C-Horizon A layer of unconsolidated material, relatively little affected by the influence of organisms and presumed to be similar in chemical, physical, and mineralogical composition to the material from which at least a portion of the overlying Solum has developed.
Cabotage (1) (From the Spanish) A nautical term denoting navigation from cape to cape along the coast without having to go out into the open sea. (2) (International Law) Navigating and trading along the coast and between coastal ports; trade or transport in coastal waters or airspace or between two points within a country.
Caisson (1) A watertight structure within which construction work is carried on under water.  (2) A large box open at the top and one side, designed to fit against the side of a ship and used to repair damaged hulls under water.  (3) A floating structure used to close off the entrance to a dock or canal lock.  Also referred to as a Camel.
Calcareous Formed of calcium carbonate or magnesium carbonate by biological deposition or inorganic precipitation in sufficient quantities to effervesce carbon dioxide visibly when treated with cold 0.1 normal hydrochloric acid.  Calcareous sands are usually formed of a mixture of fragments of mollusk shell, echinoderm spines and skeletal material, coral, foraminifera, and algal platelets.
Calcareous Fens Peatlands formed in areas of groundwater discharge, where cold, anoxic, mineral-rich water provides a specialized habitat for disproportionately large numbers of rare and endangered plants.  Many of the plants found in calcareous fens are species which would be typical of more northern habitats.  The health of such fens is inextricably linked to the presence of the upwelling groundwater.  Also see Peat (Peatlands).
Calcic Horizon A secondary Calcium Carbonate accumulation in the lower B-Horizon that occurs as coatings on Clasts and as lenses in fine-grained sediment matrices; it is at least 15 centimeters (5.9 inches) thick and contains 15 percent or more calcium carbonate.
Calcine Heated to temperature of dissociation; for example, heat gypsum to the temperature where the water of crystallization is driven off.
Calcite (Geology) Calcium carbonate (CaCO3), with hexagonal crystallization, a mineral found in the form of limestone, chalk, and marble.
Calcium Carbonate Chemical symbol: CaCO3.  The principal hardness and scale-causing compound in water.  A white precipitate that forms in water lines, water heaters, and boilers in hard water areas; also known as scale.  Also the principal chemical composition of Tufa, a calcareous and siliceous rock deposit of springs, lakes, or ground water.
Calcium Chloride A white deliquescent compound, CaCl2, used chiefly as a drying agent, refrigerant, and preservative and for controlling dust and ice on roads.
Calcium Hydroxide A white crystalline strong alkali Ca(OH)2 that is used especially to make mortar and plaster and to soften water.
Calf A large floating chunk of ice split off from a glacier, an iceberg, or a floe.
Calgon Trademark product used for a water softener.
Caliche (1) A soil layer near the surface, more or less cemented by secondary carbonates of calcium or magnesium precipitated from the soil solution.  It may occur as a soft, thin soil horizon, as a hard, thick bed just beneath the Solum, or as a surface layer exposed by erosion.  (2) Alluvium cemented with sodium nitrate, chloride, and/or other soluble salts in the nitrate deposits of Chile and Peru.  Also referred to as Hardpan.
California Doctrine A system of allocating water, first announced in California, which combines Riparian Rights and Appropriative Rights.  A number of states have applied this doctrine at one time or another.  However, most states have essentially abandoned the doctrine in favor of the Appropriation Doctrine, and it is primarily of historical significance.  Also see Alpine Decree (California and Nevada).
California Environmental Quality Act (CEQA) The California equivalent of the federal National Environmental Policy Act (NEPA).
California-Nevada Interstate Compact (California and Nevada) After thirteen years of negotiations between the two states (begun in 1955), the joint California-Nevada Interstate Compact Commission approved a provisional Interstate Compact in July 1968 for the division of the waters of Lake Tahoe, and the Truckee, Ca
California Species of Special Concern Species which are not federal or state-listed as endangered, threatened, or rare, but are declining or are so few in number in California that extirpation is a possibility.
California State Water Resources Control Board (SWRCB) See State Water Resources Control Board (SWRCB) (California).
California Water Commission See Department of Water Resources (DWR) (California).
Call the River To make a request or demand that water rights holders on a watercourse appropriate water only in accordance with the ranking of their Priority Date.
Calm A period or condition of freedom from storms, high winds, or rough activity of water.
Calorie (Abbreviation cal) (1) Basically, A unit of heat energy equal to the amount of heat needed to raise the temperature of one gram of water one degree Celsius (?C).  More precisely, any of several approximately equal units of heat, each measured as the quant
Calve To break at an edge, sot that a portion separates.  Used of a glacier or an iceberg.
Camel A device used to raise sunken objects, consisting of a hollow structure that is submerged, attached tightly to the object, and pumped free of water.  Also referred to as a Caisson.
Canal A constructed open channel for transporting water from the source of supply to the point of distribution.
Canal Automation The implementation of a control system that upgrades the conventional method of canal system operation.
Canal Check Gate Structure A structure designed to control the water surface level and flow in a canal, maintaining a specified water depth or head on outlets or turnout structures.  Most canal check structures have movable gates.
Canal Freeboard The amount of canal lining available above maximum design water depth.
Canal Losses Seepage, evaporation, and operation spills from main-line canals and regulatory reservoirs.
Canal Pool Canal section between check structures.
Canal Prism The cross-sectional shape of a typical canal.
Canal Reach The segment of the main canal system consisting of a series of canal pools between major flow control structures.
Canal System Operation Water transfer from its source to points of diversion for irrigation, municipal and industrial, fish and wildlife, and drainage purposes.
Canceled Water Right A water right that is invalidated due to the failure of the water right holder to comply with the terms and conditions of the permit.  Also see Forfeited Water Right and Withdrawn Water Right.
Candidate Species Plant or animal species designated by the Department of the Interior, U.S. Fish and Wildlife Service (USFWS) as candidates for potential future listing as an Endangered Species or Threatened Species pursuant to the Endangered Species Act (ESA) of 1973; plant or animal species that are candidates for designation as endangered (in danger of becoming extinct) or threatened (likely to become endangered).
Canopy (1) The overhanging cover formed by leaves, needles, and branches of vegetation.  (2) The more or less continuous cover of branches and foliage formed collectively by the crowns of adjacent trends and shrubs.
Canopy Resistance The resistance to transport of water and vapor away from the soil and canopy.
Canyon, also Ca?on A narrow chasm with steep cliff walls, cut into the earth by running water; a gorge.
Cap A layer of clay, or other impermeable material installed over the top of a closed landfill to prevent entry of rainwater and minimize Leachate.
Capa (Critical Aquifer Protection Area) As defined in the Safe Drinking Water Act (SDWA), is all or part of an area located within an area for which an application of designation as a sole or principal source aquifer (pursuant to Section 1424(e)) has been submitted and approved by the Administrator not later than 24 months after the date of enactment and which satisfies the criteria established by the Administrator; and all or part of an area that is within an aquifer designated as a Sole Source Aquifer (SSA), as of the date of the enactment of the Safe Drinking Water Act (SDWA) amendments of 1986, and for which an area wide ground-water protection plan has been approved under Section 208 of the Clean Water Act (CWA) prior to such enactment.
Capacitive Deionization (CDI) A relatively simple and straight forward electrochemical reaction process made unique and highly efficient through the development of a highly-porous material called carbon aerogel that absorbs huge volumes of ions.  A single cube of carbon aerogel, one inch on a side, has an effective surface area of more than 20 million square inches.  This unusually high surface area makes it possible to adsorb large numbers of ions.  Water containing salt, heavy metals, or even radioactive isotopes is pumped through a series of electrochemical cells made from the aerogel, a material sometimes called "frozen smoke."  Effluent water from the series of stacked cells is subsequently purified.  The trapped ions can be released into a relatively small stream of "rinse" water typically comprising less than one percent of the total volume of produce water.  Also see Deionization.
Capacity, Field or Soil The amount of water held in a soil sample after the excess gravitation water has drained away.
Capacity, Gross Reservoir The total amount of storage capacity available in a reservoir for all purposes from the streambed to the normal maximum operating level.  It does not include surcharge, but does include dead storage.
Cape A point or head of land projecting into a body of water.
Capillarity (1) The property of tubes or earth-like particles with hairlike openings which, when immersed in fluid, raise (or depress) the fluid in the tubes above (or below) the surface of the fluid in which they are immersed.  (2) The interaction between contacting surfaces of a liquid and a solid that distorts the liquid surface from a planar shape.  Also referred to as Capillary Action or Capillary Attraction.
Capillary Action (1) The action by which water is drawn around soil particles because there is a stronger attraction between the soil particles and the water molecules themselves.  (2) The movement of water within the interstices of a porous medium due to the forces of adhesion, cohesion, and surface tension acting in a liquid that is in contact with a solid.  Synonymous with the terms Capillarity, Capillary Flow, and Capillary Migration.
Capillary Attraction The force that results from greater adhesion of a liquid to a solid surface than internal cohesion of the liquid itself and that causes the liquid to be raised against a vertical surface, as water is in a clean glass tube.  It is the force that allows a porous material like soil to soak up water from lower levels.
Capillary Fringe (1) The zone at the bottom of the Zone of Aeration (Vadose Zone) where ground water is drawn upward by capillary force.  (2) The zone immediately above the Zone of Saturation (or Groundwater Table) in which underground water is lifted against gravity by surface tension (Capillary Action) in passages of capillary size.
Capillary Phenomena A phenomenon of water movement caused by Capillarity.
Capillary Potential The work required to move a unit mass of water from the reference plane to any point in the soil column.
Capillary Rise The height above a free water surface to which water will rise by Capillary Action.
Capillary Water (1) Water held in the soil above the Phreatic Surface by capillary forces; or soil water above hydroscopic moisture and below the field capacity.  (2) A continuous film of water found around soil particles.
Capillary Zone The soil area above the water table where water can rise up slightly through the cohesive force of Capillary Action.
Capture (1) Water withdrawn artificially from an aquifer is derived from a decrease in storage in the aquifer, a reduction in the previous discharge from the aquifer, an increase in the recharge, or a combination of these changes.  The decrease in discharge from an aquifer plus the increase in recharge.  Capture may occur in the form of decreases in the ground-water discharge into streams, lakes, and the ocean, or from decreases in that component of Evapotranspiration derived from the Zone of Saturation.  (2) Diversion of the flow of water in the upper part of a stream by the headward growth of another stream.
Capture Zone The zone around a well contributing water to the well; the area on the ground surface from which a well captures water.
Carbamates A class of new-age pesticides that attack the nervous system of organisms.
Carbon Adsorption (Water Quality) A treatment system that removes contaminants from ground water or surface water by forcing it through tanks containing activated carbon treated to attract the contaminants.
Carbon-Chloroform Extract (CCE) A measurement of the organic content of a water.  It consists of adsorbing the organic matter onto activated carbon, then extracting it with chloroform.
Carbon Filtration (Water Quality) The passage of treated wastewater or domestic water supplies through activated charcoal in an effort to remove low concentrations of dissolved chemicals.
Carbon Dioxide A colorless, odorless, nonpoisonous gas, CO2, that forms Carbonic Acid when dissolved in water.  Carbon dioxide is typically produced during combustion and microbial decomposition.  Because carbon dioxide absorbs infrared radiation, rising levels of carbon dioxide in the global atmosphere over the past century have prompted concerns about climatic change and more specifically the Greenhouse Effect.
Carbon Polishing (Water Quality) The removal of residual dissolved organic substances from wastewater by Adsorption on activated charcoal (granular activated carbon).  A form of Tertiary Wastewater Treatment.
Carbon Treatment (Water Quality) In a drinking water purification process, the removal of Colloids by Adsorption on Activated Charcoal.  This step often improves the color, taste, and odor of drinking water.  Also see Secondary Drinking Water Standards.
Carbonaceous Biochemical Oxygen Demand The incubation of a sample of water or wastewater for a relatively short period of time in order to determine the Biochemical Oxygen Demand (BOD).  The short incubation, usually 5 days, is sufficient to detect only the microbial utilization of carbon compounds.  A longer incubation (15 to 20 days) would also detect the oxidation of inorganic nitrogenous compounds (ammonia and nitrite) and the subsequent demand for molecular oxygen by chemoautotrophic bacteria.
Carbonate (1) The collective term for the natural inorganic chemical compounds related to carbon dioxide that exist in natural waterways.  (2) A sediment formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron.  The CO3-2 ion in the Carbonate Buffer System.  Combined with one proton, it becomes Bicarbonate, HCO3- and with two protons, Carbonic Acid.  The carbonate ion forms a solid precipitant when combined with dissolved ions of calcium or magnesium.
Carbonate Aquifer An aquifer found in limestone and dolomite rocks.  Carbonate aquifers typically produced hard water, that is, water containing relatively high levels of calcium and magnesium.
Carbonate Buffer System The most important buffer system in natural surface waters and wastewater treatment, consisting of a carbon dioxide, water, carbonic acid, Bicarbonate, and Carbonate ion equilibrium that resists changes in the water's pH.  For example, if acid materials (hydrogen ions) are added to this buffer solution, the equilibrium is shifted and carbonate ions combine with the hydrogen ions to form bicarbonate.  Subsequently, the bicarbonate then combines with hydrogen ions to form carbonic acid, which can dissociate into carbon dioxide and water.  Thus the system pH is unaltered even though acid was introduced.
Carbonate Hardness Water hardness caused by the presence of Carbonate and Bicarbonate of calcium and magnesium.  Also see Temporary Hardness.
Carbonate Rock (Geology) A rock consisting chiefly of carbonate minerals, such as limestone and dolomite.
Carbonated Water (1) Effervescent water, usually containing salts, charged under pressure with purified carbon dioxide gas, used as a beverage or mixer.  Also referred to as soda water, club soda, or seltzer.  (2) A solution of water, sodium bicarbonate, and acid.
Carbonation, Groundwater The dissolving of carbon dioxide in surface water as it percolates through the ground.  The carbon dioxide reacts with water to form carbonic acid, a weak acid that causes the water to have a slightly acidic pH.
Carbonic Acid A weak, unstable acid, H2CO3, present in solutions of carbon dioxide and water.  The carbonic acid content of natural, unpolluted rainfall lowers its pH to about 5.6.
Carcinogen A cancer-causing substance or agent.
Carcinogenic Cancer causing.
Carlson's Trophic State Index (TSI) A measure of Eutrophication of a body of water using a combination of measures of water transparency or turbidity (using Secchi Disk depth recordings), Chlorophyll-a concentrations, and total phosphorus levels.  TSI measures range from a scale 20-80 and from Oligotrophic waters (maximum transparency, minimum chlorophyll-a, minimum phosphorus) through Mesotrophic, Eutrophic, to Hypereutrophic waters (minimum transparency, maximum chlorophyll-a, maximum phosphorus).  Also referred to as the (Mean) Trophic State Index (TSI).  Also see Total Inorganic Nitrogen (TIN) and Total Inorganic Phosphate (TIP).
Carr, also Car (1) A pool; also, a Fen or a Bog.  (2) The yellow or brown sediment of humate of iron in water flowing from a peaty bog.
Carriage Losses (Water) A term used to describe the operational losses associated with conveying water from its point of diversion to its point of use.  These losses typically include spillage, seepage, evaporation, and phreatophyte useage along the water course, as applicable.  Water rights applicants are entitled to water for transporting their entitlement to their proposed place(s) of use.  Carriage losses are generally considered unavoidable, and are legally bearable so long as that extra water is used reasonably and economically in transporting the water to its destination.
Carriage Water (California-Central Valley Project) The amount of extra water required for Sacramento-San Joaquin Delta outflow to maintain water quality standards in the Delta as the result of an increase in exports.  Also see Bay-Delta (California).
Carrying Capacity (Ecology) The maximum number and type of species which a particular habitat or environment can support without detrimental effects.
Carson Division (Newlands Project, Nevada) The Carson Division of the Newlands Project is located entirely within Churchill County, Nevada.  It contains about 67,840 acres of water-righted land and is supplied by a combination of Carson River and Truckee River water from Lahontan Reservoir.
Carville Decree (Nevada) The Carville Decree was issued on January 24, 1935 by Judge E.P. Carville and adjudicated water rights for the Little Humboldt River.  As with the 1931 Bartlett Decree (and the 1935 Edwards Decree modifying the Bartlette Decree), the Carville Decree deter
Cascade A short, steep drop in stream bed elevation often marked by boulders and agitated white water.
Cascade Flow Regulated flow through a series of flow control structures.
Casing The steel conduit required to prevent waste and contamination of the ground water and to hold the formation open during the construction or use of the well.  A tubular structure intended to be water tight installed in the excavated or drilled hole to maintain the well opening and, along with cementing, to confine the ground waters to their zones of origin and prevent the entrance of surface pollutants.
Casual Water A temporary accumulation of water not forming a regular hazard of a golf course.
Catabolism The biological breakdown of materials into their simpler components, i.e., decomposition.  Performed by decomposer organisms, mainly bacteria and fungi.
Catadromous Used to describe fish that live in fresh water but migrate to marine waters to breed.  Contrast with Anadromous.
Catalase A red crystalline enzyme that consists of a protein complex with hematin groups and catalyzes the decomposition of Hydrogen Peroxide into water and oxygen.
Catalysis The action of a Catalyst, especially an increase in the rate of a chemical reaction.
Catalyst A substance that alters the speed of a reaction, but does not change the form or amount of product.  For example, Enzymes are biological catalysts, enhancing reactions within living organisms.
Catalytic Converter A reaction chamber typically containing a finely divided platinum-iridium Catalyst into which exhaust gases from an automotive engine are passed together with excess air so that carbon monoxide and hydrocarbon pollutants are oxidized to carbon dioxide and water.
Catalyze To modify, especially to increase, the rate of a chemical reaction by Catalysis or the action of a Catalyst.
Cataphoresis The migration of charged colloidal particles (Colloids) or Molecules through a solution under the influence of an applied electric field usually provided by immersed electrodes.  Also call Electrophoresis.
Catastrophic A property of non-linear dynamic systems (such as Biotic Communities) in which what appears to be a small disturbance (introduction of an exotic species) initiates large changes and establishes a new set of stable conditions.
Catch Basin A sieve-like device at the entrance to a sewer to stop matter that could possibly block up the sewer.
Catchment (1) The catching or collecting of water, especially rainfall.  (2) A reservoir or other basin for catching water.  (3) The water thus caught.
Catchment Area (1) The intake area of an aquifer and all areas that contribute surface water to the intake area.  (2) The areas tributary to a lake, stream, sewer, or drain.  (3) A reservoir or basin developed for flood control or water management for livestock and/or wildlife.  See also Drainage Area; Watershed.
Catchment Area (Basin) The area draining into a river, reservoir, or other body of water.
Categorical Exclusion A class of actions which either individually or cumulatively would not have a significant effect on the human environment and therefore would not require preparation of an Environmental Assessment (EA) or an Environmental Impact Statement (EIS) under the National Environmental Policy Act (NEPA).
Categorical Pretreatment Standard A technology-based effluent limitation for an industrial facility discharging into a municipal sewer system.  Analogous in stringency to Best Available Technology (BAT) for direct dischargers.
Categorical Variable (Statistics) A qualitative variable created by classifying observations into categories.  For example, a series of household incomes could be classified into the categorical variables low, medium, and high describing certain specific ranges of income levels.  Many statistical techniques are inappropriate for the use of categorical variables.  Also referred to as a Qualitative Variable.  Contrast with Quantitative Variable.
Cation The positively charged particle or ion in an electrolyzed solution which travels to the cathode and is there discharged, evolved, or deposited.  Also, by extension, any positive ion.
Cation Exchange A chemical process in which Cations of like charge are exchanged equally between a solid, such as zeolite, and a solution, such as water.  The process is often used to soften water.
Cation Exchange Capacity (CEC) The total of exchangeable cations that a soil can adsorb; expressed in milliequivalents per 100 grams (g) of soil.
Cat's-Paw, also Catspaw A light breeze that ruffles small areas of a water surface.
Cattail A tall, reedy marsh plant with brown furry fruiting spikes; an Emergent Plant.
Causeway A raised roadway, as across water or marshland.
Caustic Alkaline or basic.
Cavendish, Henry (1731-1810) A British chemist and physicist who discovered the properties of hydrogen and established that water was a compound of hydrogen and oxygen.
Cavern A large underground opening in rock (usually limestone) which occurred when some of the rock was dissolved by water.  In some igneous (formed by volcanic action) rocks, caverns can be formed by large gas bubbles.
Caving The collapse of a stream bank by undercutting due to wearing away of the toe or an erodible soil layer above the toe.
Cavitation (1) A process of erosion in a stream channel caused by sudden collapse of vapor bubbles against the channel wall.  (2) The formation of cavities filled with air and water vapor due to internal pressure reduced below atmosphere.  (3) The formation and collapse of gas pockets or bubbles on the blade of an impeller or the gate of a valve; collapse of these pockets or bubbles drives water with such force that it can cause pitting of the gate or valve surface.
Cell (Biology) The basic building block of all living matter.  The cell of a living organism contains a high percentage of water.
Cells/Volume The number of plankton cells or natural units counted using a microscope and grid or counting cell.  Results are generally reported as cells or units per milliliter.
Cells Volume (Biovolume) One of several common methods used to estimate biomass of algae in aquatic systems.  Cell members of algae are frequently used in aquatic surveys as an indicator of algal production.  However, cell numbers alone cannot represent true biomass because of co
Cellulose The fibrous part of plants used in making paper and textiles, which in turn may be made into building products.
Celsius (Temperature Scale) (C) (1) Relating to, conforming to, or having the international thermometric scale on which the interval between the triple point of water and the boiling point of water is divided into 99.99 degrees with 0.01? representing the Triple Point and 100? the boili
Cenozoic Era Of, belonging to, or designating the latest era of geologic time, extending from 65 million years before present (B.P.) to the present, and including the Tertiary Period (from 65 million years B.P. to about 2 million years B.P.), encompassing the Paleocene, Eocene, Oligocene, Miocene and Pliocene Epochs, and the Quaternary Period (from about 2 million years B.P. to the present), encompassing the Pleistocene and Holocene Epochs, and is characterized by the formation of modern continents, glaciation, and the diversification of mammals, birds, and plants.
Census A complete counting, with classification, of a population or group at a particular point in time, as regards to some well-defined characteristic(s).  Usually has governmental and economic and social connotations, e.g., the decennial census of the population; however, also used in a biological and environmental sense for plants, animals, and habitat.
Census of Agriculture A Census taken by the U.S. Department of Commerce, Bureau of the Census, every 5 years to include the number of farms, land in farms, crop acreage and production, irrigated acreage, farm spending, farm facilities and equipment, farm tenure, value of farm products sold, farm size, and other farm-related data.
Census X-11 (Seasonal Adjustment) Process (Statistics) A seasonal adjustment process for decomposing time series data into its trend-level, seasonal index, trading day, and irregular components.  It is primarily used to De-Seasonalize official government statistics for publication, but is arguably the most widely used and accepted seasonal adjusted process.
Center-Pivot Irrigation Automated sprinkler irrigation achieved by automatically rotating the sprinkler pipe or boom, supplying water to the sprinkler heads or nozzles, at a radius from the center of the field to be irrigated.  Water is delivered to the center or pivot point of the system.  The pipe is supported above the crop by towers at fixed spacings and propelled by pneumatic, mechanical, hydraulic, or electric power on wheels or skids in fixed circular paths at uniform angular speeds.  Water is applied at a uniform rate by progressive increase of nozzle size from the pivot to the end of the line.  The depth of water applied is determined by the rate of travel of the system.  Single units are ordinarily about 1,250 to 1,300 feet long (381-397 meters) and irrigate approximately a 130-acre (52.7 hectare) circular area.  Also see Irrigation Systems.
Centigrade (Temperature Scale) (C) Relating to, conforming to, or having a thermometric scale on which the interval between the freezing point of water and the boiling point of water is divided into 100 degrees with 0? representing the freezing point and 100? the boiling point at one atmosphere of pressure;  Abbreviation C;  Compare to Celsius (Temperature Scale).  The Centigrade scale is identical to the Celsius scale; however, by international agreement, the term Celsius has officially replaced Centigrade.  Contrast with the Fahrenheit Temperature Scale, using degrees Fahrenheit (?F), in which 32?F above the 0?(F) mark indicates the freezing point of water and 212?F indicates the boiling point of water (at sea level).  Also see Temperature Scale.
Central Valley Project (CVP) (California) A multipurpose water project developed mainly by the U.S. Bureau of Reclamation (USBR), extending from the Cascade Range on the north to the semiarid but fertile plains of California's Kern River on the south.  The state and federal portions of the Centra
Centralized Control (Canal) Control of a canal project from a central location by the watermaster.
Centralized Headquarters (Canal)  Control of a canal project from a central location generally by a master station, communications network, and one or more remote terminal units (RTUs).
Centrifugal Pump A device that converts mechanical energy to pressure or kinetic energy in a fluid by imparting centrifugal force on the fluid through a rapidly rotating impeller.
Centrifugation (Water Quality) In water and wastewater treatment, a method used to remove liquid from sludges through use of centrifugal forces.
CEQA See California Environmental Quality Act (CEQA).
CERCLA See Comprehensive Environmental Response, Compensation, and Liability Act.
Certificate of Water Right An official document which serves as evidence of a Perfected Water Right.  Also see Application, Water Right.
Certificated Water Right The right granted by a state water agency to use either surface or ground water.  Also see Application, Water Right and Vested Water Right.
Certificated Water Right (Nevada) The right to put surface or ground water to beneficial use that is identified by a recorded document issued by the Nevada State Engineer after satisfactory proof of "perfection of application" for a permitted water right has been filed in accordance with Nevada Revised Statues Chapter 533.
Certified Water Right A state-issued document that serves as legal evidence that an approved application has been physically developed and the water put to beneficial use.  The certificate establishes priority date, type of beneficial use, and the maximum amount of water that can be used.  Before a water right can be certified, verification of the physical development must be provided to the state through a survey conducted by an approved water rights examiner.  Even certified water rights are subject to occasional review to ensure continued beneficial use.
Cesspool An underground catch basin for combined liquid and solid waste, such as household sewage, so designed as to retain the organic matter and solids but permitting the liquids to seep through the bottom and sides.  Also see Septic Tanks.
CFS (Cubic Foot per Second) A unit of discharge for measurement of flowing liquid equal to a flow of one cubic foot per second past a given section.  A rate of flow equivalent to 448.83 gallons per minute.  Also called Second-Foot.  Also written as C.F.S. and cfs.
CFS-Day The volume of water represented by a flow of 1 cubic foot per second for 24 hours.  It equals 86,400 cubic feet, 1.983471 acre-feet, or 646,317 gallons.
CFSM (Cubic Feet per Second per Square Mile) The average number of cubic feet of water per second flowing from each square mile of area drained by a stream, assuming that the runoff is distributed uniformly in time and area.
Chalk A mineral composed mainly of the calcareous shells of various marine microorganisms, but whose matrix consists of fine particles of calcium carbonate, some of which may have been chemically precipitated.
Chalybeate Tasting like iron, as water from a mineral spring.
Channel (1) (Watercourse) A natural stream that conveys water; a natural or artificial watercourse with definite bed and banks to confine and conduct flowing water; a ditch or channel excavated for the flow of water.  River, creek, run, branch, anabranch, and tributary are some of the terms used to describe natural channels, which may be single or Braided.  Canal, aqueduct, and floodway are some of the terms used to describe artificial (man-made) channels.  (2) (Landform) The bed of a single or braided watercourse that commonly is barren of vegetation and is formed of modern alluvium.  Channels may be enclosed by banks or splayed across and slightly mounded above a fan surface and include bars and dumps of cobbles and stones.  Channels, excepting floodplain playas, are landform elements.
Channel Bank The sloping land bordering a channel.  The bank has steeper slope than the bottom of the channel and is usually steeper than the land surrounding the channel.
Channel Capacity The maximum rate of flow that may occur in a stream without causing overbank flooding; the maximum flow which can pass through a channel without overflowing the banks.
Channel Control The condition under which the stage-discharge relation of a gaging station is governed by the slope, size, geometry, and roughness of the channel.
Channel Density The ratio of the length of stream channels in a given basin to the area of the basin, expressed in feet per acre (meters per hectare).
Channel-Forming Discharge See Dominant Discharge.
Channel Inflow Water which at any instant is flowing into the channel system from surface flow, subsurface flow, base flow, and rainfall directly on the channel.
Channel Lining Protection of the channel bottom and banks with concrete or Riprap.
Channel Modification The modification of the flow characteristics of a channel by clearing, excavation, realignment, lining, or other means to increase its capacity.  Sometimes the term is used to connote Channel Stabilization.
Channel Realignment The construction of a new channel or a new alignment which may include the clearing, snagging, widening, and/or deepening of the existing channel.
Channel Stabilization Erosion prevention and stabilization of velocity distribution in a channel using jetties, drops, revetments, vegetation, and other measures.
Channel Storage The volume of water at a given time in the channel or over the flood plain of the streams in a drainage basin or river reach.  Channel storage is sometimes significant during the progress of a flood event.
Channelization (1) The artificial enlargement or realignment of a stream channel.  (2) Straightening a stream or river to allow water to travel through the area more quickly.  (3) The process of changing an straightening the natural path of a waterway.  Channelization is often used as a means of flood control, but its negative effects often outweigh its advantages.  For example, channelization often damages wetlands associated with rivers and streams.
Chaos Theory A modern development in mathematics and science that provides a framework for understanding irregular or erratic fluctuations in nature.  Chaotic systems are found in many fields of science and engineering.  Evidence of chaos occurs in models and experime for example, in complicated fluid flows.
Chaparral A type of Biome with hot, dry summers and rainfall mainly in the winter months.  Vegetation consists of shrubs, small evergreen trees, and sclerophyllous species.  Chaparral communities are found around the Mediterranean Sea, in central and southern California, along coastal Chile, in southern Australia, and in southern Africa.
Chatter Mark, also Chattermark (Geology) One of a series of short scars made by glacial drift on a surface of bedrock.
Check Dam (1) A structure placed bank to bank downhill from a headcut on a hillslope to help revegetate a gully. (2) A small dam constructed in a gully or other small watercourse to decrease the streamflow velocity, minimize channel erosion, promote deposition of sediment, and to divert water from a channel.
Check Gate A gate located at a check structure used to control flow.
Check Irrigation A method of irrigation in which an area is practically or entirely surrounded by earth ridges.
Check Structure A device or structure placed in a canal such that water must pass through, over or under it.  The check structure opening or position is typically a function of the flow rate, and is adjusted to maintain a certain flow rate or water level.  Check structures are necessary to dam the water up during low flows so that all turnouts upstream can receive water.  Also referred to as a Cross Regulator or Gate.
Check Valve See Backflow Preventer.
Chemical Feeder (Water Quality) A mechanical device for measuring quantities of chemical and applying them to a water at a preset rate.
Chemical Oxygen Demand (COD) (Water Quality) (1) A measure of the chemically oxidizable material in the water which provides an approximation of the amount of organic and reducing material present.  The determined value may correlate with Biochemical Oxygen Demand (BOD) or with carbonaceous organic pollution from sewage or industrial wastes.  (2) A chemical measure of the amount of organic substances in water or wastewater.  A strong oxidizing agent together with acid and heat are used to oxidize all carbon compounds in a water sample.  Non-biodegradable and recalcitrant (slowly degrading) compounds, which are not detected by the test for BOD, are included in the analysis.  The actual measurement involves a determination of the amount of oxidizing agent (typically, potassium dichromate) that is reduced during the reaction.  Also see Total Carbon (TC) and Total Organic Carbon (TOC).
Chemical Weathering The gradual decomposition of rock by exposure to rainwater, surface water, atmospheric oxygen, carbon dioxide and other gases in the atmosphere, as well as compounds secreted by organisms.  Compare to Physical Weathering..
Chemigation Application of pesticides or fertilizers to farmlands through irrigation systems.
Chemoautotroph An organism that utilizes oxidation of inorganic chemicals for its energy and carbon dioxide for cell growth.  Also called a Chemosynthetic Autroph.
Chemocline The transition zone between layers in a Meromictic Lake.
Chemodynamics The study of the transport, conversion, and fate of chemical substances in air, water, or soil, including their movement from one medium to another.
Chemosphere The region of the upper Atmosphere including the Mesosphere and upper Stratosphere in which various sunlight-driven chemical reactions occur.
Chemosynthesis The synthesis of carbohydrate from carbon dioxide and water using energy obtained from the chemical oxidation of simple inorganic compounds.  This form of synthesis is limited to certain bacteria and fungi.
Chimney A tall column of rock on the ocean floor that is formed by the precipitation of minerals from superheated water issuing from a vent in the earth's crust and rising through the column of rock.  Also see Black Smoker.
Chinook A downslope wind in which the air is warmed by adiabatic (gradual) heating.  Such conditions describe a warm, dry southwest wind blowing from the sea onto the coast of Oregon and Washington in the winter and spring, as well as a warm, dry wind blowing down the eastern slope of the Rocky Mountains.
Chloramines Compounds containing nitrogen, hydrogen, and chlorine, formed by the reaction between hypochlorous acid (HOCl) and ammonia (NH3) and/or organic amines in water.  The formation of chloramines in drinking water treatment extends the disinfecting power of chlorine.  Also referred to as Combined Available Chlorine.
Chlorides Negative chlorine ions, Cl-, found naturally in some surface waters and groundwaters and in high concentrations in seawater.  Higher-than-normal chloride concentrations in fresh water, due to sodium chloride (table salt) that is used on foods and present in body wastes, can indicate sewage pollution.  The use of highway deicing salts can also introduce chlorides to surface water or groundwater.  Elevated groundwater chlorides in drinking water wells near coastlines may indicate Saltwater Intrusion.
Chlorinated (Water Quality) Describes water or wastewater that has been treated with either chlorine gas or a chlorine-containing compound.
Chlorinated Hydrocarbons (Water Quality) Includes a class of persistent, broad-spectrum insecticides that linger in the environment and accumulate in the food chain.  Among them are DDT, aldrin, diedrin, heptachlor, chlordane, lindane, endrine, mirex, hexachloride, and toxaphene.
Chlorination The application of chlorine or one of its compounds to water or wastewater, often for disinfection or oxidation purposes.
Chlorinator A device for adding a chlorine-containing gas or liquid to drinking water or wastewater.
Chlorine One of a group of elements classified as the halogens.  Chlorine, Cl2, the most common halogen, is a greenish yellow gas with an irritating odor.  Chlorine is very reactive; it forms salts with metals, forms acids when dissolved in water, and combines readily with hydrocarbons.  Various forms of chlorine are used to disinfect water.  Chlorine is produced by the electrolysis of brine (a concentrated salt solution).  Atomic number 17; atomic weight 35.45; freezing point -100.98?C; boiling point -34.6?C; specific gravity 1.56 (-33.6?C).
Chlorine Breakpoint (Water Treatment) The point at which the chlorine dosage in a water treatment process has satisfied the Chlorine Demand.  To eliminate the taste and odor associated with processed water, sufficient chlorine must be added to reach the breakpoint.  Increasing the chlorine dose beyond the breakpoint produces a free chlorine residual, which is free to kill microorganisms.  When chlorine is added to water, it first combines with constituents in the water such as iron, manganese, and nitrites.  It is important to add enough chlorine to the water initially to ensure that these constituents are oxidized and to ensure that a residual is formed to react with the ammonia and organic matter in the water.  Taste and odor problems result when chlorine dosages are either below the breakpoint, or well beyond the breakpoint.
Chlorine-Contact Chamber (Water Quality) In a wastewater treatment plant, a chamber in which effluent is disinfected by chlorine before it is discharged to the receiving waters.
Chlorine Demand (Water Quality) The amount of chlorine that must be added to purify drinking water; the amount of chlorine required to react with all dissolved and particulate materials and inorganic ammonia in the water.
Chlorine Residual The concentration of chlorine remaining in water or wastewater at the end of a specified contact period which will react chemically and biologically.  May be present as either combined or free chlorine, or both.
Chlorophyll The green pigments of plants.  There are seven known types of chlorophyll, Chlorophyll a and Chlorophyll b are the two most common forms.  A green photosynthetic coloring matter of plants found in chloroplasts and made up chiefly of a blue-black ester.
Cholera An infectious waterborne disease that is characterized by severe diarrhea and its resultant dehydration and electrolyte imbalance.  The disease is caused by bacteria belonging to the genus Vibrio.  Outbreaks are associated with contamination of surface waters with human fecal material.
Chop A short, irregular motion of waves.  Also, an area of choppy water, as on an ocean.
Chott, also Shott (1) The depression surrounding a salt marsh or lake, especially in North Africa.  (2) The bed of a dried salt marsh.
Chresard Water present in the soil and available for plant absorption.
Chronic Showing effects only over a long period of time, as in chronic toxicity.
Chuckhole A rough hole in pavement, made by wear and weathering, more commonly referred to as Pothole.
Chute, or Chute Cutoff As applied to stream flow, the term "chute" refers to a new route taken by a stream when its main flow is diverted to the inside of a bend, along a trough between low ridges formed by deposition on the inside of the bend where water velocities were reduced.  Compare with Neck Cutoff.
Chute Spillway The overfall structure which allows water to drop rapidly through an open channel without causing erosion.  Usually constructed near the edge of dams.
Cienega A Southwestern United States, non-forested wetland.  Cienegas are dominated by Graminoids and may be seasonally dry.
Circulate, or Circulation Movement or passage through a system of vessels, as water through pipes.
Circumneutral Term applied to water with a pH of 5.5 (acidic) to 7.4 (alkaline).
Cirque A smallish, rounded depression with steeply sloping sides carved into the rock at the top of a ridge where a glacier has its head.  After the period of glaciation ends, the cirque may contain a small remnant of the former glacier, or it may fill with water and become a lake.  The term Tarn is also used to describe lakes that have formed in cirques.
Cirque Basin A half-amphitheater formed by alpine Glaciation with three steep sides.  Usually found at upper ends of valleys and along ridges.
Cirrocumulus Clouds A high-altitude cloud composed of a series of small, regularly arranged cloudlets in the form of ripples or grains.  Also see Cloud.
Cirrostratus Clouds A high-altitude, thin hazy cloud, usually covering the sky and often producing a halo effect.  Also see Cloud.
Cirrus Clouds A principal cloud type found at high altitudes and composed of ice crystals collected into delicate wisps or patches.  Also see Cloud.
Cistern An artificial reservoir or tank used for holding or storing water or other liquids.  Typically a tank, often underground, used for storing rain water collected from a roof.
Clam-Flat (New England) A level stretch of soft tidal mud where clams burrow.
Clammy (1) Disagreeably moist, sticky, and cold to the touch.  (2) Damp and unpleasant.
Clarification A process or combination of processes where the primary purpose is to reduce the concentration of suspended matter in a liquid.
Clarifier A device or tank in which wastewater is held to allow the settling of particulate matter.
Class A Pan The U.S. Weather Bureau evaporation pan is a cylindrical container fabricate of galvanized iron or monel metal with a depth of 10 inches and a diameter of 48 inches.  The pan is placed on an open 2- X 4-inch wooden platform with the top of the pan about 41 cm (16 inches) above the soil surface.  It is accurately leveled at a site that is nearly flat, well sodded, and free from obstructions.  The pan is filled with water to a depth of eight inches, and periodic measurements are made of the changes of the water level with the aid of a hook gage set in the still well.  When the water level drops to seven inches, the pan is refilled.  Its average pan coefficient is about 0.7 for lake evaporation.
(Injection Well) Classes Classifications of the U.S. Environmental Protection Agency (EPA) that determine the permit requirements of an Injection Well.  The following classes apply:
(1)  Class I - A well into which liquid hazardous wastes or other fluids are pumped down, with the fluids being injected into an underground formation below the lowest underground source of drinking water that is within a one-quarter mile radius of the well;
(2)  Class II - A well used to dispose of fluids produced by oil and gas wells, to introduce fluids for enhanced oil recovery, or for liquid hydrocarbon storage;
(3)  Class III - A well used to pump fluids underground for mineral extraction;
(4)  Class IV - A well used to re-inject treated fluid from a superfund cleanup site into or above an underground formation within a one-quarter mile radius of the well;
(5)  Class V - Wells not included in Classes I-IV, mainly shallow industrial disposal wells or Recharge Wells.
Classical Inference (Statistics) Statistical inference is based on two basic premises: (1) The sample data constitute the only relevant information; and (2) The construction and assessment of the different procedures for inference are based on long-run behavior under essentially similar circumstances.  Also see Statistical Inference and Bayesian Inference.
Classical Linear Regression (CLR) Model (Statistics) The standard for the Ordinary Least Squares (OLS), or Regression Analysis model.  The CLR Model has five basic assumptions:
(1)  Linearity - The dependent variable, or the variable to be explained or forecasted, can be calculated as a linear function of a specific set of independent, or explanatory variables;
(2)  Randomness of Disturbance Terms - The expected value of the disturbance term, that is the term showing the differences between the model's estimated values and the actual observed values, is zero;
(3)  Uncorrelated Disturbance Terms - The disturbance terms all have the same variance and are not correlated with each other (see Serial Correlation);
(4)  Data Conformity - The observations on the independent variable can be considered fixed in repeated samples, i.e., it is possible to repeat the sample with the same independent variables;
(5)  Sample Size and Selection - The number of observations is greater than the number of independent variables and that there are no linear relationships, i.e., no significant correlations, between the independent variables (see Multicollinearity).
Classification (Soils) The systematic arrangement of soils into groups or categories on the basis of their characteristics.  Broad groupings are made on the basis of general characteristics and subdivisions on the basis of more detailed differences in specific properties.  Soil Taxonomy is the study of soil classification systems.  For a description of soil classifications, see Land Capability Classes.
Clast (Clastic) (1) Pertaining to a rock or sediment composed principally of broken fragments that are derived from pre-existing rocks or minerals and that have been transported some distance from their places of origin.  (2) An individual constituent, grain, or fragment of a sediment or rock, produced by the mechanical weathering (disintegration) of a larger rock mass.
Clay (1a) A fine-grained, firm earth material that is plastic when wet and hardens when heated, consisting primarily of hydrated silicates of aluminum and widely used in making bricks, tiles, and pottery; (1b) A hardening or non-hardening material having a consistency similar to clay and used for modeling.  (2) (Geology) A sedimentary material with grains smaller than 0.2 millimeters in diameter.  (3) Moist, sticky earth; mud.
Clay Liner A layer of clay soil that is added to the bottom and sides of a pit designed for use as a disposal site for potentially dangerous wastes.  The clay prevents or reduces the migration of liquids from the disposal site.
Claypan (1) A dense, compact layer in the subsoil having a much higher clay content than the overlying material from which it is separated by a sharply defined boundary.  Such layers are formed by the downward movement of clay or by synthesis of clay in place during soil formation.  Claypans are usually hard when dry, and plastic and sticky when wet.  They usually impede movement of water and air, and the growth of plant roots.  (2) (Australian) A shallow depression in which water collects after rain.  Also see Hardpan.
Clayseal A barrier constructed of impermeable clay that stops the flow of water or gas.
Clay Soil A soil composed of microscopically small mineral particles that are flattened and fit closely together; spaces between particles for air and water are also small.  When clay soil gets wet it dries out slowly because the downward movement if water, i.e., drainage, is slow.
Clean (Water) Water that is free from foreign matter or pollution; not infected; unadulterated.
Clean Water Act (CWA) (Public Law 92-500) More formally referred to as the Federal Water Pollution Control Act, the Clean Water Act constitutes the basic federal water pollution control statute for the United States.  Originally based on the Water Quality Act of 1965 which began setting water quality standards.  The 1966 amendments to this act increased federal government funding for sewage treatment plants.  Additional 1972 amendments established a goal of zero toxic discharges and "fishable" and "swimmable" surface waters.  Enforceable provisions of the CWA include technology-based effluent standards for point sources of pollution, a state-run control program for nonpoint pollution sources, a construction grants program to build or upgrade municipal sewage treatment plants, a regulatory system for spills of oil and other hazardous wastes, and a Wetlands preservation program (Section 404).
Clean Water Act (CWA), Section 319 A federal grant program added by Congress to the CWA in 1987 and managed by the U.S. Environmental Protection Agency (EPA), Section 319 is specifically designed to develop and implement state Nonpoint Source (NPS) Pollution management programs, and to maximize the focus of such programs on a watershed or waterbasin basis with each state.  Today, all 50 states and U.S. territories receive Section 319 grand funds and are encouraged to use the funding to conduct nonpoint source assessments and revise and strengthen their nonpoint source management programs.  Before a grant is provided under Section 319, states are required to:  (1) complete a Nonpoint Source (NPS) Assessment Report identifying state waters that require nonpoint source control and their pollution sources; and (2) develop Nonpoint Source Management Programs that outline four-year strategies to address these identified sources.
Clean Water Standards (EPA) Generally refers to any enforceable limitation, control, condition, prohibition, standard, or other requirement which is promulgated pursuant to the Federal Water Pollution Control Act (Clean Water Act) (Public Law 92-500) or contained in a permit issued to a discharger by the U.S. Environmental Protection Agency (EPA) or by a state under an approved program, as authorized by Section 402 of the Clean Water Act, or by local governments to ensure compliance with pretreatment regulations as required by Section 307 of the Clean Water Act.
Clear Well A reservoir containing potable water which has been previously treated before entering the distribution lines.
Clepsydra An ancient device that measured time by marking the regulated flow of water through a small opening.  Also referred to as a Water Clock or Water Glass.
Climate The sum total of the meteorological elements that characterize the average and extreme conditions of the atmosphere over a long period of time at any one place or region of the earth's surface.  The collective state of the atmosphere at a given place or over a given area within a specified period of time.  Compare to Weather.  Basic types of climates include:
(1)  Continental - The climate characteristic of land areas separated from the moderating influences of oceans by distance, direction, or mountain barriers and marked by relatively large daily and seasonal fluctuations in temperature;
(2)  Oceanic - The climate characteristic of land lares near oceans which contribute to the humidity and at the same time have a moderating influence on temperature and the range of temperature variation.
Climatic Cycle The periodic changes of climate, including a series of dry years following a series of years with heavy rainfall.
Climatic Year A period used in meteorological measurements.  A continuous 12-month period during which a complete annual cycle occurs, arbitrarily selected for the presentation of data relative to hydrologic or meteorologic phenomena.  The climatic year in the United States begins on October 1st and runs through September 30th.  Similar to a Water Year.
Climatology, also Climatological The