A-HORIZON—The uppermost zone in the
Soil
Profile, from which soluble
Salts and
Colloids are leached, and in
which organic matter has accumulated. Generally this represents the most fertile soil
layer. Along with the
B-Horizon, this layer constitutes part of the
Zone of
Eluviation.
A POSTERIORI CLASSIFICATION—A
classification made based upon the results of experimentation.
A PRIORI CLASSIFICATION—A
classification made prior to experimentation.
ABANDONED WATER RIGHT—A water right
which has not been put to Beneficial Use for generally five or more years, in
which the owner of the water right states that the water right will not be used, or takes
such actions that would prevent the water from being beneficially used. Compare to Forfeited
Water Right.
ABANDONED WELL—A well which is no
longer used or a well removed from service; a well whose use has been permanently
discontinued or which is in a state of such disrepair that it cannot be used for its
intended purpose. Generally, abandoned wells will be filled with concrete or cement grout
to protect groundwater from waste and contamination.
ABANDONMENT—Failure to put a water
right to Beneficial Use for generally five or more years, in which the owner of
the water right states that the water right will not be used, or takes such actions that
would prevent the water from being beneficially used. Also see Abandoned Water Right.
ABANDONMENT OF A DAM—In a legal
sense, abandonment is most precisely described as transfer of all rights, title and
interest in a dam to the current property owner.
Abandonment may also involve the slow but resolute erosion of rights to a dam by non-use,
physical destruction, lack of maintenance or intent of same. In this latter instance the
final determination of legal abandonment can only be decided by the court holding
jurisdiction.
ABIOSESTON—Nonliving components of
the seston.
ABATEMENT—Reducing the degree or
intensity of, or eliminating, pollution, as a water pollution abatement program.
ABIOTA—Those non-living factors which
are present in and affect the characteristics of a given ecosystem.
ABIOTIC—Pertaining to any non-
biological factor or influence, such as geological or meteorological characteristics.
ABLATION—(1) The process by which ice
and snow waste away as a result of melting and/or evaporation. (2) The erosive processes
by which a glacier is reduced.
ABSCISSA (Symbol X)—(Mathematics) The
coordinate representing the position of a point along a line perpendicular to the y-axis (Ordinate)
in a Plane Cartesian Coordinate System.
ABSCISSION—The dropping of leaves
from a plant. Premature abscission in certain plant species frequently results from
excessive exposure to certain air contaminants.
ABSOLUTE HUMIDITY—The actual weight
of water vapor contained in a unit volume of the atmosphere, usually expressed in grams of
water per kilogram of air. Compare to Relative Humidity.
ABSOLUTE TEMPERATURE (T)—A
temperature expressed on the thermodynamic scale, measured from Absolute Zero, or
0 Kelvin (K), also equivalent to -273.15C or -459.67F.
ABSOLUTE ZERO—The zero value of
thermodynamic temperature, or 0 Kelvin (K), also equivalent to -273.15 Celsius (C) on the Centigrade
Temperature Scale or -459.67 Fahrenheit (F) on the Fahrenheit Temperature Scale.
ABSORBER—A material capable of taking
in a substance, such as oil, as a sponge takes up water.
ABSORPTION—(1) The entrance of water
into the soil or rocks by all natural processes, including the infiltration of
precipitation or snowmelt, gravity flow of streams into the valley alluvium into sinkholes
or other large openings, and the movement of atmospheric moisture. (2) The uptake of water
or dissolved chemicals by a cell or an organism (as tree roots absorb dissolved nutrients
in soil). (3) More generally, the process by which substances in gaseous, liquid, or solid
form dissolve or mix with other substances. Not to be confused with Adsorption.
ABSORPTION LOSS—The loss of water by Infiltration
or Seepage into the soil during the process of priming, i.e., during the initial
irrigation of a field; generally expressed as flow volume per unit of time.
ABSORPTION TOWER—(Air Quality) An air
pollution control device in which contaminated air is passed through a tower containing
substances (packing) possessing large surface area. Water is passed over the packing
material in a countercurrent fashion, i.e., in a direction opposite to the passage of the
air, and the air contaminants are then absorbed into the liquid. Also referred to as Packed
Tower, Spray Tower, or Tray Tower.
ABUTMENT (of a Dam)—The part of a
valley side wall against which a dam is constructed. An artificial abutment is sometimes
constructed as a concrete gravity section to take the thrust of an Arch Dam where
there is no suitable natural abutment. Right and left abutments are designated as one
looks downstream.
ABUTMENT SEEPAGE—Reservoir water that
moves through seams or pores in the dam's natural Abutment material and exists as
seepage.
ABYSSAL—Of or relating to the bottom
waters of the ocean depth.
ABYSSAL DEPTH—In a limnological
sense, that depth at which the water remains uniform in temperature, or is "stagnant".
ABYSSAL ZONE—The bottom of a deep
ocean. Also see Bathyal Zone and Euphotic Zone.
ACCESS—The way for a person to enter
a lake usually with a boat. Types of accesses include: easement access, funnel access,
lake access and public access.
ACCLIMATIZATION—The physiological
adjustment or adaptation by an organism to new physical and/or environmental conditions.
With respect to water, it is frequently used in reference to the ability of a species to
tolerate changes in water temperature, degradation of water quality, or increased levels
of salinity.
ACCRETION—The slow addition to land
by deposition of water-borne sediment. An increase in land along the shores of a body of
water, as by Alluvial deposit. Accretion and alluvion are often used
synonymously.
ACEC—Area of Critical Environmental
Concern.
ACEQUIA—(Southwestern U.S.) An
irrigation canal.
ACID—(1) Corrosive substances with pH
of less than 7.0; acidity is caused by high concentrations of hydrogen ions. (2) Chemicals
that release hydrogen ions (H+) in solution and produce hydronium ions (H3O+).
Such solutions have a sour taste, neutralize bases, and conduct electricity. (3) Term
applied to water with a pH of less than 7.0 on a pH scale of 0 to 14.
ACID AEROSOL—Airborne particles
composed of sulfates (SOX), sulfuric acid (H2SO4),
nitrates (NOX), and/or nitric acid (HNO3). Dry particle diameters
are typically less than 1-2 microns. Also see Acid Deposition and Acid Fog.
ACID DEPOSITION—The introduction of
acidic material to the ground or to surface waters. Involves a complex chemical and
atmospheric phenomenon that occurs when emissions of sulfur and nitrogen compounds and
other substances are transformed by chemical processes in the atmosphere, often far from
the original sources, and then become deposited on the land or surface waters in either
wet or dry forms. Wet Deposition (commonly referred to as Acid Rain or Acid
Fog) results from precipitation as rain, snow, or fog. Dry Deposition
results from particle fallout or acidic gases.
ACID FOG—Airborne water droplets
containing sulfuric acid and/or nitric acid. Typical diameters are 3-30 microns. Also see Acid
Deposition and Acid Aerosol.
ACID-FORMING MATERIAL—Material
containing sulfide minerals or other materials, which if exposed to air, water, or
weathering processes will form sulfuric acid that may create Acid Mine Drainage.
ACID LAKES— Lakes that have water
with a pH less than 6 standard units.
ACID MINE DRAINAGE (AMD)—Acidic water
that flows into streams from abandoned mines or piles of mining waste or tailings. The
acid arises from the oxidation of iron sulfide compounds in the mines by air, dissolved
oxygen in the water, and chemoautotrophs, which are bacteria that can use the iron sulfide
as an energy source. Iron sulfide oxidation products include sulfuric acid, the presence
of which has reduced or eliminated aquatic life in many streams in mining regions. Also
see Open-Pit Mining and Yellowboy. Also referred to as Acid Mine
Waste.
ACID NEUTRALIZING CAPACITY—A measure
of the ability of water or soil to resist changes in pH.
ACID PRECIPITATION—Atmospheric deposition (rain, snow and dryfall) that is composed of the hydrolyzed by-products from
oxidized halogen, nitrogen, and sulfur substances. Also see Acid Rain.
ACID RAIN—Rainfall with a pH of less
than 7.0. One of the principle sources is the combining of rain (H2O) and
sulfur dioxide (SO2), nitrous oxides (NOx), and carbon dioxide (CO2)
emissions which are byproducts of the combustion of fossil fuels. These oxides react with
the water vapor to form sulfuric (H2SO4), nitric (HNO3),
and carbonic acids (H2CO3). Long-term deposition of these acids is
linked to adverse effects on aquatic organisms and plant life in areas with poor
neutralizing (buffering) capacity. Also see Acid Deposition.
ACIDIC—The condition of water or soil
that contains a sufficient amount of acid substances to lower the pH below 7.0.
ACIDIFICATION—Raising the acidity
(lowering the pH) of a fluid by adding an acid.
ACIDITY—A measure of how acid a
solution may be. A solution with a pH of less than 7.0 is considered acidic. Solutions
with a pH of less than 4.5 contain mineral acidity (due to strong inorganic acids), while
a solution having a pH greater than 8.3 contains no acidity.
ACLs—Alternative Concentration
Limits.
ACRE—A measure of area equal to
43,560 square feet (4,046.87 square meters). One square mile equals 640 acres, and is also
referred to as a Section. An acre is slightly smaller in size than a football
field.
ACREAGE—(1) An area of land or water
measured in acres. (2)Number of acres.
ACRE-FEET (AF)—A unit commonly used
for measuring the volume of water. See Acre-Foot.
ACRE-FOOT (AF)— A unit commonly used
for measuring the volume of water; equal to the quantity of water required to cover one
acre (43,560 square feet or 4,047 square meters) to a depth of 1 foot (0.30 meter) and
equal to 43,560 cubic feet (1,234 cubic meters), or 325,851 gallons.
ACRE-INCH—The volume of water or
solids that will cover one acre to a depth of one inch, equivalent to 3,630 cubic feet or
102.7 cubic meters.
ACTIVATED CARBON—A material produced
by heating coal or wood in such a manner as to yield a porous structure, creating a very
large internal surface area. Activated carbon is available in both powdered and granular
forms, and is widely used to adsorb organic compounds from water and wastewater. It
provides a means of removing tastes and odors from drinking water. Also see Granular
Activated Carbon (GAC). Also referred to as Activated Charcoal.
ACTIVATED CARBON ADSORPTION—The
process of pollutants moving out of water and attaching on to Activated Carbon.
ACTIVATED SLUDGE—The Floc
produced in raw or settled wastewater due to the growth of bacteria and other organisms in
the presence of Dissolved Oxygen. It is the product that results when primary
effluent is mixed with bacteria-laden sludge and then agitated and aerated to promote
biological treatment, speeding the breakdown of organic matter in raw sewage undergoing
secondary waste treatment.
ACTIVATED SLUDGE PROCESS—A method of Secondary
Wastewater Treatment in which the waste is treated by microorganisms in a
well-aerated tank to degrade the organic material. A sedimentation tank is then used to
remove the resultant sludge.
ACTIVE FAULT—A fault that has
undergone movement in recent geologic time (the last 10,000 years) and may be subject to
future movement. Also see Fault.
ACTIVE SOLAR WATER HEATER—A water
heating system in which heat from the sun is absorbed by collectors and transferred by
pumps to a storage unit. The heated fluid in the storage unit conveys its heat to the
domestic hot water system of the house through a heat exchanger.
ACTIVE STORAGE CAPACITY—The total
amount of usable reservoir capacity available for seasonal or cyclic water storage. It is
gross reservoir capacity minus inactive storage capacity. More specifically, the volume of
water in a reservoir below the maximum controllable level and above the minimum
controllable level that can be released under gravity. In general, it is the volume of
water between the outlet works and the spillway crest. In some instances, Minimum Pool
operating constraints may prevent lowering the reservoir to the level of the outlet works,
and the water below the minimum pool level is not considered to be in active storage.
ACTIVITY—The effective concentration
of a chemical based on thermodynamic considerations. Activity and concentration have the
same units and have the same value in very dilute solutions.
ACUTE—Designates an exposure to a
dangerous substance or chemical in sufficient dosage to precipitate a severe reaction. Acute
Exposure refers to such dosage levels received over a period of 24 hours or less.
Longer-term exposures are referred to as Chronic Exposure.
ADAPTATION—Changes in an organism's
structure or habits that allow it to adjust to its surroundings, which usually makes them
more likely to survive and reproduce than their competitors.
ADENOSINE TRIPHOSPHATE (ATP)—An
organic, phosphate-rich compound important in the transfer of energy in organisms. Its
central role in living cells makes it an excellent indicator of the presence of living
material in water. A measure of ATP therefore provides a sensitive and rapid estimate of Biomass.
ATP is reported in micrograms per liter of the original water sample.
ADEQUATE-SIZE FARM—A farm with
resources and productivity sufficient to generate enough income to (a) provide an
acceptable level of family living; (b) pay current operating expenses and interest on
loans; and (c) allow for capital growth to keep pace with technological growth.
ADHESION—Molecular attraction that
holds the surfaces of two substances in contact, such as water and rock particles. Also,
the attraction of water molecules to other materials as a result of hydrogen bonding.
ADIABATIC—Applies to a thermodynamic
process during which no heat is added to or withdrawn from the body or system concerned.
In the atmosphere, adiabatic changes of temperature occur only in consequence of
compression or expansion accompanying an increase or decrease of atmospheric pressure.
Thus, a descending body of air undergoes compression and adiabatic heating.
ADIABATIC LAPSE RATE—The theoretical
rate at which the temperature of the air changes with altitude. The temperature change is
due to the pressure drop and gas expansion only, and no heat is considered to be exchanged
with the surrounding air through convection or mixing. The Dry Adiabatic Lapse Rate
for air not saturated with water vapor is 0.98C per 100 meters (5.4F per 1,000 feet). The Wet
Adiabatic Lapse Rate for air saturated with water vapor is about 0.60C per 100 meters
(3.3F per 1,000 feet).
ADIABATIC PROCESS—A change involving
no gain or loss of heat.
ADIT—A horizontal or nearly
horizontal passage, driven from the surface, for the working or dewatering of a mine. Also
referred to as Drift, Shaft, or Portal.
ADJUDICATION—Refers to a judicial
process whereby water rights are determined or decreed by a court of law. A court
proceeding to determine all rights to the use of water on a particular stream system or
ground water basin.
ADMINISTERED GROUNDWATER BASIN—A
groundwater basin (watershed, area, or sub-area) which, in the interest of public welfare,
is monitored by an appropriate agency to insure adequate water resources for prescribed
uses. Quite often, such basins will have Preferred Uses designated for future
development to insure that the basin's Perennial Yield is not exceeded. Also
referred to as Designated Groundwater Basin. Also see Designated Groundwater
Basin [Nevada].
ADSORBATE—Any material adsorbed onto
the surface of another.
ADSORBENT—Any material which adsorbs
another on its surface.
ADSORBER—A solid or liquid that can
hold molecules of another substance on its surface.
ADSORPTION—(1) The adherence of ions
or molecules in solution to the surface of solids. (2) The adherence of a gas, liquid, or
dissolved material on the surface of a solid. (3) The attraction and adhesion of a layer
of ions from an aqueous solution to the solid mineral surfaces with which it is in
contact. An example is the adsorption of organic materials by activated carbon. Not to be
confused with Absorption.
ADVANCED TREATMENT—A level of
wastewater treatment more stringent than secondary treatment; requires an 85 percent
reduction in conventional pollutant concentration or a significant reduction in
nonconventional pollutants.
ADVANCED WASTEWATER TREATMENT (AWT)—Any
process which reduces the level of impurities in a wastewater below that attainable
through conventional secondary or biological treatment. Includes the removal of nutrients
such as phosphorus and nitrogen and a high percentage of suspended solids. Also see Tertiary
Wastewater Treatment.
ADVANCE TIME—The time it takes for
water to travel the length of an irrigation furrow.
ADVECTION—(1) The process by which
solutes are transported by the bulk of flowing fluid such as the flowing ground water. (2)
The horizontal transfer of heat energy by large-scale motions of the atmosphere.
ADVENTIVE— Non native plant. Recently
introduced and starting to spread into new places.
AEDILE—An elected official of ancient
Rome who was responsible for public works and games and who supervised markets, the grain
supply, and the water supply.
AEOLIAN SOIL—Soil transported from
one area to another by the wind.
AERATE—To supply or charge a liquid
or body of water with a gas, as to expose a body of water to the circulation of air for
purification. See Aerated Lagoon.
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.
AERATION—Any active or passive
process by which intimate contact between air and liquid is assured, generally by spraying
liquid in the air, bubbling air through water, or mechanical agitation of the liquid to
promote surface absorption of air.
AERATION TANK—A chamber used to
inject air into water.
AERATION (UNSATURATED) ZONE—The zone
between the land surface and the water table which characteristically contains liquid
water under less than atmospheric pressure and water vapor and air or other gases at
atmospheric pressure. The term Unsaturated Zone is now generally applied.
AERIAL— Occurring above water or
land.
AEROBE—An organism which requires
oxygen for its life processes.
AEROBIC—(1) Characterizing organisms
able to live only in the presence of air or free oxygen, and conditions that exist only in
the presence of air or free oxygen. Contrast with Anaerobic. (2) Process
requiring oxygen.
AEROBIC BACTERIA—Single-celled,
microscopic organisms that require oxygen to live and are partly responsible for the Aerobic
Decomposition of organic wastes.
AEROBIC DECOMPOSITION—The
biodegradation of materials by aerobic microorganisms resulting in the production of
carbon dioxide, water, and other mineral products. Generally a faster process than Anaerobic
Decomposition. Also see Aerobic Bacteria.
AEROBIC TREATMENT—The process by
which microbes decompose complex organic compounds in the presence of oxygen and use the
liberated energy for reproduction and growth. Such processes may include extended
aeration, trickling filtration, and rotating biological contactors.
AERODYNAMIC—Refers to forces acting
upon the soil or crop surface by moving air.
AEROPONICS—A technique for growing
plants without soil or hydroponic media. The plants are held above a system that
constantly mists the roots with nutrient-laden water. Also called Aeroculture.
AEROSOL—A suspension of liquid or
solid particles in air or gas.
AESTHETICS (Lake)— Aesthetics are
given consideration in the complete evaluation of lakes as a natural resource. The overall
scenic attraction of the lake setting; natural beauty of shores and waters, or any unusual
natural phenomena; the appeal of its wildlife and aquatic plants; desirable natural
landscape for home sites on the shores are some of the matters considered under this
heading.
AESTIVAL PONDS— Those ponds existing
only in summer.
AF—Acre-Feet (or Acre-Foot).
AFFECTED PUBLIC—The people who live
and/or work near a hazardous waste site or other source of pollutant emissions.
AFFLUENT (Lake)— A tributary or
feeder stream. Streams receiving the run-off from the watershed and flowing into the lake
are its affluents; analogous to the affluent of a river. The analogy can be very
close where a lake has large inflowing and outflowing streams and is located in a valley
or elongated basin. In usage, the term may have the same meaning as influent;
although where the reference is to a single inflowing stream, the word influent
appears to be the preferred one. See Influent and Inlet.
AFFLUENT (Stream)—A stream or river
that flows into a larger one; a Tributary.
AFFORESTATION—The artificial
establishment of forest crops by planting or sowing on land that has not previously, or
recently, grown trees.
AFLOAT—Floating on water.
AFTERBAY—The tail race or reservoir
of a hydroelectric power plant at the outlet of the turbines used to regulate the flow
below the plant; may refer to a short stretch of stream or conduit, or to a pond or
reservoir. Compare with Forebay.
AFY—Acre-Feet per Year.
AGE (of Groundwater)—An approximation
of the time between the water's penetration of the land surface at one location and its
later presence at another location.
AGENCY—A department of the
government.
AGGLOMERATION—(Water Quality) The
grouping of small suspended particles into larger particles that are more easily removed
through filtration, skimming, or settling. Also see Coagulation.
AGGRADATION—(1) The build-up of
sediments at the headwaters of a lake or reservoir or at a point where streamflow slows to
the point that it will drop part or all of its sediment load. (2) Modification of the
earth's surface in the direction of uniformity of grade or slope, by Deposition,
as in a river bed.
AGGRADING—The building up of a stream
channel which is flowing too slowly to carry its sediment load.
AGGRESSIVE WATER—Water which is soft
and acidic and can corrode plumbing, piping, and appliances.
AGITATED PIT—A reservoir, pit, or
pond that ordinarily is not stirred or aerated, but which is mixed just before emptying to
suspend any settled solids.
AGITATOR/MIXER—(Water Quality) Blades
or paddles that slowly rotate in a tank to facilitate the mixing of suspended material.
AGNPS— Agricultural Nonpoint Source
Pollution Model.
AGP—Algae Growth Potential
AGRIBUSINESS—The sum of all
operations involved in the production, storage, processing, and wholesale marketing of
agricultural products.
AGRICULTURAL—Having to do with
farming or farms.
AGRICULTURAL CAPABILITY— Determines,
given the ideal state, what a given area of land is capable of producing in terms of
agricultural production and output.
AGRICULTURAL DRAINAGE—(1) The process
of directing excess water away from the root zones of plants by natural or artificial
means, such as by using a system of pipes and drains placed below ground surface level.
Also referred to as Subsurface Drainage. (2) The water drained away from
irrigated farmland.
AGRICULTURAL ECONOMICS—The
application of economic principles to the Agribusiness sector of the economy.
AGRICULTURAL LAND—Land in farms
regularly used for agricultural production; all land devoted to crop or livestock
enterprises, for example, farmstead lands, drainage and irrigation ditches, water supply,
cropland, and grazing land.
AGRICULTURAL LEVEE—A levee that
protects agricultural areas where the degree of protection is usually less than that of a
flood control levee.
AGRICULTURAL POLLUTION—Liquid and
solid wastes from all types of farming, including runoff from pesticides, fertilizers, and
feedlots; erosion and dust from plowing; animal manure and carcasses; and crop residues
and debris.
AGRICULTURAL RESTRUCTURING SCENARIO (ARS)—A
term used to describe the sensitivity of agricultural water demand and farm marketing
revenues to changes in certain cropping patterns.
AGRICULTURAL RUNOFF—The runoff into
surface waters of herbicides, fungicides, insecticides, and the nitrate and phosphate
components of fertilizers and animal wastes from agricultural land and operations.
Considered a Non-Point Source (NPS) of water pollution.
AGRICULTURAL SUITABILITY— Determines
how suitable a given area of land is, in it's present state, for agricultural purposes.
AGRICULTURAL USE—The use of any tract
of land for the production of animal or vegetable life; uses include, but are not limited
to, the pasturing, grazing, and watering of livestock and the cropping, cultivation, and
harvesting of plants.
AGRICULTURAL WATER USE—Includes water
used for irrigation and non-irrigation purposes. Irrigation water use includes the
artificial application of water on lands to promote the growth of crops and pasture, or to
maintain vegetative growth in recreational lands, parks, and golf courses. Non-irrigation
water use includes water used for livestock, which includes water for stock watering,
feedlots, and dairy operations, and fish farming and other farm needs.
AGRO-ECOSYSTEM—Land used for crops,
pasture, and livestock; the adjacent uncultivated land that supports other vegetation and
wildlife; and the associated atmosphere, the underlying soils, ground and surface waters,
irrigation channels, and drainage networks.
AGROINDUSTRIAL—Of or relating to
production (as of power for industry and water for irrigation) for both industrial and
agricultural purposes.
AGROUND—Onto or on a shore, reef, or
the bottom of a body of water.
AGUA— This Spanish word for water is
occasionally used in Southwestern U. S. in names of bodies of water such as lakes and
lagoons, as well as springs.
AIR—The colorless, odorless,
tasteless, gaseous mixture that makes up the earth's Atmosphere. Four gases
comprise 99.997 percent (by volume) of clean, dry, air: Nitrogen (78.084
percent); Oxygen (20.946 percent); Argon (0.934 percent); and Carbon
Dioxide (0.033 percent). The remaining components include neon, helium, methane,
krypton, nitrous oxide, hydrogen, xenon, and various organic vapors. Under normal
conditions, air contains up to about 3 percent water vapor (by volume) and many solid,
liquid, or gaseous contaminants introduced by human activities and natural causes such as
wind erosion and the burning of fossil fuels.
AIR BINDING—A situation where air
enters the filter media and harms both the filtration and backwash processes.
AIR-BOUND—Condition in a pipeline
wherein air trapped in a summit prevents the free flow of the material in the pipeline.
AIR CURTAIN—A method for mechanical
containment of oils spills in which air is bubbled through a perforated pipe, causing an
upward water flow that retards the spreading of oil; also used as barriers to prevent fish
from entering a polluted body of water.
AIR GAP—An open vertical gap or empty
space that separates a drinking water supply to be protected from another water system in
a treatment plant or other location. The open gap protects the drinking water
from contamination by backflow or backsiphonage.
AIR HOLE—An opening in the frozen
surface of a body of water.
AIR INJECTION—In groundwater
management, the pumping of compressed air into the soil to move water in the Unsaturated
Zone (Vadose Zone) down to the Saturated Zone (Phreatic Zone),
or Water Table.
AIR LOCK—A bubble or pocket of air or
vapor, as in a pipe, that stops the normal flow of fluid through the conducting part.
AIR MASS—A large body of air
AIR PADDING— Pumping dry air into a
container to assist with the withdrawal of liquid or to force a liquefied gas such as
chlorine out of the container.
AIR PHOTO— A photograph of the
earth's surface taken from the air. It is usually a vertical view, and one of a series of
photos taken from an aircraft flying a systematic pattern at a given altitude in order to
obtain continuous photo coverage for mapping purposes (Terrain Geology Task Group 1994).
AIR POLLUTION— Process of making the
air unclean, such as, burning wood or coal and putting its smoke into the atmosphere or
gasoline burning in cars engine and expelling the by products out the exhaust pipe.
AIR STRIPPING—(Water Quality) A
process for the removal of organic contaminants from groundwater. The groundwater flows
downward inside a tower filled with materials (the packing) over a large surface area. Air
is introduced at the bottom of the tower and is forced upward past the falling water.
Individual organic contaminants are transferred from the water to the air, according to
the gas and water equilibrium concentration values of each contaminant. Also referred to
as Packed Tower Aeration.
AIR VENT (of a Dam)—A pipe designed
to provide air to the outlet conduit to reduce turbulence and prevent negative pressures
during the release of water. Extra air is usually necessary downstream of constrictions.
ALACHLOR—A herbicide, marketed under
the trade name Lasso, listed by the U.S. Environmental Protection Agency (EPA) as
a "probable human carcinogen" and found frequently in streams and rivers,
particularly following floods and periods of heavy rain. Alachlor is used extensively for
weed control in corn, cotton, and soybean fields.
ALDOSTERONE—A steroid hormone
secreted by the adrenal cortex that regulates the salt and water balance in the human
body.
ALFALFA VALVE—A screw-type valve
placed on the end of a pipe to regulate the flow of water.
ALGAE— (1) Simple single-celled
(phytoplankton), colonial, or multi-celled, mostly aquatic plants, containing chlorophyll
and lacking roots, stems and leaves. Aquatic algae are microscopic plants that grow in
sunlit water that contains phosphates, nitrates, and other nutrients. Algae, like all
aquatic plants, add oxygen to the water and are important in the fish food chain. (2)
Algae is either suspended in water (plankton) or attached to rocks and other
substrates (periphyton). Their abundance, as measured by the amount of chlorophyll
a (green
pigment) in an open water sample, is commonly used to classify the trophic status of a
lake. Algae are a essential part of the lake ecosystem and provides the food base for most
lake organisms, including fish. Phytoplankton populations vary widely from day to day, as
life cycles are short.
ALGAE BLUE GREEN— A group of largely
microscopic, photosynthetic organisms with a bacterial structure (prokaryote), but
containing chlorophyll a and a photosynthesis biochemistry unlike other bacteria but
similar to that of other algae and higher plants. Alternative names are blue-green
bacteria, cyanophytes, cyanobacteria, or, probably the most suitable, cyanoprokaryotes.
Blue and red pigments, contained within them, give an often characteristic color.
ALGAE WASH— Shoreline drift composed
mainly of filamentous algae. The plants are carried to the shore by wind and wave action
and stranded at or near the limit of wave advance. The drift often accumulates in
considerable quantity and can become highly obnoxious on beaches.
ALGAECIDE—One of a group of plant
poisons used to kill filamentous algae and phytoplankton.
ALGAL BLOOM—Rapid growth of algae on
the surface of lakes, streams, or ponds; stimulated by nutrient enrichment (or due to
an increase in plant nutrients such as nitrates and phosphates). It is associated with Eutrophication
and results in a deterioration in water quality. Also spelled Algae Bloom.
ALGAL GROWTH POTENTIAL (AGP)—The
maximum algal dry weight biomass produced in a natural water sample under laboratory
conditions. Expressed as milligrams (mg), dry weight per liter (l) of sample.
ALGAL GROWTH RATE—A measure of algal
productivity in a body of water, the growth rate measures the mass of carbon used annually
by algae per unit area of lake surface. The growth rate, typically referred to as Primary
Productivity, is expressed as an index figure in grams of carbon per square meter per
year, and indicates the state of Eutrophication of a body of water. Algal
productivity is influenced by the quantities of nutrients that flow into, or fall onto,
the lake each year and the number of days of sunshine. Another important factor is the
mixing of the lake, which brings up to the surface where algae exist nutrients which have
accumulated near the bottom of the lake.
ALGORITHM—A series of well-defined
steps used in carrying out a specific process. May be in the form of a word description,
an explanatory note, a diagram or labeled flow chart, or a series of mathematical
equations.
ALKALI—Any strongly basic (high pH)
substance capable of neutralizing an acid, such as soda, potash, etc., that is soluble in
water and increases the pH of a solution greater than 7.0. Also refers to soluble salts in
soil, surface water, or groundwater.
ALKALI LAKES— Those containing water
very highly impregnated with alkalies. The "alkali" may be sodium carbonate or
sodium sulfate and potassium carbonate but includes other alkaline compounds as well.
Restricted to arid and semi-arid regions. See: Potash lakes and Soda lakes.
ALKALINE—Sometimes water or soils
contain an amount of Alkali substances sufficient to raise the pH value above 7.0
and be harmful to the growth of crops. Generally, the term alkaline is applied to water
with a pH greater than 7.4.
ALKALINITY—The capacity of water for
neutralizing an acid solution. Alkalinity of natural waters is due primarily to the
presence of hydroxides, bicarbonates, carbonates and occasionally borates, silicates and
phosphates. It is expressed in units of milligrams per liter (mg/l) of CaCO3
(calcium carbonate) or as microequivalents per liter (µeq/l) 20 µeq/l = 1 mg/l of CaCO3.
A solution having a pH below 4.5 contains no alkalinity. Low alkalinity is the main
indicator of susceptibility to acid rain. Increasing alkalinity is often related to
increased algal productivity. Lakes with watersheds that have sedimentary carbonate rocks
are high in dissolved carbonates (hard-water lakes). Whereas lakes in granite or igneous
rocks are low in dissolved carbonates (soft water lakes).
ALLELOPATHY— Production of substances
by one organism that inhibit the growth, activity or reproduction of another.
ALLOCTHONOUS—Materials (e.g. organic
matter and sediment) which enters a lake from atmosphere or drainage basin. See
autochthonous.
ALLOCTHONOUS DETRITUS— Particulate
matter originating outside, and carried into the lake.
ALLOGENIC—Exogenous, caused by
external factors, such as a change in a habitat or environment caused by flooding.
Contrast with Autogenic.
ALLOGENIC SUCCESSION—Predictable
changes in plant and animal communities in which changes are caused by events external to
the community, for example, fire, drought, floods, etc.
ALLUVIAL—An adjective referring to
soil or earth material which has been deposited by running water, as in a riverbed, flood
plain, or delta.
ALLUVIAL DAM LAKES— Numerous basins
which are the sites of both existing and extinct lakes in the arid regions of western U.
S. were formed by alluvial dams, especially by the coalescence of fans composed of
detritus carried down by streams from opposite sides of valleys. In glaciated regions dams
were formed in valleys by glacio-fluvial deposition during the Pleistocene; and barriers
of various kinds, which impound water have been created in river flood plains by alluvial
deposition. See Fluviatile lakes and Levee lakes.
ALLUVIAL FAN—A fan-shaped deposit of
generally coarse material created where a stream flows out onto a gentle plain; a
geomorphologic feature characterized by a cone or fan-shaped deposit of clay, silt, sand,
gravel, and boulders that have been eroded from mountain slopes, transported by flood
flows, and deposited on the valley floor.
ALLUVIAL FAN FLOODING—Flooding
occurring on the surface of an Alluvial Fan or similar landform which originates
at the apex and is characterized by high-velocity flows: active processes of erosion,
sediment transport, deposition, and unpredictable flow paths.
ALLUVIAL LAND—Areas of unconsolidated
alluvium, generally stratified and varying widely in texture, recently deposited by
streams, and subject to frequent flooding.
ALLUVIAL VALLEY FLOOR—[Public Law
95-87, Section 701] (Legal) "The unconsolidated stream laid deposits where water
availability is sufficient for subirrigation or flood irrigation. It does not include
upland areas which are generally overlain by a thin veneer of colluvial deposits composed
chiefly of debris from sheet erosion, deposits by unconcentrated runoff or
slopewash,
talus, or other mass movement accumulation and wind-blown deposits."
ALLUVION—(1) The flow of water
against a shore or bank. Inundation by water; flood. (2) (Legal) The increasing of land
area along a shore by deposited Alluvium or by the recession of water. (3) (Lake)
In its legal meaning, alluvion is an accretion to land, made gradually, composed of
detritus deposited by streams or of deposits accumulated by the action of waves and
currents. On lakes, accretions are made: by alluvial deposition on the advancing front of
a delta; by filling of shoreline lake bottom by erosion detritus carried by effluents,
gullies and superficial surface run-off or rainwash; by shifting dune sand; and by waste
disposal such as tailing from mine operations. Also natural accretions may be made to
islands, bars and beaches of lakes. The deposits are realities, but whether or not, in
specific instances, they constitute legal alluvion which involves land ownership is,
ultimately, a matter for court decisions. See: Reliction
ALLUVIUM—A general term for deposits
of clay, silt, sand, gravel, or other particulate material that has been deposited by a
stream or other body of running water in a streambed, on a flood plain, on a delta, or at
the base of a mountain. In lakes, alluvium is the sediments, or detrital matter carried by
inflowing streams and deposited on lake bottoms. Also see Alluvion.
ALPENGLOW—A rosy glow that suffuses
snow-covered mountain peaks at dawn or dusk on a clear day.
ALPINE—That portion of mountains
above tree growth; or organisms living there. Alpine vegetation is dominated by shrubs,
herbs, bryophytes, and lichens.
ALPINE DECREE [California and Nevada]—The
Federal Court adjudication of the relative water rights on the Carson River which is the
primary regulatory control of Carson River operations today. The decree is administered in
the field by a watermaster appointed by the federal district court. The decree, initiated
by the U.S. Department of the Interior on May 1, 1925 through U.S. v. Alpine Land and
Reservoir Company, et al., to adjudicate water rights along the Carson River. The decree
was finally entered 55 years later on October 28, 1980, making it the longest lawsuit
undertaken by the federal government against private parties over water rights. The decree
established the respective water rights (to surface water only) of the parties to the
original lawsuit, both in California and Nevada to Carson River water. The decree did not
make an interstate allocation of the Carson River between California and Nevada; it only
quantified individual water rights. Neither state was a party to the decree. In addition
to Carson River surface water rights, it also established the rights to reservoir storage
in the high alpine reservoirs and confirmed the historical practice of operating the river
on rotation, so that irrigators with more junior priorities could be served as long as
possible. These upper alpine reservoirs were permitted to fill out of priority order, in
accordance with historical practice. The decree also specifically recognized Riparian
Water Rights in California (as distinguished from the quantified Appropriative
Water Rights used in Nevada). For purposes of water distribution, the Carson River
and its east and west forks, were divided into eight (8) segments and when the river went
into regulation (i.e., there was not enough water in the Upper Carson River to serve the
most junior priority) each segment of the river was to be administered autonomously.
Duties of water were set forth for various locations according to Bench Land and Bottom
Land designations. For lands in the Newlands Irrigation Project (i.e., below
Lahontan Dam) in Churchill County near Fallon, the Alpine decree provided for an annual
net consumptive use of surface water for irrigation of 2.99 acre-feet per acre and a
maximum water duty of 4.5 acre-feet per acre for water-righted bench lands and 3.5
acre-feet per acre for water-righted bottom lands delivered to the land. For
lands above the Newlands Project (i.e., above Lahontan Reservoir), the net consumptive
water use was set at 2.5 acre-feet per acre with water duties of 4.5 acre-feet per acre diverted
to the canal for bottom lands, 6.0 acre-feet per acre diverted to the canal for the
alluvial fan lands and 9.0 acre-feet per acre diverted to the canal for the bench lands.
This annual net consumptive use, or Crop Water Requirement, was based on the
water duty of alfalfa as it is a dominant and the highest water-using crop grown in
Nevada. While the Alpine Decree established water duties for bench and bottom lands
throughout the Carson River Basin, it made no identification of those lands. The decree
also granted landowners on the Newlands Project an Appurtenant Water Right for
the patented lands, effectively transferring water rights to these land holders
individually.
ALPINE LAKES— Lakes in any high
mountain region, associated with snow, ice and a cold climate.
ALTERNATE CONCENTRATION LIMITS (ACLs)—One
of the three types of standards that may be applied when a leak is detected at a
treatment, storage, or disposal facility and groundwater compliance monitoring is
required. ACLs are set by the U.S. Environmental Protection Agency (EPA) for
specific hazardous waste constituents at levels that are designed to prevent a substantial
hazard to human health or the environment. Groundwater compliance monitoring can use the
following standards: (1) background concentrations, or the levels found in the area
naturally; (2) specific values set by federal regulations in Title 40, Part 264.94, of the
Code of Federal Regulations for eight metals and six pesticides and herbicides;
or (3) alternative concentration limits.
ALTERNATIVE STABLE STATES —Potential
existence of markedly different biological communities under the same external
environmental conditions.
ALTITHERMAL—(Climatology) A period of
time when it was much warmer than now, approximately 7,000-4,500 years before the present
time. Also see Anathermal and Medithermal.
ALTITUDE—The vertical distance of a
level, a point, or an object considered as a point, measured from Mean Sea Level (MSL).
ALTOCUMULUS CLOUD—A fleecy cloud,
usually a rounded mass, but which can change radically and unexpectedly, producing
intermediate forms, at an average height of 2.5 miles (4 kilometers). Also see Cloud.
ALTOSTRATUS CLOUD—A somewhat high
level, blue to grayish blue cloud that forms a sheet or layer at an average height of 3.5
miles (5.6 kilometers). Also see Cloud.
ALUM—Common name for commercial-grade
Aluminum Sulfate. Its chemical formula is generally denoted by Al2(SO4)3
12H2O (number of bound water molecules will vary from 12 to 18).
ALUM TREATMENT— Process of putting
liquid alum (Aluminum Sulfate) into the lake water, to precipitate to a floc that
settles through the water column removing fine particles to the sediment and building up a
barrier layer to contain soluble phosphorus in the lake sediments.
ALUMINUM— A light, bluish white
malleable and ductile metallic element found only in combinations. (Symbol Al).
ALUMINUM SULFATE—A white crystalline
compound, Al2(SO4)3, used chiefly in paper making, water
purification, sanitation, and tanning. See Alum.
AMBIENT WATER QUALITY STANDARDS—The
allowable amount of materials, as a concentration of pollutants, in water. The standard is
set to protect against anticipated adverse effects on human health or welfare, wildlife,
or the environment, with a margin of safety in the case of human health. Also see Primary
and Secondary Standards and 7Q10.
AMC—Antecedent Moisture Condition
AMD—Acid Mine Drainage
AMEBIC DYSENTERY—A disorder of the
gastrointestinal tract caused by a protozoan parasite belonging to the genus Entamoeba
histolytica. The disorder is commonly found in communities with poor sanitary
conditions, particularly related to water and food storage and preparation. Infected
individuals experience abdominal cramps, diarrhea, and blood and mucus in the feces. The
parasite invades the liver in some cases.
AMENITIES—(Lake) Those features or
aspects which produce a pleasurable effect, or have a sentimental value.
AMERICAN PUBLIC WORKS ASSOCIATION (APWA)—A
national organization founded in 1894 and based in Chicago, Illinois of individuals and
organizations involved in the management of municipal solid waste and in the design and
operation of wastewater treatment plants.
AMERICAN SOCIETY OF CIVIL ENGINEERS (ASCE)—A
professional organization in New York City founded in 1852 that supports the practice of,
and research in, environmental engineering, hydrology, and water and wastewater treatment.
AMERICAN WATER WORKS ASSOCIATION (AWWA)—A
national organization in Denver, Colorado, founded in 1881 of individuals involved in the
design and operation of public water supplies and systems.
AMICTIC LAKE—A lake that does not
experience mixing or turnover on a seasonal basis. Also see Dimictic Lake.
AMINO ACIDS —Components of proteins.
They are soluble in water and contain an amino (NH2) group.
AMMONIA—A form of nitrogen found in
organic materials, sewage, and many fertilizers. It is the first form of nitrogen released
when organic matter decays. It can be used by most aquatic plants and is therefore an
important nutrient. It converts rapidly to nitrate (NO3) if oxygen is present.
The conversion rate is related to water temperature. Ammonia is toxic to fish at
relatively low concentrations in pH-neutral or alkaline water. Under acid conditions,
non-toxic ammonium ions (NH4+) form, but at high pH values the toxic ammonium
hydroxide (NH4OH) occurs. The water quality standard for fish and aquatic life
is 0.02 mg/l of NH4OH. At a pH of 7 and a temperature of 68 Deg. F (20 Deg. C),
the ratio of ammonium ions to ammonium hydroxide is 250:1 at pH 8, the ratio is 26:1.
Ammonia is an important aquatic plant nutrient because it is readily available.
AMMONIA STRIPPING—A process for the
removal of ammonia from wastewater. The waste is first made alkaline to favor the NH3
form, and then aerated so that exchange between the water and the atmosphere is
encouraged. Stripping towers are often used, with the waste trickling downward as air is
forced upward through the tower.
AMMONIFICATION—The transformation of
organic nitrogen to ammonia, generally by means of bacterial activity.
AMMONIUM SULFATE—A brownish-grey to
white crystalline salt, (NH4)2SO4, used in fertilizers
and water purification.
AMOEBA, also Ameba—A protozoan of the
genus Amoeba or related genera, occurring in water and soil and as a parasite in
other animals. An amoeba has no definite form and consists essentially of a mass of
protoplasm containing one nucleus or more surrounded by a delicate, flexible outer
membrane. It moves by means of pseudopods.
AMPHIBIAN—(1) A cold-blooded,
smooth-skinned vertebrate of the class Amphibia, such as a frog or salamander,
that characteristically hatches as an aquatic larva with gills. The larva then transforms
into an adult having air-breathing lungs. (2) An animal capable of living both on land and
in water.
AMPHIBIOTIC—Living in water during an
early stage of development and on land during the adult stage.
AMPHIBIOUS—(Biology) (1) Living or
able to live both on land and in water. (2) Able to operate both on land and in water.
AMPOULES—A sealed, liquid-filled tube
which is broken to release or be filled with another fluid.
AMPROMETRIC TITRATION—A means to
measure concentrations of certain substances in water using an electric current that flows
during a chemical reaction. Also see Titration.
ANABAENA—Any of various freshwater
algae of the genus anabaena that sometimes occur in drinking water and cause a
bad taste and odor.
ANABRANCH—A diverging branch of a
river which re-enters the main stream.
ANADROMOUS—Pertaining to fish that
spend a part of their life cycle in the sea and return to freshwater streams to spawn, for
example, salmon, steelhead, and shad. Contrast with Catadromous.
ANAEROBE—An organism that does not
require oxygen to maintain its life processes.
ANAEROBIC—Characterizing organisms
able to live and grow only where there is no air or free oxygen, and conditions that exist
only in the absence of air or free oxygen.
ANAEROBIC BACTERIA— Bacteria that
lives without oxygen.
ANAEROBIC DECOMPOSITION—The
degradation of materials by Anaerobic microorganisms living beneath the ground or
in oxygen-depleted water to form reduced compounds such as methane or hydrogen sulfide.
Generally a slower process than Aerobic Decomposition.
ANAEROBIC DIGESTER—An airtight tank
in which Anaerobic microorganisms decompose organic material and produce Biogas,
mainly Methane. Sewage treatment plants often use anaerobic digesters to reduce
the volume of Sludge produced in Primary and Secondary Treatment,
and they sometimes use the methane as a heating fuel.
ANAEROBIC DIGESTION—The degradation
of organic matter by microorganisms in the absence of oxygen, particularly as related to
the treatment of sewage sludge. Sewage treatment plants often use anaerobic digesters to
reduce the volume of sludge produced in primary and secondary treatment, and they
sometimes use the resultant methane gas as a heating fuel.
ANALOG—A continuously variable
electrical signal representing a measured quantity. For example, electrical signals such
as current, voltage, frequency, or phase used to represent physical quantities such as
water level, flow, and gate position.
ANALYTICAL MODEL—A model that
provides approximate or exact solutions to simplified forms of the differential equations
for water movement and solute transport. Such models generally require the use of complex
calculations and the use of computers.
ANATHERMAL—(Climatology) The period
preceding the Altithermal; the early Holocene epoch from about
10,000-7,000 years before the present. Also see Medithermal.
ANC — Acid Neutralizing Capacity.
ANCHOR—A series of methods used to
secure a structure to its footings or foundation wall so that it will not be displaced by
flood or wind forces.
ANCHOR ICE—Frazil ice that has
collected on rocks on the stream bed. (Lake) Ice which extends down to and is attached, or
frozen, to the lake bottom. Also, called Bottom Ice, Depth Ice, or Ground Ice.
ANEROID—Not using liquid.
ANGIOSPERMS (Angiospermea)—(Botanical)
The vast majority of seed plants characterized as having ovules and seeds in a closed
ovary. Along with the Gymnosperms (Gymnospermae), Angiosperms comprise a
structurally superior class within the plant family Spermatophyta, or seed
plants. Its two sub-classes consist of Monocotyledones and Dicotyledones.
Also see Gymnosperms.
ANGLER-DAY—The time spent fishing by
one person for any part of a day.
ANHYDRIDE—A chemical compound formed
from another, often an acid, by the removal of water.
ANHYDROUS—Without water, especially
water of crystallization; not hydrated (Dehydrated).
ANIMAL WASTE — The waste by products
(manure and urine) produced by animals.
ANIMAL WASTE MANAGEMENT— A planned
process of collection, storage and application of domestic animal waste to the land.
ANION—In an electrolyzed solution,
the negatively charged particle, or ion, which travels to the anode and is therefore
discharged, evolved, or deposited. Also, by extension, any negative ion. Anions are
opposed to cations, which carry a positive charge. There must be equal amounts of
positive and negative charged ions in any water sample. Following are the common anions in
their order of decreasing concentration for most lakes: bicarbonate (HCO3-),
Sulfate(SO4--), chloride (Cl-), carbonate (CO3--), nitrate (NO3-),
Nitrite (NO2-), and phosphates (H2PO4-, HPO4--,
and PO4-- ).
ANISOTROPY—(1) The condition of
having different properties in different directions. (2) The condition under which one or
more of the hydraulic properties of an aquifer vary according to the direction of the
flow.
ANNUAL—(1) Measured by the year. (2)
A plant that completes its life cycle in one year or one season. (Seed to: flowers, set
seeds and dies)
ANNUAL FLOOD—The highest peak
discharge of a stream in a Water Year.
ANNUAL FLOOD SERIES—A list of annual
floods for a given period of time.
ANNUAL LOW-FLOW—The lowest flow
occurring each year, usually the lowest average flow for periods of perhaps 3, 7, 15, 30,
60, 120, or 180 consecutive days.
ANNUAL TURNOVER—(1) Spring/fall
turnover, mixing of the water in a lake, due to wind, annual cycle of air temperature, and
heating from the sun.
ANNULAR — In the form of a ring.
ANNULAR SPACE—The space between two
cylindrical objects, one of which surrounds the other, such as the space between the wall
of the drilled hole and the casing, or between a permanent casing and the borehole.
ANNULUS—For a well, the space between
the pipe and the outer wall (casing) of the borehole, which may be a pipe also (the well
casing).
ANNULUS PRESSURE—The positive
pressure maintained by a fluid introduced between the well piping and the outer wall
(casing) of the borehole of an underground Injection Well providing an indication
of the integrity of the well.
ANOXIA—The total deprivation of
oxygen, as in bodies of water, lake sediments, or sewage.
ANOXIA, FUNCTIONAL—Although not well
defined, generally refers to a body of water sufficiently deprived of oxygen to where Zooplankton
and fish would not survive.
ANOXIC—(1) Denotes the absence of
oxygen, as in a body of water. (2) Of, relating to, or affected with anoxia; greatly
deficient in oxygen; oxygenless as with water.
ANSWERS— Areal Nonpoint Source
Watershed Environmental Response Simulation.
ANTECEDENT MOISTURE—The degree of
wetness of soil at the beginning of a runoff, determined by summation of weighted daily
rainfall amounts for a period preceding the runoff.
ANTECEDENT MOISTURE CONDITION (AMC)—Soil
moisture at the onset of a rainfall event. The U.S. Department of Agriculture, Natural
Resources Conservation Service (NRCS), formerly the Soil Conservation Service
(SCS), defines AMC in terms of total rainfall during the 5 days immediately preceding
the rainfall event. Dry AMC conditions mean less than 1.4 inches, average is 1.4 to 2.1
inches, and wet is greater than 2.1 inches.
ANTECEDENT PRECIPITATION—Precipitation
which occurred prior to a particular time over a specific area or Drainage Basin.
Usually applied as a measure of moisture in the top layer of the soil which would affect
runoff from additional rainfall. Also see Antecedent Precipitation Index (API).
ANTECEDENT PRECIPITATION INDEX (API)—An
index of moisture stored in a basin before a storm, calculated as a weighted summation of
past daily precipitation amounts. Also see Antecedent Precipitation.
ANTECEDENT SOIL WATER—Degree of
wetness of a soil prior to irrigation or at the beginning of a runoff period, typically
expressed as an index.
ANTECEDENT STREAMS—Antecedent streams
are those in place before the rising of mountain chains. As the mountains rise, the
streams cut through at the same rate and so maintain their positions.
ANTEDILUVIAN—(1) Extremely old and
antiquated. (2) Occurring or belonging to the era before the Flood written about in the
Bible. (Ecology) Used sometimes today to denote a public growth and water policy based on
an area's natural ability to support population growth only through existing,
readily available natural resources, i.e., water.
ANTHROPOGENIC—Involving the impact of
man on nature; induced, caused, or altered by the presence and activities of man, as in
water and air pollution.
ANTHROPOGENIC SITES — Sites modified
by human activities to the extent that their initial physical properties (e.g. structures,
cohesion, consolidation) have been drastically altered. (Terrain Geology Task Group 1994)
Includes Spoil Heaps, Fill, Waste Water, or Archaeological Sites.
ANTICYCLONE—An area of relatively
high pressure in which, in the northern hemisphere, the winds tend to blow spirally
outward in a clockwise direction.
ANTIDEGRADATION POLICY (or Clause) —Rules
or guidelines that are required of each state by federal regulations implementing the Clean
Water Act (CWA), stating that existing water quality be maintained even if the
current water quality in an area is higher than the minimum permitted as defined by
federal ambient water quality standards. Some controlled degradation is permitted in
support of economic development.
ANTIFREEZE—A substance, often a
liquid such as ethylene glycol or alcohol, mixed with another liquid, such as water, to
lower its freezing point.
ANTIFLUORIDATIONIST—One who is
strongly opposed to the fluoridation of public water supplies.
ANTI-SEEPAGE COLLAR—A projecting
collar, usually of concrete, built around the outside of a pipe, tunnel, or conduit, or
conduit under or through an Embankment Dam to lengthen the seepage path along the
outer surface of the conduit.
APEX—The highest point on an Alluvial
Fan or similar landform below which the flow path of the major stream that formed the
fan becomes unpredictable and Alluvial Fan Flooding can occur.
APHOTIC—Defined as without light
(Dark zone). Of or relating to the region of a body of water that is not reached by
sunlight and in which Photosynthesis is unable to occur. The Aphotic Zone
of the ocean is the water deeper than about 800 meters (2,625 feet), beyond which no light
penetrates. Aphotic zone is the zone in which most photosynthetic algae cannot survive,
due to light deficiency. Contrast with Photic Zone.
APHOTIC ZONE—The zone in which most
photosynthetic algae can not survive due to light deficiency.
APHYTAL— The plantless zone of a lake
bottom. See: Profundal.
API—Antecedent Precipitation Index.
APM—Aquatic
Plant Management
APOTHECARIES' MEASURE—A system of
liquid volume measure used in pharmacy.
APPLICABLE or APPROPRIATE REQUIREMENTS (ARARs)—Any
state or federal statute that pertains to the protection of human life and the environment
in addressing specific conditions or use of a particular cleanup technology at a Superfund
Site.
APPLICATION RATE—For irrigation, the
rate at which water is applied per unit of land area, usually expressed in terms of inches
per hour.
APPLICATION, WATER RIGHT—An official
request for permission to develop a source of water or to change an existing water right;
includes a description of the proposed project, a map of the project, and a legal
description of the property involved. The application for a water right will typically
consists of the following information:
[1] the total amount of water to be diverted or pumped;
[2] the rate of flow (diversion);
[3] the point of diversion or pumpage;
[4] the point or place of use;
[5] the manner of (beneficial) use; and
[6] the period of use (continuous pumpage, seasonal diversion, etc.).
The application process is the first step in a process of
obtaining a certificate of use or a Perfected Water Right. This process includes:
[1] the filing of the application, which establishes the
priority date for appropriation purposes;
[2] the permit which is issued by the State Engineer or other approving
authority;
[3] the proof of completion which is filed by the applicant;
[4] the proof of beneficial use which is also filed by the applicant; and
[5] the certificate or perfected water right which is issued by the State Engineer or
other approving authority.
APPLIED WATER DEMAND—The quantity of
water delivered to the intake of a city's water system or factory, the farm headgate, or a
marsh or other wetland, either directly or by incidental drainage. For in-stream use, it is
the portion of the stream flow dedicated to in-stream use or reserved under federal or
state Wild and Scenic River Acts. Applied water includes the water that returns
to groundwater, a stream, canal, or other supply source that can be reused or recycled and
thus is not the same as Net Water Demand.
APPROPRIATE—To authorize the use of a
quantity of water to an individual requesting it.
APPROPRIATED WATER—A quantity of
water from a well, stream, river, reservoir, or other source reserved for a specific use
and place of use under state water-right laws, statutes, or regulations.
APPROPRIATE TECHNOLOGY—The
application of current scientific knowledge and technology in such a way so as to conform
with existing economic, infrastructure, social, and cultural conditions and practices. By
extension, the concept implies the implementation of low-technology solutions
incorporating simplicity of design, use, and maintenance.
(PRIOR) APPROPRIATION DOCTRINE—The
system for allocating water to private individuals used in most Western states. The
doctrine of Prior Appropriation was in common use throughout the arid west as
early settlers and miners began to develop the land. The prior appropriation doctrine is
based on the concept of "First in Time, First in Right." The first
person to take a quantity of water and put it to Beneficial Use has a higher
priority of right than a subsequent user. Under drought conditions, higher priority users
are satisfied before junior users receive water. Appropriative rights can be lost through
nonuse; they can also be sold or transferred apart from the land. Contrasts with Riparian
Water Rights.
APPROPRIATIVE WATER RIGHTS [Nevada]—Nevada's
water law is based on statutes enacted in 1903 and 1905 and are founded on the principal
of Prior Appropriation. Unlike some other states, Nevada has a statewide system
for the administration of both ground water and surface water. Appropriative water rights
are based on the concept of applying water to Beneficial Use and "First
in Time, First in Right." Appropriative water rights can be lost through nonuse
and they may be sold or transferred apart from the land. Due in large part to the relative
scarcity of water in Nevada and numerous competing uses, Nevada has had a thriving market
for water transfers for a number of years. A person in Nevada who desires to place water
to beneficial use must file an application with the State Engineer to initiate the process
of acquiring an appropriative water right. Also see Riparian Water Rights, Prescribed
Water Rights, and Reserved Water Rights (Federal).
APPROXIMATE ORIGINAL CONTOUR—The
surface configuration achieved by backfilling and grading of mined areas so that the
reclaimed area, including any terracing or access roads, closely resembles the general
surface configuration of the land prior to strip mining and blends into and complements
the drainage pattern of the surrounding terrain.
APPURTENANT—(1) (Legal) A right,
privilege, or property that is considered incident to the principal property for purposes
such as passage of title, conveyance, or passage of title. (2) (Water-Related) A right to
water that is incident to the ownership or possession of the land.
APPURTENANT STRUCTURES (of a Dam)—Auxiliary
features of a dam such as an outlet, spillway, powerhouse, tunnel, etc.
APPURTENANT TO PLACE OF USE—A water
right has several characteristics, one of which is the location of where the water will be
put to beneficial use. An Appurtenant Water Right is a water right that belongs
to the legal owner of the land described as the place of use on the water right.
APPURTENANT WATER RIGHT—A water right
that is incident to the ownership or possession of land.
APRON—(1) A platform, as of planking,
at the entrance to a dock. (2) A covering or structure along a shoreline for protection
against erosion. A platform serving a similar purpose below a dam or in a sluiceway. (3)
An area covered by sand and gravel deposited in the front of a glacial moraine.
APWA—American Public Works
Association.
AQUA—Water; an Aqueous
solution. A prefix meaning water, e.g., Aquaculture.
AQUACADE—(1) A water spectacle
originated at Cleveland, Ohio, in 1937; (2) A water spectacle that consists usually of
exhibitions of swimming and diving with musical accompaniment.
AQUACULTURE, also Aquiculture—The
science, art, and business of cultivating marine or freshwater food fish or shellfish,
such as oysters, clams, salmon, and trout, under controlled conditions for commercial
purposes. Examples of aquaculture plant products include rice and cranberries.
AQUALUNG—Equipment used by a person
to breath underwater.
AQUAMARSH—A water body in which the
original open water is nearly or completely obscured by emergent, and floating aquatic
vegetation. A stage in the evolution between open water and land marsh.
AQUANAUT—A person trained to live in
underwater installations and conduct, assist in, or be a subject of scientific research.
Also called Oceanaut.
AQUAPONICS—The culture of plants in
water areas (which includes lakes) in contrast to cultivation of plants on land, or
geoponics.
AQUARIUM—(1) A tank, bowl, or other
water-filled enclosure in which living fish or other aquatic animals and plants are kept.
(2) A place for the public exhibition of live aquatic animals and plants.
AQUARIUS—(1) A constellation in the
equatorial region of the Southern Hemisphere near Pisces and Aquila also referred to as
the Water Bearer. (2) The 11th sign of the zodiac in astrology.
AQUASOL—A water soil. Water is the
medium in which the plants grow.
AQUATIC—(1) Consisting of, relating
to, or being in water; living or growing in, on, or near the water. (2) Taking place in or
on the water. (3) An organism that lives in, on, or near the water.
AQUATIC ALGAE—Microscopic plants that
grow in sunlit water containing phosphates, nitrates, and other nutrients. Algae, like all
aquatic plants, add oxygen to the water and are important in the fish food chain.
AQUATIC BIOLOGY—Field of biological
study that deals with aquatic plants and animals.
AQUATIC ECOSYSTEM—The basic unit of
aquatic organisms and nonliving environment they live in.
AQUATIC INVERTEBRATES—Aquatic animals
without an internal skeletal structure such as insects, mollusks, and crayfish.
AQUATIC LIFE—All forms of living
things found in water, ranging from bacteria to fish and rooted plants. Insect larva and
zooplankton are also included.
AQUATIC MACROPHYTES—Macrophytes
(large plants versus microscopic) that live completely or partially in water.
AQUATIC MACROPHYTES HARVESTING—The
manual and mechanical cutting and collecting of aquatic plants from lakes.
AQUATIC MICROBIOLOGY—Study of
microscopic plants and animals and their interrelationships.
AQUATIC PLANT
MANAGEMENT—Steps taken to evaluate, establish a management plan, and do
something to change the amount and types of aquatic plants in a lake.
AQUATIC WEEDS—A
common, unsightly, troublesome aquatic (water) plant, that grows in abundance or out of
place. See Water Weeds.
AQUEDUCT—(1) A pipe, conduit, or
channel designed to transport water from a remote source, usually by gravity. (2) A
bridge-like structure supporting a conduit or canal passing over a river or low ground.
AQUEOUS—(1) Relating to, similar to,
containing, or dissolved in water; watery. (2) (Geology) Formed from matter deposited by
water, as certain sedimentary rocks.
AQUI—A prefix for water, e.g., Aquifer.
AQUIC—A mostly reducing soil moisture
regime nearly free of dissolved oxygen due to saturation by groundwater or its capillary
fringe and occurring at periods when the soil temperature at 50 centimeters is above 5C
(41F).
AQUICLUDE (Confining Bed)—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 spring. Aquicludes are characterized
by very low values of "leakage" (the ratio of vertical Hydraulic
Conductivity to thickness), so that they transmit only minor inter-aquifer flow and
also have very low rates of yield from compressible storage. Therefore, they constitute
boundaries of aquifer flow systems.
AQUICULTURE—See Aquaculture.
Compare with Mariculture.
AQUIFER—A geologic formation, a group
of formations, or a part of a formation that is water bearing. A geological formation or
structure that stores or transmits water, or both, such as to wells and springs. Use of
the term is usually restricted to those water-bearing structures capable of yielding water
in sufficient quantity to constitute a usable supply.
AQUIFER, BASIN-FILL—An aquifer
located in a basin surrounded by mountains and composed of sediments and debris shed from
those mountains. Sediments are typically sand and gravel with some clay.
AQUIFER COMPACTION—Term used to
describe the effects of emptying or overdrawing an aquifer; overdrafts tend to collapse
the structure of the aquifer such that the original volume cannot be restored. May also be
associated with a general Land Subsidence in the surrounding ground level as the
result of such compaction.
AQUIFER, CONFINED—An aquifer which is
bounded above and below by formations of impermeable or relatively impermeable material.
An aquifer in which ground water is under pressure significantly greater than atmospheric
and its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than
that of the aquifer itself. See Artesian Aquifer.
AQUIFER, FRACTURED BEDROCK—An aquifer
composed of solid rock, but where most water flows through cracks and fractures in the
rock instead of through pore spaces. Flow through fractured rock is typically relatively
fast.
AQUIFER, LEAKY (Semi-confined)—An
aquifer overlaid and/or underlain by a thin semipervious layer through which flow into or
out of the aquifer can take place.
AQUIFER, PERCHED—A groundwater unit,
generally of moderate dimensions, that occurs whenever a groundwater body is separated
from the main groundwater supply by a relatively impermeable stratum and by the Zone
of Aeration above the main water body.
AQUIFER, SALINE/POOR QUALITY—An
aquifer containing water that is high in total dissolved solids, and is unacceptable for
use as drinking water.
AQUIFER, SANDSTONE—The type of
aquifer supplying groundwater to large parts of the United States upper Middle West,
Appalachia, and Texas. The water-bearing formation is often contained by shale strata, and
the water has high levels of iron and magnesium.
AQUIFER SYSTEM—A body of permeable
and relatively impermeable materials that functions regionally as a water-yielding unit.
It comprises two or more permeable units separated at least locally by confining units (Aquitards)
that impede ground-water movement but do not greatly affect the regional hydraulic
continuity of the system. The permeable materials can include both saturated and
unsaturated sections.
AQUIFER TEST—A test to determine
hydrologic properties of an aquifer, involving the withdrawal of measured quantities of
water from, or the addition of water to, a well and the measurement of resulting changes
in head in the aquifer both during and after the period of discharge or addition
(recharge).
AQUIFER, UNCONFINED—An Aquifer
made up of loose material, such as sand or gravel, that has not undergone lithification
(settling). In an unconfined aquifer the upper boundary is the top of the Zone of
Saturation (water table).
AQUIFER, VOLCANIC ROCK—An aquifer
composed of rock that originated from a volcano, such as basalt. This type of rock may or
may not be very permeable.
AQUIFUSE—A formation that has no
interconnected openings and hence cannot absorb or transmit water.
AQUITARD—A saturated, but poorly
permeable bed that impedes ground-water movement and does not yield water freely to wells,
but which may transmit appreciable water to or from adjacent aquifers and, where
sufficiently thick, may constitute an important ground-water storage unit. Aquitards are
characterized by values of leakance that may range from relatively low to relatively high.
Aerial extensive aquitards of relatively low leakance may function regionally as
boundaries of aquifer flow systems.
ARABLE LAND—Land capable of being
cultivated and suitable for the production of crops. The (U.S. Department of the Interior)
Bureau of Reclamation (USBR) defines arable land as: "Land which, in
adequate units and when properly provided with the essential improvements of leveling,
drainage, buildings, irrigation facilities and the like, will have a productive capacity,
under sustained irrigation agriculture, sufficient to: meet all production expenses,
including a reasonable return on investment; repay reasonable irrigation and improvement
costs; and provide a satisfactory level of living for the farm family."
ARARs—Applicable, Relevant,
Appropriate Requirements.
ARBORETUM—A collection of plants,
trees, and shrubs grown for public exhibition, public enjoyment, recreation, education, or
research.
ARBORICULTURE—The planting, care, and
tending of trees and shrubs, individually or in small groups, for utilitarian purposes.
ARC VIEW—Desktop computer software
program that allows viewing, manipulation, and printing of maps of lands and lakes. It
allows for spatial analysis to help local land/lake use planning.
ARCH DAM—Curved masonry or concrete
dam, convex in shape upstream, that depends on arch action for its stability; the load or
water pressure is transferred by the arch to the Abutments. Also see Dam.
ARCH-GRAVITY STRUCTURE—A structure
which derives its resistance to the pressure of water from both an arching effect and its
own weight.
ARCHIMEDEAN SCREW—An ancient
apparatus for raising water, consisting of either a spiral tube around an inclined axis or
an inclined tube containing a tight-fitting, broad-threaded screw. Also referred to as Archimedes'
Screw.
ARCTIC—Referring to the region of the
earth between the North Pole and Arctic Circle.
ARCTIC TUNDRA—The grassland Biome
characterized by permafrost (subsurface soil that remains frozen throughout the year).
ARE—A metric unit of land measure
equal to 100 square meters or 1/100 Hectare (119.6 square yards). Also see Metric
System.
AREA-CAPACITY CURVE—A graph showing
the relation between the surface area of the water in a reservoir and the corresponding
volume.
AREA FLOODED—Area of a floodplain
that is flooded in a specific stream reach, watershed, or river basin; may be for a single
flood event, but is usually expressed as an average, annual value based on the sum of
areas from all individual flood events over a long period of time, such as 50 to 100
years, and adjusted to an average value.
AREA (SUB-AREA), HYDROGRAPHIC—Primarily
these are sub-drainage systems, typically valleys, within a more comprehensive drainage
basin. Hydrographic Areas (Valleys) may be further subdivided into Hydrographic
Sub-Areas based on unique hydrologic characteristics (e.g., differences in surface
flows) within a given valley or area.
AREA (SUB-AREA), HYDROGRAPHIC [Nevada]—Nevada's
14 major drainage Basins or Hydrographic Regions are divided further
into 232 Hydrographic Areas (valleys) and 256 Hydrographic Areas and Hydrographic
Sub-Areas as defined by the U.S. Geological Survey (USGS) and the Nevada
Division of Water Resources, Department of Conservation and Natural Resources. See Basins
[Nevada]. [A listing of these Hydrographic Areas and Sub-Areas is presented in
Appendix A-1 (listed sequentially by Hydrographic Area number and Hydrographic
Region/Basin), Appendix A-2 (listed alphabetically by Hydrographic Area and Sub-Area
name), and Appendix A-3 (listed alphabetically by principal Nevada county(ies) in which
located).]
AREA OF A LAKE—The space occupied by
the water surface. The area of a lake, generally, is something that cannot be determined
with great exactitude; often the figure given is an arbitrary one, and figures from
different sources show considerable disagreements. This comes about, because some error is
inherent in any of the procedures devised for determining area; because measurements may
be made from hydrographic maps which differ in accuracy and detail, and in time at which
the map was made. This latter becomes important where lakes fluctuate greatly in levels.
Some differences may arise also where different mathematical procedures are followed in
making measurements. Also, often arbitrary decisions must be made as to location of shore
line, the inclusion or exclusion of islands, and boundaries between a lake and connecting
water, all of which consequently affect the computed area. Area is usually expressed
square miles and acres; or where the metric system is used in square kilometers and square
meters.
AREA OF CRITICAL ENVIRONMENTAL CONCERN (ACEC)—An
area on Public Lands where special management attention is required to protect
and prevent irreparable damage to historic, cultural, or scenic values, fish and wildlife
resources, or other natural systems or processes, or to protect people from natural
hazards.
AREA OF INFLUENCE—The area
surrounding a pumping or recharging well within which the water table or potentiometric
surface has been changed due to the well's pumping or recharge.
AREA OF ORIGINS PROTECTION—State and
federal laws, dating back to 1931, enacted to guarantee that the counties that contribute
water to state and federal water projects will get priority for water when it is needed to
match future growth. As yet, these statutes have not received close legal scrutiny by the
courts.
AREA OF REVIEW—The area around an
underground injection well that may be influenced adversely by fluid injection. Typically,
the extent of this area may be calculated by using the specific gravity and rate of
introduction of the injected fluids, the size, storage capacity, and hydraulic
conductivity of the injection zone, and certain underground formation pressures.
AREA OF SHALLOW FLOODING—Designated Flood
Zones AO and AH on a community's Flood Insurance Rate Map (FIRM) with a one
percent or greater annual chance of flooding to an average depth of one to three feet
where a clearly defined channel does not exist, where the path of flooding is
unpredictable and where velocity flow may be evident. Such flooding is characterized by
ponding or sheet flow. Also referred to as Sheet Flow Area.
AREA OF SPECIAL FLOOD-RELATED EROSION HAZARD—The
land within a community which is most likely to be subject to experience flood-related
erosion losses. The area may be designated as Zone E on the Flood Insurance Rate Map
(FIRM). See Flood Zones.
ARGILLIC ALTERATION (ARGILLIZATION)—A
form of Hydrothermal alteration in which certain minerals of rock are converted to
clay minerals.
ARHIZOUS—Plant without roots.
ARID—A term applied to a climate or
region where precipitation is so deficient in quantity, or occurs so infrequently, that
crop production is impractical without irrigation.
ARIDIC—A soil moisture regime that
has no moisture available for plants for more than half the cumulative time that the soil
temperature at 19.7 inches (50 centimeters) is above 5C (41F) and has no period as long as
90 consecutive days when there is moisture for plants while the soil temperature at 50
centimeters is continuously above 8C (46.4F).
ARIDITY—The quality or state of being
arid, dry, or barren.
ARITHMETIC GROWTH—(Statistics) A rate
of increase (or decrease) by a constant amount per time period, for example a population
increase of X persons per year, year after year. Compare to Exponential Growth
and Sigmoid Growth.
ARITHMETIC MEAN—(Statistics) The sum
of a set of observations divided by the number of observations. Also referred to as simply
the Mean, or the Sample Mean. Compare to Mode and Median.
ARM—(1)An inlet of water (as from the
sea). (2) (Lakes) A long and relatively narrow body of water extending inland from a main
body. Usually the term arm is applied to a reach of water, greater in length and narrower
than one called a bay, but often on maps no clear distinction exists between arm
and bay: nor between arm and lobe.
ARMA—AutoRegressive Moving Average.
ARMORING—A facing layer (protective
cover), or Rip Rap, consisting of very large stones placed to prevent erosion or
the sloughing off of a structure or embankment. Also, a layer of large stones, broken
rocks or boulders, or pre-cast blocks placed in random fashion on the upstream slope of an Embankment
Dam, on a reservoir shore, or on the sides of a channel as a protection against
waves, ice action, and flowing water. The term armoring generally refers only to very
large rip rap.
(UNITED STATES) ARMY CORPS OF ENGINEERS (Corps or
COE)—Originally formed in 1775 during the Revolutionary War by General
George Washington as the engineering and construction arm of the Continental Army.
Initially, the Corps of Engineers built fortifications and coastal batteries to strengthen
the country's defenses and went on to found the Military Academy at West Point, help open
the West, and to develop the nation's water resources. In its military role, the COE
plans, designs, and supervises the construction of facilities to insure the combat
readiness of the U.S. Army and Air Forces. In its civilian role, the COE has planned and
executed national programs for navigation and commerce, flood control, water supply,
hydroelectric power generation, recreation, conservation, and preservation of the
environment. In a very general sense, the U.S. Army Corps of Engineers has a primary
responsibility for water projects which protect property from potential flood damage,
whereas the (U.S. Department of the Interior) Bureau of Reclamation (USBR) is
responsible for primarily western water projects with respect to developing water sources
for agriculture and commerce. In reality, however, quite often these federal agencies'
project goals overlap with USBR's dams and reservoirs providing important flood protection
and the COE's water projects—dams, locks, and canals—providing important water
transportation linkages and benefits to commerce. [See Appendix C-2 for the U.S. Army
Corps of Engineers' organizational structure and primary missions and objectives.]
ARRANGED DELIVERY—Operation of a
water delivery system to meet predetermined needs, generally based on user water orders.
Also referred to as Scheduled Delivery.
ARRASTRA—A crude drag-stone mill for
pulverizing ores, especially those containing free gold or silver; frequently powered by
falling water.
ARROYO—A water-carved channel or
gully in an arid country which is usually rather small with steep banks and is dry much of
the time due to infrequent rainfall and the shallowness of the cut, which does not
penetrate below the level of permanent ground water.
ARS—Agricultural Research Service.
ARS—Agricultural Restructuring
Scenario.
ARTESIAN—A commonly used expression,
generally synonymous with Confined and referring to subsurface (ground) bodies of
water which, due to underground drainage from higher elevations and confining layers of
soil material above and below the water body (referred to as an Artesian Aquifer),
result in underground water at pressures greater than atmospheric.
ARTESIAN AQUIFER—A commonly used
expression, generally synonymous with (but a generally less favored term than) Confined
Aquifer. An artesian aquifer is an aquifer which is bounded above and below by
formations of impermeable or relatively impermeable material. An aquifer in which ground
water is under pressure significantly greater than atmospheric and its upper limit is the
bottom of a bed of distinctly lower hydraulic conductivity than that of the aquifer
itself.
ARTESIAN PRESSURE—The pressure under
which Artesian Water in an Artesian Aquifer is subjected, generally
significantly greater than atmospheric.
ARTESIAN WATER—Ground water that is
under pressure when tapped by a well and is able to rise above the level at which it is
first encountered. It may or may not flow out at ground level. The pressure in such an
aquifer commonly is called Artesian Pressure, and the formation containing
artesian water is an Artesian Aquifer or Confined Aquifer.
ARTESIAN WELL—(1) A well bored down
to the point, usually at great depth, at which the water pressure is so great that the
water is forced out at the surface. The name is derived from the French region of Artois,
where the oldest well in Europe was bored in 1126. (2) A well tapping a Confined
or Artesian Aquifer in which the static water level stands above the top of the
aquifer. The term is sometimes used to include all wells tapping confined water. Wells
with water levels above the unconfined water table are said to have positive artesian head
(pressure) and those with water level below the unconfined water table, negative artesian
head. If the water level in an artesian well stands above the land surface, the well is a Flowing
Artesian Well. If the water level in the well stands above the water table, it
indicates that the artesian water can and probably does discharge to the unconfined water
body.
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.
ARTICULATION—(of a lake) The ratio of
area of inlets and bays to the total area of the lake.
ARTIFICIAL BEACH—A bathing beach
created by removing peat or muck and subsequently filling with sand or fine gravel. Sand
may also be spread over clay shore to create a more desirable beach. In a few instances
sand is placed on a polyethylene (plastic) blanket which has been spread over soft bottom,
but this kind of beach is not considered permanent. Groins are frequently
constructed on the Great Lakes shoreline to trap shore drift thereby creating a beach.
ARTIFICIAL CIRCULATION—The mixing of
lake water using an air bubble stream or other mechanical means rather or in addition to
the wind mixing.
ARTIFICIAL LAKES, PONDS—Basins
purposely excavated by man and filled with water by catchment from run-off, by pumping or
diversion of natural water bodies. Definitely artificial are those ponds constructed for
farm use, for receiving factory wastes, sewage, etc. However, there are degrees of
artificiality. Bodies of water impounded by dams across rivers are artificial only to a
degree as are lakes whose basins have been altered by dredging or filling or whose levels
has been raised or lowered respectively by dams across outlets or by dredging outlets. A
gravel pit or stone quarry is patently an artificial basin, but its filling with water,
after abandonment, may be a natural process. Ponds occupying mine cave-in pits can hardly
be accepted as natural geomorphological features, neither are they intentionally
constructed and filled with water by man. Wherever man has made use of the water or
occupied the adjacent land, he has modified natural lakes to some degree, and to that
degree made them artificial.
ARTIFICIAL RECHARGE—The designed (as
per man's activities as opposed to the natural or incidental) replenishment of ground
water storage from surface water supplies such as irrigation or induced infiltration from
streams or wells. There exist five (5) common techniques to effect artificial recharge of
a groundwater basin:
[1] Water Spreading consisting of
the basin method, stream-channel method, ditch method, and flooding method, all of which
tend to divert surface water supplies to effect underground infiltration;
[2] Recharge Pits designed to take advantage of permeable soil
or rock formations;
[3] Recharge Wells which work directly opposite of pumping
wells, although they generally have limited scope and are better used for deep, confined
aquifers;
[4] Induced Recharge which results from pumping wells near
surface supplies, thereby inducing higher discharge towards the well; and
[5] Wastewater Disposal which includes the use of secondary
treatment wastewater in combination with spreading techniques, recharge pits, and recharge
wells to reintroduce the water into deep aquifers thereby both increasing the available
groundwater supply and also further improving the quality of the wastewater.
Also referred to as Induced Recharge. Also see Natural
Recharge, Incidental Recharge, Injection, and Perennial Yield.
ARTIFICIAL SUBSTRATE—A device placed
in the water for a specified period of time that provides living spaces for a multiplicity
of organisms; for example, glass slides, concrete blocks, multi-plate samplers, or rock
baskets; used primarily to collect organisms in areas where the physical habitat is
limiting or cannot be adequately sampled using conventional methods.
ASBESTOS—A mineral fiber that can
pollute air or water and cause cancer or Asbestosis when inhaled. The U.S.
Environmental Protection Agency (EPA) has banned or severely restricted its use in
manufacturing and construction.
ASBESTOSIS—A disease associated with
inhalation of Asbestos fibers. The disease makes breathing progressively more
difficult and can be fatal.
ASC—Atmospheric Sciences Center
(DRI).
ASCE—American Society of Civil
Engineers.
ASEXUAL REPRODUCTION—Plants
reproducing without the sexual process by fragmentation, turions, tubers, and/or other
vegetative structures.
ASOS—Automated Surface Observing
System (NWS/NOAA)
ASPECT—The compass direction toward
which a sloping land area faces. The direction is measured downslope and normal to the
contours of elevation.
ASPERSE—To sprinkle, especially with
holy water.
ASSESSMENT REPORT—A comprehensive
record of historical, existing and projected water quality conditions of a particular
watershed.
ASSIGNMENT OF WATER—The transfer of a
water right application or permit from one person to another. This can be done in
conjunction with the sale of land.
ASSIMILATION—The ability of a body of
water to purify itself of pollutants.
ASSIMILATIVE CAPACITY—(1) The ability
of air, a natural body of water, or soil to effectively degrade and/or disperse chemical
substances. If the rate of introduction of pollutants into the environment exceeds its
assimilative capacity for these substances, then adverse effects may result to habitat and
wildlife. (2) Its the ability of a lake to absorb nutrients or other potential pollutants
without showing averse effects.
ASSOCIATION—(Lake) A voluntary union
of riparians whose purpose is management or development, or use or conservation of
riparian lands and lake surface. Their union may vary from a gentlemen's agreement or may
be in the form of a profit or non-profit corporation.; In some instances the prospective
buyer must become a member of the lake association prior to the purchase of frontage;
continuous membership in the association becomes part of the purchase contract.
ASSOCIATION OF BOARDS OF CERTIFICATION—An
international organization representing boards which certify the operators of waterworks
and wastewater facilities.
ASTHENOSPHERE—The zone inside the
earth beneath the Lithosphere constituting the source of Igneous rock (Magma).
ATHALASSOHALINE LAKE—A term used to
describe a saline lake which is not of marine origin. In this respect athalassohaline
lakes differ from lakes formed by the isolation of part of the ocean in as much as those
lakes originating from evaporation of fresh water is the importance of bivalent ions such
as calcium, magnesium, and sulfate relative to the dominance of two monovalent ions
(sodium and chloride) in sea water. The different ionic ratios are important biologically
because the osmotic strength of a solution at a given level of Total Dissolved Solids
(TDS) changes with the valence of the dominant ions. The individual ion
concentrations are also important in that some ions are more toxic to fish than others.
ATMOMETER—An instrument used to
measure the rate of evaporation.
ATMOSPHERE—The gaseous layer covering
the earth. The regions of the atmosphere are the Troposphere, Stratosphere,
Mesosphere, Chemosphere, and the Thermosphere (which overlaps
the Ionosphere and the Exosphere). The atmosphere is one of the four
components, together with the Lithosphere, Hydrosphere, and Biosphere,
that comprise the earth's ecosystem. Also see Air.
ATP—Adenosine TriPhosphate.
ATRAZINE—A herbicide listed by the U.S.
Environmental Protection Agency (EPA) as a "possible human carcinogen" and
found frequently in streams and rivers, particularly following floods and periods of heavy
rain and runoff from agricultural lands. Atrazine is used extensively for weed control for
corn, sorghum, and sugarcane. Along with another common farm herbicide, Cyanazine,
atrazine concentrations can soar to levels much higher than federal standards during the
peak growing season.
ATTACHED GROUND WATER—The portion or
amount of alkali substances in the ground sufficient to raise the pH value above 7.0 or to
be harmful to the growth of crops, a condition called alkaline.
ATTENUATION—(1) Generally, a term
used to describe the slowing, modification, or diversion of the flow of water as with Detention
and Retention. (2) (Water Quality) The process of diminishing contaminant
concentrations in ground water, due to filtration, biodegradation, dilution, sorption,
volatilization, and other processes. (3) The process where by the magnitude of an event is
reduced, as the reduction and spreading out of the impact of a storms effect. Also see Natural
Attenuation.
ATTERBERG LIMITS—The transition
points between various states of soil consistency. The Atterberg Limits consist of: (1)
the liquid limit (water content at which the soil passes from the liquid to the plastic
state); (2) the plastic limit (water content at which the soil passes from the plastic to
the semi-solid state); and (3) the shrinkage limit (water content at which the soil passes
from the semi-solid to the solid state).
AUDUBON SOCIETY (NATIONAL)—A national
environmental organization founded in 1905 and dedicated to the conservation and
restoration of natural ecosystems with a focus on birds and other wildlife species for the
benefit of humanity and the earth's biological diversity. Named after John James Audubon
(1785-1851) who was one of the first American conservationists and who gained widespread
recognition for his paintings of birds.
AUM—Animal Unit Month.
AUSTRAL—Southern as in southern pine
forest. See Boreal.
AUTO-QI—Automated Q-ILLUDAS.
AUREOLE—(Astronomy) A faintly colored
luminous ring appearing to surround a celestial body visible through a haze or thin cloud
of water vapor, especially such a ring around the moon or sun, caused by the diffraction
of light from suspended matter in the intervening medium. Also referred to as Corona.
AUTOCHTHONOUS—Pertaining to
substances (organic matter from plankton), materials, or organisms originating within a
particular waterway or lake and remaining in that waterway.
AUTOREGRESSION, or Autoregressive Process—(Statistics)
A condition which exists whenever a lagged (i.e., prior period) value of the Dependent
Variable, or the variable to be explained, appears as a regressor, that is, as an Explanatory
Variable. The fundamental assumption is that future data values may be expressed as
linear combinations of past observations. It is not uncommon in economics and other areas
of scientific study for a variable to be influenced by its own behavior in prior periods.
The problem with this equation (model) format is to insure that the lagged variable,
represented below as Yt-1, is independent of the disturbance term, t.
An example of a (first-order) autoregressive process, commonly termed AR(1), would be
represented by:
Yt = ø1Yt-1 + ð + et
where the parameter ø1 < 1, and ð is the
(constant, time insensitive) trend component, and et is the residual or
disturbance term associated with each observation of Yt.
AUTOTROPHIC—Plants that produce their
own nutrients. If photosynthetic and green then it contains chlorophyll.
AUTUMN TURNOVER—The mixing of the
entire water mass of a lake in the autumn.
AUTUMNAL—Appearing or flowering in
the fall.
AUXILIARY SPILLWAY—A dam spillway
built to carry runoff in excess of that carried by the principal spillway; a secondary
spillway designed to operate only during exceptionally large floods. Also referred to as Emergency
Spillway. Also see Spillway.
AVAILABLE WATER—The portion of water
in a soil that can be absorbed by plant roots, usually considered to be that water held in
the soil against a tension of up to approximately 15 atmospheres.
AVAILABLE WATER HOLDING CAPACITY—The
capacity of a soil to hold water in a form available to plants. Also, the amount of
moisture held in the soil between field capacity, or about one-third atmosphere of
tension, and the wilting coefficient, or about 15 atmospheres of tension.
AVALANCHE—A fall or slide of a large
mass, as of snow or rock, down a mountainside.
AVERAGE ANNUAL FLOOD DAMAGES—The
weighted average of all flood damages that would be expected to occur yearly under
specified economic conditions and development. Such damages are computed on the basis of
the expectancy in any one year of the amounts of damage that would result from floods
throughout the full range of potential magnitude.
AVERAGE ANNUAL RECHARGE—The amount of
water entering an aquifer on an average annual basis. In many, if not most, hydrologic
conditions, "average" has little significance for planning purposes as there may
exist so few "average" years in fact.
AVERAGE ANNUAL RUNOFF (YIELD)—The
average of water-year (October 1-September 30) runoff or the supply of water produced by a
given stream or water development project for a total period of record; measured in cubic
feet per second or acre-feet.
AVERAGE DISCHARGE—In the annual
series of the U.S. Geological Survey's (USGS) reports on surface-water supply,
the arithmetic average of all complete water years of record whether or not they are
consecutive. Average discharge is not published for less than 5 years of record. The term
"average" is generally reserved for average of record and "mean" is
used for averages of shorter periods, namely daily mean discharge.
AVERAGE WATER YEAR—A tern denoting
the average annual hydrologic conditions based upon an extended or existing period of
record. Because precipitation, runoff, and other hydrologic variables vary from year to
year, planners typically project future scenarios based on hydrologic conditions that
generally include average, wet (high-water), and drought (low-water) years.
AVERAGE YEAR WATER DEMAND—The demand
for water under average hydrologic conditions for a defined level of development.
AVERAGE YEAR WATER SUPPLY—The average
annual supply of a water development system over a long period. For a dedicated natural
flow, it is the long-term average natural flow for wild and scenic rivers or it is Environmental
Flows as required for an average year under specific agreements, water rights, court
decisions, and congressional directives.
AVIGATIONAL TRESPASS—Persons using a
float plane to gain access to a private lake without permission, trespass first on the air
or avigational rights of the lake owners, then by landing on the surface of the lake, they
commit simple trespass.
ÄVJA-GYTTJA—Lake bottom deposit
composed largely of the remains of algae. See Gyttja.
AVOIRDUPOIS WEIGHT—The system in
common use in English-speaking countries for weighing all commodities except precious
stones, precious metals, and drugs. In it 16 drams (dr.) make 1 ounce (oz.), 16 ounces
make 1 pound (lb.). The pound contains 7,000 grains (453.59 grams) and is equal to 1.2153
pounds troy (or, 1 lb.=14.5833 troy oz.). There are two avoirdupois tons, the long ton
(2,240 pounds) and the short ton (2,000 pounds), of which the long ton is the
customary one in Great Britain and the short ton is used in the United States. Also see Metric
System.
AVULSION—(1) The sudden movement of
soil from one property to another as a result of a flood or a shift in the course of a
boundary stream. (2) A forcible separation or detachment; a sudden cutting off of land by
flood, currents, or change in course of a body of water; especially one separating land
from one person's property and joining it to another's.
AW—Applied Water
AWASH—Washed by the sea as level with
or washed by waves. In such a position or way as to be covered with or as if with water.
AWT—Advanced Wastewater Treatment
AWWA—American Water Works
Association.
AXIAL FLOW—Fluid flow in the same
direction as the axis of symmetry of the duct, vessel, or tank.
AXIS (of a Dam)—The horizontal
centerline of a dam in the longitudinal direction.
AZOTOBACTER—Any of various
rod-shaped, nonpathogenic, nitrogen-fixing bacteria of the genus azotobacter,
found in soil and water.