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 
Meter - See http://www.flowmeterdirectory.com/meter.html
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