Glossary of Water Terms
Glossary of Water Terms
Use this glossary to find definitions, examples, and context for EMWD water, recycled and wastewater terms.
A
Acre Foot (AF)
Covers one acre to a depth of one foot (football field). An acre
foot is 325,900 gallons which is enough to meet the needs of two
average southern California households a year.
The Act
The Metropolitan Water District Act. State legislation signed
into law by the governor on May 10, 1927, effective July 29,
1927. Metropolitan incorporated December 6, 1928.
AFY
Acre-foot per year.
Arsenic
A naturally occurring element in the environment. Arsenic in
drinking water commonly comes from natural sources in the ground,
but some can come from industrial pollution. At high
concentrations it can cause cancer.
Aquifer
Natural underground layer of porous, water-bearing materials
usually capable of yielding a large amount or water supply.
B
BMP
Best Management Practice . Methods that have been determined to
be the most effective, practical means of preventing or reducing
pollution.
Backflow
A reverse flow condition, created by a difference in water
pressures.
Biosolids
The solids, or sludge. That remain after wastewater treatment.
This material is separated from the cleaned water, treated and
composted into fertilizer. Biosolids are often referred to as
sludge.
Brackish Water
Water containing dissolved minerals in amounts that exceed
normally acceptable standard municipal, domestic, and irrigation
uses. Considerably less saline than seawater.
Brown Act
Ralph M. Brown Act enacted by the State legislature governing all
meetings of legislative bodies known as the Open Meeting
requirements.
C
California Plan
Officially “California’s draft Colorado River Water Use Plan,”
also sometimes called the “4.4 Plan.” A planning document
designed to reduce California’s reliance on surplus Colorado
River water over the next 15 years through conservation, water
transfers, and conjunctive use measures.
Carcinogen
Any substance that can cause or aggravate cancer.
CBO
Community-based organization. Local organization with which
Metropolitan works on mutually beneficial programs.
Chromium
A naturally occurring element found in air, soil, water and
food.
Chromium VI
One of the most common species of chromium, chromium VI can be
carcinogenic and can constitute anywhere from 7 to 80% of the
total chromium in drinking water.
CEQA
California Environmental Quality Act that requires an assessment
of the possible environmental impacts of public projects.
Chlorination
The application of chlorine to water, sewage, or industrial
wastes, generally to disinfect or to oxidize undesirable
compounds.
Clean Water Act (CWA)
The primary federal law that protects our nation’s waters,
including lakes, rivers, aquifers, and coastal areas. The CWA
provides a comprehensive framework of standards, technical tools,
and financial assistance to address the causes of pollution and
improve water quality.
Coliform
Type of bacteria – main habitat being human intestinal tract.
Conjunctive use
The planned use of groundwater in conjunction with surface water
in overall management to optimize total water resources.
Conservation Factor
The Conservation Factor (CF) is based on a landscape’s water use
efficiency. A landscape with an efficient irrigation system and
more low-water using plants will have a lower CF and require less
water to maintain.
Cubic foot
A 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.
CRA
Colorado River Aqueduct, built 1933-1941 and owned and operated
by the Metropolitan Water District of Southern California.
D
Desalination
Removing salts from ocean or brackish water by using various
technologies.
E
Ecosystem
Recognizable, relatively homogeneous units, including the
organisms they contain, their environment and all the
interactions among them.
Effluent
Wastewater–treated or untreated–that flows out of a treatment
plant, sewer, or industrial outfall.
EIR
Environmental impact report; a study and report on the possible
effects of a proposed project, and what can be done to avoid or
mitigate them.
F
Fallowing
A 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.
G
Gray water reuse
Reuse, generally without treatment, of domestic type wastewater
for toilet flushing, garden irrigation and other nonpotable uses.
Excludes water from toilets, kitchen sinks, dishwashers, or water
used for washing diapers.
Groundwater
The supply of fresh water found beneath the Earth’s surface,
usually in aquifers, which supply wells and springs. Because
groundwater is a major source of drinking water, there is growing
concern over contamination from leaching agricultural or
industrial pollutants or leaking underground storage tanks.
Groundwater basin
A groundwater reservoir defined by all the overlying land surface
and the underlying aquifers that contain water stored in the
reservoir. Boundaries of successively deeper aquifers may differ
and make it difficult to define the limits of the basin.
Groundwater mining
The withdrawal of water from an aquifer in excess of recharge
over a period of time. If continued, the underground supply would
eventually be exhausted or the water table could drop below
economically feasible pumping lifts.
Groundwater overdraft
The condition of a groundwater basin in which the amount of water
withdrawn by pumping exceeds the amount of water that recharges
the basin over a period of years during which water supply
continues approximate average.
Groundwater recharge
The action of increasing groundwater storage by natural
conditions or by human activity.
Groundwater table
The upper surface of the zone of saturation (all pores of subsoil
filled with water), except where the surface is formed by an
impermeable body.
GPM
Gallons per minute.
I
Imported water
Water that has originated from one hydrologic region and is
transferred to another hydrologic region.
Influent
Water, wastewater, or other liquid flowing into a reservoir,
basin, or treatment plant.
Interceptor Sewer
A sanitary sewer which collects flow from a number of trunk
sewers and conveys wastewater to a treatment plant, lift station,
or another interceptor sewer.
IRP (Integrated Resources Plan)
The Metropolitan Water District (MWD) program is a coordinated
effort of interested stakeholders to determine how best to meet
the region’s water supply reliability objectives.
L
Lift Station
A facility within a sanitary sewer system which pumps sewage from
a lower elevation to a higher elevation.
M
MGD
Million gallons per day.
MG/L
Milligrams per liter.
Microfiltration
A physical separation process where tiny, hollow filament members
separate particles from water.
N
NPDES (National Pollutant Discharge Elimination
System)
A federal permit authorized by the Clean Water Act which is
required for discharge of pollutants to navigable waters of the
United States which includes any discharge to surface waters -
lakes, streams, rivers, bays, the ocean, wetlands, and storm
sewer tributary to any surface water body.
O
Ozone
A gas that is bubbled through water during the treatment
processes to kill bacteria.
P
Perchlorate
A chemical used in manufacturing rocket fuel that has
contaminated some Southern California groundwater basins.
Percolation
The downward movement of water through the soil or alluvium to
the groundwater table.
Potable Water
Suitable and safe for drinking.
Purified Water Replenishment
The proposed Purified Water Replenishment (PWR) project is part
of EMWD’s Groundwater Reliability Plus (GRP) program to improve
the quality and quantity of water in local groundwater basins.
Purified Water Replenishment includes recharging a blend of
advanced treated water (purified water) and recycled water into
spreading ponds along the San Jacinto River corridor. Proposed
facilities include an advanced treatment plant adjacent to the
San Jacinto Valley Regional Water Reclamation Facility, brine
evaporation ponds, a recycled water pipeline, and use of a raw
water pipeline for water delivery.
Primary treated water
First major treatment in a wastewater treatment facility, usually
sedimentation but not biological oxidation.
Public Water System
A system that provides piped water for human consumption to at
least 15 service connections or regularly serves 25 individuals.
Q
Quantification
Refers to Quantification Settlement Agreement, a proposed
agreement among Metropolitan Water District, Coachella Valley
Water District and Imperial Irrigation District to settle a
variety of long-standing disputes regarding the priority, use and
transfer of Colorado River water within California.
R
Recharge
Replenishing an aquifer with storm water or imported water.
Recycled Water
Wastewater that becomes suitable for a specific beneficial use as
a result of treatment.
Reverse Osmosis
The application of pressure to a concentrated solution which
causes the passage of a liquid from the concentrated solution to
a weaker solution across a semipermeable membrane. The membrane
allows the passage of the water but not the dissolved solids. The
liquid produced is a demineralized water.
S
Salinity
The scaling or white deposits that accumulate on coffee pots,
water heaters and plumbing fixtures resulting from dissolved
mineral salts in the water.
Secondary Treatment
A wastewater treatment process used to convert dissolved or
suspended materials into a form more readily separated from the
water being treated.
Sludge
The settleable solids separated from liquids during processing or
the deposits of foreign materials on the bottoms of streams or
other bodies of water.
T
Tertiary Treatment
A process of water renovation that upgrades treated wastewater to
meet specific reuse requirements. Also called Advanced Waste
Treatment.
Trihalomethanes
Byproduct of chlorinating water that contains natural organics.
Recent U.S. Environmental Protection Agency changes in national
drinking water quality standards now require that water treatment
systems begin to reduce TTHM.
W
Watershed
The region or land area that contributes to the drainage or
catchment area above a specific point on a stream or river.
Water table
The top level of water stored underground.
Wetlands
An area that is saturated by surface or groundwater with
vegetation adapted for life under those soil conditions, as
swamps, bogs, fens, marshes, and estuaries.