GLOSSARY OF WATER TERMINOLOGY
A
acid - a substance that has a pH value between 0 and 7
acid deposition (“acid rain”) - water that falls to or condenses on the Earth’s surface as
rain, drizzle, snow, sleet, hail, dew, frost, or fog with a pH of less than 5.6
acre-foot - the amount of water needed to cover one acre of land one foot deep; about
326,000 gallons
adhesion - the attraction between molecules that causes matter to cling to or stick
to other matter
adjudication - a court determination of water rights for a groundwater basin or a stream;
adjudication sets priorities during shortages
aeration - the addition of air to water or to the pores in soil
aesthetic - sensitive to beauty
alkaline - the quality of being bitter due to alkaline content (pH is greater than 7)
alluvial - sediment deposited by flowing water, such as in a riverbed
alum - aluminum sulfate: a chemical, which is mixed into water to cause particles
in the water to clump together so they can be removed
anadramous - any fish which spends a portion of its life cycle in freshwater and a
portion in the sea
aquifer - an underground layer of rock, sediment or soil that is filled or saturated
with water
aquifer system - a heterogeneous body of introduced permeable and less permeable
material that acts as a water-yielding hydraulic unit of regional extent
aqueduct - man-made canal or pipeline used to transport water
B
bacteria - any of a number of one-celled organisms, some of which cause disease
base - a substance that has a pH value between 7 and 14
basin - a groundwater reservoir defined by the overlying land surface and underlying
aquifiers that contain water stored in the reservoir
benefit - an advantage to be gained in a trade-off
benefit/cost analysis - a process of evaluating the advantages and disadvantages
of a proposed purchase or project
BMPs (Best Management Practices) - structural or management practices which are
implemented to reduce pollution (e.g., using a permeable material for parking lots to
reduce urban runoff)
boiler scale - mineral deposits from water, such as those found inside pipes or teakettles
bond - a promise to repay money borrowed, plus interest, over a specified period of time
bond issue - a means of raising large amounts of money for major projects by
selling bonds
brackish - water containing too much salt to be useful to people but less salt than
ocean water
by-products - something produced in addition to the principal product
C
capillarity - the 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 upward
capital cost - all the implements, equipment, machinery and inventory used in the
production of goods and services
cesspool - a covered hole or pit for receiving sewage
chloramination - the treatment of a substance, such as drinking water, with chlorine and
ammonia (chloramines) in order to kill disease-causing organisms
chlorination - the treatment of a substance, such as drinking water, with chlorine in order
to kill disease-causing organisms
cloud - a mass of suspended water droplets and/or ice crystals in the atmosphere
cloud droplets - the tiny liquid pieces of water that many clouds are made of. When
cloud droplets join together and become heavy enough they form raindrops.
coagulation - the 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
cohesion - the ability of a substance to stick to itself and pull itself together
coliform - a group of bacteria used as indicators of microbiological contamination
colloidal suspension - a method of sediment transport in which water turbulence
(movement) supports the weight of the sediment particles, thereby keeping them
from settling out or being deposited
condensation - water vapor changing back into liquid
condensation surfaces - small particles of matter, such as dust and salt suspended in the
atmosphere, which aid the condensation of water vapor in forming clouds
confined aquifer - an aquifer that is bound above and below by dense layers of rock and
contains water under pressure
conjunctive use - the planned use of groundwater in conjunction with surface water to
optimize total water resources
conservation - saving; not wasting; using water wisely
constituents - parts of a whole; components
consumer - one who consumes or uses economic goods or services
contaminate - to make unfit for use; to pollute
contractor - a water agency that signs a contract to acquire given amounts of water from
another agency, usually under specified conditions
contour plowing - plowing 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
cost - the outlay or expenditure (as of money, effort or sacrifice) made to achieve an
object or advantage
cost-effective - able at least to pay for itself or make a profit
county water authority - a public water district serving a county-wide area
cubic foot of water - the amount of water needed to fill a cube that is one foot on all
sides; about 7.5 gallons
D
dam - a structure built to hold back a flow of water
debt service - the repayment of borrowed money, plus interest
deficit - the amount by which a sum of money falls short of an expected amount
delta - fan-shaped area at the mouth of a river (where seas are relatively calm)
demand - the quantity of goods or services that consumers are willing and able to buy at a
given price
deposition - the process of dropping or getting rid of sediments by an erosional agent
such as a river or glacier; also called sedimentation
desalination - the process of removing salt from seawater or brackish water
dew - moisture in the air that condenses on solid surfaces when the air is saturated with
water vapor
dew point - the temperature at which the air becomes saturated with water vapor
discharge - the 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 per minute
disinfect - to destroy harmful microorganisms
dissolve - to enter into a solution
divert - to direct a flow away from its natural course
divide - a ridge or high area of land that separates one drainage basin from another
drainage basin - all of the area drained by a river system
drought - a prolonged period of below-average precipitation
E
economic benefit - a gain that can be measured in dollars
economic cost - a cost involved in a trade-off that requires spending money
ecosystem - an interacting network of groups of organisms together with their non-living
or physical environment
efficiency - effective operation as measured by a comparison of production with cost
endangered species - a species of animal or plant threatened with extinction
environment - the surroundings that affect the growth and development of an organism
environmental impacts - factors that affect organisms and the surroundings of organisms
Environmental Impact Report (EIR) - a state-mandated written summary of the positive
and negative effects on the environment caused by the construction and operation of a
project
erosion - the processes (including soil erosion) of picking up sediments, moving
sediments, shaping sediments, and depositing sediments by various agents; erosional
agents include streams, glaciers, wind and gravity
Escherichia coli (E. coli) - a common bacterium found in fecal matter; member of the
coliform group
evaporation - water changing into vapor and rising into the air
exchange - the act of trading goods or services for those produced by people who are
located elsewhere
expense - something spent (such as money, time or effort) to secure a benefit or bring
about a result
F
factors of production - the resource inputs involved in the production of goods and
services: for example, labor, land and capital
feces - waste excreted from the bowels of humans and animals
filtration - passing water through coal, sand and gravel to remove particles
filtration plant - place where water is cleaned and made safe to drink
financing cost - the fees charged by financial specialists and the interest charged on
money borrowed to pay for a project
fish ladder - a device to help fish swim around a dam
fishery - the aquatic region in which a certain species of fish lives
floc - clumps of impurities removed from water during the purification process; formed
when alum is added to impure water
flocculation - a step in water filtration in which alum is added to cause particles to clump
together
floodplain - area 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
fog - clouds that form at the Earth’s surface
frost - the ice that forms on surfaces as a result of the temperature of that surface reaching
freezing before the air becomes saturated with water
G
gallon - a unit of measure equal to four quarts or 128 fluid ounces
geyser - a thermal spring that erupts intermittently and to different heights above the
surface of the Earth; eruptions occur when water deep in the spring is heated enough to
turn into steam, which forces the liquid water above it out into the air
glacial striations - lines carved into rock by overriding ice, showing the direction of
glacial movement
glacier - a large mass of ice formed on land by the compacting and recrystallization of
snow; glaciers survive from year to year, and creep downslope or outward due to the
stress of their own weight
groundwater - water under ground, such as in wells, springs and aquifiers
gullying - small-scale stream erosion
H
habitat - the place or type of site where a plant or animal naturally or normally lives and
grows
hail - transparent or layered (ice and snow) balls or irregular lumps of solid water
hardness - a characteristic of water determined by the levels of calcium and magnesium
hatcheries - a place for hatching fish eggs
humus - decomposed bits of plant and animal matter in the soil
hydroelectric plant - a power plant that produces electricity from the power of rushing
water turning turbine-generators
hydrologic cycle - the natural recycling process powered by the sun that causes water to
evaporate into the atmosphere, condense and return to earth as precipitation
hydrology - the scientific study of the behavior of water in the atmosphere, on the Earth’s
surface and underground
I
iceberg - large chunks of ice that break off of coastal glaciers and float away
igneous - rock solidified from a molten state, such as lava and obsidian
impermeable - having a texture that does not permit water to move through quickly
imported water - water brought into an area from a distant source, such as from one part
of a state to another via an aqueduct
impound - to confine in an enclosure, such as impounding water in a reservoir
impurity - any component which causes another substance to become contaminated
indicator - a device or substance used to show the presence of another substance
infiltration (also called percolation) - the entrance or flow of water into the soil, sediment
or rocks of the Earth’s surface
inorganic - chemicals not containing the element carbon
interest - payments made to an investor for the use of borrowed money
intrusion - the entrance of an unwanted element, such as saltwater, into freshwater
supplies
inundation - covering over or flooding, such as flood waters covering a valley
irrigation - supplying water to agriculture by artificial means, such as pumping water
onto crops in an area where rainfall is insufficient
L
labor - the mental and/or physical talents contributed by people for the production of
goods or services
lactose - a white organic substance made from milk that is used in infant foods, bakery
products and confections; also used as a “culture” in laboratories
landfill - an open area where trash is buried
leach - to remove components from the soil by the action of water trickling through
levees - dikes or other embankments which contain water within a given course
local runoff - water running off a local area, such as rainfall draining into a nearby creek
M
manufacturer - one who makes a product
marginal land - land which, in its natural state, is not well suited for a particular purpose,
such as raising crops
member agency - one of 27 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
microorganism - an organism of microscopic size, such as bacterium
migratory - moving from one area to another on a seasonal basis
mitigation - a way in which an agency may offset negative environmental impacts of a
project or make the impacts less serious
mulch - material spread on the ground to reduce soil erosion and evaporation of water;
include hay, plastic sheeting and wood chips
municipal water district - a public water provider, owned and operated by more than one
city government, which supplies water to its member cities
N
natural environment - all living and nonliving things that occur naturally on the earth;
not made
nomad - a wanderer, a person or animal which moves from place to place
non-economic benefit - a gain resulting from a trade-off that cannot be measured in
dollars
nonpoint source pollution - pollution which comes from diffuse sources such as urban
and agricultural runoff
NPDES (National Pollutant Discharge Elimination System) permits - permits issued to
point sources for the purpose of limiting pollution in discharges
O
organic - any chemical containing the element carbon
overdraft - condition that occurs in a groundwater basin when pumping exceeds the
amount of replenishment over a period of years
ozone - a gas that is bubbled through water to kill germs
P
pathogenic - capable of causing disease
percolation - water soaking into the ground
perennial yield - maximum 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
permeability - the capacity or ability of a porous rock, sediment, or soil to allow the
movement of water through its pores
PEROXONE - a combination of peroxide and ozone used to kill germs in water
pH - a 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
photosynthesis - process in which chlorophyll-containing cells convert light into
chemical energy, forming organic compounds from inorganic compounds
pipeline - carries water underground to homes and businesses
plankton - minute plants and animals floating in bodies of water; often a major source of
nutrition for larger aquatic life forms
pollutant - any inorganic or organic substance that contaminates air, water or soil
point source pollution - pollution which comes from a well-defined source such as
sewage treatment plant effluent from industrial dischargers. . .for purposes of the Clean
Water Act, agricultural return flows are not regulated as a point source
pore spaces - the open areas, or spaces, in soil, sediments, and rocks that are filled by air
or water
porosity - a measure of the ratio of open space within a rock or soil to its total volume
POTWs (Public Owned Treatment Works) - sewage treatment plants
precipitation - water falling toward the Earth’s surface in the form of rain, drizzle, hail,
sleet, or snow
pumping lift - distance water must be lifted in a well from the pumping level to the
ground surface
pumping plant - facility that lifts water up and over hills
R
reclaimed water - wastewater that has been cleaned so that it can be reused for most
purposes except drinking
recharge - increases in groundwater storage from precipitation, infiltration from streams,
or human activity (artificial recharge), such as putting surface water into spreading basins
relative humidity - the ratio of the amount of moisture in the air to the maximum amount
of moisture the air could hold under the same conditions; usually expressed as a
percentage
reservoir - a pond or lake where water is collected and stored until it is needed
rills - small grooves, furrows, or channels in soil made by water flowing down over its
surface; also another name for a stream - usually a small stream
runoff - liquid 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
S
saltation - the movement of sand or fine sediment by short jumps above a streambed
under the influence of a water current too weak to keep it permanently suspended in the
moving water
salinity - saltiness
saturation - the condition of being filled to capacity
sea ice - solid water that forms when ocean or sea water freezes
section 319 grants - grants for nonpoint source pollution programs
sediments - fragments of material produced by weathering and erosion of rocks
sedimentation - the process of particles in water settling to the bottom of a tank
selenium - a non-metallic element in the same chemical group as sulfur; its compounds
are harmful to wildlife or people when found above certain levels in water
septic tank - a sewage disposal tank in which bacteria decompose waste
sheet wash - a flow of rainwater that covers the entire ground surface with a thin film and
is not concentrated into streams
sleet - precipitation that consists of clear pellets of ice; sleet is formed when raindrops
fall through a layer of cold air and freeze
snow - precipitation that consists of frozen flakes formed when water vapor accumulates
on ice crystals, going directly to the ice phase
soil - sediment on or near the Earth’s surface that is formed by the chemical and physical
weathering of rocks as well as the decay of living matter
soil subsidence - the lowering of the normal level of the ground, usually due to
overpumping of water or oil from wells
spawn - to produce or deposit eggs, as those of aquatic animals
spring - groundwater seeping or flowing out of the Earth’s surface; springs occur where
the water table reaches the surface
SRF (State Revolving Fund) - funding, in the form of loans, available for the control of
point and nonpoint source pollution
steam - water vapor that rises from boiling water
stream - the type of runoff where water flows in a channel downhill because of the pull
of gravity
sublimation - formation of a gas from a solid, or vice-versa, without passing through the
liquid phase
subsidence - sinking of the land surface due to a number of factors, of which
groundwater extraction is one
subsurface water - all water - solid, liquid or gaseous - that occurs beneath the Earth’s
surface; located below the water table in the zone of saturation
surface runoff - water flowing along the ground into rivers, lakes, and oceans
surface water - all water, fresh and salty, on the Earth’s surface
suspended - the state of floating in water rather than being dissolved in it
suspension - a method of sediment transport in which air or water turbulence supports the
weight of the sediment particles, thereby keeping them from settling out or being
deposited
T
thermal spring - a warm or hot water spring; many occur in regions of recent volcanic
activity and are fed by water heated by contact with hot rocks far below Earth’s surface
till - a deposit of sediment formed under a glacier, consisting of an unlayered mixture of
clay, silt, sand, and gravel ranging widely in size and shape
topsoil - the 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 layers
toxic - poisonous; harmful to living organisms
transpiration - evaporation of water through the leaves of plants
trihalomethanes, trichloroethylene, perchloroethylene - organic compounds which may
be harmful to health at certain levels in drinking water
turbidity - the state of having sediment or foreign particles suspended or stirred up in
water
U
unconfined aquifer - an aquifer that discharges and recharges with an upper surface that
is the water table
unsaturated zone - the subsurface zone, usually starting at the land surface and ending at
the water table, that includes both water and air in spaces between rocks
usable storage capacity - the quantity of groundwater of acceptable quality that can be
economically withdrawn from storage
W
wastewater - water that has waste material in it
wastewater treatment - cleaning wastewater
water cycle - the movement of water from the air to and below the Earth’s surface and
back into the air
water quality - the condition of water as it relates to impurities
water reclamation - treating wastewater so that it can be used again
water table - (1) the boundary in the ground between where the ground is saturated with
water (zone of saturation) and where the ground is filled with water and air (zone of
aeration); (2) the upper surface of the saturated zone that determines the water level in a
well in an unconfined aquifer
water vapor - the gaseous state of water
watershed - a 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 area
well - a hole or shaft drilled into the earth to get water or other underground substances
X
xeriscape - landscaping that doesn’t require a lot of water
Z
zanja - Spanish word for ditch
zone of aeration - the portion of the ground from the Earth’s 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
Definitions Provided By: Metropolitan Water District of Southern California
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