Basin Plan - Glossary of Terms

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Abatement - Corrective action to stop or clean up pollution or nuisance.

Acre Foot (AF) - The amount of water required to cover an acre one foot deep (325,861 gallons). A family of five uses about one acre-foot of water per year.

Action Level - A concentration established by environmental protection agencies for a substance in a particular medium (water, soil, etc.) that may present a health risk or affect beneficial uses when exceeded. If contaminants are found at concentrations above their action levels, measures must be taken to decrease the contamination.

Activated Sludge - Sludge floc produced in raw or settled wastewater by the growth of zoogleal bacteria and other organisms in the presence of dissolved oxygen.

Acute Toxicity - Relatively short-term lethal or other effect, usually defined as occurring within four days for fish and macroinvertebrates and shorter times (two days) for organisms with shorter life spans.

Adjudication - A determination of water rights for an entire stream or ground water basin. Adjudication sets priorities of rights during shortages.

Advisory Level - The level above which an environmental protection agency suggests it is potentially harmful to be exposed to a contaminant, although no action is mandated.

Aerated Pond (see Oxidation Pond) - A natural or artificial wastewater treatment pond in which mechanical or diffused-air aeration is used to supplement the oxygen supply

Aeration - Passing air through a solid or liquid, especially a process promoting breakdown or movement of contaminants in soil or water by exposing them to air.

Aerobic - In the presence of oxygen.

Algae - Unicellular to multicellular plants that occur in fresh water, marine water, and damp terrestrial environments.  All algae possess chlorophyll, the pigment (e.g. green, brown, and/or red) essential for photosynthesis.

Alluvium - A general term for detrital deposits made by streams or river beds, flood plains, and alluvial fans.  The term applies to stream deposits of recent time.  It does not include sub-aqueous sediments of seas and lakes. 

Ammonia (NH3) - A naturally occurring, gaseous compound of nitrogen.  Sometimes referred to as unionized ammonia.

Ammonium (NH4)  - Ionized ammonia referred to as the ammonium-ion or dissociated ammonia.

Anaerobic - In the absence of oxygen.

Anti-degradation - That portion of federal water quality requirements prohibiting deterioration where pollution levels are above the legal limit.

Appropriative Rights - "First in time, first in right" principle that developed from the gold miners in 1849. Water claims were staked out by posting notice.

Aquaculture - The art of cultivating the natural produce of water; the raising or fattening of fish in enclosed ponds.

Aqueous - (a) Of, relating to, or resembling water (b) Water-based.

Aquifer - Any underground formation that stores, transmits and yields water to wells and springs.

Aquifer, Confined - An aquifer that is overlain by a confining bed.  The confining bed has a significantly lower hydraulic conductivity than the aquifer

Aquifer, Unconfined - An aquifer in which there are no confining beds between the zone of saturation and the surface.  There will be a water table in an unconfined aquifer.  Water-table aquifer is a synonym

Areas of Special Biological Significance (ASBS) - Thirty-four locations along California coast and offshore islands that the State Water Board has officially designated as having unique biological value and/or fragility.

Artesian Well  - A well in which the water rises above the top of the aquifer, whether or not it flows out at the land surface.  Sometimes restricted to mean a flowing artesian well

Artesian Well, Flowing - An artesian well whose head [pressure] is sufficient to raise the water above the land surface.

Assimilative Capacity  - The capacity of a natural body of water to receive (a) wastewaters, without deleterious effects, (b) toxic materials, without damage to aquatic life or humans who consume the water, (c) BOD, within prescribed dissolved oxygen limits.

Autotrophic Organisms  - Bacteria that thrive by using inorganic materials for energy and growth.

Attention Level  - A guideline established by the Central Coast Regional Water Quality Control Board to identify the concentration of a substance in a particular medium (water, soil, etc.) that may be of concern when exceeded. If contaminants are found at concentrations above their attention levels, measures should be taken to address the pollution.


Backfill - The word is used in two contexts; to refill an excavated area with uncontaminated soils; and the material used to refill an excavated area.

Background - The concentrations or measures of indicator parameters in water, air or other media that have not been affected by waste discharges.

Bacteria - Any of a division (Bacteria) of typically one-celled microorganisms that have no chlorophyll, multiply by simple division, and can be seen only with a microscope.  They occur in three main forms, spherical (cocci), rod shaped (bacilli), and spiral (spirilla).  Some bacteria can cause disease and others are necessary for fermentation, nitrogen fixation, etc.

Bacteriophage - Any virus that infects bacteria.

Bank full Capacity - The rate of water flow that completely fills a channel (i.e.: the rate at which the water surface is level with the flood plain). The bank full state is the most effective or dominate channel-forming flow.

Base Flow - The part of stream flow contributed by ground water that seeps into surface streams.

Basin Plan  - see Water Quality Control Plan.

Bedload - The particles in a stream channel that mainly move by jumping, sliding or rolling on or near the bottom of the stream.

Beneficial Uses of Water - Water used for the following purposes: domestic (homes, human consumption, etc.), irrigation (crops, lawns), power (hydroelectric), municipal (water supply of a city or town), mining (hydraulic, drilling), industrial (commerce, trade, industry), fish and wildlife preservation, aquaculture (raising fish etc. for commercial purposes), recreational (boating, swimming), stock watering (for commercial livestock), water quality, frost protection (misting or spraying crops to prevent frost damage), heat control (water crops to prevent heat damage), ground water recharge, agriculture, etc.

Best Management Practices (BMP) - A practice which is determined to be the most effective and practicable method of preventing or reducing the amount of pollution generated by pollution sources. Determination is made after public participation and review of all other alternatives (From the Federal Water Pollution Control Act).

Bioassay - Laboratory analytical test in which the effects of a waste stream or effluent upon living organisms are measured.

Bioaccumulation  - The process by which the concentrations of some toxic chemicals gradually increase in living tissue, such as in plants, fish, or people as they breathe contaminated air, drink contaminated water, or eat contaminated food.

Biochemical - Pertaining to chemical change resulting from biological action.

Biochemical Action - Chemical change resulting from the metabolism of living organisms.

Biochemical Oxidation - An oxidation brought about by biological activity that results in chemical combination of oxygen with organic material.

Biochemical Oxygen Demand (BOD)  - An empirical test in which standardized laboratory procedures are used to determine the relative oxygen requirements of wastewaters, effluents, and polluted waters.

Biodegradation - The destruction or mineralization of either natural or synthetic organic materials by the microorganisms populating soils, natural bodies of water, or wastewater treatment system.

Biological Oxidation - The process whereby living organisms in the presence of oxygen convert the organic matter contained in wastewater into a more stable or a mineral form.

Biomass - Energy produced from biological sources, such as wood, grain and animal manure. Biomass energy can be released through combustion, gasification or conversion to alcohol.

Bioremediation - A process that uses microorganisms to change toxic compounds into non-toxic compounds.

Biosolids - Residuals generated by the treatment of wastewater with activated sludge. See Activated Sludge.

Biostimulatory - Promote or enhance biologic activity.

Biostimulatory Substances - Constituents (e.g. nutrients, temperature, etc.) that promote or enhance biologic activity.

Biota - The plant and animal life of a region.

Biotransformation - Transformation of one chemical to others by populations of microorganisms in the soil.

Blow down - The water discharged from a boiler or cooling tower to dispose of accumulated salts.

Boring - Usually, a vertical hole drilled into the ground from which soil samples can be collected and analyzed to determine the presence of chemicals and the physical characteristics of the soil.

Brackish Water - Water containing more than 1,000 mg/L (1,000 parts per million) of dissolved solids.

Brine - Highly saline water.

Buffer Zone - A zone delineated to provide protection for beneficial uses.


California Environmental Quality Act (CEQA)  - Established law of environmental protection, maintenance and enhancement.

California Code of Regulations (CCR) - The California Code of Regulations (CCR) contains the text of the regulations formally adopted by state agencies, reviewed and approved by the Office of Administrative Law, and filed with the Secretary of State. The CCR consists of 28 titles and contains the regulations of approximately 200 regulatory agencies.

California Water Code (CWC)  - The Porter Cologne Water Quality Control Act.

Cap  - A layer, such as clay or a synthetic material, used to prevent rainwater from percolating through soil and waste and spreading contamination.

Capillary Forces - Forces that cause ground water to rise above the surface of the saturated zone into the spaces between soil particles in the unsaturated zone.

Carbon Adsorption - A treatment system in which organic contaminants are removed from air, ground water, and surface water by contact with activated carbon, a specially-treated material that retains such compounds.

Catalyst - A substance that accelerates chemical change yet is not permanently affected by the reaction (e.g., platinum in an automobile catalytic converter helps change carbon monoxide to carbon dioxide).

Cease and Desist Order (C&D) - An Order issued by Regional Boards for violation of waste discharge requirements and NPDES permits, or illegal discharge without waste discharge requirements.

Chloride - A compound in which chlorine is combined with any of certain other elements or with a radical.

Chlorophyll a - A green pigment found in the chloroplasts of plant cells essential to the photosynthetic process.

Chlorination - The application of chlorine to water or wastewater, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results.

Chlorine Demand - The difference between the amount of chlorine added to water or wastewater and the amount of residual chlorine remaining at the end of a specified contact period.   The demand for any given water varies with the amount of chlorine applied, time of contact, temperature, and organic content of the water or wastewater.

Chronic Toxicity - Toxicity involving a stimulus that lingers or continues for a relatively long period of time, often one-tenth the life span or more. “Chronic” should be considered a relative term depending on the life span of an organism.  A chronic toxic effect can be measured in terms of reduced growth, reduced reproduction, etc., in addition to lethality.

Class I Landfill - A landfill permitted to accept hazardous waste.

Class II Landfill - A landfill permitted to accept designated and municipal solid waste.

Class III Landfill - A landfill permitted to accept only non-hazardous municipal solid waste.

Clean Water Act (CWA) - Federal legislation enacted in 1972 which requires every state to submit a biennial report to the EPA, describing the quality of its surface, ground and marine waters.

Cleanup or Abatement Order (CAO)- An order that requires a discharger to clean up a waste, abate its effects, or, in a case of threatened pollution, take necessary remedial action.

Closure - The placement of signs at an area of a public beach that informs the public an area is closed to swimming and water contact. These signs should indicate the nature of the public health concern (e.g., sewage spill), and should, by nature of their language, color, and design, enable the recreating public to differentiate from advisories provided by posting. Closure is envisioned to occur when health risks are considered greater than those associated with posting, as with sewage spills or at areas at which monitoring results show that multiple indicator organism standards are exceeded, for both single sample and 30-day average values.

Coastal Waters - Waters of the Pacific Ocean outside of enclosed bays and estuaries that are within the territorial limits of California.

Cold Interstate Waters - Streams and lakes having a range of temperatures generally suitable for trout and salmon.

Coliform (also referred to as Total Coliform) - All facultative anaerobic, gram negative, non-spore forming, rod shaped bacteria that ferment lactose with gas and acid formation within 48 hours at 35C.  Coliform bacteria are found in soil, water, fruit, vegetables, grains, flowering plants and trees, and in the intestinal tract of animals.

Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) - Also known as Superfund, this Federal law authorizes U.S. EPA to respond directly to releases of hazardous substances that may endanger public health or the environment.

Conductivity - A measure of the ability of an aqueous solution to carry an electric current (see Electrical Conductivity).

Confined Groundwater - A body of groundwater overlain by material sufficiently impervious to prevent free hydraulic connection with overlying groundwater.

Confining Bed  - A body of impermeable or distinctly less permeable material stratigraphically adjacent to [i.e. above or below] one or more aquifers.

Constituent - A component or attribute of waste that is detectable.

Containment - The use of waste management unit characteristics or installed systems and structures to prevent or restrict the release of waste constituents or leachate.

Contamination - (a) Water quality impairment to a degree that creates a public health hazard through poisoning or through the spread of disease, (b) includes any equivalent effect resulting from the disposal of waste, whether or not waters of the state are affected.

Contiguous Zone - The portion of ocean waters between the state and federal territorial limits.

Cooling Water - Water used to reduce temperature.

Correlative - Having a mutual or reciprocal relation that is that the existence of one necessarily implies the existence of the other.

Criteria - (a) A standard, rule, or test by which something can be judged; measure of value, (b) Specific levels of water quality which, if reached, are expected to render a body of water suitable for its designated beneficial use.

Critical Area - The terrestrial or riparian area on either side of the critical reach that is influenced by the amount of stream flow.

Critical Reach - The section of a stream extending either from the point of diversion or, if the project includes an impoundment, the most upstream point of the impoundment to the point of return.

Cross-contamination - A condition created when a drill hole, boring, or improperly constructed well forms a pathway for fluid movement between a saturated zone which contains pollutants and a formerly separated saturated zone containing ground water. Also where portable and sanitary services are interconnected.

Cubic Feet per Second (cfs) - The rate of flow passing any point equal to the volume of one cubic foot of water every second. One cfs is equal to 7.48 gallons per second; 448.8 gallons per minute; 646,317 gallons per day (86,406 cubic feet per day).

Cumulative Impact  - The term cumulative impact is used in several ways: as the effect of exposure to more than one compound; as the effect of exposure to emissions from more than one facility; the combined effects of a facility and surrounding facilities or projects on the environment; or some combination of these.


Decomposable Waste - Waste which, under suitable natural conditions, can be transformed through biological and chemical processes into compounds that do not impair the quality of waters of the State. Incomplete decomposition may result in some water quality degradation (i.e.: hardness, taste, odor, etc.).

Degrade - Degradation shall be determined by comparison of the waste field and reference site(s) for characteristic species diversity, population density, contamination, growth anomalies, debility, or supplanting of normal species by undesirable plant and animal species. Degradation occurs if there are significant differences in any of three major biotic groups, namely, demersal fish, benthic invertebrates, or attached algae. Other groups may be evaluated where benthic species are not affected, or are not the only ones affected.

De Minimis Risk - A level of risk that the scientific and regulatory community asserts is too insignificant to regulate.

Deoxyribonucleic Acid (DNA) - A nucleic acid that is bound in double helical chains by hydrogen bonds between bases, forming the basic material in the chromosomes of the cell nucleus; it contains the genetic code and transmits the heredity pattern.

Deposition - The laying down of material from erosion and transported by water or air.

Designated Waste - Non-hazardous waste that consists of or contains pollutants which, under ambient environmental conditions at the waste management unit, could be released at concentrations in excess of applicable water quality objectives, or which could cause degradation of waters of the state. Also applies to hazardous waste that has been granted a variance from hazardous waste management requirements.

Dewater - To remove water from wastes, soils or chemicals.

Dewatered Sludge - Residual semi-solid waste from which a portion of the free liquid has been evaporated or otherwise removed. It is usually 20 percent solids by volume.

Diligence - Persistent effort in the completion of a specific task, such as the construction of a water diversion structure and placing water to beneficial use.

Dilution - (a) To thin down or weaken as by mixing with water or other liquid. (b) Disposal of wastewater or treated effluent by discharging it into a stream or body of water.

Dilution Factor - The ratio of the quantity of wastewater (untreated, partly treated, or completely treated) effluent to the average quantity of diluting water available at the point of disposal or at any point under consideration; usually expressed in percentage.  Also called available dilution.

Discharge - (a) As applied to a stream or conduit, the rate of flow, or volume of water flowing in the stream or conduit at a given place and within a given period of time, (b) The passing of water or other liquid through an opening or along a conduit or channel, (c) The rate of flow of water, silt, or other mobile substance which emerges from an opening, pump, or turbine, or passes along a conduit or channel, usually expressed as cubic feet per second, gallons per minute, or million gallons per day.

Discharge Prohibitions - see Prohibition.

Discharger - Any person who discharges waste which could affect the quality of California waters, and includes any person who owns a waste management unit or who is responsible for the operation of a waste management unit.

Disinfect - To destroy harmful bacteria, viruses, etc., in wastewater.

Disinfected Wastewater - Wastewater to which chlorine or other disinfecting agent has been added, during or after treatment, to destroy pathogenic organisms.

Disposal System - A septic tank and drain field for sub-surface disposal of wastewater.

Dissolved Oxygen (DO) - The oxygen dissolved in water, wastewater, or other liquid, usually expressed in milligrams per liter, parts per million, or percent of saturation.

Dormant - Unexercised, not active, but capable of becoming exercised.

Down Gradient - The direction in which groundwater flows.

Down Stream - In the direction of the current of a stream.

Down Stream Ocean Waters - Waters downstream with respect to ocean currents.

Dredged Material - Any material excavated or dredged from the navigable waters of the United States, including material otherwise referred to as “spoil”.

Dredging - The removal of material from the bottom of water bodies using a scooping, scraping, or suction machine.


Ecosystem - A complex system composed of a community of fauna and flora taking into account the chemical and physical environment with which the system is interrelated.

Effluent - Solid, liquid or gaseous wastes that enter the environment as a by-product of human-oriented processes; or water that has undergone treatment to remove pollutants.

Effluent Limitation - Any restriction established on quantities, rates and concentrations of chemical, physical, biological, and other constituents which are discharged from point sources into navigable waters, the waters of the contiguous zone, or the ocean, including schedules of compliance. The restriction may be narrative or numeric.

Electrical Conductivity  - The relative ability of water to conduct electrical current. It depends on the ion concentration and can be used to approximate the total filterable residue (total dissolved solids) in the water.

Elevated Temperature Waste  - Liquid, solid, or gaseous material including thermal waste discharged at a temperature higher than the natural temperature of receiving water.

Emergent Wetland - Wetlands dominated by erect, rooted, herbaceous aquatic plants (e.g. cattails, bulrush, etc.), which extend above the standing water level. 

Enclosed Bays - Indentations along the coast that enclose an area of oceanic water within a distinct headlands or harbor works. Enclosed bays include all bays where the narrowest distance between headlands or outermost harbor works is less than 75 percent of the greatest dimension of the enclosed portion of the bay.

Endangered Species - Animal populations are be determined to be endangered when populations are severely depleted, as defined by the Endangered Species Act.

Enteric  - Intestinal; of the enteron.

Enterococcus - A streptococcus (bacteria) normally present in the intestinal tract (of humans and warm blooded animals), may cause illness when found in other parts of the body.

Environmental Impact Report (EIR) - A document required by the 1970 California Environmental Quality Act (CEQA) that assesses the possible environmental effects of a project.

Environmental Impact Statement (EIS) - Required by the National Environmental Policy Act, this document analyzes the effects of major federal projects on the environment. It must be filed with the President and the Council on Environmental Quality, and must be made available to the public.

Ephemeral Stream - Carries water runoff only in times of rainfall and remains as a dry channel during the rest of the year.

Erosion - Wearing away of earth and rock by running water, glaciers, winds, and waves.

Escherichia Coli (E. Coli)  - One of the group of bacteria referred to as fecal coliforms.

Estuary - Water at the mouth of a stream that serves as mixing zones for fresh and ocean waters during a major portion of the year. Estuarine waters generally extend from a bay or the open ocean to the upstream limit of tidal action but may be considered to extend seaward if significant mixing of fresh and salt water occurs in the open coastal waters. (Basically, where a freshwater river meets the sea.)

Existing Discharge - Any discharge (a) which is presently taking place, or (b) for which waste discharge requirements have been established and construction commenced, or (c) any material change in an existing discharge for which construction has commenced. 

Exposure Pathways - Existing or hypothetical routes by which chemicals in soil, water or other media can come in contact with humans, animals or plants.

Extraction Wells - Wells that are used primarily to remove contaminated groundwater from the ground. Water level measurements and water samples can also be collected from extraction wells.


Fecal Coliform - A sub-classification of the total coliform group.  Fecal coliforms are characterized by facultative anaerobic, gram negative, non-spore forming, rod shaped bacteria that ferment lactose with gas and acid formation within 48 hours at 44.5C.  Fecal coliform bacteria are primarily found in the intestinal track of humans and warm-blooded animals.

Flood Plain - The land area that  is subject to flooding in any year from any source.

Freeboard - The vertical distance between the lowest point along the top of a surface impoundment dike, berm, levee, treatment works or other similar feature and the surface of the liquid contained therein.

French Drain System - A pit or trench filled with crushed rock and used to collect and divert ground water.

Fresh Waters - All freshwater lakes and streams downstream to the limit of tidal action.


Geophysical Logging - A general term for techniques used to infer physical or chemical properties of subsurface strata (e.g. porosity or permeability).  These techniques typically involve lowering a sensing device into a borehole to measure the properties of the strata.

Gradient - The rate of change of a physical quantity with distance.

Ground Water - The water below the land surface.

Ground Water Recharge - Refers to the addition to the water within the earth that occurs naturally from infiltration of rainfall and from water flowing over the earth materials that allow water to infiltrate below the land surface.


Habitat - The place where an organism lives.

Halomethanes- The sum of bromoform, bromomethane (methyl bromide) and chloromethane (methyl chloride).

Hazardous Waste - Pollutants that are harmful to people, fish, wildlife or plants.

Heavy Metals - Toxic, high-density, metallic elements such as lead, silver, mercury and arsenic.

Herbicide - Chemical used to kill plants.

Horizontal Wells - A well constructed in a horizontally drilled borehole.  A horizontal well can provide a means for greater access to a laterally extensive plume, thus improving contaminant recovery rates. 

Hydraulic Conductivity - A coefficient of proportionality describing the rate at which water can move through a permeable medium.

Hydraulic Gradient  -The change in total head [pressure] with a change in distance in a given direction.  The [down gradient] direction is that which yields a maximum rate of decrease in head.  [In an unconfined aquifer, the hydraulic gradient describes the slope of the water table.]

Hydrogeology - The geology of ground water, with particular emphasis on the chemical composition and movement of the water.

Hydrologic Unit - An area of land dealing with properties , distribution, and circulation of water.


Impervious - Not allowing, or allowing only with great difficulty, the movement of water; impermeable

Impoundment - A body of water or sludge confined by a dam, dike, floodgate or other barrier.

Indicator - A species of plant, animal or bacterium whose presence is indicative of a particular environmental condition.

Individual Septic Disposal System (ISDS) - See disposal system.

Inert Waste - Does not contain hazardous waste or soluble pollutants at concentrations in excess of applicable water quality objectives, and does not contain significant quantities of decomposable waste. This type of waste does not need to be discharged at classified waste management units.

Infiltration- To pass, or cause (a fluid, cell, etc.) to pass, through small gaps or openings; filter.

Initial Dilution - The process that results in the rapid and irreversible turbulent mixing of effluent and receiving water around the point of discharge.

Injection Well - Any bored, drilled or driven shaft, dug pit, or hole in the ground into which waste or fluid is discharged, and any associated subsurface appurtenances, and the depth of which is greater than the circumference of the shaft, pit, or hole.

Inspection - Critical examination or review.

Interstate Waters  - All rivers, lakes, artificial impoundments, and other waters that flow across or form a part of the boundary with other states or Mexico.

Intermittent Stream - Carries water runoff only in times of rainfall and remains as a dry channel during other times of the year.

Invertebrate - An animal without a back-bone or spinal column.


Jackson Turbidity Unit (JTU)- A measurement based on the light path of a suspension which just causes the image of the flame of a standard candle to disappear when viewed through the suspension.


Kelp Beds - Significant aggregations of marine algae throughout the water column.


Landfill - A waste management unit at which waste is discharged in or on land for disposal. It does not include surface impoundments or land treatment units.

Leachate - (a) Any fluid, formed by the drainage of liquids from waste or by the percolation of liquid through waste. It includes any constituents extracted from the waste and dissolved or suspended in the fluid. Often refers to liquid leaking from landfills which usually contains contaminates. (b) A solution obtained by leaching; e.g. water that has percolated through soil containing soluble substances and that contains certain amounts of these substances in solution. [This term is commonly used in describing water that has percolated through a landfill and contains landfill-related substances in solution.].

Leach field - A drain field designed to discharge septic tank effluent below ground into the natural soil for final treatment.

Liner - A continuous layer of natural or artificial materials or a continuous membrane of artificial material installed beneath or on the sides of a waste management unit, which acts as a barrier to vertical or lateral fluid movement.


Mariculture - The culture of plants and animals in marine waters independent of any pollution source.

Marsh - A frequently or continually inundated wetland characterized by emergent herbaceous vegetation adapted to saturated soil conditions.

Master Recycling Permit - A permit issued to a supplier or a distributor, or both, of recycled water that includes waste discharge requirements prescribed pursuant to Section 13263 and water recycling requirements prescribed pursuant to Section 13523.1.

Material - (a) In common usage: (1) the substance or substances of which a thing is made or composed (2) substantial; (b) matter of any kind or description which is subject to regulation as waste, or any material dredged from the navigable waters of the United States. See also, Dredged Material.

Maximum Contaminant Level (MCL) - Enforceable drinking water standards adopted either by the California Department of Health Services or the federal EPA. It is the maximum permissible level of a contaminant in drinking water.

Method Detection Limit (MDL) - The minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero, as defined in 40 CFR PART 136 Appendix B.

Methane - The chief constituent of natural gas, produced by decaying plant material or by coal gasification processes. It is a greenhouse gas believed to contribute to global warming.

Microgram per gram (µg/g) - A measurable unit of concentration for a solid. A mercury level of 1.0 µg/g means that one microgram (one millionth of a gram) of mercury was detected in one gram of sample. It is equivalent to one part per million.

Migration - Movement of a substance from one place to another through natural processes.

Milligram per Kilogram (mg/Kg)  - A unit of concentration for a solid. A mercury level of 1.0 mg/kg in fish means that one milligram (one thousandth of a gram) of mercury was found in each kilogram of sampled fish. (A kilogram is 1,000 grams or approximately 2.2 pounds). Also equals one part per million.

Milligram per Liter (mg/L) - A unit of the concentration of water or wastewater constituent.  It is 0.001 gm of the constituent in 1,000 ml of water.  One mg/L is approximately equal to one part per million.

Million Gallons per Day (MGD) - A measurement of water flow equal to about 0.5 cubic feet per second.

Minimum Level (ML) - The concentrations at which the entire analytical system must give a recognizable signal and acceptable calibration point. The ML is the concentration in a sample that is equivalent to the concentration of the lowest calibration standard analyzed by a specific analytical procedure, assuming that all the method-specified sample weights, volumes and processing steps have been followed.

Mitigation - To make less severe; lessen the hardship.

Mixing Zone - A designated volume of a receiving water where wastewaters and receiving water mix.  Allocation of a mixing zone provides limited dilution of a wastewater discharge before certain water quality objectives must be met.

Moisture Holding Capacity - The amount of liquid that can be held against gravity by waste materials without generating free liquid.

Monitoring  - The measurement, sometimes continuous, of water quality.

Monitoring Well - Specially constructed wells used for collecting representative samples of ground water for water quality testing.

Most Probable Number (MPN) - An index of the number of coliform bacteria that, more probably than any other number, would give the results shown by laboratory examination; it is not an actual enumeration.


National Pollutant Discharge Elimination System (NPDES) Permit - Permit required for all point sources discharges of pollutants to surface waters. It has the following characteristics: issued for up to five years; provides for inspection and monitoring; requires notice to the public, the USEPA and any other affected state, provides for the protection of navigation, and mandates a pre-treatment program as necessary.

Natural Light - Reduction of natural light may be determined by the measurement of light transmissivity or total irradiance, or both.

Natural Receiving Water Temperature - The temperature of the receiving water at locations, depths, and times which represent conditions unaffected by any elevated temperature waste discharge or irrigation return waters.

Navigable Water - Any surface body of water.

Negative Declaration - A California Environmental Quality Act document issued by the lead regulatory agency when the initial environmental study reveals no substantial evidence the proposed project will have a significant adverse effect on the environment, or when any significant effects would be avoided or mitigated by revisions agreed to by the applicant.

New Discharge - Any discharge (a) that is not presently taking place unless waste discharge requirements have been established and construction has commenced, or (b) which is presently taking place and for which a material change is proposed but no construction has commenced.

Nitrate (NO3) - A class of chemical compounds having the form NO3.  Typically formed when ammonia is degraded by microorganisms in soil or groundwater.

Nitrite (NO2) - An intermediate product in many nitrogen transformations.

Nitrogen (N2) - A gas that comprises 78% of the earth’s atmosphere by volume. An essential plant nutrient.

Non-hazardous Solid Waste - All putrescible (able to rot quickly enough to cause odors and attract flies) and nonputrescible solid, semi-solid and liquid wastes, including garbage, trash, refuse, paper, rubbish, ashes, industrial wastes, demolition and construction wastes, abandoned vehicles and parts thereof, discarded home and industrial appliances, manure, vegetable or animal solid and semi-solid wastes and other discarded solid or semisolid waste; provided that such wastes do not contain wastes which must be managed as hazardous wastes, or wastes which contain soluble pollutants in concentrations which exceed applicable water quality objectives, or could cause degradation of waters of the state (i.e.: designated waste).

Nonpoint Source - Diffuse discharges of waste throughout the natural environment that may be a major cause of water pollution. Difficult to pinpoint physically, but can be classified by type: urban runoff, agriculture, mining, septic tank leach fields and silviculture.

Nuisance - Anything which meets all of the following requirements (a) Is injurious to health, or is indecent or offensive to the senses, or an obstruction to the free use of property, so as to interfere with the comfortable enjoyment of life or property, (b) Affects at the same time an entire community or neighborhood, or any considerable number of persons, although the extent of the annoyance or damage inflicted upon individuals may be unequal, (c) Occurs during, or as a result of, the treatment or disposal of wastes.

Nutrients - A nutritious ingredient (e.g. nitrogen, phosphorus, etc.).


Objectives (see Water Quality Objectives)

Ocean Plan - Limits waste discharge into the ocean. Adopted by the State Water Board in 1972.

Ocean Waters - Territorial marine waters of the state to the extent that these waters are outside of enclosed bays, estuaries, and coastal lagoons.

Office of Administrative Law (OAL) - A State agency charged with administering the Administrative Procedures Act, reviewing and approving regulations for other State agencies, which once approved, are codified in the California Code of Regulations.

Onsite Septic Disposal System (OSDS) - See disposal system.

Organic Nitrogen  - All substances in which nitrogen is bonded to carbon.

Organic Phosphate - Phosphate that is bound to plant or animal tissue.

Orthophosphate - Orthophosphate is the dissolved, inorganic fraction of phosphorus that is biologically available for uptake.


Particulates- Small solid or liquid particles.

Parts per Billion (PPB) - The number of weight or volume units of a substance in each billion units of a solution or mixture.

Parts per Million (PPM) - The number of weight or volume units of a substance in each million units of a solution or mixture.

Pathogen - Any agent, especially a microorganism (e.g. viruses or bacteria), able to cause disease.

Peak Stream Flow - The maximum expected flow of surface water at a waste management facility from a tributary watershed for a given recurrence interval.

Perennial Stream - Water bodies, or segments thereof, that contain flow throughout the year.

Perched Groundwater - Unconfined groundwater separated from the underlying main body of groundwater by unsaturated rock or other strata.  Water that accumulates beneath the earth’s surface but above the primary water-bearing zone (aquifer) is termed perched groundwater.  Typically, perched groundwater collects above laterally discontinuous, less permeable deposits (e.g. clay lenses) contained in an otherwise permeable deposit.

Percolation - The flow or filtering of water or other liquids through subsurface rock or soil layers, usually continuing to groundwater.

Permeability - The ability of a natural and artificial materials to transmit fluids.

Permit - Official document allowing the performance of a specified activity with set limitations. If all requirements are met, a water appropriation permit can mature into a license.

Pesticide - (a) Chemical used to kill destructive insects or other small animals. (b) A general term for insecticides, herbicides and fungicides. Insecticides kill or prevent the growth of insects. Herbicides control or destroy plants. Fungicides control or destroy fungi. Some pesticides can accumulate in the food chain and contaminate the environment.

pH - A measure of the acidity or alkalinity of a substance. Waters that are too acid (low pH) or alkaline (high pH) can be unfit for animal or plant life. On the pH scale, which runs from zero to 14, a value of 7 is neutral. There is a tenfold difference between each number (if the pH drops from 7 to 6, the acidity is ten times greater).

Phosphate - Phosphates are formed from elemental phosphorus.  They exist in three forms: Orthophosphate, metaphosphate (or polyphosphate), and organically bound phosphate.

Phosphorus (P) - An element.  It is an essential nutrient for plants and animals.

Photosynthesis - The biological synthesis of chemical compounds in the presence of light.

Piezometer - A non-pumping well, generally of small diameter, which is used to measure the elevation of the water table or potentiometric surface.  A piezometer generally has a short well screen through which water can enter.

Planktonic Organism - Phytoplankton, zooplankton, and the larvae and eggs of worms, mollusks, and arthropods, and the eggs and larval forms of fishes.

Plume - A body of contaminated groundwater flowing from a specific source.  The movement of the [contaminated] groundwater is influenced by such factors as local groundwater flow patterns, the character of the aquifer in which the [contaminated] groundwater is contained, and the density [and other physical and chemical properties] of the contaminants. 

Point Source - A discernible, confined and discrete conveyance such as a pipe, ditch or channel, tunnel, conduit, well container, concentrated animal feeding operation or vessel, from which pollutants are or may be discharged. Does not include agricultural storm water discharges and return flows from irrigated agriculture.

Pollutant - Dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt and industrial, municipal and agricultural waste discharged into water.

Pollution - (a) An alteration of the quality of state waters by waste to a degree that unreasonably affects their beneficial uses or facilities that serve their beneficial uses, (b) Pollution may include contamination.

Porter Cologne Water Quality Control Act - Enacted by California Legislature in 1970, it contains a complete framework for the regulation of waste discharges to both surface and ground waters of the State. It further provides for the adoption of water quality control plans and the implementation of these plans by adopting waste discharge requirements for each discharge of waste that could impact the waters of the state.

Posting - The placement of a sign or signs at an area of a public beach that informs the public of contamination of recreational water and the risk of possible illness, and advises against swimming and/or water contact. The placement of signs may be temporary, as a result of monitoring that indicates a single microbiological indicator standard is exceeded (e.g., or more permanent, where monitoring indicates regular or sporadic contamination (e.g., a storm drain, or a water body with poor water circulation), or where sources of contamination are identifiable and can be explained (e.g., storm drain water, or residential wild or domestic animal populations).

Pretreatment - Removal of toxic or hazardous substances from wastewater before it is discharged into a wastewater collection, treatment and disposal system.

Primary Treatment - A treatment process, utilizing a sedimentation tank, wherein a portion of the suspended matter is removed from the wastewater, but little or no colloidal or dissolved matter.  Primary treatment generally removes from 50 to 75 percent of the suspended matter and 20 to 40 percent of the BOD from the wastewater.

Priority Pollutant- Those pollutants listed by the Administrator of the USEPA in Section 307 (a) of the Clean Water Act.

Prohibition - An order or law forbidding something to be done.

Publicly Owned Treatment Work (POTW) - A wastewater treatment plant owned by a state or municipality. The term also may include devices and systems used in the storage, treatment, recycling and reclamation of municipal sewage or industrial wastes of a liquid nature.

Pump Test - A field test by which a well is pumped for a period of time and data are collected for use in assessing characteristics of subsurface water-bearing zones, or aquifers.


Quality Assurance/Quality Control (QA/QC) - A set of operating principles that, if strictly followed during sample collection and analysis, will produce data of known and defensible quality.

Quality of the water - Refers to chemical, physical, biological, bacteriological, radiological, and other properties and characteristics of water that affect its use.


Reclaimed Water (also known as Recycled Water) - Water which, as a result of treatment of waste, is suitable for direct beneficial use or a controlled use that would not otherwise occur.

Regional Water Quality Control Board (RWQCB) - Any California regional water quality control board for a region as specified in Porter- Cologne Water Quality Control Act, Section13200.

Remediation  - Cleanup of a site to levels determined to be health-protective for its intended use, or protective of beneficial uses of water.

Residual Chlorine - Chlorine remaining in water or wastewater at the end of a specified contact period as combined or free chlorine.

Resource Conservation and Recovery Act (RCRA) - A 1976 act to reduce or eliminate the generation of hazardous waste as expeditiously as possible. Waste that is generated should be treated, stored or disposed of to minimize the threat to the environment.

Responsible Party - An individual or corporate entity considered legally liable for contamination found at a property and, therefore, responsible for cleanup of the site.

Return Flow - Applied water that drains as surface flow from irrigated lands.

Risk Assessment - A risk assessment looks at the chemicals detected at a site, the frequency and concentration of detected chemicals, the toxicity of the chemicals and how people can be exposed, and for how long. Routes of exposure to people are generally through ingestion, such as eating, contact with the skin, or inhalation. The most significant potential routes of exposure are trough ingestion and contact with the skin. Based on the standard risk assessment guidelines established for use nationwide by USEPA, exposures for an on-site resident are generally assumed to be daily contact over a 30-year period starting with children ages 0-6, and continuing from 6-30 years. The health risk assessment cannot predict health effects; it only describes the increased possibility of adverse health effects, based on the best scientific information available.

Retrofitting - Installing modern pollution control devices on older power generating facilities without making major changes in plant design.

Riparian - Of, adjacent to, or living on the bank watercourse (e.g. stream, river, lake, etc.).

Riparian Rights - Comes with ownership of land adjacent to a water source, ground water rights are held by those owning land over a ground water basin.

Riparian Vegetation - The vegetation along a watercourse which is distinguished from other vegetation by its dependence on the combination of soil moisture and other environmental factors provided by a permanent or intermittent stream.

Runoff - Rainfall or snow melt which is not absorbed by soil, evaporated, or transpired by plants, but finds its way into streams as surface flow.


Salinity - Of, characteristic of, or containing common salt, or sodium chloride; salty.

Salt Water Intrusion - The invasion of a body of fresh water (surface or ground water) by a body of salt water.

Sanitary Landfill - A landfill operated in accordance with applicable regulations to maintain sanitary conditions.

Saturated Zone - (a) An underground zone in which all openings in and between natural geologic materials are filled with water.  (b) The zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric.  The water table is the top of the saturated zone in an unconfined aquifer.

Schedule of Compliance - A schedule of remedial measures including an enforceable sequence of actions or operations leading to compliance with an effluent limitation, other limitation prohibition or standard.

Secondary Containment - A structure designed to capture spills or leaks, as from a container or tank. For containers and aboveground tanks, it is usually a bermed area of coated concrete. For underground tanks, it may be a second, outer, wall or a vault. Construction of such containment must meet certain requirements, and periodic inspections are required.

Secondary Treatment - The treatment of wastewater by biological methods usually preceded by primary sedimentation.  Secondary treatment removes from 80 to 95 percent of suspended matter and BOD.

Sediment - The soil, sand and minerals at the bottom of surface waters, such as streams, lakes and rivers. The term may also refer to solids that settle out of any liquid.

Semi-solid waste - Waste containing less than 50 percent solids.

Septage - Waste (water and solids) pumped from a septic tank.

Septic System - See disposal system.

Septic Tank - A large volume, water-tight tank that provides initial treatment of wastewater.

Settleable Solids (SS) - Solids in suspension that will settle under quiescent conditions.

Sewage Treatment - Treating wastewater in three stages: 1. primary treatment - first state which refers to the settling/floating out of large suspended solids by screening and sedimentation before either discharging the treated wastewater or subjecting it to further treatment; 2. secondary treatment-additional treatment by biological processes to break down organic matter remaining in the sewage following primary treatment; and 3. tertiary treatment additional treatment of sewage beyond the secondary state to accomplish a very high degree of pollution reduction. Typical pollutants removed are organic chemicals, nutrients and excessive salts. Typically, primary treatment is physical, secondary treatment is biological and tertiary treatment is chemical and/or physical.

Shellfish - Organisms identified by the California Department of Health Services as shellfish for public health purposes (i.e., mussels, clams and oysters).

Significant - A statistically significant difference in the means of two distributions of sampling results at the 95 percent confidence level.

Silviculture - The art of cultivating a forest or forestry.

Slough - A slowly moving shallow marsh.

Sludge - Residual solids and semi-solids from the treatment of water, wastewater, and other liquids.

Slurry Wall - Barriers used to contain the flow of contaminated groundwater or subsurface liquids. Slurry walls are constructed by digging a trench around a contaminated area and filling the trench with an material that tends not to allow water to pass through it. The groundwater or contaminated liquids trapped within the area surrounded by the slurry wall can be extracted and treated.

Soil borings  - Soil samples taken by drilling a hole in the ground.

Solid Waste - Any garbage, refuse, sludge from treatment facilities, and other discarded material (including solid, liquid and contained gaseous material) resulting from industrial, commercial, mining and agricultural operations and from community activities. Sewage and certain other wastes are exempted.

Solvent - A liquid capable of dissolving another substance to form a solution. Water is sometimes called “the universal solvent” because it dissolves so many things, although often to only a very small extent. Organic solvents are used in paints, varnishes, lacquers, industrial cleaners and printing inks, for example. The use of such solvents in coatings and cleaners has declined over the last several years, because the most common ones are toxic, contribute to air pollution and may be fire hazards.

Spoils - Loose rock, solid and vegetation debris left from construction or mining activities.

Stakeholder - Any person or group who directly or indirectly affects, is affected by or has an interest in the actions of the State and Regional Water Boards.

Standard - see Water Quality Standard.

State Mussel Watch Program (SMW) - Monitors toxic pollutant levels in resident and transplanted California mussels from coastal, bay and estuarine areas.

Stock Pond - A pond, having a capacity of 10 acre-feet or less, which is used primarily for watering livestock.

Storm Water - Storm water runoff, snow melt runoff and surface run off and drainage.

Sump - A pit or tank that catches liquid runoff for drainage or disposal.

Superfund - (a) State and federal funding mechanisms and programs to clean up hazardous waste sites that pose a threat to public health, (enacted in 1976). (b) Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA)

Surface Impoundment - A waste management unit which is a natural topographic depression, excavation or diked area, and which is designed to contain liquid wastes or wastes containing free liquids and which is not an injection well.

Surge Tanks - A tank used to absorb irregularities in flow of liquids, including liquid waste materials, so that the flow out of the tank is constant.

Surveillance - Constant observation of a place or process.

Suspended Solids - The small, solid particles in water or wastewater that cause a cloudy condition.  Solids that either float on the surface of, or are in suspension in water or wastewater which are removable by filtering.


Tailings or Mine Tailings - Crushed waste rock deposited on the ground during mining and ore processing, including some of the rock in which the ore is found. Unless they are handled carefully, they frequently release contaminants. As they age under the effects of air, rainfall and bacteria, some oxidize to produce new toxic materials, such as sulfuric acid, that can leach out and poison streams, rivers and lakes.

Tailings Pond - An excavated or diked area that is intended to contain liquid and solid wastes from mining and milling operations.

Tailwater - Applied water which drains as surface flow from irrigated lands.

Tertiary Treatment - Wastewater treatment beyond primary and secondary treatment.  For example, chemical treatment, carbon filtration, etc.

Thermal Waste - Cooling water and industrial process water used for the purpose of transporting waste heat.

Threatened Species - Under the Endangered Species Act, animal populations may be determined to be threatened when populations are less severely depleted than populations classed as endangered.

Time Schedule Order - Set of specific actions a discharger shall take to correct or prevent violation of requirements.

Total Ammonia - The combined concentrations of the unionized (NH3) and ionized (NH4) forms of ammonia.

Total Kjeldahl Nitrogen (TKN) - The sum of organic nitrogen and total ammonia nitrogen.

Total Maximum Daily Load (TMDL) - A specific water quality attainment strategy for a water body and related impairment identified on the 303(d) list. The strategy defines specific measurable features that describe attainment of the relevant water quality standards. The strategy includes a description of the total allowable level of the pollutant(s) in question and allocation of allowable loads to individual sources or groups of sources of the pollutant(s) of concern.

Toxic Hot Spots - Waters that have toxic pollution problems even after industries have installed cleanup technologies required by the Clean Water Act. EPA put out a national list in June 1989 on such toxic waterways.

Toxic Pits Cleanup Act (TPCA) - Prevents drinking water supply contamination from and improper storage treatment, and disposal of liquid hazardous wastes in surface impoundments.

Toxic Substance - A substance that either directly poisons living things or alters their environment so they die.

Toxic Substances Control Act (TSCA) - A federal law of 1976 to regulate chemical substances or mixtures that may present an unreasonable risk of injury to health or the environment.

Toxic Substances Monitoring Program (TSM) - Designed to detect the presence and concentration of toxic pollutants in fish and other aquatic organisms in selected California streams and lakes.

Toxic Pollutant - Those pollutants or combinations of pollutants including disease-causing agents, which after discharge and upon exposure, ingestion, inhalation or assimilation into any organism, either directly from the environment or indirectly by ingestion through food chains, will, on the basis of information available, cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions or physical deformations, in such organism or their offspring.

Toxicity - Ability to harm human health or environment, such as injury, death or cancer. One of the criteria used to determine whether a waste is a hazardous waste (the "Toxicity Characteristic").

Transient - Staying only for a short time.

Tributary - Connected to another body of water.

Turbidity - Suspended and colloidal matter (e.g. clay, silt, organic and inorganic matter, etc.) in water.


Underground Injection - The placing of fluids below the surface of the ground through wells. Fluids injected include hazardous wastes, brine from oil and gas recovery, liquids used in mining, radioactive waste, sewage, natural gas and oil products and storm water runoff. USEPA and states regulate underground injection under the Safe Drinking Water Act and RCRA.

Unsaturated Zone - see Vadose Zone.

Up Gradient - The direction from which water flows in an aquifer.

Up Stream - In the direction against the current of a stream.


Vadose Zone - The zone between the ground surface and the regional water table or in cases where the upper most aquifer is confined, the zone between the ground surface and the top of the saturated portion of the aquifers confining layer.

Vector - An animal, especially an insect that transmits a disease-producing organism from a host to a non-infected animal.

Vernal Pool - A shallow pond which temporarily holds water from spring precipitation and runoff, but which is dry during the summer.

Vertebrate - An animal with a segmented spinal cord together with a few primitive forms in which the back-bone is represented by a notochord.

Virus - Any of a kingdom (Virus) of prokaryotes, usually ultramicroscopic, that consists of nucleic acid, either RNA or DNA, within a case of protein.  They infect animals, plants, and bacteria and can reproduce only within living cells so they are considered as being either living organisms or inert chemicals.

Viscosity - A measure of the ease with which a liquid can be poured or stirred. The higher the viscosity, the less easily a liquid pours.

Volatile  - Describes substances that readily evaporate at normal temperatures and pressures.

Volatile Organic Compound (VOC) - A group of chemicals that react in the atmosphere with nitrogen oxides, heat, and sunlight to form ozone.

Volatility - The tendency of a liquid to evaporate.


Warm Interstate Waters - Interstate streams and lakes having a range of temperature generally suitable for warm water fishes such as bass and catfish. 

Waste - (a) Includes sewage and any and all other waste substances, liquid, solid, gaseous, or radioactive, associated with human habitation, or of human or animal origin, or from any producing, manufacturing, or processing operation, including waste placed within containers of whatever nature prior to, and for purposes of, disposal.  (b) Waste includes a discharger’s total discharge, of whatever origin, i.e., gross, not net, discharge.

Waste Discharge Requirement (WDR) - Orders adopted by Regional Boards regulating discharges of waste.

Waste Load Allocation  - The maximum load of pollutants each discharger of waste is allowed to release into a particular water body.

Waste Management Facility - The entire parcel of property where waste discharge operations are conducted. Such a facility may include one or more waste management units.

Waste Management Unit (WMU) - An area of land or a portion of a waste management facility where waste is discharged.

Waste Pile - A waste management unit where only non-containerized, bulk, dry solid waste is discharged and piled for treatment or storage on an engineered liner system that prevents waste from contacting the underlying land surface.

Water Column - The "column" of water between the water surface and the water body floor.

Water Quality - Refers to chemical, physical, biological, radiological, and other properties and characteristics of the water.

Water Quality Control Plan (Basin Plan) - The Basin Plan defines and designates beneficial uses of waters, establishes water quality objectives to protect those uses, identifies water quality threats and outlines corrective measures to be implemented. It is used to develop discharge limits and guide Regional Board decisions on specific cases.

Water Quality Control - The regulation of any activity or factor that may affect the quality of the waters of the state and includes the prevention and correction of water pollution and nuisance.

Water Quality Criteria - see water quality standard.

Water Quality Objectives - The limits or levels of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area.

Water Quality Standard - (a) A state adopted ambient standard for a surface or ground water body.  The standard covers the beneficial use of the water and the water quality criteria, which must be met to protect the designated use or uses. (b) Pursuant to the federal Clean Water Act, a combination of the designated beneficial uses of water and criteria or water quality objectives to protect those uses.

Water Reclamation - The treatment of waste water to render it suitable for recycle or reuse, the transportation of treated wastewater to the place of use and the actual use of treated wastewater for a direct beneficial use or controlled use that would not otherwise occur.

Water Table - The surface between the zone of saturation [saturated zone] and zone of aeration [unsaturated zone]; that surface of a body of unconfined groundwater at which the pressure is equal to that of the atmosphere.

Waters of the State - Any surface water or groundwater, including saline waters, within the boundaries of the state.

Watershed - The total land area that contributes water to a river, stream, lake or other body of water. Synonymous with drainage area, drainage basin, and catchment.

Wetlands- Marshes or swamps that are saturated with surface or ground water; they often serve as wildlife refuges.


Xeric - Of, pertaining to, or having dry or desert-like conditions.



Zone of Aeration -That subsurface soil zone above the free groundwater table wherein soil pores contain both air and water.

Zone of Initial Dilution (ZID)  - When wastewater is discharged into a water body, its transport can be divided into two stages with distinctive mixing characteristics.  Turbulent mixing in the first stage is determined by the initial momentum and buoyancy of the discharge.  The second stage covers a more extensive area in which the waste is mixed primarily by ambient laminar mixing and diffusion.  The in which the first stage turbulent mixing occurs is the zone of initial dilution.

Zone of Saturation - That subsurface soil zone wherein soil pores are completely filled with water.