unicellular organism that lacks a nuclear membrane. Some
can cause disease.
BailerA 10- to 20-foot-long pipe equipped with
a valve at the lower end. It is used to remove slurry
from the bottom or the side of a well as it is being drilled.
BaseA substance that has a pH value between
7 and 14.
BedrockThe solid rock that underlies
all soil, sand, clay, gravel and other loose materials
on the earth's surface. Unfractured bedrock is impermeable
while fractured bedrock may store and transmit groundwater.
BlackwaterWater that contains
animal, human or food wastes.
BMPsBest management practices.
Generally, a set of standardized efficiencies. At Met,
refers to a set of water conservation measures agreed
to by participants in the California Urban Water Conservation
BondA promise to repay money borrowed,
plus interest, over a specified period of time.
Bond IssueA means of raising large
amounts of money for major projects by selling bonds.
BrackishA mixture of freshwater and saltwater.
BufferA solution or liquid whose
chemical makeup neutralizes acids or bases without a great
change in pH.
California Environmental Quality
Act (CEQA)Requires an assessment of the possible
environmental impacts of projects.
California PlanOfficially "Californias
draft Colorado River Water Use Plan," also sometimes
called the "4.4 Plan." A planning document designed
to reduce Californias reliance on surplus Colorado
River water over the next 15 years through conservation,
water transfers, and conjunctive use measures.
CallTo order, request or retrieve stored
water; to call upon.
CapillarityThe process by which
water rises through rock, sediment or soil caused by the
cohesion between water molecules and an adhesion between
water and other materials that "pulls" the water
CBOCommunity-based organization. Local organization
with which Metropolitan works on mutually beneficial programs.
CUWCCCalifornia Urban Water Conservation
Council. Created to increase efficient water use statewide
through partnerships among urban water agencies, public
interest organizations and private entitites. The Council's
goal is to integrate urban water conservation Best Management
Practices into the planning and management of California's
mechanical device that uses centrifugal or rotational
forces separate substances of different densities, such
as solids from liquids or liquids from other liquids.
CesspoolA covered hole or pit for
CFSCubic Feet Per Second.
Chloraminationthe treatment of
a substance, such as drinking water, with chlorine and
ammonia (chloramines) in order to kill disease-causing
of the major anions commonly found in water and wastewater.
Its presence is often
determined by ion chromatographic or volumetric analysis.
Consumers who drink water with concentrations of
chloride exceeding a secondary maximum contaminant level
of 250 milligrams per liter may notice a salty taste.1
Chlorination The treatment of a
substance, such as drinking water, with chlorine in order
to kill disease-causing organisms.
ChromiumA naturally occurring element found
in air, soil, water and food.
"chrome 6." One of the most common species of
chromium, chromium VI is known to cause cancer through
exposure to airborne chromium compounds in industrial
settings. The evidence of its carcinogenicity by ingestion
is not compelling. The U.S. Environmental Protection Agency
determined that chromium VI was not carcinogenic by ingestion.
of liquid, as measured by a variety of methods.1
CIIMetropolitans water conservation
program for commercial, industrial and institutional entities.
CoachellaCoachella Valley Water District.
Primarily agricultural irrigation district receiving Colorado
River water through Coachella Canal and serving portions
of Riverside, Imperial and San Diego counties north of
the Salton Sea. Has priority 3(b) to Californias
apportionment of Colorado River water, after (1) PVID;
(2.) U.S. Bureau of Reclamations Yuma Project; (3a)
Imperial Irrigation District. MWD has fourth priority.
CoagulationThe process, such as
in treatment of drinking water, by which dirt and other
suspended particles become chemically “stuck together”
so they can be removed from water.
of the family Enterobacteriaceae, commonly found in the
intestinal tracts of warm-blooded animals. In sanitary
bacteriology, these organisms are defined as all aerobic
and facultative anaerobic, gram-negative, nonspore-forming,
rod-shaped bacteria that ferment lactose with gas and
acid formation within 48 hours at 95° Fahrenheit (35°
characteristic describing the appearance of water (different
from turbidity, which is the
cloudiness of water). Color is frequently caused by fulvic
and humic acids.1
Combined SewersA sewer system that
carries both sewage and storm-water runoff.
CondensationWater vapor changing
back into liquid.
Condensation SurfacesSmall particles
of matter, such as dust and salt suspended in the atmosphere,
which aid the condensation of water vapor in forming clouds.
Confined AquiferAn aquifer that
is bound above and below by dense layers of rock and contains
water under pressure.
Conjunctive UseStoring imported water in
a local aquifer, in conjunction with groundwater, for
later retrieval and use.
Contour PlowingPlowing done in
accordance with the natural outline or shape of the land
by keeping the furrows or ditches at the same elevation
as much as possible to reduce runoff and erosion.
A condition in which specific quality criteria have been
achieved in a laboratory analysis. (2) A type of sample
used to assess the quality of an analytical process.1
indication of the corrosiveness of water. The corrosiveness
of water is described by the
water’s pH, alkalinity, hardness, temperature, total
dissolved solids, dissolved oxygen concentration, and
Langelier saturation index.1
Cost EffectiveAble to at least
pay for itself or make a profit.
County Water AuthorityA public
water district serving a county-wide area.
CRAColorado River Aqueduct, built 1933-1941
and owned and operated by the Metropolitan Water District
of Southern California.
group of widespread intestinal coccidian protozoan parasites
about 5 micrometers in
diameter, causing diarrhea and capable of infecting humans,
birds, fish, and snakes. It is responsible for waterborne
CRWUAColorado River Water Users Association.
CRWUA is a non-profit, non-partisan organization, formed
to plan, study, formulate and advise on ways to protect
and safeguard the interests of all whom use the Colorado
CT—The product of
disinfectant concentration (in milligrams per liter) determined
before or at the first customer
and the corresponding disinfectant contact time (in minutes).
It is also called the CT value. Units are milligram
minutes per liter.1
Cubic footA frequent water industry term
of measurement, as in cubic feet per second. One cubic
foot (cf) equals 7.48 gallons. A cubic foot per second
is 450 gallons per minute.
CUWACalifornia Urban Water Agencies.
Group of 11 member agencies serving two-thirds of state's
CVPCentral Valley Project. A series
of dams, reservoirs and canals in the San Joaquin Valley
stage for Giardia, 7 to 10 micrometers long and refractile
to light when viewed with a
area at the mouth of a river.
DepositionThe process of dropping
or getting rid of sediments by an erosional agent such
as a river or glacier; also called sedimentation.
DesalinationThe process of removing
salt from seawater or brackish water.
DiemerRobert B. Diemer, Metropolitan general
manager 1952-1961, after whom Metropolitan treatment plant at Yorba Linda, in Orange County, was named.
Dischargethe amount of water flowing
past a location in a stream/river in a certain amount
of time - usually expressed in liters per second or gallons
that destroys or inactivates harmful microorganisms.
Disinfection By-Product (DBP)—A
chemical by-product of the disinfection process. Disinfection
by-products are formed by the reaction of the disinfectant,
natural organic matter, and the bromide ion (Br–).
Some disinfection by-products are formed through halogen
(e.g., chlorine or bromine) substitution reactions; i.e.,
halogen-substituted by-products are produced. Other disinfection
by-products are oxidation by-products of natural organic
matter (e.g., aldehydes—RCHO). Concentrations are
typically in the microgram-per-litre or nanogramper-litre
Disinfection By-Product Precursor
(DBPP)—A substance that can be converted
into a disinfection by-
product during disinfection. Typically, most of these
precursors are constituents of natural organic matter.
addition, the bromide ion (Br–) is a precursor material.
See also bromide; disinfection by-product; natural
DomenigoniThe name of a pioneer family in
southwestern Riverside County and of one of the two valleys
dammed to create Diamond Valley Lake, Metropolitans
major reservoir near Hemet in southwestern Riverside County.
DRIPDesalination Research and Innovation
Partnership. A landmark research partnership among the
water and electric industries, state and federal agencies
DroughtA prolonged period of below-average
DVLDiamond Valley Lake. Metropolitans
major reservoir near Hemet, in southwestern Riverside
DWRCalifornia Department of Water Resources.
Guides development and management of Californias
water resources; owns and operates State Water Project
and other water-development facilities.
network of groups of organisms together with their nonliving
or physical environment.
from a structure such as a treatment plant. Contrast with
influent.1Effluent—Water flowing from a structure
such as a treatment plant. Contrast with influent.1
EIREnvironmental Impact Report; a state-mandated
written summary of the positive and negative effects on
the environment caused by the construction and operation
of a project.
Endangered SpeciesA species of
animal or plant threatened with extinction.
oxide, C3H5OCl) —A highly volatile, unstable
liquid epoxide. It is a major
raw material for epoxy and phenoxy resins and has other
industrial uses. It is a treatment chemical that is
regulated in drinking water under the Phase II Rule for
synthetic organic contaminants and inorganic
ErosionThe processes of picking
up, moving, shaping and depositing sediments by various
agents; erosional agents include streams, glaciers, wind
Escherichia coli (E. coli)—A
gram-negative, facultatively anaerobic, nonspore-forming
found in the intestinal tracts of humans and other warm-blooded
animals. In sanitary bacteriology, Escherichia
coli is considered the primary indicator of recent fecal
EvaporationWater changing into
vapor and rising into the air.
FallowingA program to
generate water by paying farmers to fallow land, i.e.,
not grow crops. The water not used for irrigation is then
transferred to urban areas or stored for future use.
Fecal Coliform (FC)—Members
of the total coliform group of bacteria that are characterized
by their ability to
ferment lactose at 112.1° Fahrenheit (44.5° Celsius)
and that are considered more specific indicators of fecal
contamination than are coliforms that ferment lactose
only at 95° Fahrenheit (35° Celsius). Escherichia
coli and some Klebsiella pneumoniae strains are the principal
FERCFederal Energy Regulatory Commission.
An independent regulatory agency within the Department
iron salt used as a coagulant in water treatment. The
iron has a valence of +3.1
Filtrationpassing water through
coal, sand and gravel to remove particles.
Fish LadderA device to help fish
swim around a dam.
FisheryThe aquatic region in which
a certain species of fish lives.
FlocClumps of impurities removed
from water during the purification process; formed when
alum is added to impure water.
FlocculationA step in water filtration
in which alum is added to cause particles to clump together.
FloodplainArea formed by fine sediments
spreading out in the drainage basin on either side of
the channel of a river as a result of the river’s
fluctuating water volume and velocity.
Fluoride Ion (F–)—A
halide ion. Fluoride salts are added to drinking water
for fluoridation. Fluoride is regulated
by the US Environmental Protection Agency.1
GeneAka Gene Camp. Small
community on the California bank of the Colorado River,
near Parker Dam and Lake Havasu, at and around which are
located facilities of Metropolitans Colorado River
Aqueduct. Reputedly the first name of a miner who had
established "Genes Camp" at the site.
genus name for a group of single-celled, flagellated,
pathogenic protozoas found in a variety of
vertebrates, including mammals, birds, and reptiles. These
organisms exist either as trophozoites or as cysts,
depending on the stage of the life cycle.1
carved into rock by overriding ice, showing the direction
of glacial movement.
Gross Alpha (a) Particle
Activity The total radioactivity caused by
alpha particle emission as inferred from
measurements on a dry sample. It is regulated by the US
Environmental Protection Agency.1
Gross Beta (b) Particle
Activity The total radioactivity caused by
beta particle emission as inferred from measurements on
a dry sample. It is regulated by the US Environmental
GroundwaterWater that has percolated into
natural, underground aquifers; water in the ground, not
water puddled on the ground.
Groundwater Recharge or ReplenishmentPumping
or percolating storm water runoff or imported water into
an aquifer to replenish its supplies.
Haloacetic Acid (HAA)—(CX3COOH,
where X = Cl, Br, H in various combinations) A class of
disinfection by-products formed primarily during the chlorination
of water containing natural organic matter. When bromide
(Br–) is present, a total of nine chlorine-, bromine-and-chlorine-,
or bromine-substituted species may be formed. Trihalomethanes
and haloacetic acids are the two most prevalent classes
of by-products formed during chlorination; and subject
to regulation under the Disinfectant/Disinfection by-products
of water determined by the levels of calcium and magnesium.
Heterotrophic Plate Count (HPC)
—A bacterial enumeration procedure used to estimate
bacterial density in
an environmental sample, generally water. Other names
for the procedure [within the water industry] include
total plate count, standard plate count, plate count,
and aerobic plate count.1
HindsJulian B. Hinds, Metropolitan general manager
1941-1951, after whom the western-most of the five pumping
plants along the Colorado River Aqueduct was named.
power plant that produces electricity from the power of
rushing water turning turbine-generators.
scientific study of the behavior of water in the atmosphere,
on the Earth's surface and underground.
Program. The Innovative Conservation Program portion is
designed to provide grants to explore the water savings
potential and practicality of new water conserving technologies.
Special consideration will be given to projects promoting
water-landscape saving products or technologies.
IICPIncremental Interruption and Conservation
Plan, which was in effect during the states 1987-92
drought and was replaced by the WSDM Plan.
IIDImperial Irrigation District, primarily
agricultural irrigation district in Imperial County south
of the Salton Sea. Has priority 3(a) to Californias
apportionment of Colorado River water. Coachella has priority
3(b). MWD has fourth.
emission of visible light by a compound that has been
irradiated with ultraviolet
light. For example, a fluorescent compound (i.e., a fluorescein)
can be attached to an antibody. Bacterial, viral,
or other antigens that react with the antibody can then
be observed by illuminating the sample with ultraviolet
I/OInlet-outlet facility at a reservoir.
to material such as sand, salt, iron, calcium salts, and
other mineral materials. Inorganic
substances are of mineral origin, whereas organic substances
are usually of animal or plant origin and contain carbon.1
IRPIntegrated Water Resources Plan. The districts
plan to ensure reliable water delivery to its customer
member agencies despite population growth, dry spells
and droughts. The IRP resources mix includes water storage,
conservation, best management practices (BMPs), recycling,
desalination, and groundwater recovery, among others.
IrrigationSupplying water to agriculture
by artificial means, such as pumping water onto crops
in an area where rainfall is insufficient.
ISPInnovated Supply Program. The
ISP will provide up to a total of $250,000 in grants on
a competitive basis to stimulate and advance new innovative
ideas that have potential to produce new sources of water
supply for Southern Californa.
JensenJoseph Jensen, Metropolitan board chairman 1949-1974, after whom the Metropolitan treatment plant at Granada Hills, in Los Angeles County, was named.
Laguna DeclarationA Dec.
16, 1952 policy statement by Metropolitans Board
of Directors that it will "provide its service area
with adequate supplies of water to meet expanding and
increasing needs in the years ahead."
Law of the RiverA complex body of laws, court
decrees, contracts, agreements, regulations and an international
treaty used to govern allocation and management of Colorado
LeachTo remove components from
the soil by the action of water trickling through.
genus of bacteria of the family Legionellaceae. It currently
consists of at least 51 serogroups comprising 34 species.1
It has the ability to colonize water in distribution systems
(heating tanks, cooling towers, air conditioning lines,
etc). It can cause disease in humans (e.g., Legionnaires’
disease or Legionellosis) that is progressive and sometimes
fatal, or a milder form of pneumonic illness (Pontiac
fever) that is self-limited (i.e., heals on its own) with
respiratory symptoms similar to influenza.
Marginal LandLand which, in its natural state,
is not well suited for a particular purpose, such as raising
MCLMaximum Contaminant Level. According
to health agencies, the maximum amount of a substance
that can be present in water that's safe to drink and
which looks, tastes and smells good.
Member AgencyOne of 26 member public water
providers associated with the Metropolitan Water District
of Southern California, from which it purchases water
and on whose board it is represented.
MGDMillion gallons per day, a measure used for
water treatment plants and other facilities.
to microorganisms and their life processes.1
MicroorganismAn organism of microscopic
size, such as bacterium.
MillsHenry J. Mills, Metropolitan general
manager 1967-1971, after whom Metropolitan treatment plant at Riverside was named.
MitigationA way in which an agency
may offset negative environmental impacts of a project
or make the impacts less serious.
MoabA site near Moab, Utah, where a 10.5
million ton mountain of uranium mill tailings (scrap)
is leaching pollutants, including uranium, into the nearby
Monterey AgreementA December 1994 statement
of principles to settle disputes over water allocations
and operational aspects of the State Water Project, providing
greater water management flexibility and financial stability.
MTBEMethyl tertiary butyl ether. An oxygenate
used in California gasoline to help prevent air pollution.
The chemical has a long life and has been determined to
have polluted lakes, reservoirs and groundwater after
leaking from watercraft, underground tanks and pipelines.
Required to be phased out by Dec. 31, 2002.
MulchMaterial spread on the ground
to reduce soil erosion and evaporation of water; include
hay, plastic sheeting and wood chips.
Municipal Water DistrictA public
water provider governed by a locally elected board of
directors, which supplies water to the public directly
or through subagencies.
MWQIMunicipal Water Quality Investigation.
Government agencies conduct water quality studies in the
Sacramento watershed, the Sacramento-San Joaquin Delta,
and the San Francisco Bay Area.
living and nonliving things that occur naturally on the
oxidized ion of nitrogen. Nitrifying bacteria can convert
nitrite (NO2–) to nitrate in the
nitrogen cycle. Sodium nitrate (NaNO3) and potassium nitrate
(KNO3) are used as fertilizer. The nitrate ion is
regulated by the US Environmental Protection Agency.1
intermediate oxidized ion of nitrogen. Nitrifying bacteria
can convert ammonia (NH3) to nitrite (NO2–) to nitrate
(NO3–) in the nitrogen cycle. Sodium nitrite (NaNO2)
is used in curing meats. The nitrite ion is regulated
by the US Environmental Protection Agency.1
Nonpoint Source PollutionPollution
which comes from diffuse sources such as urban and agricultural
NWRANational Water Resources Association.
Advocates federal policies, legislation and regulations
promoting the development, management, protection and
beneficial use of water resources.
minimum odor of a water sample that can just be detected
after successive dilutions
with odorless water.1
The odor threshold is reported as the threshold odor number.
that is produced by [some] coccidian protozoa (i.e., Cryptosporidium)
as a result of sexual
reproduction during the life cycle. The oocyst is usually
the infectious and environmental stage, and it contains
sporozoites. For the enteric protozoa, the oocyst is excreted
in the feces.1
chemical having a carbon–hydrogen structure.1
derived from oxygen that is bubbled through water during
the treatment processes to kill microorganisms.
Palo VerdePalo Verde Irrigation
District, PVID; primarily agricultural irrigation district
lying along the Colorado River 110 miles north of Mexico.
Has first priority to river water from Californias
apportionment. MWD has fourth priority.
quality attribute. For example, the presence of certain
bacteria, the hardness, and the level
of sodium are all parameters.1
agent. An organism capable of causing infection or infectious
chemical used in manufacturing rocket fuel that has contaminated
some Southern California groundwater basins. Perchlorate
interferes with the iodide uptake into the thyroid gland.
The disruption of thyroid functions leads to changes in
metabolism in adults and normal growth and development
Perennial YieldMaximum quantity
of water that can be annually withdrawn from a groundwater
basin over a long period of time (during which water supply
conditions approximate average conditions) without developing
an overdraft condition.
of peroxide and ozone used to kill germs and oxidize taste-and-odor
compounds in water.
pHA relative scale of how acidic
or basic (alkaline) a material is; the scale goes from
0 to 14; 7 is neutral, acids have pH values less than
7 and bases have pH values higher than 7.
water above or underground to homes and businesses.
PotableDrinkable water. Nonpotable means
Preferential RightsA member agency has a
preferential right to a percentage of Metropolitans
available water supply based on a formula established
by the Legislature and set forth in Section 135 of the
Metropolitan Act. That percentage is equal to the ratio
of each member agencys total accumulated payments
to Metropolitans capital costs and operating expenses
compared to the total of all member agencies payments
towards those costs, specifically excepting payments for
the purchase of water. The Preferential Rights section
has never been invoked.
animal-like, eukaryotic organisms of the kingdom Protista.
Protozoans can occur wherever moisture exists. There are
many parasites and commensals of plants and animals, as
well as free-living species. They cause a number of diseases,
such as African sleeping sickness, malaria, and dysentery.
They are an economically and scientifically important
group. It is thought that the organisms of the kingdom
Animalia evolved from ancestors which were protozoans.
Pumping LiftDistance water
must be lifted in a well from the pumping level to the
Pumping PlantFacility that lifts water up
and over the hills.
QuantificationRefers to Quantification Settlement Agreement, a proposed agreement among MWD, CVWD and IID to settle a variety of long-standing disputes regarding the priority, use and transfer of Colorado River water within California.
with an unstable atomic nucleus that spontaneously decays
Radium (Ra)—A naturally
occurring radioactive element (in the form of radium-226
or radium-228) created in
the decay of the uranium and thorium series. Radium can
be removed from water by cation exchange
Radium-226 + Radium-228 (Ra-226 +
Ra-228)—The sum of the naturally occurring
radioactive isotopes of
radium. The regulation for radium by the US Environmental
Protection Agency is for the sum of the [two] isotopes.1
aquifer with stormwater or imported water
Reclaimed WaterWastewater that has been cleaned
so that it can be reused for most purposes except drinking.
ReclamationHistorically, a wide-ranging federal
program to irrigate arid lands throughout the West. More
recently, a euphemism for treating sewage water so it
can be reused for nonpotable purposes. See recycled.
RecycledWastewater cleaned for re-use, usually
for nonpotable purposes such as irrigating landscape and
ReservoirsA pond or lake where
water is collected and stored until it is needed.
liquid, or solid by-product of a treatment process that
ultimately must be disposed of.
For example, in a fixed-bed filter for removing particles
from water, both the filter backwash water and the
solids in the backwash water are residuals.1
RillsSmall grooves, furrows, or
channels in soil made by water flowing down over its surface;
also another name for a stream-usually a small stream.
RunoffLiquid water that travels
over the surface of the Earth, moving downward due to
the law of gravity; runoff is one way in which water that
falls as precipitation returns to the ocean.
RUWMPRegional Urban Water Management Plan.
State law requires that every urban water retailer and
wholesaler prepare and adopt a water management plan every
five years. A dictionary of MWD programs, projects and
Association of Governments. It has evolved as the largest
of nearly 700 councils of government in the United States,
functioning as the Metropolitan Planning Organization
for six counties. As the designated Metropolitan Planning
Organization, the Association of Governments is mandated
by the federal government to research and draw up plans
for transportation, growth management, hazardous waste
management and air quality. Additional mandates exist
at the state level.
SalinityThe scaling or white deposits that accumulate
on coffee pots, water heaters and plumbing fixtures resulting
from dissolved mineral salts in the water. Also known
as total dissolved solids or TDS.
SkinnerRobert A. Skinner, Metropolitan general
manager 1962-1967, after whom Metropolitan treatment plant near Winchester, in southwestern Riverside County,
Source water— The
supply of water for a water utility. Source water is usually
treated before distribution to
consumers, but some groundwaters are of such a quality
that they can be distributed untreated. This term is
preferred over raw water.1
measure of the ability of a solution to conduct electrical
current. Its value is
inversely proportional to the solution’s electrical
resistance. The conductivity value is commonly used in
desalting processes as a means to evaluate desalting efficiency
and to estimate the total dissolved solids
concentration; the conductivity value of a water sample
is multiplied by an empirical factor representative
of the typical total dissolved solids/conductivity ratio
for the specific type of water. The units of conductivity
often reported as micromhos per centimetre at 25°
Celsius, but this is not a Système International
multiplying such a value by 10–4 converts the value
to units of siemens per meter.1
A recommended practice in the manufacturing of products
or materials or in the conduct of a
business, art, or profession. Such standards may or may
not be used as (or called) specifications. (2) A
document that specifies the minimum acceptable characteristics
of a product or material, issued by an
organization that develops such documents (e.g., an American
Water Works Association standard). (3) A
numerical contaminant limit set by a regulatory agency
(e.g., a US Environmental Protection Agency maximum contaminant
Strategic PlanThe product of a strategic
planning process, a comprehensive approach to how Metropolitan
does business. The plans components include a composite
rate structure, a resource management plan, the determination
of prices and a compatible board governance and management
structure with comprehensive ethical standards.
inorganic ion that is widely distributed in nature. It
may be present in natural waters in
concentrations ranging from a few to several thousand
milligrams per liter.1
Surface RunoffWater flowing along
the ground into rivers, lakes and oceans.
Surface WaterAll water, fresh and
salty, on the Earth's surface.
SWPState Water Project, of which Metropolitan
Water District is the largest contractor. Owned and operated
by the California Department of Water Resources.
SWRCBState Water Resources Conrol
Board. Regulates water quality and water rights to protect
beneficial water use in the Bay/Delta estuary.
trihalomethanes. By-products of chlorination.
TopsoilThe top layer of soil; topsoil can grow
better crops partly because it has more organic matter
(humus), allowing it to hold more water than lower soil
Residual—The total amount of chlorine residual
present after a given contact time in a water
sample, regardless of the type of chlorine. See also residual
chlorine; total chlorine.1
Total Coliform Rule (TCR)—A
rulemaking of the US Environmental Protection Agency that
Primary Drinking Water Regulations for total coliforms,
fecal coliforms, and Escherichia coli. The rule was promulgated
June 29, 1989 (54 Federal Register 27544–27568)
and amended Jan. 15, 1991 (56 Federal Register 1556–1557).1
Total Coliforms (TC)—The
group of bacteria used as warm-blooded animal fecal pollution
of drinking water quality. Total coliforms are regulated
by the US Environmental Protection Agency.1
Total Dissolved Solids (TDS)
—The weight per unit volume of filtered water. The
liquid passing the filter are evaporated to dryness. The
filter pore diameter and evaporation temperature are frequently
Total Organic Carbon (TOC)—A
measure of the concentration of organic carbon in water,
oxidation of the organic matter into carbon dioxide (CO2).
TOC includes all the carbon atoms covalently bonded in
organic molecules. Most of the organic carbon in drinking
water supplies is dissolved organic carbon, with the remainder
referred to as particulate organic carbon. In natural
waters, total organic carbon is composed primarily of
nonspecific humic materials. Total organic carbon is used
as a surrogate measurement for disinfection by-product
precursors, although only a small fraction of the organic
carbon will react to form these by-products. Quantitatively,
total organic carbon is determined by removing interfering
inorganic carbon, such as bicarbonate (HCO3–), and
oxidizing the organic carbon to carbon dioxide. Typically,
the carbon dioxide is then measured with a nondispersive
Total Trihalomethanes (TTHM)
—The sum of the four chlorine and bromine-containing
chloroform, bromodichloromethane, dibromochloromethane,
and bromoform). The US Environmental Protection Agency
regulates the sum of these four species on a weight concentration
TranspirationEvaporation of water
through the leaves of plants.
which may be harmful to health at certain levels in drinking
TurbidityThe state of having sediment
or foreign particles suspended or stirred up in water.
ULFUltra-low-flow, as in
water-saving toilet fixtures. Currently ULF toilets use
1.6 gallons per flush.
Unconfined AquiferAn aquifer that discharges
and recharges with an upper surface that is the water
Uranium (U) —A
metallic element that is naturally occurring with three
main radioactive isotopes (i.e., U-234, U-235, and U-238).
Uranium is carcinogenic and can also cause damage to the
kidney. Total uranium is regulated by the US Environmental
Usable Storage CapacityThe quanitity
of groundwater of acceptable quality that can be economically
withdrawn from storage.
USBRUnited States Bureau of Reclamation.
UWIUrban Water Institute. This
organization provides programs and publications geared
to policy makers who can no longer afford to be uninformed
on water, wastewater, flood control, runoff and environmental
minute organism not visible by light microscopy. A virus
is an obligate parasite dependent on
nutrients inside cells for its metabolic and reproductive
needs. It consists of a strand of either deoxyribonucleic
acid or ribonucleic acid, but not both, [inside] a protein
covering called a capsid.1
WadsworthHiram W. Wadsworth,
prominent Pasadena proponent of building an aqueduct to
urban Southern California from the Colorado River and
a founder of the Metropolitan Water District, after whom
the pumping plant at Diamond Valley Lake was named.
that is used to clean a unit process. Wash water is typically
identified as backwash water and is associated with the
wastewater resulting from the cleaning of filter media
to remove attached particles.1
WastewaterWater that has waste
material in it.
Water CycleThe movement of water
from the air to and below the Earth's surface and back
into the air.
Water ReclamationTreating wastewater
so that it can be used again.
WatershedA geographical portion
of the Earth's surface from which water drains or runs
off to a single place like a river; also called a drainage
WeymouthF.E. Weymouth, Metropolitans
first chief engineer and general manager, 1929-41; after
whom Metropolitans first treatment plant at La Verne,
in Los Angeles County, was named.
WSDM PlanWater Surplus and Drought Management
Plan, developed by Metropolitan and its member agencies
in 1998 and 1999, and adopted by the board in April 1999.
Replaced IICP. Identifies the expected sequence of resource
management actions Metropolitan will take during surpluses
xeriscape - landscaping that doesnt require a lot of water
zanja - Spanish
word for ditch
zone of aeration - the portion of the ground from
the Earths surface down to the water table - the
zone of aeration is not saturated with water because its
pores are filled partly by air and partly by water
zone of saturation - the portion of the ground
below the water table where all the pores in rock, sediment,
and soil are filled with water
The Drinking Water Dictionary, by permission. Copyright
© 2000, American Water Works Association