Glossary of Water Terms




The process in which water pools in large bodies (such as oceans, seas and lakes).

Acid Rain
Rain with pH below 5.5.

The quantity of water required to cover one acre to a depth of one foot; equal to 43,560 cubic feet, or approximately 325,851 gallons.

A report giving information on beach contamination status and often recommending action to be taken.

The process of mixing air with water; this increases the oxygen level.

Sediment deposited by flowing water, such as in a riverbed.

A very sticky substance added to water during treatment that causes particles in the water to stick together.

An underground layer of rock, sediment or soil that is filled or saturated with water.

A layer of rock over an aquifer through which water cannot soak.

Artificial Recharge
The addition of water to a ground water reservoir by human activity, such as irrigation or induced in

form streams, wells, or recharge basins. See also Groundwater Recharge, Recharge Basin.


Prokaryotic unicellular round, spiral, or rod-shaped single-celled microorganisms that live in soil, water, organic matter, or the bodies of plants and animals (singular bacterium).

Brackish Water
Water containing dissolved minerals in amounts that exceed normally acceptable standards for municipal, domestic, and irrigation uses. Considerably less saline than sea water.


The uppermost spreading branchy layer of vegetation.

Catch basin
An opening on the side of street which is the entrance to the stormdrain.

Caused by adding alum to water, coagulation occurs when small particles cling together, creating particles large enough to be filtered out.

Coliform Bacteria
Many strains of coliform bacteria are naturally present in our environment. Fecal coliform bacteria are present in the feces of humans and other warm-blooded animals but are rare or absent in unpolluted waters. Fecal coliform bacteria should not be found in sources of drinking water. Their presence in water serves as a reliable indication of contamination from human sewage or animal droppings. Although coliform bacteria themselves are not pathogenic, they occur with intestinal pathogens that are dangerous to human health.

The process of water changing from a vapor (gas state) to a liquid state.

The wise use of a resource with minimum waste.

The addition of an undesirable and potentially harmful material; pollution.

A stream that is smaller than a river and larger than a brook.

Critical Dry Period 
A series of water-deficient years, usually an historical period, in which a full reservoir storage system at the beginning is drawn down (without any spill) to minimum storage at the end.

Critical Dry Year 
A dry year in which the full commitments for a dependable water supply cannot be met and deficiencies are imposed on water deliveries.

Cubic Feet Per Second
A unit of measurement describing the flow of water. A cubic foot is the amount of water needed to fill a cube that is one foot on all sides, about 7.5 gallons.


A process that converts sea water or brackish water to fresh water or an otherwise more usable condition through removal of dissolved solids. Also called "desalting."

The removal or killing of bacteria and other disease causing organisms.

Dissolved Oxygen (DO)
Dissolved Oxygen is important to the health of aquatic ecosystems. All aquatic animals need oxygen to survive. Natural waters with consistently high dissolved oxygen levels are most likely healthy and stable environments, and are capable of supporting a diversity of aquatic organisms. Natural and human-induced changes to the aquatic environment can affect the availability of dissolved oxygen.

Drip Irrigation
A method of watering plants using hoses and emitters with small holes through which water drips.

An extended period of limited or no precipitation (rain or snow).

California Department of Water Resources (or successor agency).


The process of mountains and rocks breaking down into smaller particles.

the wide lower course of a river where its current is met by the tides of the ocean.

Too many nutrients entering an ecosystem (nutrient loading) can cause large algal blooms or other growth spurts followed by natural die-off and decay which results in a decreased amount of oxygen available. This can lead to a dangerous cycle of die-offs, which use oxygen in the decay process leading to more die-offs due to low oxygen levels.

The change of liquid to a vapor or gas, usually by contact with heat.

The total amount of water loss in plants due to evaporation and water loss through plant tissue.

Fecal coliform bacteria
Bacteria present in the feces of humans and other warm-blooded animals but rare or absent in unpolluted waters. Fecal coliform bacteria should not be found in sources of drinking water. Their presence in water serves as a reliable indication of contamination from human sewage or animal droppings. Although coliform bacteria themselves are not pathogenic, they occur with intestinal pathogens that are dangerous to human health.

The process of running water through a filter to remove undissolved impurities. Filtration occurs naturally through soil.

Particles produced by coagulation.

The spreading of pesticide to kill unwanted creatures.

Furrow Irrigation
A type of irrigation which allows water to flood furrows between crop rows.


Geological maps
Maps which show boundaries of countries, cities, and roads.

Water that is stored underground in the pore space of aquifers.

Groundwater Basin
 A groundwater reservoir, together with all the overlying land surface and underlying aquifers that contribute water to the reservoir.

Groundwater Mining
The withdrawal of water from an aquifer greatly in excess of replenishment; if continued, the underground supply will eventually be exhausted or the water table will 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 replenishes the basin over a period of years.

Groundwater Recharge
Increases in groundwater by natural conditions or by human activity. See also ARTIFICIAL RECHARGE.

Groundwater Storage Capacity
The space contained in a given volume of deposits. Under optimum use conditions, the usable groundwater storage capacity is the volume of water that can, within specified economic limitations, be alternately extracted and replaced in the reservoir.

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.


The area or environment in which an organism lives.

The scientific study of the properties, distribution and effects of water in the atmosphere, on the earth's surface and in soil and rocks.

A theory or assumption that can be tested by further investigation.


The process by which water seeps into the soil.

Invasive species
Non-native plants and animal species; plants and animal species that have been introduced to an area where they do not occur naturally.


Municipal and Industrial (water use); generally urban uses for human activities.

Abbreviation for "milligrams per Liter," the mass (milligrams) of any substance dissolved in a standard volume (liter) of water. Nearly the same as parts per million (ppm).

Representation on a flat surface (paper, plastic) of Earth or any part of it. Maps can also represent your hand or the sky.

An organism of microscopic or ultramicroscopic size Pathogen Ñ a specific causative agent (as a bacterium or virus) of disease.

The smallest unit of matter which holds its characteristics.


Growing, living or produced originally in a certain place: indigenous.

Native species
Plants and animal species that have evolved in a specific area over a period of time; naturally occurring species; indigenous.

Native Vegetation
Plants that are adapted to and occur naturally in s specific location. Non-native Vegetation: Plants that are not native to the local area. These plants are often invasive and compete with or replace native vegetation. This can affect habitat and food supply for native animal species.

Nitrate is a nutrient needed by all aquatic plants and animals to build protein. The decomposition of dead plants and animals and the excretions of living animals release nitrate into the aquatic system. Excess nutrients, like nitrate, increase plant growth and decay, promote bacterial decomposition, and therefore decrease the amount of oxygen available in the water. Sewage is the main source of excess nitrate added to natural waters, while fertilizer and agricultural runoff also contribute to high levels of nitrate.

Nonpoint Source Pollution
Pollution which cannot usually be traced back to its source. Pollution coming from many varied indeterminable sources. An example of point source pollution is a chemical spill from a factory. Nonpoint source pollution usually comes from stormwater run-off from urban, suburban or agricultural areas. Human activities that add to nonpoint source pollution in stormwater run-off include improper disposal of pet and yard waste, use of pesticides and construction.


Organic Matter
Material that contains or is derived from living organisms.

Withdrawal of groundwater in excess of a basin's perennial yield. See also PROLONGED OVERDRAFT.


pH is a measurement of the acidic or basic (or alkaline) quality of a substance. The pH scale ranges from a value of 0 (very acidic) to 14 (very basic), with 7 being neutral. The pH of natural water is usually between 6.5 and 8.2. In Santa Barbara, the pH of most of our water is higher than 8. Most aquatic organisms are adapted to a specific pH level and may die if the pH of the water changes even slightly.

Abbreviation for "parts per million," a measure of a substance's concentration in a solution or other mixture. Nearly the same as milligrams per liter (mg/l).

Percolate / Infiltrate
To ooze or trickle through a permeable substance.

Water soaking into the ground through particles of soil.

Phosphate is a nutrient needed for plant and animal growth and is also a fundamental element in metabolic reactions. High levels of this nutrient can lead to overgrowth of plants, increased bacterial activity, and decreased dissolved oxygen levels. Phosphate comes from several sources including human and animal waste, industrial pollution, and agricultural runoff.

Point Source Pollution
Pollution that can be traced back to one specific source.

Any substance, biological or chemical, in which an identified excess is known to be harmful to desirable organisms (both plants and animals).

Items and chemicals that endanger the quality of life and life itself. Some pollutants are toxic or poisonous. Others are dangerous because they stick to feathers (oil and tar) making it impossible for birds to fly or find food, or clog throats and stomachs, and entangle necks (plastic bags and strips) of marine creatures.

Pore Space
The space found between particles of soil, sand or gravel; in saturated aquifers, pore space is filled with water.

Water that is safe to drink.

The fall of condensed moisture as rain, snow or sleet.

Primary Treatment
The first stage of wastewater treatment; involves passing through a comminutor, grit chamber, and sedimentation.

Prolonged Overdraft
Net extractions in excess of a basin's perennial yield, averaged over a period of ten or more years.


The process of water seeping through soil into an aquifer or groundwater basin.

Recharge Basin
A surface facility, often a large pond, used to increase the infiltration of water into a groundwater basin.

Reclaimed Water
Water that is treated at a treatment plant after is was used once, and is now safe to use again for certain purposes.

Using a resource more than once.

Relief Map
Maps which show depth in real three-dimensional structures.

Return Flow
The portion of withdrawn water that is not consumed by evapotranspiration and returns instead to its source or to another body of water.

Habitat found near the source of fresh water.

Riparian vegetation
Plants normally found along the banks and beds of streams, creeks, and rivers. 'Riparian vegetation' includes understory, ground cover, and wetland plants, not just trees.

Rain that is not absorbed by the soil, and flows into the surface of the soil.


Safe Yield
The amount of water that can be taken from a water storage that will be replaced naturally.

Generally, the concentration of mineral salts dissolved in water. Salinity may be measured by weight (total dissolved solids), electrical conductivity, or osmotic pressure. Where seawater is the major source of salt, salinity is often used to refer to the concentration of chlorides in the water. See also TDS.

Seawater Intrusion
A condition resulting from salt water penetration into a fresh water aquifer.

Secondary Treatment
The second stage of wastewater treatment during which the water goes through aeration, followed by the addition of aerobic bacteria.

Soil particles which have been moved by water.

A step in water treatment where particles in water fall to the bottom of a tank and are removed.

Serious Overdraft
Prolonged overdraft that results, or would result, within ten years, in measurable, unmitigated adverse environmental or economic impacts, either long-term or permanent. Such impacts include but are not limited to seawater intrusion, other substantial quality degradation, land surface subsidence, substantial effects on riparian or other environmentally sensitive habitats, or unreasonable interference with the beneficial use of a basin's resources.

Sediments which are removed from water at a treatment plant.

Sediments which are removed from water at a treatment plant.

Sprinkler Irrigation
A method of watering plants by sprinkling them.

State Water Project (SWP)
A system of pipes, canals and reservoirs designed to collect, store and distribute water from northern California, where most of the state's rainfall occurs, to southern California, where most of the state's population lives.

Storm Drain
Low area or device designed to carry away extra rainwater. A pipe that travels from the catch basin to the creeks and ocean.

A current of water; a small river.

Surface Water
Water which is found on the earth's surface: lakes, streams, rivers, reservoirs, etc.

California State Water Resources Control Board (or successor agency).


Tertiary Treatment
The third stage of wastewater treatment where water goes through coagulation, sedimentation, filtration, and the addition of chlorine.

Topographical maps
Maps that describe high and low areas on earth by thin lines labeled with elevation numbers.

Total Dissolved Solids (TDS)
A quantitative measure of the residual minerals dissolved in water that remain after evaporation of a solution. Usually expressed in milligrams per liter (mg/l) or in parts per million (ppm). See also SALINITY.

The exchange of water from plants and trees to the atmosphere.

Turbidity is the measure of the relative clarity of water. Turbid water is caused by suspended and colloidal matter such as clay, silt, organic and inorganic matter, and microscopic organisms. Water high in turbidity appears murky and contains sediments in suspension. Turbidity should not be confused with color, since darkly colored water can still be clear and not turbid. Turbid water may be the result of soil erosion, urban runoff, algal blooms, and bottom sediment disturbances which can be caused by boat traffic and abundant bottom feeders. Turbid water may also result in higher concentrations of contaminants and pathogens, that bond to the particles in the water.


The underlying layer of vegetation between the canopy and the ground.

Understory Plants
Medium height vegetation, including bushes and shrubs, which grows below the tree canopy.


Any of a large group of submicroscopic infective agents that are regarded either as extremely simple microorganisms or as extremely complex molecules that are capable of growth and multiplication only in living cells, and that cause various important diseases in humans, lower animals, or plants.


Water that has been used by either humans or industry; any water that enters the sewage system.

Wastewater (Sewage) Treatment Plant
A treatment facility where the wastewater (sewer) is cleaned.

Water Cycle
The continuous cycle of evaporation, condensation, and precipitation in which water is continually being recycled.

Water Quality
A term used to describe the chemical, physical, and biologic characteristics of water with respect to its suitability for a particular use.

Water Right
A legally protected right, granted by law, to take possession of water occurring in a water supply and to divert the water and put it to beneficial uses.

Water Table
The surface of underground, gravity-controlled water.

Water Treatment Plant
A plant where water is treated to make it fit for potable use.

Water Vapor
Water in an invisible gaseous state or in a visible liquid state consisting of extremely small particles suspended in the air.

A natural or artificial channel through which water flows.

A gathering place for water. It is an area of land where water flows off of the land forming streams, creeks, and rivers, which come together flowing to a larger body of water (the ocean or a lake).

The disintegration and decomposition of rock at or near the surface; the breakdown of parent rock into sediment.


Landscape that thrives naturally in a dry climate and requires minimal watering.


Zone of Saturation
The part of the soil where all the pore spaces are full of water.