or more aquifers.
- confluent growth
- in coliform testing, abundant or
overflowing bacterial growth which makes accurate
measurement difficult or impossible.
- conjunctive management
- integrated management and use of two
or more water resources, such as an aquifer and a surface
- connate water
- water trapped in the pore spaces of a sedimentary rock at the time it was deposited. It is
usually highly mineralized.
- refers to the movement and exchange of water, nutrients, sediments, organic matter, and organisms within a riverine ecosystem. Connectivity occurs laterally (between the stream and its floodplain), longitudinally (along the stream), vertically (between the stream and groundwater), and temporally.
- to protect from loss and waste.
Conservation of water may mean to save or store water for
- an informal term used to
describe a detectable element or component or attribute of waste or
- consolidated formation
- naturally occurring geologic
formations that have been lithified (turned to stone).
The term is sometimes used interchangeably with the term
"bedrock." Commonly, these formations will
stand at the edges of a bore hole without caving.
- consumptive use
- the quantity of water not available
for reuse. Evapotranspiration, evaporation, incorporation
into plant tissue, and infiltration into groundwater are
some of the reasons water may not be available for reuse.
Compare nonconsumptive use.
- contact recreation
- activities involving a significant
risk of ingestion of water, such as wading by children,
swimming, water skiing, diving and surfing. Compare noncontact
- the introduction into water of sewage
or other foreign matter that will render the water unfit
for its intended use.
- control variables
- large-scale environmental factors that control patterns found in local geomorphic features. For example, geology, soils, land use, hydrology, channel features, and valley characteristics.
- conveyance loss
- water loss in pipes,
channels, conduits, and ditches by leakage or evaporation.
- cooling tower
- large tower used to transfer the heat
in cooling water from a power or industrial plant to the
atmosphere either by direct evaporation or by convection
- correlative rights
- rights that are coequal or that relate
to one another, so that any one owner cannot take more
than his share.
- a small stream of water which serves
as the natural drainage course for a drainage basin. The
term is relative according to size. Some creeks in a
humid region would be called rivers if they occurred in
an arid area.
- the top of a dam, dike, or spillway,
which water must reach before passing over the structure;
the summit or highest point of a wave; the highest
elevation reached by flood waters flowing in a channel.
- critical low flow
- low flow conditions below which some
standards do not apply. The impacts of permitted
discharges are analyzed at critical low-flow.
- any actual or potential
connection between a drinking water system and an unapproved water supply or
other source of contamination.
- a condition created when a
drill hole, boring, or improperly constructed well forms a pathway for fluid
movement between a saturated zone which contains pollutants and a formerly
separated saturated zone containing uncontaminated groundwater. Also, where
potable water supplies and sanitary services are interconnected.
- cubic foot per second (CFS)
- the rate of discharge representing a
volume of one cubic foot passing a given point during 1
second. This rate is equivalent to approximately 7.48
gallons per second, or 1.98 acre-feet per
- the portion of a stream or body of
water which is moving with a velocity much greater than
the average of the rest of the water. The progress of the
water is principally concentrated in the current. See
- current velocity
- the velocity of water flow in a stream, measured in units of length per unit of time, such as feet per second (fps).
- where the stream cuts through the neck of a meander bend.
- a structure of earth, rock, or
concrete designed to form a basin and hold water back to
make a pond, lake, or reservoir.
- dead end
- the end of a water main
that is not connected to other parts of the distribution system.
- decomposable waste
- waste that under suitable
natural conditions can be transformed through biological and chemical
processes into compounds that do not impair water quality.
- deionized water
- water free of inorganic chemicals.
- an alluvial deposit made of rock
particles (sediment, and debris) dropped by a stream as
it enters a body of water.
- the number of units of something that
will be purchased at various prices at a point in time.
- dense non-aqueous phase liquid (DNAPL)
- non-aqueous phase liquids,
such as chlorinated hydrocarbon solvents or petroleum fractions, with a
specific gravity greater than 1.0 that sink through the water column until
they reach a confining layer. Because they are at the bottom of aquifers
instead of floating on the water table, typical monitoring wells do not
indicate their presence.
- a measure of how heavy a
specific volume of a solid, liquid, or gas is in comparison to water.
- dental fluorosis
- disorder caused by excessive
absorption of fluorine and characterized by brown
staining of teeth.
- depletion curve
- in hydraulics, a graphical
representation of water depletion from storage stream channels, surface
soil, and groundwater. A depletion curve can be drawn for base flow, direct
runoff, or total flow.
- something dropped or left behind by
moving water, as sand or mud.
- the laying down of
material by erosion or transport by water or air.
- the process of salt removal from sea
or brackish water.
- detection limit
- the lowest level that can be
determined by a specific analytical procedure or test
- detention time
- the time required for a
volume of water to pass through a tank at a given rate of flow; in storage
reservoirs, the length of time water will be held before being used.
- synthetic washing agent
that helps remove dirt and oil. Some contain compounds toxic to bacteria
that are useful in the wastewater treatment process; other contain nutrients
such as phosphorous that may encourage algae growth when they are in
wastewater that reaches receiving waters.
- decaying organic matter (mostly leaves and other matter from vegetation).
- remove or separate a
portion of the water in a sludge or slurry to dry the sludge so it can be
handled and disposed; remove or drain the water from a tank, trench, or
- consisting of or abounding in diatoms,
a class of unicellular or colonial algae having a
silicified cell wall that persists as a skeleton after
- in wastewater treatment, a
unit in which anaerobic bacterial action is induced and accelerated in order
to break down and stabilize organic matter removed from the treatment
- diluting water
- distilled water that has been
stabilized, buffered, and aerated. Used in the BOD test.
- dilution ratio
- the critical low flow of
the receiving water at the point of recycled water discharge divided by the
flow of the discharge. Is used in the biomonitoring test to simulate
in-stream conditions that organisms will be exposed to during critical
- the volume of water that passes a
given point within a given period of time. It is an
all-inclusive outflow term, describing a variety of flows
such as from a pipe to a stream, or from a stream to a
lake or ocean.
- discharge permit
- a permit issued by a state or the
federal government to discharge effluent into waters of
the state or the United States. In many states both State
and federal permits are required.
- any person who discharges
waste that could affect the quality of state waters. The term includes any
person who owns, or is responsible for the operation of, a waste management
unit such as a wastewater treatment plant.
- a chemical or physical
process that kills or inactivates pathogenic organisms in water.
Chlorine is the most commonly used disinfectant for recycled water, potable
water supplies, wells, and swimming pools. Other disinfectants include
ozone, bromine, iodine, chlorine dioxide, heat, and ultraviolet light.
- the killing of the larger portion of
the harmful and objectionable bacteria in the sewage.
Usually accomplished by introduction of chlorine, but
more and more facilities are using exposure to
ultraviolet radiation, which renders the bacteria
- disinfection byproducts
- halogenated organic chemicals formed
when water is disinfected.
- the movement and spreading of
contaminants out and down in an aquifer.
- distance by which portions of the same
geological layer are offset from each other by a fault.
- the process by which solid particles
mix molecule by molecule with a liquid and appear to
become part of the liquid.
- dissolved oxygen (DO)
- amount of oxygen gas dissolved in a
given quantity of water at a given temperature and
atmospheric pressure. It is usually expressed as a
concentration in parts per million or as a percentage of
- dissolved solids
- inorganic material contained in water
or wastes. Excessive dissolved solids make water
unsuitable for drinking or industrial uses. See TDS.
- water treatment method where water is
boiled to steam and condensd in a separate reservoir.
Contaminants with higher boiling points than water do not
vaporize and remain in the boiling flask.
- distilled water
- water that has been treated by boiling
and condensation to remove solids, inorganics, and some
- to remove water from a water body.
Diversions may be used to protect bottomland from
hillside runoff, divert water away from active gullies,
or protect buildings from runoff.
- the direction that
groundwater flows; similar to “downstream” for surface water.
- the act of drawing or
removing water from a tank, reservoir or groundwater supply.
- drainage area
- of a stream at a specified location is
that area, measured in a horizontal plane, enclosed by a
topographic divide from which direct surface runoff from
precipitation normally drains by gravity into the stream
above the specified location.
- drainage reuse
- reuse of agricultural
drainage on salt-tolerant crops.
- drainage well
- a well drilled to carry
excess water off agricultural fields. Because they act as a drain from the
surface to the groundwater below, drainage wells can contribute to
- the drop in the water
table or level of groundwater when water is being pumped from a well; the
amount of water used from a tank or reservoir; the drop in the water level
of a tank or reservoir.
- removal of mud from the
bottom of water bodies. This can disturb the ecosystem and cause silting
that kills aquatic life. Dredging of contaminated mud can expose biota (the
flora and fauna of a region) to heavy metals and other toxics.
Dredging activities may be subject to regulation under state and federal
- driller's well log
- a log kept at the time of drilling
showing the depth, thickness, character of the different
strata penetrated, location of water-bearing strata,
depth, size, and character of casing installed.
- deposits of calcium carbonate that include stalactites, stalagmites, columns, and cave pearls.
- although there is no universally
accepted definition of drought, it is generally the term
applied to periods of less than average precipitation
over a certain period of time. In south Texas ranchers
say drought begins as soon as it stops raining.
- two separate samples with separate
containers taken at the same time at the same place.
- a geographic area over which the macroclimate is sufficiently uniform to permit development of similar ecosystems on sites with similar geophysical properties.
- 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.
- the interacting system of
a biological community and its non-living environmental surroundings; a
complex system composed of a community of fauna and flora, taking into
account the chemical and physical environment with which the system is
- a transition zone between two distinctly different ecosystems or communities.
- eddy viscosity
- a model parameter that reproduces the effects of turbulent mixing in fluid flow.
- Edwards Aquifer
- an arch-shaped belt of porous, water
bearing limestones 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.
- Edwards outcrop
- where the Edwards and associated
limestone formations are found at the surface. This area
is also referred to as the Recharge Zone.
- effective porosity
- the portion of pore space in saturated
permeable material where the movement of water takes
- 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.
- any substance, particularly a liquid,
that enters the environment from a point source.
Generally refers to wastewater from a sewage treatment or
- effluent limitation
- restrictions established
by a a regulating agency such as a State or the EPA in an NPDES permit on
quantities, rates, and concentrations in wastewater discharges.
- 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.
- a biological collection method that uses electric current to facilitate capturing fishes.
- a measure of the degree that gravel and larger substrates are surrounded by fine particles (silt and sand).
- endangered species
- one having so few individual survivors
that the species could soon become extinct in all or part
of its region.
- the characteristic of being confined to or indigenous in, a certain area or region.
- the addition of nutrients
such as nitrogen and phosphorous from wastewater effluent or agricultural
runoff to surface water. Enrichment greatly increases the growth potential
for algae and other aquatic plants.
- enteric viruses
- a category of viruses related to human
excreta found in waterways.
- to trap bubbles in water
either mechanically through turbulence or chemically through a reaction.
- aggregate of external conditions that
influence the life of an individual organism or
- environmental indicator
- a measurement, statistic
or value that provides evidence of the effects of environmental management
programs or of the state or condition of the environment.
- Environmental Impact Statement (EIS)
- a document that analyzes
the effects of major federal projects on the environment. Required by the
National Environmental Policy Act. It must be filed with the President
and the Council on Environmental Quality, and made available to the public.
- Environmental Protection
Agency. The federal regulatory agency responsible for protecting
environmental quality throughout the nation. Also acts in an oversight role
to state environmental agencies that carry out federal laws.
- warm, less dense top layer in a
stratified lake. Compare hypolimnion.
- the wearing away of the land surface
by wind, water, ice or other geologic agents. Erosion
occurs naturally from weather or runoff but is often
intensified by human land use practices.
- the topographic expression of a fault.
- 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).
- estuarine zone
- area near the coastline that consists
of estuaries and coastal saltwater wetlands.
- thin zone along a coastline where
freshwater system(s) and river(s) meet and mix with a
salty ocean (such as a bay, mouth of a river, salt marsh,
- 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.
- having a large or excessive supply of
plant nutrients (nitrates and phosphates). Compare oligotrophic.
- eutrophication (natural)
- an excess of plant nutrients from
natural erosion and runoff from the land in an aquatic
ecosystem supporting a large amount of aquatic life that
can deplete the oxygen supply.
- the change by which any substance is
converted from a liquid state and carried of in vapor.
Compare condensation, sublimation.
- combination of evaporation and
transpiration of water into the atmosphere from living
plants and soil. Distinguish transpiration.
- external cost
- cost of production or consumption that
must be borne by society; not by the producer.
- complete disappearance of a species
because of failure to adapt to environmental change.
- facultative bacteria
- bacteria that can live
under aerobic or anaerobic conditions.
- fecal coliform
- the portion of the coliform bacteria
group which is present in the intestinal tracts and feces
of warm-blooded animals. A common pollutant in water.
- a type of wetland that accumulates
peat deposits, but not as much as a bog. Fens are
less acidic than bogs, deriving most of their water from
groundwater rich in calcium and magnesium.
- fermentation, anaerobic
- process in which carbohydrates are
converted in the absence of oxygen to hydrocarbons (such
- field capacity
- the amount of water held in soil
against the pull of gravity.
- a device used to remove solids from a
mixture or to separate materials. Materials are
frequently separated from water using filters.
- the mechanical process which removes
particulate matter by separating water from solid
material, usually by passing it through sand.
- finite difference
- a method of solving the governing equations of a numerical model by dividing the spatial domain into a mesh of nodes. Solution of the governing equations is approximated from values at the node locations.
- finite element
- a method of solving the governing equations of a numerical model by dividing the spatial domain into elements in each of which the solution of the governing equations is approximated by a continuous function.
- finite volume
- a method of solving the governing equations of a numerical model by dividing the spatial domain into a mesh of nodes and corresponding volumes around each node. Solution of the governing equations is obtained from approximation of the fluxes across the boundaries of adjacent volumes.
- "first in time, first in right"
- phrase indicating that older water
rights have priority over more recent rights if there is
not enough water to satisfy all rights.
- fixed ground water
- water held in saturated material that
it is not available as a source of water for pumping.
- a measure of a river or stream's tendency to carry a high percentage of its flow volume in large, infrequent events rather than more moderate flows that occur frequently.
- large scale treatment process
involving gentle stirring whereby small particles in
flocs are collected into larger particles so their weight
causes them to settle to the bottom of the treatment
- an overflow or inundation that comes
from a river or other body of water and causes or
threatens damage. It can be any relatively high
streamflow overtopping the natural or artificial banks in
any reach of a stream. It is also a relatively high flow
as measured by either gage height or discharge quantity.
- flood frequency
- how often, on average, a discharge of a given magnitude occurs at a particular location on a stream. Usually expressed as the probability that the discharge will exceed some size in a single year (for example, the 100 year flood has a 1 percent probability of being equaled or exceeded in any one year).
- land next to a river that becomes
covered by water when the river overflows its banks .
- plant population of a region.
- the rate of water discharged from a
source expressed in volume with respect to time.
- flow augmentation
- the addition of water to meet flow
- flow duration curve
- a measure of the range and variability of a stream's flow. The flow duration curve represents the percent of time during which specified flow rates are exceeded at a given location. This is usually presented as a graph of flow rate (discharge) versus percent of time that flows are greater than, or equal to, that flow.
- flow meter
- a gauge indicating the
velocity and/or volume of a flowing liquid.
- flow-sensitive habitats
- habitats that show hydraulic response to relatively small changes in streamflow. Responses may be reflected in changes in depth, velocity patterns, wetted width and/or habitat area. Example are shallow-water, edge, and riffle habitats.
- flowing artesian well
- a special case of an artesian well where a water well drilled into a confined aquifer has enough hydraulic pressure for the water to rise to a height above ground surface and to flow at the surface without pumping.
- a natural or artificially
made channel that diverts water.
- to open a cold-water tap
to clear out all the water which may have been sitting for a long time in
the pipes; to force large amounts of water through a system to clean out
piping or tubing and storage or process tanks.
- a model structure used to represent the links between organisms within an environment, based upon the order in which various organisms consume one another.
- the water behind a dam.
- forfeited water right
- a water right canceled because of
several consecutive years of nonuse.
- the vertical distance
between the lowest point along the top of a surface impoundment dike, berm,
levee, treatment works or other similar feature and the surface of the
liquid contained therein.
- free ground water
- water in interconnected pore spaces in
the zone of saturation down to the first impervious
barrier, moving under the control of the water table
- the change of a liquid into a solid as
temperature decreases. For water, the freezing point is
32 F or 0 C.
- fresh water
- water containing less than 1,000 parts
per million (ppm) of dissolved solids of any type.
Compare saline water.
- fresh water inflow requirements
- freshwater flows required to maintain the natural salinity, nutrient, and sediment delivery in a bay or estuary that supports their unique biological communities and ensures a healthy ecosystem.
- fresh:salt water interface
- the region where fresh water and salt
water meet. In the Edwards region, it is commonly
referred to as the "bad water line", although
it is zone and not a line.
- a covering of minute ice crystals on a
- Froude number
- a dimensionless number comparing inertial and gravitational forces. Used to quantify the resistance of an object moving through water, and compare objects of different sizes. Froude numbers greater than 1 correspond to supercritical flow, less than 1 to subcritical flow.
- furrow irrigation
- irrigation method in which
water travels through the field by means of small channels between each
group of rows.
- gaging station
- the site on a stream, lake or canal
where hydrologic data is collected.
- A unit of volume. A U.S. gallon
contains 231 cubic inches, 0.133 cubic feet, or 3.785
liters. One U.S. gallon of water weighs 8.3 lbs.
- game fish
- a species such as trout,
salmon, or bass, caught for sport.
- gas chromatograph
- an instrument that
identifies the molecular composition and concentrations of various chemicals
in water and soil samples.
- a term which denotes the branch of
hydrology relating to subsurface or subterranean waters;
that is, to all waters below the surface.
- geologic erosion
- normal or natural erosion caused by
geological processes acting over long geologic periods
and resulting in the wearing away of mountains, the
building up of floodplains, coastal plains, etc.
- geopressured reservoir
- a geothermal reservoir consisting of
porous sands containing water or brine at high
temperature or pressure.
- a periodic thermal spring that results
from the expansive force of super heated steam.
- giardia lamblia
- a protozoa found in the
feces of infected humans and animals that can cause severe gastrointestinal
ailments. It is a common contaminant of surface waters.
- a huge mass of land ice that consists
of recrystallized snow and moves slowly downslope or
- grab sample
- a sample taken at a given place and
time. Compare composite sample.
- granular activated carbon
- pure carbon heated to promote
"active" sites which can adsorb pollutants.
Used in some home water treatment systems to remove
certain organic chemicals and radon.
- grassed waterway
- natural or constructed
watercourse or outlet that is shaped or graded and planted in suitable
vegetation for the disposal of runoff water without erosion.
- wastewater from clothes washing
machines, showers, bathtubs, handwashing, lavatories and
sinks that are not used for disposal of chemical or
- water within the earth that supplies
wells and springs; water in the zone of saturation where
all openings in rocks and soil are filled, the upper
surface of which forms the water table.
- groundwater hydrology
- the branch of hydrology that deals
with groundwater; its occurrence and movements, its
replenishment and depletion, the properties of rocks that
control groundwater movement and storage, and the methods
of investigation and utilization of ground water.
- groundwater law
- the common law doctrine of riparian
rights and the doctrine of prior appropriation as applied
to ground water.
- groundwater recharge
- the inflow to a ground water
- groundwater reservoir
- an aquifer or aquifer system in which
ground water is stored. The water may be placed in the
aquifer by artificial or natural means.
- groundwater runoff
- the portion of runoff which has passed
into the ground, has become ground water, and has been
discharged into a stream channel as spring or seepage
- groundwater storage
- the storage of water in groundwater
- a group of species or organisms that use the same environmental resources (habitat, food source, etc.) or life history strategy (such as reproduction) in the same way.
- a deeply eroded channel caused by the
concentrated flow of water.
- gully reclamation
- use of small dams of manure and straw;
earth, stone,or concrete to collect silt and gradually
fill in channels of eroded soil.
- the native environment or specific surroundings where a plant or animal naturally grows or lives. Habitat includes physical factors such as temperature, moisture, and light together with biological factors such as the presence of food or predator organisms.
- habitat indicator
- a physical attribute of
the environment measured to characterize conditions necessary to support an
organism, population, or community in the absence of pollutants. For
example, salinity of estuarine waters or substrate type in streams or lakes.
- a form of precipitation which forms
into balls or lumps of ice over 0.2 inch in diameter.
Hail is formed by alternate freezing and melting as
precipitation is carried up and down in highly turbulent
- a shallow layer of earth material
which has become relatively hard and impermeable, usually
through the deposition of minerals. In the Edwards region
hardpans of clay are common.
- hard water
- water containing a high level of
calcium, magnesium, and other minerals. Hard water
reduces the cleansing power of soap and produces scale in
hot water lines and appliances.
- hardness (water)
- condition caused by dissolved salts of
calcium, magnesium, and iron, such as bicarbonates,
carbonates, sulfates, chlorides, and nitrates.
- hardwood bottomland
- hardwood forested lowlands adjacent to some rivers, especially valuable for wildlife breeding, nesting, and habitat.
- the pressure of a fluid owing to its
elevation, usually expressed in feet of head or in pounds
per square inch, since a measure of fluid pressure is the
height of a fluid column above a given or known point.
- the gate that controls water flow into
irrigation canals and ditches. A watermaster regulates
the headgates during water distribution and posts
headgate notices declaring official regulations.
- heat of vaporization
- the amount of heat necessary to
convert a liquid (water) into vapor.
- heavy water
- water in which all the hydrogen atoms
have been replaced by deuterium.
- a chemical used to kill
nuisance plants. Herbicides can contain pollutants found in runoff.
- heterogenic aquifer
- an aquifer that has a variety of forms or characteristics, such as differering permeabilities. The Edwards is highly heterogenic. Contrast homogenous aquifer.
- high flow pulses
- the component of an instream flow regime that represents short-duration, in-channel, high flow events following storm events. They maintain important physical habitat features and longitudinal connectivity along the river channel.
- holding pond
- a small basin or pond designed to hold
sediment laden or contaminated water until it can be
treated to meet water quality standards or be used in
some other way.
- holding time
- the maximum amount of time
a sample may be stored before analysis.
- homogenous aquifer
- an aquifer that has similar forms or characteristics throughout, such as a uniform gravel aquifer. The Edwards is not homogenous, it is highly heterogenic.
- hydraulic conductivity
- the rate at which water
can move through a permeable medium.
- hydraulic control
- a feature in a stream (such as a constriction or a weir) that controls the upstream water surface elevation.
- hydraulic gradient
- the direction of
groundwater flow due to changes in the depth of the water table.
- hydraulic model
- a computer model of a segment of river used to evaluate hydraulic conditions. Compare hydrologic model.
- hydraulic roughness
- an estimate of the resistance to flow due to energy loss caused by friction between the channel and the water. Chezy's and Manning's roughness are two different ways to express this parameter.
- chemical compounds that
consist entirely of carbon and hydrogen; also referred to as volatile
- hydroelectric plant
- electric power plant in which the
energy of falling water is used to spin a turbine
generator to produce electricity.
- the geology of
groundwater, with particular emphasis on the chemistry and movement of
- a chart that measures the amount of
water flowing past a point as a function of time.
- hydrologic balance
- an accounting of all water
inflow to, water outflow from, and changes in water storage within a
hydrologic unit over a specified period of time.
- hydrologic basin
- the drainage area upstream
from a given point on a stream.
- hydrologic cycle
- natural pathway water follows as it
changes between liquid, solid, and gaseous states;
biogeochemical cycle that moves and recycles water in
various forms through the ecosphere. Also called the
- hydrologic model
- a computer model of a watershed used to evaluate how precipitation contributes to flow in streams. Compare hydraulic model.
- hydrologic unit
- is a geographic area representing part
or all of a surface drainage basin or distinct hydrologic
- the science dealing with
the properties, distribution, and circulation of water.
- the decomposition of
organic compounds by interaction with water.
- an instrument used to measure the
density of a liquid.
- a water delivery system,
usually small, that maintains water pressure in the distribution system by
means of pressure in a compressed air tank.
- electrical energy produced by falling
- hygroscopic nuclei
- piece of dust or other particle around
which water condenses in the atmophere. These tiny
droplets then collide and coalesce, with as many as
10,000 nuclei contributing to formation of a raindrop.
- region that includes all the earth's
liquid water, frozen water, floating ice, frozen upper
layer of soil, and the small amounts of water vapor in
the Earth's atmosphere.
- hydrostatic head
- a measure of pressure at a given point
in a liquid in terms of the vertical height of a column
of the same liquid which would produce the same pressure.
- hydrostatic pressure
- pressure exerted by or existing within
a liquid at rest with respect to adjacent bodies.
- bottom layer of cold water in a lake.
- hyporheic zone
- the zone under a river or stream comprising substrate whose interstices are filled with water.
- a solid form of water.
- imhoff cone
- a clear, cone-shaped
container used to measure the volume of settleable solids in a specific
volume of water.
- the inability of two or
more substances or liquids to readily dissolve into one another, such as
soil and water.
- impaired water body
- a water body that has been
determined under state and federal law as not meeting water quality
standards, or having the potential to do so in the future.
- imperiled species
- declining, rare, or uncommon species; species federally listed as threatened or endangered, or candidates for such; and species with limited distributions.
- material that does not permit fluids
to pass through.
- the quality or state of being
impermeable; resisting penetration by water or plant
roots. Impervious ground cover like concrete and asphalt
affects quantity and quality of runoff.
- a body of water such as a pond,
confined by a dam, dike, floodgate or other barrier. It
is used to collect and store water for future use.
- Index of Biotic Integrity
- a multi-metric measure of biological condition developed from collection of data for fish or other organisms. It consists of metrics in three broad categories: species composition, trophic composition, and organism abundance and condition.
- in-line filtration
- a pretreatment method in
which chemicals are mixed by flowing water; commonly used in pressure
- in-situ flushing
- introduction of large
volumes of water, at times supplemented with cleaning compounds, into soil,
waste, or groundwater to flush hazardous contaminants from a site.
- in-situ oxidation
- technology that oxidizes
contaminants dissolved in groundwater, converting them into insoluble
- in-situ stripping
- treatment system that
removes or strips volatile organic compounds from contaminated groundwater
or surface water by forcing an air stream through the water and causing the
compounds to evaporate.
- in-situ vitrification
- technology that treats contaminated soil in place at high temperatures, at 3,000 degrees Fahrenheit or more.
- inchoate water right
- an unperfected water right.
- indicator organisms
- microorganisms, such as coliforms,
whose presence is indicative of pollution or of more
- indicator parameters
- measurable physical or
chemical characteristics or attributes of water or soil-pore moisture used
to indicate the possible presence of waste constituents, or the effects of
waste constituents on waters.
- indicator tests
- tests for a specific contaminant,
group of contaminants, or constituent which signals the
presence of something else (ex., coliforms indicate the
presence of pathogenic bacteria).
- the penetration of water
through the ground surface into sub-surface soil or the penetration of water
from the soil into sewer or other pipes through defective joints,
connections, or manhole walls.
- infiltration rate
- the quantity of water that
can enter the soil in a specified time interval.
- entry of rainwater into a
sewer system from sources other than infiltration, such as basement drains,
manholes, storm drains, and street washing.
- water, wastewater, or
other liquid flowing into a reservoir, basin, or treatment plant.
- initial dilution
- the process that results
in the rapid and irreversible turbulent mixing of effluent and receiving
water around the point of discharge.
- injection well
- as defined by the U.S.
EPA, any bored, drilled or driven shaft, dug pit or hole in the ground into
which waste or fluid is discharged, and any associated subsurface
appurtenances, the depth of which is greater than the largest surface
dimension of the shaft, pit or hole.
- injection zone
- a geological formation
receiving fluids through a well.
- inland freshwater wetlands
- swamps, marshes, and bogs found inland
beyond the coastal saltwater wetlands.
- instream cover
- overhanging or instream structure, such as tree roots, undercut streambanks, boulders, or aquatic vegetation that offer protection for aquatic organisms.
- instream use
- use of water that does not require
withdrawal or diversion from its natural watercourse; for
example, the use of water for navigation, recreation, and
support of fish and wildlife.
- interbasin transfer
- the physical transfer of water from
one watershed to another; regulated by the Texas Water
- interceptor sewer
- very large sewer lines
that collect the flow from main and trunk lines and carry them to treatment
- the common boundary
between two substances such as water and a solid, water and a gas, or two
liquids such as water and oil.
- interfacial tension
- the strength of the film
separating two immiscible fluids (e.g., oil and water) measured in dynes
per, or millidynes per, centimeter.
- intermittent stream
- one that flows periodically. Compare perennial stream.
- interstate water
- according to law, interstate waters
are defined as (1) rivers, lakes and other waters that
flow across or form a part of state or international
boundaries; (2) waters of the Great Lakes; (3) coastal
waters whose scope has been defined to include ocean
waters seaward to the territorial limits and waters along
the coastline (including inland streams) influenced by
- the void or empty portion of rock or
soil occupied by air or water.
- inert waste
- waste that does not
contain hazardous waste or soluble pollutants at concentrations in excess of
applicable water quality objectives, and does not contain significant
quantities of decomposable waste.
- irrigation efficiency
- the percentage of water applied, and
which can be accounted for, in the soil moisture increase
for consumptive use.
- irrigation return flow
- water which is not consumptively used
by plants and returns to a surface or ground water
supply. Under conditions of water right litigation, the
definition may be restricted to measurable water
returning to the stream from which it was diverted.
- irrigation water
- water which is applied to assist crops
in areas or during times where rainfall is inadequate.
- line that connects points of equal
- line that connects points of equal
- jar test
- a laboratory procedure that simulates a water treatment plant's coagulation/flocculation units with differing chemical doses, mix speeds,
and settling times to estimate the minimum or ideal coagulant dose
required to achieve certain water quality goals.
- jet stream
- a long narrow meandering current of
high-speed winds near the tropopause blowing from a
generally westerly direction and often exceeding a speed
of 250 miles per hour.
- a jet of water.
- one (as a geyser) that sends out a
- a structure (as a pier or mole of wood
or stone) extending into a sea, lake, or river to
influence the current or tide or to protect a harbor.
- a violent surf that occurs on the
coast of the Guinea region, West Africa.
- a short ridge, hill, or mound of
stratified drift deposited by glacial meltwater.
- kame terrace
- a terrace of stratified sand and and
gravel deposited by streams between a glacier and an
adjacent valley wall.
- kelp beds
- significant aggregations of a large, fast growing marine algae throughout the water column.
- key habitats
- flow-sensitive habitats as well as habitats that support key species.
- key species
- species that are targeted for instream flow assessment or more generally taxa of interest; may include lotic-adapted species, imperiled species, sport fishes, or other species related to study objectives.
- kinetic energy
- energy possessed by a moving object or water body.
- one thousand grams.
- laboratory water
- purified water used in the laboratory
as a basis for making up solutions or making dilutions.
Water devoid of interfering substances.
- lag time
- the time from the center of a unit
storm to the peak discharge or center of volume of the
corresponding unit hydrograph.
- a shallow pond where sunlight,
bacterial action, and oxygen work to purify wastewater.
Lagoons are typically used for the storage of
wastewaters, sludges, liquid wastes, or spent nuclear
- an inland body of water, usually fresh
water, formed by glaciers, river drainage etc. Usually
larger than a pool or pond.
- land application
- discharge of wastewater onto the ground for treatment or reuse.
- landscape impoundment
- body of reclaimed water which is used
for aesthetic enjoyment or which otherwise serves a
function not intended to include contact recreation.
- Langelier Saturation Index (LSI)
- an index reflecting the equilibrium pH of a water with respect to calcium and alkalinity; used in stabilizing water to control both corrosion and scale deposition.
- water containing contaminants which
leaks from a disposal site such as a landfill or dump.
- leachate collection system
- a system that gathers leachate and pumps it to the surface for treatment.
- extraction or flushing out of
dissolved or suspended materials from the soil, solid
waste, or another medium by water or other liquids as
they percolate down through the medium to groundwater.
- lentic system
- a nonflowing or standing body of fresh
water, such as a lake or pond. Compare lotic system.
- a natural or man-made earthen
obstruction along the edge of a stream, lake, or river.
Usually used to restrain the flow of water out of a river
- rock that consists mainly of calcium
carbonate and is chiefly formed by accumulation of
- limiting factor
- factor such as temperature, light,
water, or a chemical that limits the existence, growth,
abundance, or distribution of an organism.
- scientific study of physical,
chemical, and biological conditions in lakes, ponds, and streams.
- a pesticide that causes adverse health effects when present in domestic water supplies and is toxic to freshwater fish and aquatic life.
- a relatively impermeable barrier designed to keep leachate inside a landfill; an insert or sleeve for sewer pipes to prevent leakage or infiltration.
- a state of matter, neither gas nor
solid, that flows and takes the shape of its container.
- littoral zone
- area on or near the shore of a body of
- lotic-adapted species
- species for which all or part of their life history is dependent on flowing water.
- lotic system
- a flowing body of fresh water, such as
a river or stream. Compare lentic system.
- an animal without a backbone, large enough to be seen without magnification and unable to pass through a 0.595 mm mesh.
- macroscopic plants in the aquatic environment. The most common macrophytes are the rooted vascular plants that are usually arranged in zones in aquatic ecosystems and restricted in their area by the extent of illumination through the water and sediment deposition along the shoreline.
- Manning's equation
- an empirical equation used to estimate the average hydraulic conditions of flow within a channel cross section.
- Manning's roughness
- a coefficient in Manning's equation that accounts for energy loss due to the friction between the channel and the water. Many hydraulic models use this coefficient to estimate resistance to flow.
- cultivation of fish and shellfish in
estuarine and coastal areas. Compare aquiculture.
- an area periodically inundated and
treeless and often characterized by grasses, cattails,
and other monocotyledons
- MCL - Maximum Contaminant Level
- the maximum level of a contaminant
allowed in water by federal law. Based on health effects
and currently available treatment methods.
- mean column velocity
- the average velocity of fluid flow measured in a column extending from the surface of the water to the bed of the channel. Often referred to simply as "velocity" or "current velocity". Compare point velocity.
- meander bend
- a windings or sinuous section of a stream channel. May become an oxbow lake if cut off from the mainstem.
- median particle size
- value for which half the particles in a sample have a greater diameter and half a lesser diameter.
- median streamflow
- the rate of discharge of a stream for
which there are equal numbers of greater and lesser flow
occurrences during a specified period.
- the changing of a solid into a liquid.
- water that comes from the melting ice
of a glacier or a snowbank.
- a fabled marine creature usually
represented as having the head, trunk, and arms of a
woman and a lower part like the tail of a fish.
- basic structural elements of a river or stream such as pools, backwaters, runs, glides, and riffles.
- reservoirs and lakes that contain moderate quantities of nutrients and are moderately productive in terms of aquatic animal and plant life.
- meteoric water
- groundwater which originates in the atmosphere and reaches the zone of saturation by infiltration and percolation.
- method blank
- laboratory grade water taken through
the entire analytical procedure to determine if samples
are being accidentally contaminated by chemicals in the
- methyl tertiary butyl ether (MTBE)
- an additive originally put in gasoline to reduce air pollution, but later found to be a source of groundwater pollution.
- pesticide that causes adverse health effects when found in domestic water supplies. It is also toxic to aquatic life.
- methyl orange alkalinity
- A measure of the total alkalinity in a water sample in which the color of methyl orange reflects the change in level.
- micrograms per liter - Ug/L
- micrograms per liter of water. One
thousands micrograms per liter is equivalent to 1
milligram per liter. This measure is equivalent to parts per billion (ppb)
- zones of similar physical characteristics within a mesohabitat unit, differentiated by aspects such as substrate type, water velocity, and water depth.
- the movement of oil, gas,
contaminants, water, or other liquids through porous and
- milligrams per liter - mg/L
- milligrams per liter of water. This
measure is equivalent to parts per million (ppm).
- minimum streamflow
- the specific amount of water reserved
to support aquatic life, to minimize pollution, or for
recreation. It is subject to the priority system and does
not affect water rights established prior to its
- mixed liquor
- a mixture of activated sludge and water containing organic matter undergoing treatment in an aeration tank.
- mixing zone
- a limited volume of receiving water that is allocated for diluting a wastewater discharge without causing adverse effects to the overall water body.
- moisture content
- the amount of water lost from soil upon drying to a constant weight, expressed as the weight per unit of dry soil or as the volume of water per
unit bulk volume of the soil.
- moisture holding capacity
- the amount of liquid that can be held against gravity, by waste materials or soil, without generating free liquid.
- the smallest division of a compound that still retains or exhibits all the properties of the substance.
- modified Wentworth scale
- a specific scale used to classify substrate particles by their diameter. Categories in this scale include boulder, cobble, pebble, gravel, sand, silt, and clay.
- monitoring well
- a well used to obtain water quality samples or measure groundwater levels.
- lakes and reservoirs that are relatively deep, do not freeze over during winter, and undergo a single stratification and mixing cycle during the
year (usually in the fall).
- round material that forms in filters and gradually grows when not removed by backwashing.
- multiple use
- Use of bodies of water for more than one purpose, such as recreational purposes, fishing, and water supply.
- municipal discharge
- discharge of effluent from treatment plants that receive wastewater from households, commercial establishments, and industries.
- municipal sewage
- sewage from a community which may be
composed of domestic sewage, industrial wastes or both.
- municipal sludge
- semi-liquid residue remaining from the treatment of municipal water and wastewater.
- National Estuary Program
- a program established under the Clean Water Act Amendments of 1987
to conserve and manage estuaries, restore and maintain their chemical, physical, and biological integrity, and control point and nonpoint pollution sources.
- National Municipal Plan
- a U.S. EPA policy created in 1984 to bring all publicly owned treatment
works (POTWs) into compliance with Clean Water Act requirements.
- National Oil and Hazardous Substances Contingency Plan
- the federal regulation that guides determination of the sites to be
corrected under the Superfund program, and the program to prevent or control spills into surface waters or elsewhere.
- National Pollutant Discharge Elimination System (NPDES)
- a provision of the Clean Water Act that prohibits discharge of pollutants
into waters of the United States unless a permit is issued that complies with the Clean Water Act. In Texas, the Texas Commission on Environmental Quality (TCEQ) administers the NPDES program and issues TPDES permits.
- National Priorities List (NPL)
- EPA's list of the most serious uncontrolled or abandoned hazardous waste
sites identified for possible long-term remedial action under Superfund. The list is based primarily on the score a site receives from the Hazard Ranking System. EPA is required to update the NPL at least once a year. A site must be on the NPL to receive money for remedial action from the Superfund Trust Fund.
- National Response Team (NRT)
- representatives of 13 federal agencies that, as a team, coordinate
federal responses to nationally significant incidents of pollution and provide advice and technical assistance to the responding agencies.
- National Response Center
- The 24-hour a day federal operations center receives notifications of all
releases of oil and hazardous substances into the environment. Operated by the U.S. Coast Guard, the Center evaluates all reports and notifies the appropriate agency.
- natural flow
- the rate of water movement past a
specified point on a natural stream. The flow comes from
a drainage area in which there has been no stream
diversion caused by storage, import, export, return flow,
or change in consumptive use caused by man-controlled
modifications to land use. Natural flow rarely occurs in
a developed country.
- natural resource
- any form of matter or energy obtained
from the environment that meets human needs.
- naturalized conditions
- an estimate of natural conditions obtained by attempting to remove effects of human activities from a set of measured conditions.
- Navier-Stokes equations
- a set of equations that describe the physics governing the motion of a fluid. In addition to applications in hydraulic studies of rivers and streams, these equations are used to model weather, ocean currents, and aerodynamics.
- method of measuring turbidity in a water sample by passing light through
the sample and measuring the amount of light deflected.
- National Interim Primary Drinking
- a compound containing nitrogen that can exist in water as a dissolved
gas. It can have harmful effects on humans and animals. Nitrates in water can cause severe illness in infants and domestic animals. A plant nutrient and inorganic fertilizer, nitrate is found in septic systems, animal feed lots, agricultural fertilizers, manure, industrial wastewaters, sanitary landfills, and garbage dumps.
- a plant nutrient that
can cause an overabundance of bacteria and algae when
high amounts are present, leading to a depletion of
oxygen and fish kills. Several forms occur in water,
including ammonia, nitrate, nitrite or elemental
nitrogen. High levels of nitrogen in water are usually
caused by agricultural runoff or improperly operating
wastewater treatment plants. Also see phosphorous.
- non-aqueous phase liquid (NAPL)
- contaminants that remain undiluted as the original bulk liquid in the
subsurface, such as spilled oil.
- nonconsumptive use
- using water in a way that does not
reduce the supply. Examples include hunting, fishing,
boating, water-skiing, swimming, and some power
production. Compare consumptive use.
- noncontact recreation
- recreational pursuits not involving a
significant risk of water ingestion, including fishing,
commercial and recreational boating, and limited body
contact incidental to shoreline activity. Compare contact recreation.
- an environmental policy that does not allow any lowering of naturally
occurring water quality regardless of pre-established health standards.
- something which does not allow water
to pass through it. Compare porous.
- nonpoint source
- source of pollution in which wastes
are not released at one specific, identifiable point but
from a number of points that are spread out and difficult
to identify and control. Compare point source.
- not suitable for drinking. Compare potable.
- nonthreshold pollutant
- substance or condition harmful to a
particular organism at any level or concentration.
- nephlometric turbidity units.
- as a pollutant, any element or
compound, such as phosphorous or
nitrogen, that fuels abnormally high organic growth
in aquatic ecosystems. Also see eutrophic.
- nutrient cycle
- the cyclic conversions of nutrients from one form to another within biological communities. For example, the production and release of molecular oxygen from water during photosynthesis by plants and the subsequent reduction of atmospheric oxygen to water by the respiratory metabolism of other biota.
- having a low supply of plant
nutrients. Compare eutrophic.
- on-site sewage treatment
- any individual residential sewage treatment and wastewater dispersal
system, such as a septic system.
- open system
- system in which energy and matter are
exchanged between the system and its environment, for
example, a living organism.
- operable unit
- a term used by the Superfund program to describe a discrete
action that comprises an incremental step toward comprehensively addressing site problems. The cleanup of a site can be divided into a number of operable units, depending on the complexity of the problems associated with the site. Operable units may address geographical portions of a site, specific site problems, or initial phases of an action, or may consist of any set of actions performed over time or any actions that are concurrent but located in different parts of a site. A typical operable unit would be removal of drums and tanks from the surface of a site.
- organic chemicals
- chemicals containing carbon.
- any form of animal or plant life.
- organism abundance and condition
- that portion of an Index of Biotic Integrity that is a metric measuring species abundance and condition, including proportion of individuals as hybrids and proportion of individuals with disease, tumors, physical damage, or physical anomalies.
- chemical compounds used in antifoulant paints to protect the hulls of
boats and ships, buoys, and pilings from marine organisms such as barnacles.
- period of mountain-building.
- orographic precipitation
- rainfall that occurs as a result of
warm, humid air being forced to rise by topographic
features such as mountains. Precipitation on the Edwards
Plateau is slightly higher because of the orographic
effect of the escarpment and hills.
- the passage of a liquid from a weak solution to a more concentrated
solution across a semi-permeable membrane that allows passage of the solvent (water) but not the dissolved solids.
- exposed at the surface. The Edwards
limestone outcrops in its recharge zone.
- the place where a wastewater treatment
plant discharges treated water into the environment.
- a deposit of sand and gravel formed by
streams of meltwater flowing from a glacier.
- overbank flows
- the component of an instream flow regime that represents infrequent, high flow events that exceed the normal channel. These flows maintain riparian areas and provide lateral connectivity between the river channel and active flood plain. They may also provide life-cycle cues for various species.
- pumping water from a groundwater basin or aquifer in excess of the
supply flowing into the basin; results in a depletion or “mining” of the groundwater in the basin.
- overflow rate
- one of the guidelines for design of the settling tanks and clarifiers in a
- overland flow
- a land application technique that cleanses wastewater by allowing it to
flow over a sloped surface. As the water flows over the surface, contaminants are absorbed and the water is collected at the bottom of the slope for reuse.
- a U-shaped bend in a river or stream that may or may not be cut off from the mainstem.
- oxbow lake
- a U-shaped water body formed when a meander bend is cut off from the mainstem of a river or stream to create a lake.
- oxygen demanding waste
- organic water pollutants that are
usually degraded by bacteria if there is sufficient
dissolved oxygen (DO) in the water.
- microorganisms which can cause
- peak flow
- in a wastewater treatment plant, the
highest flow expected to be encoutered under any
operational conditions, including periods of high
rainfall and prolonged periods of wet weather.
- Peclet number
- the relationship between properties of the mesh, fluid velocity, and eddy viscosity for a hydraulic computer model.
- toxic substance usually used as a wood preservative.
- perched water table
- groundwater standing unprotected over
a confined zone.
- a chlorinated solvent commonly used in dry cleaning. Also known as
- the movement of water through the
subsurface soil layers, usually continuing downward to
the groundwater or water table reservoirs.
- percolating waters
- waters passing through the ground
beneath the Earth's surface without a definite channel.
- perfected water right
- a water right which indicates that the
uses anticipated by an applicant, and made under permit,
were made for beneficial use. Usually it is irrevocable
unless voluntarily canceled or forfeited due to several
consecutive years of nonuse.
- perennial stream
- one that flows all year round. Compare
- the ability of a water bearing
material to transmit water. It is measured by the
quantity of water passing through a unit cross section,
in a unit time, under 100 percent hydraulic gradient.
- petroleum derivatives
- chemicals formed when gasoline breaks down in contact with water.
- numeric value that describes the
intensity of the acid or basic (alkaline) conditions of a
solution. The pH scale is from 0 to 14, with the neutral
point at 7.0. Values lower than 7 indicate the presence
of acids and greater than 7.0 the presence of alkalis
(bases). Technically speaking, pH is the logarithm of the
reciprocal (negative log) of the hydrogen ion
concentration (hydrogen ion activity) in moles per liter.
- phenolphthalein alkalinity
- the alkalinity in a water sample measured by the amount of standard
acid needed to lower the pH to a level of 8.3 as indicated by the change of color of the phenolphthalein from pink to clear.
- organic compounds that are byproducts of petroleum refining; tanning;
and textile, dye, and resin manufacturing. Low concentrations cause taste and odor problems in water; higher concentrations can kill aquatic life and humans.
- a plant nutrient that
can cause an overabundance of bacteria and algae when
high amounts are present, leading to a depletion of
oxygen and fish kills. High levels of phosphorous in
water are usually caused by agricultural runoff or
improperly operating wastewater treatment plants. Also
- phreatic zone
- the area in an aquifer in which relatively all pores and fractures are saturated with water. The phreatic zone may fluctuate with changes of season and during wet and dry periods. Compare vadose zone.
- plants that send their roots into or
below the capillary zone
to use ground water.
- physical weathering
- breaking down of parent rock into bits
and pieces by exposure to temperature and changes and the
physical action of moving ice and water, growing roots,
and human activities such as farming and construction.
Compare chemical weathering.
- physiographic province
- an area with similar characteristics based on geology, soil type, and topography.
- free-floating, mostly microscopic
- a nonpumping well, generally of small diameter, for measuring the
elevation of a water table.
- piezometric surface
- the imaginary surface to which
groundwater rises under hydrostatic pressure in wells or
- microscopic floating plant and animal
organisms of lakes, rivers, and oceans.
- plate tectonics
- refers to the folding and faulting of
rock and flow of molten lava involving lithospheric
plates in the earth's crust and upper mantle.
- cement, grout, or other material used
to fill and seal a hole drilled for a water well.
- plug flow
- type of flow that occurs in tanks, basins, or reactors when a slug of water
moves through without ever dispersing or mixing with the rest of the water flowing through.
- the area taken up by contaminant(s) in
- pertaining to precipitation.
- point source
- source of pollution that involves
discharge of wastes from an identifiable point, such as a
smokestack or sewage treatment plant. Compare nonpoint source.
- point velocity
- velocity measured at a single point in the water column of flowing water. Compare mean column velocity.
- undesireable change in the physical,
chemical, or biological characteristics of the air,
water, or land that can harmfully affect the health,
survival, or activities of human or other living
- polychlorinated biphenyls (PCBs)
- toxic industrial chemical compound substances that were used in the
manufacture of plastics and as insulating fluids in electrical transformers and capacitors. Banned since 1979, PCBs continue to be found in fish/animals.
- a body of water usually smaller than a
lake and larger than a pool either naturally or
- something which allows water to pass
through it. Compare nonporous.
- suitable, safe, or prepared for
drinking. Compare non-potable.
- potentiometric surface
- the surface to which water in an aquifer can rise by hydrostatic pressure. For karst aquifers like the Edwards, the potentiometric surface is not an especially meaningful concept. Every well is different, because of the complexity of the underground formation with many conduits, caverns, and different units separated by faults. The potentiometric surface is a more relevant measure when the aquifer involved is homogenous, such as one composed of gravel.
- ppb - parts per billion
- number of parts of a chemical found in
one billion parts of a solid, liquid, or gaseous mixture.
Equivalent to micrograms per liter (Ug/L).
- ppm - parts per million
- number of parts of a chemical found in
one million parts of a solid, liquid, or gaseous mixture.
Equivalent to milligrams per liter (mg/L).
- a solid which has come out of an
aqueous solution. (ex., iron from groundwater
precipitates to a rust colored solid when exposed to
- a chemical added to a water sample to
keep it stable and prevent compounds in it from changing
to other forms or to prevent microorganism densities from
changing prior to analysis.
- processes used to reduce, eliminate, or alter the nature of wastewater pollutants from non-domestic sources before they are discharged into publicly owned treatment works (POTWs).
- price at equilibrium
- where supply and demand curves
intersect. The price at equilibrium is what allocates
- primary treatment
- mechanical treatment in which large
solids are screened out and suspended solids in the
sewage settle out as sludge. Compare secondary
treatment, tertiary treatment.
- prior appropriation
- a doctrine of water law that allocates the rights to use water on a first in
time, first in right, basis.
- priority date
- the date of establishment of a water
right. It is determined by adjudication of rights
established before the passage of the Water Code. The
rights established by application have the application
date as the date of priority.
- profundal zone
- a lake's deep-water region that is not
penetrated by sunlight.
- public water system
- a system for the provision
to the public of water for human consumption through pipes or other
constructed conveyances. In Texas, a public water system is one that
serves at least 15 service connections or serve at least 25 individuals at
least 60 days out of the year.
- publicly-owned treatment works (POTW)
- a wastewater treatment plant that is owned by a state, unit of local
government or Indian tribe, usually designed to treat domestic wastewaters. The term also may include devices and systems used by those entities in the storage, treatment, recycling and reclamation of municipal sewage or liquid industrial wastes.
- a small pool of water, usually a few
inches in depth and from several inches to several feet
in its greatest dimension.
- a device which moves, compresses, or
alters the pressure of a fluid, such as water or air,
being conveyed through a natural or artificial channel.
- pump station
- mechanical device installed in sewer or water system or other liquidcarrying
pipelines to move the liquids to a higher level.
- pumped hydroelectric storage
- storing water for future use in
generating electricity. Excess electrical energy produced
during a period of low demand is used to pump water up to
a reservoir. When demand is high, the water is released
to operate a hydroelectric generator.
- pumping test
- a test conducted to determine aquifer or well characteristics.
- to force a gas through a water sample
to liberate volatile chemicals or other gases from the
water so their level can be measured.
- purgeable organics
- volatile organic chemicals which can
be forced out of the water sample with relative ease
- quarry water
- the moisture content of freshly
quarried stone, esp. if porous.
- quicksilver water
- a solution of mercury nitrate used in
- the part of a stream that has a strong
current; an artificial current or bubbling patch of water
just astern of a moving boat.
- water drops which fall to the earth
from the air.
- rain gage
- any instrument used for recording and
measuring time, distribution, and the amount of rainfall.
- a radioactive particle, man-made or natural, with a
distinct atomic weight number. Can have a very long life as a soil or water pollutant.
- radius of influence
- the radial distance from the center of a wellbore to the point where
there is no lowering of the water table or potentiometric surface; the edge of the cone of depression.
- rating curve
- a graph showing the relationship between water surface elevation and discharge of a stream or river at a given location. Also called a stage-discharge curve.
- in general, a length of stream with relatively homogenous characteristics.
- process in which carbon dioxide is bubbled into water being treated to
lower the pH.
- receiving waters
- a river, ocean, stream, or other
watercourse into which wastewater or treated effluent is discharged.
- refers to water entering an
underground aquifer through faults, fractures, or direct absorption.
- recharge rate
- the quantity of water per unit of time that replenishes or refills an aquifer.
- recharge zone
- the area where a formation allows
available water to enter the aquifer. Generally, that
area where the Edwards Aquifer and associated limestones
crop out in Kinney, Uvalde, Medina, Bexar, Comal, Hays,
Travis, and Williamson counties and the outcrops of other
formations in proximity to the Edwards limestone, where
faulting and fracturing may allow recharge of the surface
waters to the Edwards Aquifer.
- reclaimed water
- domestic wastewater that is under the
direct control of a treatment plant owner/operator which has been treated to a quality suitable for a beneficial
- survival of young plants and animals from birth to a life stage less vulnerable to environmental change.
- recurrence interval
- average amount of time between events
of a given magnitude. For example, there is a 1% chance
that a 100-year flood will occur in any given year.
- as defined by the federal Superfund program, any spilling, leaking,
pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment of a hazardous or toxic chemical or extremely hazardous substance.
- methods used to remove or contain a toxic spill or hazardous materials
from a Superfund site; a generic term used to describe cleanup activities.
- amount of a particular resource in
known locations that can be extracted at a profit with
present technology and prices.
- a pond, lake, tank, or basin (natural
or human made) where water is collected and used for
storage. Large bodies of groundwater are called
groundwater reservoirs; water behind a dam is also called
a reservoir of water.
- amount of a pollutant remaining in the environment after a natural or
technological process has occurred.
- residual chlorine
- the available chlorine which remains in solution after the demand has been satisfied. Compare chlorine demand.
- residual saturation
- saturation level below which fluid drainage will not occur.
- the dry solids remaining after the evaporation of a sample of water or
- the ability of an ecosystem to maintain or restore biodiversity, biotic integrity, and ecological structure and processes following disturbance.
- Resource Conservation and Recovery Act (RCRA)
- a federal statute that requires the safe management and disposal
of waste generated nationwide. RCRA was passed in 1976 as an amendment to the Solid Waste Disposal Act of 1956 and was last amended in 1984. The 1984 amendments are referred to as the Hazardous and Solid Waste Amendments (HSWA). There are three RCRA interrelated programs, which include: 1)the Solid Waste Program (Subtitle D) which sets criteria for municipal solid waste and other non-hazardous waste disposal facilities and prohibits open dumping of solid waste; 2)the Hazardous Waste Program (Subtitle C) which manages hazardous waste from the time it is generated until it is disposed (referred to as cradle to grave); and 3) the Underground Storage Tank Program (Subtitle I), which regulates underground storage, tanks storing petroleum or other hazardous substances.
- response variables
- environmental features of a river channel on a local or site-specific scale, such as channel shape, cross-sectional dimensions, substrate, bank shape, floodplain characteristics, vegetation, and channel patterns.
- installing modern pollution control devices at facilities without making
major changes to the facility’s design.
- return flow
- surface water that returns to the natural environment after diversion for
beneficial uses, such as for irrigation.
- reverse osmosis
- a water treatment method whereby water
is forced through a semipermeable membrane which filters
- right of capture
- the idea that the water under a
person's land belongs to that person and they are free to
capture and use as much as they want. Also called the
"law of the biggest pump".
- a small channel eroded into the soil by surface runoff; can be easily
smoothed out or obliterated by normal tillage.
- riparian water right
- the legal right held by an owner of
land contiguous to or bordering on a natural stream or lake, to take water from the source for use on the
- riparian zone
- a stream and all the vegetation on its banks.
- a natural stream of water of
- river basin
- the area drained by a river and its
- routing parameters
- coefficients that, along with mathematical routing equations, can be used to estimate the attenuation and lag (time delay) associated with the movement of flow through a length of stream channel.
- surface water entering rivers, freshwater lakes, or reservoirs.
- safe yield
- the annual amount of water that can be taken from a source of supply
over a period of years without depleting that source beyond its ability to be replenished naturally in “wet years.”
- saline water
- water containing more than 1,000 parts
per million (ppm) of dissolved solids of any type.
- amount of dissolved salts in a given
volume of water.
- salt water intrusion
- the invasion of fresh surface or ground water by salt water. It may be
called seawater intrusion if it comes from the ocean.
- minerals that cause salinity. Water may pick up salts as it
passes through the air, over and under the ground, or as households and industry use it.
- sand filters
- devices that remove suspended solids from a wastewater treatment plant effluent or water treatment plant product.
- sanitary landfill
- landfill that is lined with plastic or concrete or located in clay-rich soils to prevent hazardous substances from leaking into the environment.
- sanitary sewers
- underground pipes that carry off only domestic or industrial waste, not
- saturated zone
- the area below the water table where all open spaces are filled with
water under pressure equal to or greater than that of the atmosphere.
- the condition of a liquid when it has taken into solution the maximum possible quantity of a given substance at a given temperature and pressure.
- the erosive action of running water in streams, which excavates and carries away material from the bed and banks. Or, pertaining to a place on a streambed scoured by running water.
- the impermeable material, such as
cement grout bentonite, or puddling clay placed in the
annular space between the borehole wall and the casing of
a water well to prevent the downhole movement of surface
water or the vertical mixing of artestian waters.
- secondary treatment
- second step in most waste treatment
systems, in which bacteria break down the organic parts
of sewage wastes; usually accomplished by bringing the
sewage and bacteria together in trickling filters or in
the activated sludge process. Compare primary treatment,
tertiary treatment. Compare primary treatment, tertiary
- soil particles, sand, and minerals
washed from the land into aquatic systems as a result of
natural and human activities.
- sediment trapping efficiency
- the ratio of sediment retained within the reservoir to the sediment inflow to the reservoir.
- sedimentary cycle
- biogeochemical cycle in which
materials primarily are moved from land to sea and back
- a large scale water treatment process
where heavy solids settle out to the bottom of the
treatment tank after flocculation.
- a spot where water contained in the
ground oozes slowly to the surface and often forms a pool; a small spring.
- percolation of water through the soil from unlined canals, ditches, laterals, watercourses, or water storage facilities.
- a water body or portion of a water body that is individually defined and classified. A segment is intended to have relatively homogenous chemical, physical, and hydrological characteristics.
- semi-confined aquifer
- an aquifer partially confined by soil layers of low permeability in which
recharge and discharge can still occur.
- the aging process. Sometimes used to describe lakes or other bodies of
water in advanced stages of eutrophication. Also used to describe plants and animals.
- separate sewer
- a sewer system that carries only
sanitary sewage, not stormwater runoff. When a sewer is
constructed this way, wastewater treatment plants can be
sized to treat sanitary wastes only and all of the water
entering the plant receives complete treatment at all
times. Compare combined sewer.
- septic system
- an on-site system designed to treat and dispose of domestic sewage. A
typical septic system consists of a tank that receives waste from a residence or business and a system of drainage lines or a pit for disposal of the liquid effluent that remains after decomposition of the solids by bacteria in the tank.
- septic tank
- underground receptacle for wastewater from a home. The bacteria in the sewage decopose the organic wastes, and the sludge settles to the bottom of the tank. The effluent flows out of the tank into the
ground through drain lines.
- settleable solids
- in sewage, suspended solids that will
settle when the sewage is brought to a quiet state for a
reasonable length of time, usually two hours.
- seven-day two-year low flow (7Q2)
- the lowest average streamflow for seven consecutive days within a recurrence interval of two years, as statistically determined from historical data. Used in wastewater discharge modeling and permitting to estimate the impact of an effluent discharge on a water body under low-flow conditions.
- The waste and wastewater produced by residential and commercial
sources and discharged into sewers.
- the entire system of sewage collection, treatment, and disposal.
- shear stress
- the frictional force per unit area exerted on a streambed by flowing water. An important factor in the movement of bed material and description of habitat for some organisms.
- short circuiting
- when some of the water in tanks or basins flows faster than the rest; shortcircuiting may result in shorter contact, reaction, or settling times than calculated or presumed.
- the deposition of finely divided soil
and rock particles upon the bottom of stream and river
beds and reservoirs.
- controlling oil spills by using an agent to trap the oil and sink it to the
bottom of the body of water where the agent and the oil are biodegraded.
- using a machine to remove oil or scum from the surface of the water.
- precipitation which is a mixture of
rain and ice.
- a smooth striated polished surface
produced on rock by movement along a fault.
- solid matter that settles to the
bottom of sedimentation tanks in a sewage treatment plant
and must be disposed of by digestion or other methods or
recycled to the land.
- sludge digester
- tank in which complex organic substances like sewage sludge are
biologically dredged. Energy is released and much of the sewage is converted to methane, carbon dioxide, and water.
- a watery mixture of insoluble matter resulting from some pollution control
- precipitation in the form of branched
hexagonal crystals, often mixed with simple ice crystals,
which fall more or less continuously from a solid cloud
sheet. These crystals may fall either separately or in
cohesive clusters forming snowflakes.
- soft water
- any water that does not contain a significant amount of dissolved
minerals such as salts of calcium or magnesium.
- soil erodibility
- An indicator of a soil's susceptibility to raindrop impact, runoff, and other eroding processes.
- soil moisture
- the water contained in the pore space of the unsaturated zone.
- sole-source aquifer
- an aquifer that supplies 50 percent or more of the drinking water of an
- the amount of mass of a compound that will dissolve in a unit volume of
- any substance derived from the
atmosphere, vegetation, soil, or rock that is dissolved
- soil erosion
- the processes by which soil is removed
from one place by forces such as wind, water, waves,
glaciers, and construction activity and eventually
deposited at some new place.
- species composition
- that portion of an Index of Biotic Integrity that is a metric measuring the number and identity of species.
- specific conductance
- a measure of the ability of a water to
conduct an electrical current. Specific conductance is
related to the type and concentration of ions in solution
and can be used for approximating the dissolved solids
concentration in water. In general, for the San Antonio
River basin, conductivity * .6 approximates TDS. People
monitoring water quality can measure electrical
conductivity quickly in the field and estimate TDS
without doing any lab tests at all. See TDS.
- specific heat
- the amount of heat required to raise
the temperature of a kilogram of a substance (water) by 1
- specific yield
- the amount of water a unit volume of saturated permeable rock will yield
when drained by gravity.
- the channel or passageway around or
over a dam through which excess water is diverted.
- spray irrigation
- application of finely divided water
droplets to crops using artificial means.
- an issue of water from the earth; a
natural fountain; a source of a body or reservoir of water.
- spring melt/thaw
- the process whereby warm temperatures melt winter snow and ice.
Because various forms of acid deposition may have been stored in the frozen water, the melt can result in abnormally large amounts of acidity entering streams and rivers, sometimes causing fish kills.
- standard solution
- any solution in which the concentration is known.
- lack of motion in water that holds pollutants in place.
- state revolving funds (SRF)
- a program, capitalized in part by federal funds, that provides low-interest
loans for construction of publicly owned wastewater treatment and water recycling facilities, for implementation of nonpoint source and storm drainage pollution control management programs, and for the development and implementation of estuary conservation and management programs.
- static water depth
- the vertical distance from the centerline of the pump discharge down to
the surface level of the free pool while no water is being drawn from the pool or water table.
- static water level
- elevation or level of the water table in a well when the pump is not
operating; the level or elevation to which water would rise in a tube connected to an artesian aquifer or basin in a conduit under pressure.
- steady-state mass balance
- the mathematical concept that the sum of upstream pollutant loads,
each determined by the product of their concentration times flow, equals a resultant downstream load after mixing.
- a pond used primarily for watering livestock.
- a national U.S. EPA computerized data base (Storage and Retrieval)
containing both surface and groundwater chemistry data.
- stormwater discharge
- precipitation that does not infiltrate
into the ground or evaporate due to impervious land surfaces but instead flows onto adjacent land or water
areas and is routed into drain/sewer systems.
- a general term for a body of flowing
- stream piracy
- the tendency of one stream to capture the flow of another by eroding a channel that intercepts the other stream's flow.
- stream power
- a measure of energy available to move sediment, or any other particle in a stream channel. It is affected by discharge and slope.
- stream segment
- refers to the surface waters of an
approved planning area exhibiting common biological,
chemical, hydrological, natural, and physical
characteristics and processes. Segments will normally
exhibit common reactions to external stress such as
discharge or pollutants.
- the discharge that occurs in a natural
- in general, a portion of a river basin.
- subcritical flow
- flow characterized by low velocity and a Froude number less than 1. When the Froude number is less than 1, gravitational forces are greater than inertial forces.
- the transition of water directly from
the solid state to the gaseous state, without passing
through the liquid state; or vice versa. Compare condensation, evaporation.
- sinking down of part of the earth's
crust due to underground excavation, such as removal
- subsistence flows
- the component of an instream flow regime that represents infrequent, naturally occurring low flow events that occur for a seasonal period of time. They maintain water quality criteria and provide sufficient habitat to ensure organism populations capable of recolonizing the river system once normal, base flows return.
- supercritical flow
- flow characterized by high velocity and a Froude number greater than 1. When the Froude number is greater than 1, inertial forces are greater than gravitational forces.
- supercritical water
- a type of thermal treatment using moderate temperatures and high
pressures to enhance the ability of water to break down large organic molecules into smaller, less toxic ones. Oxygen injected during this process combines with simple organic compounds to form carbon dioxide and water.
- a schedule that shows the various
quantities of things offered for sale at various prices
at a point in time. Compare demand.
- surface impoundment
- an indented area in the land's
surface, such a pit, pond, or lagoon.
- surface irrigation
- application of water by means other
than spraying such that contact between the edible
portion of any food crop and the irrigation water is
- surface water
- water that flows in streams and rivers
and in natural lakes, in wetlands, and in reservoirs
constructed by humans.
- suspended load
- specific sediment particles maintained in the water column by turbulence
and carried with the flow of water.
- suspended solids
- the small solid particles in water that cause turbidity. Particles of
suspended sediment tend to settle at the channel bottom, but upward currents in turbulent flow counteract gravitational settling.
- the long-term capacity of an ecosystem to maintain ecological processes and functions, biological diversity, and productivity.
- sustainable management
- method of exploiting a resource that
can be carried on indefinitely. Removal of water from an
aquifer in excess of recharge is, in the long term, not a
sustainable management method.
- sustained overdraft
- long term withdrawal from the aquifer
of more water than is being recharged.
- a type of wetland dominated by woody vegetation but without
appreciable peat deposits. Swamps may be fresh or salt water and tidal or non-tidal.
- synthetic organic chemicals (SOCs)
- man-made organic chemicals. Some SOCs are volatile, while others tend to stay dissolved in water instead of evaporating.
- tail water
- the runoff of irrigation water from the lower end of an irrigated field.
- tailings pond
- An excavated or diked area that is intended to contain liquid and solid
wastes from mining and milling operations.
- The channel that is downstream of the draft tube that carries the water
discharged from a turbine. The draft tube is the discharge section of the turbine.
- technology-based treatment requirements
- NPDES permit requirements based on the
application of pollution treatment or control
technologies including BTP (best practicable technology),
BCT (best conventional technology), BAT (best available
technology economically achievable), and NSPS (new source
- tertiary treatment
- removal from wastewater of traces or
organic chemicals and dissolved solids that remain after primary
treatment and secondary
- the line of maximum depth in a stream.
The thalweg is the part that has the maximum velocity and
causes cutbanks and channel migration.
- thermal gradient
- temperature difference between two
- thermal pollution
- an increase in air or water
temperature that disturbs the climate or ecology of an
- fairly thin zone in a lake that
separates an upper warmer zone (epilimnion) from a lower
colder zone (hypolimnion).
- threatened species
- Under the Federal Endangered Species Act, animal populations
may be determined to be either threatened or endangered. Populations listed as threatened are less severely depleted than populations classed as endangered.
- threshold pollutant
- substance that is harmful to a
particular organism only above a certain concentration,
or threshold level.
- tidal marsh
- low, flat marshlands traversed by channels and tidal hollows, subject to
tidal inundation; normally, the only vegetation present is salt-tolerant bushes and grasses.
- TDS - total dissolved solids
- the sum or all inorganic and organic
particulate material. TDS is an indicator test used for
wastewater analysis and is also a measure of the mineral
content of bottled water and groundwater. There is a
relationship between TDS and conductivity. In general,
for the San Antonio River basin, TDS/.6 approximates
conductivity. Or, conductivity * .6 approximates TDS.
People monitoring water quality can measure electrical
conductivity quickly in the field and estimate TDS
without doing any lab tests at all. See specific
- Total Maximum Daily Load (TMDL)
- a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.
- chemical that causes adverse health effects in domestic water supplies
and is toxic to fresh water and marine aquatic life.
- toxic hot spot
- location in enclosed bay, estuary, or any adjacent waters that has
toxic pollution problems in the water or sediment in excess of applicable standards.
- toxic pollutant
- those pollutants or combinations of pollutants, including disease-causing
agents, which after discharge and upon exposure, ingestion, inhalation or assimilation into any organism can, on the basis of information available, cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions or physical deformation in such organism or their offspring. The quantities and exposures necessary to cause these effects can vary widely.
- Toxicity Reduction Evaluation(TRE)
- a study conducted to determine the
source(s) of toxicity in a discharge effluent so that
these sources can be controlled sufficiently to allow a
discharger to comply with their permit limits.
- toxicity test
- the means to determine the toxicity of
a chemical or an effluent using living organisms. A
toxicity test measures the degree of response of an
exposed test organism to a specified chemical or
- Tragedy of the Commons
- the idea that no one takes
responsibility for things that everybody owns.
- refers to the rate at which limestone
allows the transmission of water. Limestone can be highly
porous, but not very transmissive if the pores are not
connected to each other. Technically speaking, it is the
rate at which water is transmitted through a unit width
of aquifer under unit hydraulic gradient. Transmissivity
is directly proportional to aquifer thickness, thus it is
high where the Edwards is thick and low where it is thin,
given the same hydraulic conductivity.
- direct transfer of water from the
leaves of living plants to the atmosphere. Distinguish evapotranspiration.
- transport capacity
- the capacity of a river to carry sediment in suspension or to move sediment along the riverbed.
- any method, technique, or process designed to remove solids and/or
pollutants from solid waste, waste-streams, and effluents.
- trickle irrigation
- method in which water drips to the soil from perforated tubes or emitters.
- trickling filter
- a treatment system in which wastewater is trickled over a bed of stones or
other material covered with bacteria that break down the organic waste and produce clean water.
- a stream that contributes its water to
another stream or body of water.
- trihalomethanes (THM)
- chemical compounds in which three of the four hydrogen atoms of methane (CH4) are replaced by halogen atoms. Widely used in industry as solvents or refrigerants. THMs are also environmental pollutants, and many are considered carcinogenic. THMs are generally by-products of chlorination of drinking water that contains organic material.
- trophic composition
- that portion of an Index of Biotic Integrity that is a metric measuring the proportion of species and proportions of omnivores, insectivores, and omnivores.
- trophic structure
- the feeding relationships among species within a food web.
- the layer of atmosphere closest to the
Earth, extending seven to ten miles above the surface,
containing most of the clouds and moisture.
- tube settler
- device using bundles of tubes to let solids in water settle to the bottom for removal by conventional sludge collection means. Sometimes used in sedimentation basins and clarifiers to improve particle removal.
- development or formation of small mounds of corrosion products on the
inside of iron pipe. These tubercles roughen the inside of the pipe, increasing its resistance to water flow.
- thick or opaque with matter in
suspension. Rivers and lakes may become turbid after a rainfall.
- a device that measures the cloudiness of suspended solids in a liquid; a
measure of the quantity of suspended solids.
- a cloudy condition in water due to suspended silt or organic matter.
- United States Geological Survey
- unclassified waters
- those waters for which no
classification has been assigned and which have not been
identified in Appendix A of 31 Texas Administrative Code,
Chapter 307.10 of Title 31 (relating to definitions).
- unconfined aquifer
- an aquifer containing water that is not under pressure; the water level in a
well is the same as the water table outside the well. Compare confined aquifer.
- unconsolidated formations
- naturally occurring earth formations
that have not been lithified. Alluvium, soil, gravel,
clay, and overburden are some of the terms used to
describe this type of formation.
- a current below the upper currents or
surface of a fluid body.
- a concealed drain with openings
through which the water enters when the water table
reaches the level of the drain.
- movement of water through subsurface
- the current beneath the surface that
sets seaward or along the beach when waves are breaking
on the shore.
- under the surface of the water; lying,
growing, performed, worn, or operating below the surface
of the water, as underwater caverns, underwater operation
of a submarine.
- unsaturated zone
- the area above the water table where soil pores are not fully saturated,
although some water may be present.
- an upward flow.
- urban runoff
- storm water from city streets and adjacent domestic or commercial
properties that carries pollutants of various kinds into the sewer systems and receiving waters.
- vadose zone
- the zone between land surface and the water table where the moisture
content is less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Soil pore space also typically contains air or other gases. The capillary fringe is included in the vadose zone. Compare phreatic zone.
- comparison of computer model results with a set of data that were not used for calibration.
- vapor plumes
- flue gases that are visible because they contain water droplets.
- vegetative controls
- non-point source pollution control practices that utilize vegetative cover
to reduce erosion and minimize loss of pollutants.
- vested water right
- the right granted by a state water
agency to use either surface or ground water.
- virgin flow
- the streamflow which exists or would
exist if man had not modified the conditions on or along
the stream or in the drainage basin.
- the pore space or other openings in
rock. The openings can be very small to cave size and are
filled with water below the water table.
- volatile organic compounes (VOCs)
- a group of chemicals that react in the atmosphere with nitrogen oxides,
heat and sunlight to form ozone; VOCs are referred to as hydrocarbons.
- the tendency of a liquid to evaporate.
- wasteload allocation
- term used in conjunction with the TMDL Program, a WLA is the portion of a
receiving water’s loading capacity that is allocated to one of its existing or future point sources of pollution. Discharge limits are usually required for the specific water quality criterion addressed by the TMDL.
- water containing waste including
greywater, blackwater or water contaminated by waste
contact, including process-generated and contaminated
- the liquid that descends from the
clouds as rain; forms streams, lakes, and seas, and is a
major constituent of all living matter. It is an
odorless, tasteless, colorless, very slightly
- water availability model
- a numerical surface water flow model used to determine the availability of surface water for water right permitting.
- water column
- an imaginary column extending through a water body from its floor to its
surface. Ambient water quality monitoring programs may seek to quantify the water quality of a representative water column. Samples may be taken from a point or points throughout the depth of the water column.
- water cycle
- natural pathway water follows as it
changes between liquid, solid, and gaseous states;
biogeochemical cycle that moves and recycles water in
various forms through the ecosphere. Also called the
- water pollution
- degradation of a body of water by a
substance or condition to such a degree that the water
fails to meet specified standards or cannot be used for a
- water purveyor
- a public utility, mutual water company, county water district, or
municipality that delivers drinking water to customers.
- water quality
- the chemical, physical, biological, radiological, and thermal condition of water.
- water quality-based toxics control
- an integrated strategy used in NPDES
permitting to assess and control the discharge of toxic
pollutants to surface waters. There are two approaches:
the whole-effluent approach involves the use of toxicity
tests to measure discharge toxicity; the chemical
specific approach involves the use of water quality
criteria or State standards to limit specific toxic
- water quality criteria
- scientifically derived ambient limits
developed and updated by EPA, under section 304(a)(1) of
the Clean Water Act, for specific pollutants of concern.
Criteria are recommended concentrations, levels, or
narrative statements that should not be exceeded in a
waterbody in order to protect aquatic life or human
- water quality standards
- laws or regulations, promulgated under
Section 303 of the Clean Water Act, that consist of the
designated use or uses of a waterbody or a segment of a
waterbody and the water quality criteria that are
necessary to protect the use or uses of that particular
waterbody. Water quality standards also contain an
antidegradation statement. Every State is required to
develop water quality criteria standards applicable to
the various waterbodies within the State and revise them
every 3 years.
- water recycling
- the treatment of wastewater making it suitable for reuse.
- water solubility
- the maximum possible concentration of a chemical compound dissolved in water.
- water-soluble substance
- a substance that can readily disperse through the environment.
- water supplier
- one who owns or operates a public water system.
- water surface elevation
- the elevation of a water surface above or below an established reference level, such as sea level.
- water table
- level below the earth's surface at
which the ground becomes saturated with water. The
surface of an unconfined aquifer which fluctuates due to
- water table aquifer
- an aquifer confined only by
atmospheric pressure (water levels will not rise in the
well above the confining bed).
- water well
- any artificial excavation constructed
for the purpose of exploring for or producing ground
- Water Year
- a division based on a general pattern of annual wet and dry periods rather than a calendar year. In Texas, the Water Year is from October 1
through September 30. The Water Year is designated by the
calendar year in which it ends. Thus, the year ending September 30, 2009 is called the 2009 Water Year.
- a sudden, nearly vertical drop in a
stream, as it flows over rock.
- saturation of soil with irrigation
water so the water table rises close to the surface.
- An employee of a water department who
distributes available water supply at the request of
water right holders and collects hydrographic data.
- land area from which water drains
toward a common watercourse in a natural basin.
- watershed approach
- a coordinated framework for environmental management that focuses
public and private efforts on the highest priority problems within hydrologically defined geographic areas.
- watershed management
- sater resource protection, enhancement, and restoration. Ideally,
watershed management means developing a solution for each watershed that considers all its problems, includes all stakeholders in
defining the problems, proposing solutions, and participating in implementing a common solution.
- day to day variation in atmospheric
conditions. Compare climate.
- a wall or plate placed in an open channel to measure the flow of
water; a wall or obstruction used to control flow from settling tanks and clarifiers to ensure a uniform flow rate and avoid short-circuiting.
- a bored, drilled, or driven shaft or a dug hole whose depth is greater than
the largest surface dimension and whose purpose is to reach underground water supplies or oil or to store or bury fluids below ground.
- area containing one or more wells that produce usable amounts of water
- well injection
- the subsurface placement of fluids into a well.
- well monitoring
- measurement by on-site instruments or laboratory methods of well water
- well plug
- a seal installed in a borehole or well preventing movement of fluids.
- wellhead protection area
- a protected surface and subsurface zone surrounding a well or well field
supplying a public water system to keep contaminants from reaching the well water.
- area that is regularly wet or flooded
and has a water table that stands at or above the land
surface for at least part of the year, such as a bog, pond, fen, estuary, or marsh.
- the degree to which a fluid will spread into or coat a solid surface in the
presence of other fluids into which it will not dissolve.
- wettable powder
- dry formulation that must be mixed with water or other liquid before it is
- whole-effluent toxicity
- the aggregate toxic effect of an
effluent measured directly by a toxicity test.
- creative landscaping for water and
energy efficiency and lower maintenance. The seven
xeriscape principles are: good planning and design;
practical lawn areas; efficient irrigation; soil
improvement; use of mulches; low water demand plants;
- the quantity of water expressed either
as a continuous rate of flow (cubic feet per second,
etc.) or as a volume per unit of time. It can be
collected for a given use, or uses, from surface or
groundwater sources on a watershed.
- zone of aeration
- a region in the Earth above the water
table. Water in the zone of aeration is under atmospheric
pressure and will not flow into a well.
- zone of saturation
- the space below the water table in
which all the interstices (pore spaces) are filled with
water. Water in the zone of saturation is called
- tiny aquatic animals eaten by fish.