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A B C D E F G H I J K L M N O P Q R S T U V W X Y ZAAbsorbed dose—The amount of a chemical that enters the body of an exposed organism. Absorption—The uptake of water or dissolved chemicals by a cell or an organism (as tree roots absorb dissolved nutrients in the soil). Absorption factor—The fraction of a chemical making contact with an organism that is absorbed by the organism. Accuracy—How closely an instrument measures the true or actual value of the process variable being measured or sensed. Accumulated overdraft—The amount of water necessary to be replaced into the groundwater basin to prevent the landward movement of ocean water into the fresh groundwater body. Acid rain —Precipitation which has been rendered (made) acidic by airborne pollutants. Acidic—The condition of water or soil, which contains a sufficient amount of acid substances to lower the pH below 7.0. ACOE— United States Army Corps of Engineers Acre-foot—A volume of water that covers one acre to a depth of one foot, or 43,560 cubic feet (1233.5 cubic meters). ACWA—Association of California Water Agencies AFY—Acre-foot per year. Activated carbon—Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood). These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water. Active transport—An energy-expending mechanism by which a cell moves a chemical across the cell membrane from a point of lower concentration to a point of higher concentration, against the diffusion gradient. Action level—The concentration of lead or copper in water specified at Code of Federal Regulations 141.80(c), which determines, in some cases, the treatment requirements contained in subpart I of this part that a water system is required to complete. Acute—Occurring over a short period of time; used to describe brief exposures and effects, which appear promptly after exposure. Acute exposure—A single exposure to a toxic substance, which results in severe biological harm or death. Acute exposures are usually characterized as lasting no longer than a day. Acute toxicity—The ability of a substance to cause poisonous effects resulting in severe biological harm or death soon after a single exposure or dose. Also, any severe poisonous effect resulting from a single short-term exposure to a toxic substance. Ad-Hoc Santa Ana Sucker Discussion Team--In 1998, members of a group of concerned public agencies from throughout the Santa Ana River watershed began meeting with the goal of determining the reasons for the decline of the Santa Ana Sucker (Catostomus santaanae) and correspondingly, to devise strategies for recovering the species. Early on, the U.S. Fish & Wildlife Service (USFWS) and the California Department of Fish & Game joined the effort. SAWPA hosts the monthly meetings and served as the administering agency for the effort. The group has become known as the Ad-Hoc Santa Ana Sucker Discussion Team. This group has since been renamed the Santa Ana Sucker Conservation Team. Adsorbate—The material being removed by the adsorption process. Adsorbent—The material (activated carbon) that is responsible for removing the undesirable substance in the adsorption process. Adsorption—The process by which chemicals are held on the surface of a mineral or soil particle (compare with Absorption). Aeration—The process of adding air to water. Air can be added to water by either passing air through water or passing water through air. Aerobic—A condition in which atmospheric or dissolved oxygen is present in the water. Age tank—A tank used to store a chemical solution of known concentration for feed to a chemical feeder. Also called a day tank. Aggregate—A mass or cluster of soil particles, often having a characteristic shape. Air binding—A situation where air enters the filter media. Air is harmful to both the filtration and backwash processes. Air can prevent the passage of water during the filtration process and can cause the loss of filter media during the backwash process. Air gap—An open vertical drop, or vertical empty space, that separates a drinking (potable) water supply to be protected from another water system in a water treatment plant or other location. This open gap prevents the contamination of drinking water by backsiphonage or backflow because there is no way raw water or any other water can reach the drinking water. Air stripping—A treatment process used to remove dissolved gases and volatile substances from water. Large volumes of air are bubbled through the water being treated to remove (strip out) the dissolved gases and volatile substances. Also see packed tower aeration. Alarm contact—A switch that operates when some pre-set low, high or abnormal condition exists. Algae—Microscopic plants which contain chlorophyll and live floating or suspended in water. They also may be attached to structures, rocks or other submerged surfaces. They are food for fish and small aquatic animals. Excess algal growths can impart tastes and odors to potable water. Algae produce oxygen during sunlight hours and use oxygen during the night hours. Their biological activities appreciably affect the pH and dissolved oxygen of the water. Algal bloom—Sudden, massive growths of microscopic and macroscopic plant life, such as green or blue-green algae, which develop in lakes and reservoirs. Algicide—Any substance or chemical specifically formulated to kill or control algae. Alkali—Various soluble salts, principally of sodium, potassium, magnesium, and calcium, that have the property of combining with acids to form neutral salts and may be used in chemical water treatment processes. Alkaline—The condition of water or soil, which contains a sufficient amount of alkali substances to raise the pH above 7.0. Alkalinity—The capacity of water to neutralize acids. This capacity is caused by the water's content of carbonate, bicarbonate, hydroxide and occasionally borate, silicate, and phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high alkalinity. Alkalinity is a measure of how much acid can be added to a liquid without causing a great change in pH. Alluvial—Relating to mud and/or sand deposited by flowing water. Alluvial deposits may occur after a heavy rainstorm. Alluvium—A stratified bed of sand, gravel, silt, and clay deposited by flowing water. Ambient—Environmental or surrounding conditions. Ambient temperature—Temperature of the surrounding air (or other medium). For example, temperature of the room where a gas chlorinator is installed. AMIGA—Agua Mansa Industrial Growth Association. Anaerobic—A condition in which "free" (atmospheric) or dissolved oxygen is NOT present in water. Analog—The readout of an instrument by a pointer (or other indicating means) against a dial or scale. Animal studies—Investigations using animals as surrogates for humans, on the expectation that results in animals are pertinent to humans. Annexation—The inclusion of land within a government agency's jurisdiction. Annual overdraft—The quantity by which the production of water from the groundwater supplies during the water year exceeds the natural replenishment of such groundwater supplies during the same water year. Annular space—A ring-shaped space located between two circular objects, such as two pipes. Appropriative—Water rights to or ownership of a water supply, which is acquired for the beneficial use of water by following a specific legal procedure. Appurtenance—Machinery, appliances, structures and other parts of the main structure necessary to allow it to operate as intended, but not considered part of the main structure. Aquatic—Plants of animal life living in, growing in, or adapted to water. Aqueous—Something made up of, similar to, or containing water; watery. Aqueduct—A structure for transporting water form one place to another by means of a pipeline, canal, conduit, tunnel or a combination of these things. Aquifer—A natural underground layer of porous, water-bearing materials (sand, gravel) usually capable of yielding a large amount or supply of water. Arlington Desalter—The existing Arlington Desalter facility, operating since 1990, extracts and treats impaired groundwater from the Arlington basin in the southwestern area of the City of Riverside. The Desalter, using Reverse Osmosis (RO) technology, produces up to six (6) million gallons per day (MGD) of blended desalinized water, with another estimated one (1) MGD of concentrated brine (high salinity water) generated by the plant discharged to the Santa Ana Regional Interceptor (SARI) line. The blended desalinized water, which is non-potable, is currently discharged to the Arlington Channel, and ultimately to the Santa Ana River for recharge use by Orange County Water District (OCWD). Arsenic—A naturally occurring element in the environment. Arsenic in drinking water commonly comes from natural sources in the ground, but some can come from industrial pollution. At high concentrations it can cause cancer. Artesian—An aquifer in which the water is under sufficient pressure to cause it to rise above the bottom of the overlying confining bed, if opportunity to do so should be provided. Artificial recharge—The addition of surface water to a groundwater reservoir by human activity, such as putting surface water into recharge basins. (See also: groundwater recharge and recharge basin.) ASCE—American Society of Civil Engineers Aseptic—Free from the living germs of disease, fermentation or putrefaction. Sterile. Asymmetric—Not similar in size, shape, form or arrangement of parts on opposite sides of a line, point or plane. Atom—The smallest unit of a chemical element; composed of protons, neutrons and electrons. Available chlorine—A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials that are used as a source of chlorine when compared with that of elemental (liquid or gaseous) chlorine. Available expansion--The vertical distance from the sand surface to the underside of a trough in a sand filter. This distance is also called freeboard. BBack pressure—A pressure that can cause water to backflow into the water supply when a user's water system is at a higher pressure than the public water system. Backflow—A reverse flow condition, created by a difference in water pressures, which causes water to flow back into the distribution pipes of a potable water supply from any source or sources other than an intended source. Also see backsiphonage and cross-connection. Background level—In toxic substances monitoring, the average presence of a substance in the environment, originally referring to naturally occurring phenomena. Backsiphonage—A form of backflow caused by a negative or below atmospheric pressure within a water system. Also see backflow and cross-connection. Backwashing—The process of reversing the flow of water back through the filter media to remove the entrapped solids. Bacteria—Singular: bacterium. Microscopic living organisms usually consisting of a single cell. Bacteria can aid in pollution control by consuming or breaking down organic matter in sewage, or by similarly acting on oil spills or other water pollutants. Some bacteria in soil, water or air may also cause human, animal and plant health problems. Baffle—A flat board or plate, deflector, guide or similar device constructed or placed in flowing water or slurry systems to cause more uniform flow velocities, to absorb energy, and to divert, guide, or agitate liquids (water, chemical solutions, slurry). Bailer—A 10- to 20-foot-long pipe equipped with a valve at the lower end. A bailer is used to remove slurry from the bottom or the side of a well as it is being drilled. Base flow—River surface flow, not counting storm flow and/or purchased imported water. Base flow of streams—Water slowly percolates underground and then spread laterally until it reaches the surface (not pumped up) becoming part of the natural flow in rivers and streams, its base flow. This seeping ground water is what maintains the flow in a river due to the return flow of groundwater. BAT- Best Available Technology Batch process—A treatment process in which a tank or reactor is filled, the water is treated or a chemical solution is prepared, and the tank is emptied. The tank may then be filled and the process repeated. Beneficial uses—historical, existing or potential uses of a body of water. The Regional Water Quality Control Boards designate uses for individual bodies of water, with the intent of preserving or restoring those uses. There are 24 beneficial uses designations in California, including wildlife habitat, industrial processes, agricultural supply, and ground water recharge. Best available technology (BAT)—The best technology treatment techniques, or other means which the Administrator finds, after examination for efficacy under field conditions and not solely under laboratory conditions, are available (taking cost into consideration). For the purposes of setting MCLs for synthetic organic chemicals, any BAT must be at least as effective as granular activated carbon. . Bioaccumulation—The retention and concentration of a substance by an organism. Bioassay—Test which determines the effect of a chemical on a living organism. Biochemical oxygen demand (BOD)—The amount of oxygen consumed by microorganisms (mainly bacteria) and by chemical reactions in the biodegradation of organic matter. Bioconcentration—The accumulation of a chemical in tissues of an organism (such as fish) to levels that are greater than the level in the medium (such as water) in which the organism resides (see bioaccumulation). Biocontrol agents—Organisms that are released into an ecosystem for the purpose of reducing the abundance of, or climinating, a pest species. They often are imported from the pest organism’s geographic region of origin. Often biocontrol agents are insects. Biodegradation—Decomposition of a substance into more elementary compounds by the action of microorganisms such as bacteria. Biodiversity- See Diversity. Biofouling—The formation of bacterial film (biofilm) on fragile reverse osmosis membrane surfaces. Biological growth—The activity and growth of any and all living organisms. Bioremediation—A process of adding nutrient to ground water to speed up the natural process in which bacteria break down gasoline or other contaminants into harmless compounds. Biosolids—Is a primarily organic, accumulated solids separated from wastewater, that has been stabilized by treatment and that can be beneficially used. Class A biosolids products cannot have more than 1,000 fecal coliforms/gm (dry weight) and undetectable enterovirus and viable helminth. Class A materials have few restrictions on their use. Class B biosolids products must only be below 1,000,000 fecal coliforms/gm (dry weight). The uses of Class B biosolids products are somewhat more restricted Biotic—Living; usually applied to the biological aspects of an organism’s environment. Biotransformation—Conversion of a substance into other compounds by organisms; includes biodegradation.
Blank—A bottle containing only dilution water or distilled water; the sample being tested is not added. Tests are frequently run on a SAMPLE and a BLANK and the differences are compared.
BMPs—Best management practices. BOR—U.S. Bureau of Reclamation Brackish—A mixture of freshwater and saltwater. Breakpoint chlorination—Addition of chlorine to water until the chlorine demand has been satisfied. At this point, further additions of chlorine will result in a free residual chlorine that is directly proportional to the amount of chlorine added beyond the breakpoint. Brown Act—Ralph M. Brown Act enacted by the State legislature governing all meetings of legislative bodies. Also know as the Open Meeting requirements. Browse. Leaves, twigs, and young shoots of trees or shrubs that animals feed on. Feeding on the leaves, twigs and young shoots of trees or shrubs. That is, woody plants as forage. This use is as opposed to graze, used in this report to refer to leaves and stems of non-woody plants (grasses & forbs) that animals feed on, or feeding on non-woody plants. Buffer capacity—A measure of the capacity of a solution or liquid to neutralize acids or bases. This is a measure of the capacity of water for offering a resistance to changes in pH. Buffer strips—Strips of grass or other close-growing vegetation that separate a waterway (ditch, stream, creek) from an intensive land use area (subdivision, farm); also referred to as filter strips, vegetated filter strips, and grassed buffers. C
Calcium carbonate equivalent—An expression of the concentration of specified constituents in water in terms of their equivalent value to calcium carbonate. For example, the hardness in water which is caused by calcium, magnesium and other ions is usually described as calcium carbonate equivalent.
Calibration—A procedure which checks or adjusts an instrument's accuracy by comparison with a standard or reference.
California Plan—Officially "California’s draft Colorado River Water Use Plan," also sometimes called the "4.4 Plan." A planning document designed to reduce California’s reliance on surplus Colorado River water through conservation, water transfers, and conjunctive use measures.
Cancer—A disease characterized by the rapid and uncontrolled growth of aberrant cells into malignant tumors.
Capillary action—The movement of water through very small spaces due to molecular forces.
Capillary forces—The molecular forces which cause the movement of water through very small spaces.
Capillary fringe—The porous material just above the water table which may hold water by capillarity (a property of surface tension that draws water upwards) in the smaller void spaces.
Capital costs—Costs (usually long-term debt) of financing construction and equipment. Capital costs are usually fixed, one-time expenses which are independent of the amount of water produced.
Carcinogen—Any substance which tends to produce cancer in an organism.
Carcinogenic—Cancer-producing. Carrying capacity—The maximum number of a given species of animal that a habitat can support without damage to soil and vegetation resources. CAS registration number—A number assigned by the Chemical Abstracts Service to identify a chemical. Catchment planter—A planting bed that has been specially designed to hold and absorb storm flows from adjacent area, usually from parking lots. CBWCD—Chino Basin Water Conservation District CBWM—Chino Basin Watermaster CDA—Chino Basin Desalter Authority CEP—Corona Energy Partners CEQA—California Environmental Quality Act, which requires an assessment of the possible environmental impacts of public projects in the state of California.
Check valve—A special valve with a hinged disc or flap that opens in the direction of normal flow and is forced shut when flows attempt to go in the reverse or opposite direction of normal flow.
Chemical oxygen demand (COD)—An indirect measure of the amount of oxygen used by inorganic and organic matter in water. The measure is a laboratory test based on a chemical oxidant and therefore does not necessarily correlate with biochemical oxygen demand. Chloramines—Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia. Chlorination—The application of chlorine to water, generally for the purpose of disinfection, but frequently for accomplishing other biological or chemical results (aiding coagulation and controlling tastes and odors).
Chlorinator—A metering device which is used to add chlorine to water.
Chlorine-contact chamber—That part of a water treatment plant where effluent is disinfected by chlorine.
Chlorine requirement—The amount of chlorine which is needed for a particular purpose. Some reasons for adding chlorine are reducing the number of coliform bacteria (Most Probable Number), obtaining a particular chlorine residual, or oxidizing some substance in the water. In each case a definite dosage of chlorine will be necessary. This dosage is the chlorine requirement.
Chromium—A naturally occurring element found in air, soil, water and food.
Chronic exposure—Long-term, low-level exposure to a toxic chemical.
Chino Basin TMDL—The RWQCB has requested SAWPA’s assistance in serving as a neutral facilitator for the TMDL development process for Chino Creek, the Santa Ana River Reach 3, and Prado Park Lake. Activities include administering all monitoring and review meetings, taking minutes, conducting meetings, building consensus, and encouraging involvement of all interested stakeholders in the TMDL development process. Full staffing costs are covered by the RWQCB and no SAWPA member district contributions are required.
Circle of influence—The circular outer edge of a depression produced in the water table by the pumping of water from a well. Also see cone of influence and cone of depression.
Cistern—A small tank (usually covered) or a storage facility used to store water for a home or farm. Often used to store rain water. CIW—California Institute for Women Clarifer—A large circular or rectangular tank or basin in which water is held for a period of time, during which the heavier suspended solids settle to the bottom. Clarifiers are also called settling basins and sedimentation basins.
Class (pipe and fittings)—The working pressure rating of a specific pipe for use in water distribution systems which includes allowances for surges. This term is used for cast iron, ductile iron, asbestos cement and some plastic pipe. Class A Biosolids—Products that cannot have more than 1,000 fecal coliforms/gm (dry weight) and undetectable enterovirus and viable helminth. Class A materials have few restrictions on their use. Class B biosolids—Are products that must only be below 1,000,000 fecal coliforms/gm (dry weight). The uses of Class B biosolids products are somewhat more restricted Clay—One type of soil particle with a diameter of approximately one ten-thousandth of an inch.
Clay soil—A soil containing more than 40 percent clay, but less than 45 percent sand, and less than 40 percent silt.
Clear well—A reservoir for the storage of filtered water of sufficient capacity to prevent the need to vary the filtration rate with variations in demand. Also used to provide chlorine contact time for disinfection.
Clinical studies—Studies of humans suffering from symptoms induced by chemical exposure.
Closed basin—A groundwater basin whose topography and geology prevent subsurface outflow of water. CMP—California Milk Producers Coagulants—Chemicals that cause very fine particles to clump together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.
Coagulation—The clumping together of very fine particles into larger particles caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles and cause destabilization of the particles. This clumping together makes it easier to separate the solids from the water by settling, skimming, draining, or filtering.
Cohesion—Molecular attraction that holds two particles together.
Coliform—A group of bacteria found in the intestines of warm-blooded animals (including humans) also in plants, soil, air and water. Fecal coliforms are a specific class of bacteria, which only inhibit the intestines of warm-blooded animals. The presence of coliform is an indication that the water is polluted and may contain pathogenic organisms.
Coliform organism—Microorganisms found in the intestinal tract of humans and animals. Their presence in water indicates fecal pollution and potentially dangerous bacterial contamination by disease-causing microorganisms.
Colloids—Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in water have a negative electrical charge, they tend to repel each other. This repulsion prevents the particles from clumping together, becoming heavier, and settling out. Colonization potential—Likelihood that birds will emigrate to other sites. Combined available residual chlorine—The concentration of residual chlorine which is combined with ammonia (NH3) and/or organic nitrogen in water as a chloramine (or other chloro derivative) yet is still available to oxidize organic matter and utilize its bactericidal properties.
Combined sewer—A sewer that transports surface runoff and human domestic wastes (sewage), and sometimes industrial wastes. Wastewater and runoff in a combined sewer may occur in excess of the sewer capacity and cannot be treated immediately. The excess is frequently discharged directly to a receiving stream without treatment, or to a holding basin for subsequent treatment and disposal.
Community water system (C.W.S.)—A public water system which serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. Also see non-community water system, transient water system and non-transient non-community water system.
Complete treatment—A method of treating water which consists of the addition of coagulant chemicals, flash mixing, coagulation - flocculation, sedimentation and filtration. Also called conventional filtration.
Composite samples—A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a 24-hour time span. Each individual sample is combined with the others in proportion to the rate of flow when the sample was collected The resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the sampling period. Compost—Decaying vegetation. Can be used as ground cover or mulch, and as fertilizer. Composting—A controlled microbial degradation of organic waste yield an environmentally sound, nuisance-free product of potential value as a soil conditioner.
Compound—A substance composed of two or more elements whose composition is constant. For example, table salt (sodium chloride - NACl) is a compound.
Concentration polarization—1) The ratio of the salt concentration in the membrane boundary layer to the salt concentration in the bulk stream. The most common and serious problem resulting from concentration polarization is the increasing tendency for precipitation of sparingly soluble salts and the deposition of particulate matter on the membrane surface. 2) Used in corrosion studies to indicate a depletion of ions near an electrode. 3) The basis for chemical analysis by a polarograph.
Conductance—A rapid method of estimating the dissolved-solids content of a water supply. The measurement indicates the capacity of a sample of water to carry an electrical current, which is related to the concentration of ionized substances in the water. Also called specific conductance.
Conductivity—A measure of the ability of a solution (water) to carry an electric current.
Conductor—A substance, body, device or wire that readily conducts or carries electrical current.
Cone of depression—The depression, roughly conical in shape, produced in the water table by the pumping of water from a well. Also see circle of influence and cone of influence.
Cone of influence—The depression, roughly conical in shape, produced in the water table by the pumping of water from a well. Also see circle of influence and cone of depression.
Confined aquifer—An aquifer in which ground water is confined under pressure which is significantly greater than atmospheric pressure. See artesian aquifer.
Conjunctive Use—Storing imported water in a local aquifer, in conjunction with groundwater, for later retrieval and use.
Consumptive use—Water removed from available supplies without direct return to a water resource system for uses such as manufacturing, agriculture, and food preparation.
Contaminant—Any physical, chemical, biological, or radiological substance or matter that has an adverse effect on air, water, or soil.
Contamination—The introduction into water of microorganisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the water unfit for its next intended use.
Contour farming—A conservation-based method of farming in which all farming operations (for example, tillage and planting) are performed across (rather than up and down) the slope. Ideally, each crop row is planted at right angles to the ground slope.
Contour strip farming—A kind of contour farming in which row crops are planted in strips, between alternating strips of close-growing, erosion resistant forage (grass, grain, hay) crops. Controlled burns or prescribed burns—Fires set by humans within a delimited area under a discrete set of environmental and staffing conditions to achieve certain management goals such as ecosystem restoration, forage production, or wildfire prevention. Conventional filtration—A method of treating water to remove particulates. The method consists of the addition of coagulant chemicals, flash mixing, coagulation-flocculation, sedimentation and filtration. Also called complete treatment; also see direct filtration and in-line filtration.
Conventional filtration treatment—A series of processes including coagulation, flocculation, sedimentation, and filtration resulting in substantial particulate removal.
Conventional tillage—The traditional method of farming in which soil is prepared for planting by completely inverting it with a moldboard plow. Subsequent working of the soil with other implements is usually performed to smooth the soil surface. Bare soil is exposed to the weather for some varying length of time depending on soil and climatic conditions.
Conventional treatment—See conventional filtration also called complete treament.
Conveyance loss—Water lost in conveyance (pipe, channel, conduit, ditch) by leakage or evaporation.
Corrosion—The gradual decomposition or destruction of a material by chemical action, often due to an electrochemical reaction. Corrosion may be caused by: 1) stray current electrolysis, 2) galvanic corrosion caused by dissimilar metals, or 3) differential concentration cells. Corrosion starts at the surface of a material and moves inward.
Corrosivity—An indication of the corrosiveness of a water. The corrosiveness of a water is described by the water's pH, alkalinity, hardness, temperature, total dissolved solids, dissolved oxygen concentration, and the Langelier Index.
Cost/beneflt analysis—A quantitative evaluation of the costs which would be incurred versus the overall benefits to society of a proposed action such as the establishment of an acceptable dose of a toxic chemical.
Cost sharing—A publicly financed program through which society, as the beneficiary of environment protection, shares part of the cost of pollution control with those who must actually install the controls.
Cover crop—A crop that provides temporary protection for delicate seedlings and/or provides a canopy for seasonal soil protection and improvement between normal crop production periods. Except in orchards where permanent vegetative cover is maintained, cover crops usually are grown for one year of less. When plowed under and incorporated into the soil, cover crops are also referred to as gren manure crops. CRA—Colorado River Aqueduct, built 1933-1941 and owned and operated by the Metropolitan Water District of Southern California. CRC—California Rehabilitation Center Critical habitat—A specific geographic area (occupied or not occupied by the species) that is essential for the conservation of a threatened or endangered species and that may require special management and protection. Crop rotation—A system of farming in which a regular succession of different crops are planted on the same land area, as opposed to growing the same crop time after time (monoculture).
Cross connection—Any actual or potential connection between a drinking (potable) water system and an unapproved water supply or other source of contamination. For example, if you have a pump moving non-potable water and hook into the g water system to supply water for the pump seal, a cross-connection or mixing between the two water systems can occur. This mixing may lead to contamination of the drinking water. Also see backsiphonage and backflow. CRWQCB—California Regional Water Quality Control Board. The Santa Ana wastershed is in Region 8 of the CRWQCB. Cubic foot—A frequent water industry term of measurement, as in cubic feet per second. One cubic foot (cf) equals 7.48 gallons. A cubic foot per second is 450 gallons per minute. cfs—Cubic feet per second Cumulative exposure—The summation of exposures of an organism to a chemical over a period of time.
Curb stop—A water service shutoff valve located in a water service pipe near the curb and between the water main and the building. This valve is usually operated by a wrench or valve key and is used to start or stop flows in the water service line to a building. DDay tank—A tank used to store a chemical solution of known concentration for feed to a chemical feeder. A day tank usually stores sufficient chemical solution to properly treat the water being treated for at least one day. Also called an age tank. Dead end—The end of a water main which is not connected to other parts of the distribution system by means of a connecting loop of pipe Debris basin—Facility constructed to contain debris flows (water, rocks, mud, sediment vegetation and other debris) that occur during major storm events, particularly in area that have been subject to wildfires. Decant—To draw off the upper layer of liquid (water) after the heavier material (a solid or another liquid) has settled. Dechlorination—The deliberate removal of chlorine from water. The partial or complete reduction of residual chlorine by any chemical or physical process. Decomposition—The conversion of chemically unstable materials to more stable forms by chemical or biological action. If organic matter decays when there is no oxygen present (anaerobic conditions or putrefaction), undesirable tastes and odors are produced. Decay of organic matter when oxygen is present (aerobic conditions) tends to produce much less objectionable tastes and odors. Deep percolation—The percolation of surface water through the ground beyond the lower limit of the root zone of plants into a groundwater aquifer. Defluoridation—The removal of excess fluoride in drinking water to prevent the mottling (brown stains) of teeth. Degasification—A water treatment process which removes dissolved gases from the water. The gases may be removed by either mechanical or chemical treatment methods or a combination of both. Degradation—Chemical or biological breakdown of a complex compound into simpler compounds. Degraded water—Water within the groundwater basin that, in one characteristic or another, does not meet primary drinking water standards. Demineralization—A treatment process which removes dissolved minerals (salts) from water. Demographic analysis—Identifies the life history aspect or parameter (fecundity, juvenile survival, adult survival) that has the greatest effect on population growth. Demography—The science of the interrelated life history factors that determine how populations grow, shrink, or change in other ways. Denitrification—The biochemical conversion of nitrate; and nitrite nitrogen in the soil dissolved in water to gaseous nitrogen. Density—A measure of how heavy a substance (solid, liquid or gas) is for its size. Density is expressed in terms of weight per unit volume, that is, grams per cubic centimeter or pounds per cubic foot. The density of water is 1.0 gram per cubic centimeter or about 62.4 pounds per cubic foot. Desalinization—The removal of dissolved salts (such as sodium chloride, NACI) from water by natural means (leaching) or by specific water treatment processes. Desalting (or desalination)—Specific treatment processes, such as reverse osmosis or multi-stage flash distillation, to demineralize seawater or brackish (saline) waters for reuse. Also sometimes used in wastewater treatment to remove salts other pollutants. Desiccant—A drying agent which is capable of removing or absorbing moisture from the atmosphere in a small enclosure. Desiccation—A process used to thoroughly dry air; to remove virtually all moisture from air. Desiccator—A closed container into which heated weighing or drying dishes are placed to coot in a dry environment. The dishes may be empty or they may contain a sample. Desiccators contain a substance, such as anhydrous calcium chloride, which absorbs moisture and keeps the relative humidity near zero so that the dish or sample will not gain weight from absorbed moisture. Design storm—The size of a storm, defined by duration, intensity, and amount of precipitation, that storm drain systems are designed to accommodate. As development paves over the land, increasing the volume of runoff, the design capacity of built storm drains can become inadequate. Desilting—The physical process of removing suspended particles from water. Destratification—The development of vertical mixing within a lake or reservoir to eliminate (either totally or partially) separate layers of temperature, plant, or animal life. This vertical mixing can be caused by mechanical means (pumps) or through the use of forced air diffusers, which release air into the lower layers of the reservoir. Detention basin—Temporary storage to reduce the peak flow, but not the total volume of storm water during a storm. Deterministic model—Model in which the life history aspects or parameter (fecundity, juvenile survival, adult survival) remain constant over time. Dew point—The temperature to which air with a given quantity of water vapor must be cooled to cause condensation of the vapor in the air. Dewater—1) To remove or separate a portion of the water present in a sludge or slurry. To dry sludge so it can be handled and disposed. 2) To remove or drain the water from a tank or a trench. DHS—California Department of Health Services Diffusion—The movement of suspended or dissolved particles from a more concentrated to a less concentrated region as a result of the random movement of individual particles; the process tends to distribute them uniformly throughout the available volume. Dilute solution—A solution that has been made weaker usually by the addition of water. Dimictic—Lakes and reservoirs which freeze over and normally go through two stratification and two mixing cycles within a year. Disinfection—Water treatment that destroys potentially harmful bacteria. Direct filtration—A filtration method of treating water which consists of the addition of coagulant chemicals, flash mixing, coagulation, minimal flocculation, and filtration. The flocculation facilities may be omitted, but the physical chemical reactions will occur to some extent. The sedimentation process is omitted. Also see conventional filtration and in-line filtration. Direct runoff—Water that flows over the ground surface or through the ground directly into streams, rivers, or lakes. Discharge head—The pressure (in pounds per square inch or psi) measured at the centerline of a pump discharge and very close to the discharge flange, converted into feet. Disinfectant—Any oxidant, including but not limited to chlorine, chlorine dioxide, chloramines, and ozone, that is added to water in any part of the treatment or distribution process and is intended to kill or inactivate pathogenic microorganisms. Disinfection—The process designed to kill most microorganisms in water, including essentially all pathogenic (disease causing) bacteria. There are several ways to disinfect, with chlorine being most frequently used in water treatment. Compare with sterilization. Disinfection by-product—A compound formed by the reaction of a disinfectant such as chlorine with organic material in the water supply. Dissolved oxygen (DO)—Measure of water quality indicating free oxygen dissolved in water. Distillate—In the distillation of a sample, a portion is evaporated; the part that is condensed afterwards is the distillate. Disturbance—Any discrete event, usually of short duration and great intensity, that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment. Diversion—1) Use of part of a stream flow as a water supply. 2) A structural conveyance (or ditch) constructed across a slope to intercept runoff flowing down a hillside, and divert it to some convenient discharge point. Diversity or biodiversity—The total variety of life and its processes. Includes the variety represented by all species, or population structure and changes resources, substrate availability, or the physical environment. Domestic or Other Non-distribution System Plumbing Problem—A coliform contamination problem in a public water system with more than one service connection that is limited to the specific service connection from which the coliform positive sample was taken. Downgradients—The direction that ground water flows; similar in concept to: downstream for surface water, such as a river. Draft—1) The act of drawing or removing water from a tank or reservoir. 2) The water which is drawn or removed from a tank or reservoir. Drainage—A technique to improve the productivity of some agricultural land by removing excess water from the soil; surface drainage is accomplished with open ditches; subsurface drainage uses porous conduits (drain tile) buried beneath the soil surface. Drainage basin—The area of land that drains water, sediment, and dissolved materials to a common outlet at some point along a stream channel. Also see watershed. Drainage flow defector—A ridge and/or a depression in a flat paved surface for the purpose of redirecting sheet flow in a channel, thus changing the destination of storm water. Drawdown—1) The drop in the water table or level of water in the ground when water is being pumped from a well. 2) The amount of water used from a tank or reservoir. 3) The drop in the water level of a tank or reservoir. Drinking Water Equivalent Level- See DWEL. Dry flow—The continuous flow in a storm drain system that occurs even during extended periods without rain. Dry well—A constructed well designed to receive water for groundwater recharge. DWEL (Drinking Water Equivalent Level)—Estimated exposure (in mg/L) which is interpreted to be protective for non carcinogenic endpoints of toxicity over a lifetime of exposure. DWEL was developed for chemicals that have a significant carcinogenic potential (Group B). Provides risk manager with evaluation on non-cancer endpoints, but infers that carcinogenicity should be considered the toxic effect of greatest concern. DWR—California Department of Water Resources. Dynamic pressure—When a pump is operating, the vertical distance (in feet) from a reference point (such as a pump centerline) to the hydraulic grade line is the dynamic head. EEA—Environmental Assessment Ecosystem functions—Processes that control the products and rates of change of the ecosystem (e.g. soil erosion, water discharge, succession) or that are intrinsic to the perpetuation of the ecosystem (such as cycling of nutrients or balanced rates of soil production and erosion). Effective size (E.S.)—The diameter of the particles in a granular sample (filter media) for which 10 percent of the total grains are smaller and 90 percent larger on a weight basis. Effective size is obtained by passing granular material through sieves with varying dimensions of mesh and weighing the material retained by each sieve. The effective size is also approximately the average size of the grains.
Effluent—Water or some other liquid-raw, partially or completely treated-flowing from a reservoir, basin, treatment process or treatment plant. EIR—Environmental impact report; a study and report on the possible effects of a proposed project, and what can be done to avoid or mitigate them. See CEQA. EIS—Environmental Impact Statement. See NEPA. Ejector. A device used to disperse a chemical solution into water being treated.
Element—A substance which cannot be separated into its constituent parts and still retain its chemical identity. For example, sodium (Na) is an element. EMWD—Eastern Municipal Water District Endangerment assessment—A site-specific risk assessment of the actual or potential danger to human health or welfare and the environment from the release of hazardous substances or waste. The endangerment assessment document is prepared in support of enforcement actions under CERCLA or RCRA.
Endemic—Something peculiar to a particular people or locality, such as a disease which is always present in the population.
Enteric—Of intestinal origin, especially applied to wastes or bacteria.
Entrain—To trap bubbles in water either mechanically through turbulence or chemically through a reaction.
Enzymes—Organic substances (produced by living organisms) which cause or speed up chemical reactions. Organic catalysts and/or biochemical catalysts.
EPA—United States Environmental Protection Agency.
Epidemic—Widespread outbreak of a disease, or a large number of cases of a disease in a single community or relatively small area. Disease may spread from person to person, and/or by the exposure of many persons to a single source, such as a water supply.
Epidemiologic study—Study of human populations to identify causes of disease. Such studies often compare the health status of a group of persons who have been exposed to a suspect agent with that of a comparable non-exposed group.
Epidemiology—A branch of medicine which studies epidemics (diseases which affect significant numbers of people during the same time period in the same locality). The objective of epidemiology is to determine the factors that cause epidemic diseases and how to prevent them.
Epilimnion—The upper layer of water in a thermally stratified lake or reservoir. This layer consists of the warmest water and has a fairly uniform (constant) temperature. The layer is readily mixed by wind action.
Erosion—Wearing away of soil by timing water, wind, or ice; erosion is the process by which the earth's surface is shaped and occurs even in remote, uninhabited areas at a slow rate (geologic erosion); of more concern is accelerated erosion caused by people's activities.
Eutrophic—Reservoirs and lakes which are rich in nutrients and very productive in terms of aquatic animal and plant life.
Eutrophication—The increase in the nutrient levels of a lake or other body of water; this usually causes an increase in the growth of aquatic animal and plant life.
Evaporation—The process by which water or other liquid becomes a gas (water vapor or ammonia vapor). Water from land areas, bodies of water, and all other moist surfaces is absorbed into the atmosphere as a vapor.
Evapotranspiration—The combined processes of evaporation and transpiration. It can be defined as the sum of water used by vegetation and water lost by evaporation. EVMWD—Elsinore Valley Municipal Water District Exemption—A State with primacy may relieve a public water system from a requirement respecting an MCL, treatment technique or both, by granting an exemption if certain conditions exist. These are: 1) the system cannot comply with a MCL or treatment technique due to compelling factors which may include economic factors; 2) the system was in operation on the effective date of the MCL or treatment technique requirement; and 3) the exemption will not result in an unreasonable public health risk. Also see variance. Exotic species—A non-native species introduced into a new ecosystem as a result of human intervention. If that species establishes self-sustaining population, it is then considered a naturalized exotic. FFacultative—Facultative bacteria can use either molecular (dissolved) oxygen or oxygen obtained from food material such as sulfate or nitrate ions. In other words, facultative bacteria can live under aerobic or anaerobic conditions. Fallowing—A program to generate water by paying farmers to fallow land, i.e., not grow crops. The water not used for irrigation is then transferred to urban areas or stored for future use. Fecal coliform bacteria—Bacteria found in the intestinal tracts of animals. Their presence in water or sludge is an indicator of pollution and possible contamination by pathogens. Fecundity—Number of young fledged per female. Fed-X—Federal Express Feedback—The circulating action between a sensor measuring a process variable and the controller which controls or adjusts the process variable . Filter medium—Any item or substance that is used for filtering impurities. Soil, sand, and mulch are used as a filter media. Filtration—A process for removing particulate matter from water by passage through porous media.
Finished water—Water that has passed through a water treatment plant; all the treatment processes are completed or "finished". This water is ready to be delivered to consumers. Also called product water. Fire regime—The spatial and temporal patterns of a fire within a given biotic community type, including intensity (temperature or amount of combustible fuels consumed), duration (burn time), size (amount of land area burned) and distribution (patchiness), timing (season of occurrence), and frequency (number of years elapsed between fires). First draw—The water that immediately comes out when a tap is first opened. This water is likely to have the highest level of lead contamination from plumbing materials.
First draw sample—A one-liter sample of tap water, collected in accordance with CFR Section 141.86(b)(2), that has been standing in plumbing pipes at least 6 hours and is collected without flushing the tap. First-flush rain—In the Los Angeles area, many months can pass between one rainstorm and the next. During this time, pollution and grime build up on all of the city’s outdoor surfaces, and in particular, on its streets. When the next rainstorm finally comes, it washes the accumulated grime and pollution off of the streets and into the underground storm drain system. This is the “first flush rain.” As you might expect, it carries a very large amount of suspended and dissolved pollutants. Fix, sample—A sample is fixed in the field by adding chemicals that prevent the water quality indicators of interest in the sample from changing before final measurements are performed later in the lab.
Flagellates—Microorganisms that move by the action of tail-like projections.
Floc—Clumps of bacteria and particulate impurities that have come together and formed a cluster. Found in flocculation tanks and settling or sedimentation basins.
Flocculation—The gathering together of fine particles in water by gentle mixing after the addition of coagulant chemicals to form larger particles. Flood regime—The magnitude, timing, duration, and frequency of flooding that are characteristic of streams in a particular ecoregion. Floodplain—The flat or nearly flat land on the floor of a steam valley or tidal area that is covered by water during floods. Flow regime—The magnitude, timing, duration, and frequency of surface flows (including low flows and flood flows) that are characteristic of a particular stream type in a particular ecoregion. Fluidized—A mass of solid particles that is made to flow like a liquid by injection of water or gas is said to have been fluidized. In water treatment, a bed of filter media is fluidized by backwashing water through the filter.
Fluoridation—The addition of a chemical to increase the concentration of fluoride ions in drinking water to a predetermined optimum limit to reduce the incidence (number) of dental caries (tooth decay) in children. Defluoridation is the removal of excess fluoride in drinking water to prevent the mottling (brown stains) of teeth.
Fluorosis—An abnormal condition caused by excessive intake of fluorine, characterized chiefly by mottling of the teeth.
Flush—I) To open a cold-water tap to clear out all the water which may have been sitting for a long time in the pipes. M new homes, to flush a system means to send large volumes of water gushing through the unused pipes to remove loose particles of solder and flux. 2) To force large amounts of water through liquid to clean out piping or tubing. storage or process tanks.
Flushing—A method used to clean water distribution lines. Hydrants are opened and water with a high velocity flows through the pipes, removes deposits from the pipes, and flows out the hydrants. Fluvial—Pertaining to or formed by a river. Fluvial geomorphology—River processes and forms related to earth materials and surfaces, particularly the sediment that is eroded, transported, and deposited by channel flow in streams and rivers. Flux—A flowing or flow.
Foot valve—A special type of check valve located at the bottom end of the suction pipe on a pump. This valve opens when the pump operates to allow water to enter the suction pipe but closes when the pump shuts off to prevent water from flowing out of the suction pipe. Forebay—A portion of a groundwater basin where large quantities of surface water can recharge the basin through infiltration; also a reservoir or pond situated at the intake of a pumping plant or power plant to stabilize water level. Formation—A group of similar consolidation (that is, relatively solid) rocks of unconsolidated (that is, relatively loose) minerals.
Free available residual chlorine—That portion of the total available residual chlorine composed of dissolved chlorine gas cl2), hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-) remaining in water after chlorination. This does not include chlorine that has combined with ammonia, nitrogen, or other compounds.
Free residual chlorination—The application of chlorine to water to produce a free available chlorine residual equal to at least 80 percent of the total residual chlorine (sum of free and combined available chlorine residual).
Freeboard—1) The vertical distance from the normal water surface to the top of the confining wall. 2) The vertical distance from the sand surface to the underside of a trough in a sand filter. This distance is also called available expansion.
Friction losses—The head, pressure or energy (they are the same) lost by water flowing in a pipe or channel as a result of turbulence caused by the velocity of the flowing water and the roughness of the pipe. channel walls, and restrictions caused by fittings. Water flowing in a pipe loses pressure or energy as a result of friction losses. Also see head loss. Fresh water—Water that generally contains less than 1,000 milligrams-per-liter of dissolved solids Fuel load—Amount of flammable plant biomass in an area. Fungi—Mushrooms, molds, mildews, rusts, and smuts that are small non-chlorophyll-bearing plants lacking roots, stems and leaves. They occur in natural waters and grow best in the absence of light. Their decomposition may cause objectionable tastes and odors in water. GGage pressure—The pressure within a closed container or pipe as measured with a gage. In contrast, absolute pressure is the sum of atmospheric pressure (14.7 lbs/sq in) PLUS pressure within a vessel (as measured by a gage). Most pressure gages read in gage pressure or psig (pounds per square inch gage pressure). Gastroenteritis—An inflammation of the stomach and intestine resulting in diarrhea, with vomiting and cramps when irritation is excessive. When caused by an infectious agent, it is often associated with fever.
Gauge, pipe—A number that defines the thickness of the sheet used to make steel pipe. The larger the number, the thinner the pipe wall. GCCC—Golden Cheese Company of California Geological log—A detailed description of all underground features discovered during the drilling of a well (depth, thickness and type of formations).
Geophysical log- A record of the structure and composition of the earth encountered when drilling a well or similar type of test hole or boring. This log is based on the use of electrical, electromagnetic, or some other geophysical equipment to measure the properties of the structure and composition of the sediments, rock, etc. Geomorphology—The study of the physical features of the Earth’s surface and their relationship to its geological structures. Germicide-A substance formulated to kill germs or microorganisms. The germicidal properties of chlorine make it an effective disinfectant.
Giardia lamblia—Flagellate protozoan which is shed during its cyst stage into the feces of man and animals. When water containing these cysts is ingested, the protozoan causes a severe gastrointestinal disease called giardiasis.
Giardiasis—Intestinal disease caused by an infestation of Giardia flagellates. Grass filter strips—A grassy edge or swale that filters storm water in the root layer before percolating the water into the soil below or discharging the water overland. Glass, pipe and fittings—The working pressure rating of a specific pipe for use in water distribution systems which includes allowances for surges. This term is used for cast iron, ductile iron, asbestos cement and some plastic pipe. GM—General Manager Gooseneck—A portion of a service connection between the distribution system water main and a meter. Sometimes called a pigtail.
Grab sample—A single sample collected at a particular time and place which represents the composition of the water only at that time and place.
Grade—1) The elevation of the invert of the bottom of a pipeline. canal, culvert or similar conduit. 2) The inclination or slope of a pipeline, conduit, stream channel, or natural ground surface; usually expressed in terms of the ratio or percentage of number of units of vertical rise or fall per unit of horizontal distance. A 0.5 percent grade would be a drop of one-half foot per hundred feet of pipe.
Gram—A unit of mass equivalent to one milliliter of water at 4 degrees Celsius. 1/454 of a pound.
Gravimetric—A means of measuring unknown concentrations of water quality indicators in a sample by WEIGHING a precipitate or residue of the sample.
Grey water—Wastewater other than sewage, such as sink drainage or washing machine discharge. GRGC—Green River Golf Course Ground water—The supply of fresh water found beneath the Earth's surface. usually in aquifers. which is often used for supplying wells and springs. Because ground water is a major source of drinking water there is growing concern over areas where leaching agricultural or industrial pollutants or substances from leaking underground storage tanks are contaminating ground water. Groundwater basin—A groundwater reservoir defined by all the overlying land surface and the underlying aquifers that contain water stored in the reservoir. Boundaries of successively deeper aquifers may differ and make it difficult to define the limits of the basin.
Groundwater overdraft—The condition of a groundwater basin in which the amount of water withdrawn by pumping exceeds the amount of water that recharges the basin over a period of years during which water supply conditions approximate average. Groundwater Recharge or Replenishment—Pumping or percolating storm water runoff or imported water into an aquifer to replenish its supplies. Groundwater table—The upper surface of the zone of saturation (all pores of subsoil filled with water), except where the surface if formed by an impermeable body. gpm—Gallons per minute Groundwater under the direct influence (UDI) of surface water—Any water beneath the surface of the ground with: 1) significant occurrence of Insects or other macroorganisms algae. or large-diameter pathogens such as Giardia lamblia or, 2) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Direct influence must be determined for individual sources in accordance with criteria established by the State. The State determination of direct influence may be based on site-specific measurements of water quality and/or documentation of well construction characteristics and geology with field evaluation. GWRS—Groundwater Replenishment System HHabitat—A place where a species normally lives, often described in terms of physical features (such as topography) and in a biological features (such as plant species composition). Habitat complexity—The extent to which an area provides habitat for multiple species, by providing a variety of physical features and biological associations. Half-life—The length of time required for the mass, concentration, or activity of a chemical or physical agent to be reduced by one-half. Halogen—One of the chemical elements chlorine, bromine, or iodine.
Hard water—Alkaline water containing dissolved salts that interfere with some industrial processes and prevent soap from lathering. Water may be considered hard if it has a hardness greater than the typical hardness of water from the region. Some textbooks define hard water as water with a hardness of more than 100 mgAL as calcium carbonate.
Hardness, water—A characteristic of water caused mainly by the salts of calcium and magnesium, such as bicarbonate, carbonate, sulfate, chloride and nitrate. Excessive hardness in water is undesirable because it causes the formation of soap curds, increased use of soap, deposition of scale in boilers, damage in some industrial processes, and sometimes causes objectionable tastes in drinking water.
Hazard evaluation—A component of risk assessment that involves gathering and evaluating data on the types of health injury or disease (e.g., cancer) that may be produced by a chemical and on the conditions of exposure under which injury or disease is produced.
Head—The vertical distance (in feet) equal to the pressure (in psi) at a specific point. The pressure head is equal to the pressure in psi times 2.31 ft/psi.
Head loss—The head, pressure or energy (they are the same) lost by water flowing in a pipe or channel as a result of turbulence caused by the velocity of the flowing water and the roughness of the pipe, channel walls or restrictions caused by fittings. Water flowing in a pipe loses head, pressure or energy as a result of friction losses. Also see friction losses.
Header—A large pipe to which a series of smaller pipes are connected. Also called a MANIFOLD.
Heat gain—Heat can slowly build up in an object over time. This is called heat gain. In a building, heat gain is most often the consequence of many hours of sunshine striking and warming the exterior walls and roof. Heat island effect—Many urban areas lack shade trees. In these areas the sun strikes pavement and rooftops, heating them to very high temperatures. These surfaces re-radiate heat back into the air, raising air temperatures by five or more degrees. Urban areas that contain dense tree canopy avoid the heat island effect because trees absorb virtually all of the sun’s energy without radiating heat back into the air. Heat sensor—A device that opens and closes a switch in response to changes in the temperature. This device might be a metal contact, or a thermocouple which generates a minute electrical current proportional to the difference in heat, or a variable resistor whose value changes in response to changes in temperature. Also called a TEMPERATURE SENSOR.
Heavy metals—Metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead. They can damage living things at low concentrations and tend to accumulate in the food chain.
Hectare—A measure of area in the metric system similar to an acre. One hectare is equal to 10,000 square meters and 2.4711 acres.
Hematopoiesis—The production of blood and blood cells; hemopoiesis. Herbaceous—A seed plant whose stem withers away to the ground after each season’s growth, as distinguished from woody plants – i.e., grasses and forbs. Herbicide—A compound, usually a man made organic chemical, used to kill or control plant growth. Herbivores—Animals that feed on plants. Hertz—The number of complete electromagnetic cycles or waves in one second of an electrical or electronic circuit. Also called the frequency of the current. Abbreviated Hz.
Heterotrophic microorganisms—Bacteria and other microorganisms that use organic matter synthesized by other organisms for energy and growth.
Heterotrophic plate count (HPC)—The number of colonies of heterotrophic bacteria grown on selected solid media at a given temperature and incubation period, usually expressed in number of bacteria per milliliter of sample. HGSD—Home Gardens Sanitary District High crowns—Virtually all roads and parking areas have some kind of crown, or high point, to insure that water flows off promptly. Usually this high point is a ridge along the center line of the road or parking bay. This ridge is ordinarily only a few inches higher than the edges. “High crown” suggest a condition where this crown is made artificially higher to allow the road or bay to hold more water than it otherwise could. High-line jumpers—Pipes or hoses connected to fire hydrants and laid on top of the ground to provide emergency water service for an isolated portion of a distribution system.
High-to-low-dose extrapolation—The process of prediction of low exposure risks to rodents from the measured high exposure-high risk data.
Histology—The study of the structure of cells and tissues; usually involves microscopic examination of tissue slices. Holding pond—A depression where rainwater is directed and held temporarily. Holding pinds function to slow the rate at which water is discharge from a site to the rate more typical of undeveloped natural sites. Hose bib—Faucet. A location in a water line where a hose is connected.
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