F. X. Browne, Inc. Glossary - C

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C-CELSIUS—Centigrade Temperature Scale

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.

CAA—Clean Air Act (EPA)

CABOTAGE—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 FENSPeatlands 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).

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—(Ca++) The most abundant cation found in Wisconsin lakes. Its abundance is related to the presence of calcium-bearing minerals in the lake watershed. Reported as milligrams per liter (mg/l) as calcium carbonate (CaCO3), or milligrams per liter as calcium ion(Ca++).

CALCIUM CARBONATE—(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 CARBONATE TREATMENT—The adding of limestone (calcium carbonate) to an acid lake to raise the pH.

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.

CALCIUM NITRATE TREATMENT—A method of adding nitrate to lake sediments.

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 STATE WATER RESOURCES CONTROL BOARD (SWRCB)—See State Water Resources Control Board (SWRCB) [California].

CALIFORNIA WATER COMMISSION—See Department of Water Resources (DWR) [California].

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 quantity of heat required to raise the temperature of 1 gram of water by 1C from a standard initial temperature, especially from 3.98C (corresponding to the maximum density of water), 14.5C, or 19.5C, at 1 atmosphere pressure. Also referred to as the Gram Calorie and the Small Calorie. (2) The unit of heat equal to 1/100 the quantity of heat required to raise the temperature of 1 gram of water from 0C (its freezing point) to 100C (its boiling point) at 1 atmosphere pressure. Also referred to as the Mean Calorie. (3) The unit of heat equal to the amount of heat required to raise the temperature of 1 kilogram of water by 1C at 1 atmosphere pressure. Also referred to as the Kilocalorie, Kilogram Calorie, and Large Calorie. (4) A unit of energy-producing potential equal to this amount of heat that is contained in food and released upon oxidation by the body. Also referred to as the Nutritionist's Calorie. The calorie is used when temperature is measured in degrees Celsius (C) on the Centigrade Scale. The British Thermal Unit (BTU) is used when the measurement is in degrees Fahrenheit (F) on the Fahrenheit Scale.

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.

CAMP SCAR—Camp sites on wilderness and primitive lakes are easily recognized from the water surface and air by their lighter tone and barren character. Landing beaches are cleared, ground cover is destroyed and large trees are dead or dying from soil compaction. Damage to the aesthetic image is frequently accentuated by blazes, temporary structures and bark stripping.

CANAL—A constructed open channel for transporting water.

CANAL, BOAT—A dredged canal between separate lakes or lakes and streams to provide convenient boat passage.

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 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).

CANOE— A light narrow boat made of bark, aluminum, or fiberglass. A paddle is used to steer and move it.

CANOE TRAIL—Connected lakes or closely associated lakes and streams used as canoe routes. Portages used in overland travel between water bodies and camp sites may be either marked or developed; (1) wilderness area canoe routes are long and provide no facilities, (2) primitive area canoe routes are of variable length and have developed portages and camp sites, (3) canoe routes in populated agricultural and forest areas may be quite short and have hotels, organized campgrounds and pick-up service.

CANOPY—The overhanging cover formed by leaves, needles, and branches of vegetation.

CANOPY CLOSURE—The degree of canopy cover relative to openings (Forestry Canada 1992). Class 1 has a cover of a few individuals, and class 9 has continuous canopy cover with no gaps.

CANYON, also Cañon—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—(1) A point or head of land projecting into a body of water. (2) A rounded projection, out into the water, and either high land or low land. For inland lakes, cape rarely appears on maps as a place name and also only infrequently in descriptions. Point and head according to present usage appears to be preferred to cape.

CAPILLARITY—(1) The property of tubes or earth-like particles with hair-like 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—A nonmetallic element found in all organic substances and in some inorganic substances, as diamonds, coal, graphite, charcoal and lampblack.

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).

CARNIVORE—An organism that feeds primarily on other animals.

CARNIVOROUS—Flesh eating organisms.

CARP—A fresh water fish that sometimes lives in schools in lakes. Sometimes used for food.

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 usage 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.

CARRYING CAPACITY—(Biologic) The carrying capacity of a lake refers to its natural productivity. In relation to fish production, or other aquatic life, the numbers which the natural food supply, or pasturage, will support adequately.

CARRYING CAPACITY—(Commercial) The measure of the capacity of a lake for boating, skiing, bathing - recreational use in general - and residential occupation of the shore and shore border land without patent overcrowding, pollution and consequent danger to health and safety. Carrying capacity may be greatly limited if a single use is given priority; also it may be expanded if the surface area of the lake is zoned for particular uses and the time for use in each zone is specified. Some of the factors involved in determining carrying capacity: size, shape, depth, character and location of swimming areas and beaches, regulatory and zoning restrictions, season of year, accessibility (public or private), available services (boat liveries, marinas), level of pollution or smirchment, parking facilities, usable frontage and fish (abundance, species).

CARRYING CAPACITY—(Ecology) The maximum number and type of species which a particular habitat or environment can support without detrimental effects.

CARRYING CAPACITY—(Lake) The amount of human development that can occur in the lake's watershed without causing a significant change in its water quality.

CARRYING PLACES—Land portaged in navigation of lakes and streams, and legally a part of the navigation route.

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.

CAT ICE—"Ice forming a thin shell from under which the water has receded." (Navigation Dictionary USHO, Bulletin 220, 1956) The term has some application to ice on lakes.

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.

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. (4) The land (and including the streams, rivers, wetlands and lakes) from which water runs off to supply a particular location in a freshwater system. In North America, the term watershed is often used instead of catchment area.  In the UK, watershed means the line separating two adjacent catchments.

CATCHMENT AREA (BASIN)—The area draining into a river, reservoir, or other body of water.

CATCHMENT BASIN—The entire area from which drainage is received by a river or a lake; most generally used in reference to surface runoff.

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.

CATFISH—A fish found in freshwater rivers and has long feelers around its mouth. Often used as food.

CATHOLE—A localism used by early settlers in southern Michigan for very small (usually less than an acre) shallow depressions or holes. The name presumably originated from the characteristic aquatic plant, the cattail, (Typha spp.). Later, the term came to be applied loosely to any shallow boggy or miry depression especially in the till clay plains. These depressions represented minor inequalities in the plains left by the ice sheet and were originally numerous but have been largely obliterated by land clearing and land drainage. The term cathole is also an old colloquialism for a hole or pond, in a stream, or swamp, frequented by catfish.

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. The common cations present in lakes in normal order of decreasing concentrations follows: calcium (Ca++), magnesium (MG++), potassium (K+), sodium (Na+), ammonium (NH4+), ferric iron (FE+++), or ferrous iron (FE++), manganese (Mn++), and hydrogen (H+).

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 formed by filling across wet or marshy ground, or the surface of a lake from shore to shore.

CAUSTIC—Alkaline or basic.

CAVE-IN LAKES—Kettle lakes, sink lakes, thaw lakes, thermo-karst.

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.

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.

CCE—Carbon - Chloroform Extract

CDI—Capacitive Deionization

CE-QUAL-ICM—Three-dimensional, time variable, integrated-compartment eutrophication model.

CE-QUAL-RIV—Hydrodynamic and water quality model for streams.

CE-QUAL-WZ—Two-dimensional, laterally averaged hydrodynamic and water quality model.

CEAM—Center for Exposure Assessment Modeling.

CEC—Cation Exchange Capacity

CELL—(Biology) The basic building block of all living matter. The cell of a living organism contains a high percentage of water.

CELLULAR—Made up of small compartments.

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 boiling point at one atmosphere of pressure; Abbreviation C; Compare to Centigrade [Temperature Scale]. The Celsius scale, which is identical to the centigrade scale, is named for the 18th-century Swedish astronomer Anders Celsius, who first proposed the use of a scale in which the interval between the freezing and boiling points of water is divided into 100 degrees. By international agreement, the term Celsius has officially replaced Centigrade. (2) Unit of measure for the Centigrade Temperature Scale of measuring temperature, as contrasted with the Fahrenheit unit of measure. The formula for converting a Celsius temperature to Fahrenheit temperature is °F = [9/5°C + 32]. Also see Temperature Scale.

CENOZOIC—Of, belonging to, or designating the latest era of geologic time, which includes the Tertiary Period and the Quaternary Period 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 spacing 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 Central Valley Project (CVP) encompass a number of dams, reservoirs, pumping facilities, canals, and aqueducts providing protection from saltwater intrusion into the Bay-Delta region (also referred to as the Sacramento-San Joaquin Delta), irrigation water for San Joaquin Valley farms, and municipal and industrial water for some of California's most populated urban areas. The construction of the CVP was approved by California voters in a 1933 referendum of the California Central Valley Project Act. Due to the effects of the Great Depression, the state was unable to construct the project at that time. Subsequently, portions of the CVP were authorized and constructed by the federal government. Other portions were later constructed by California after the Depression as part of the State Water Project (SWP), as authorized under the 1960 Burns-Porter Act. Principal facilities of the SWP include Oroville Dam, Delta Facilities, the California Aqueduct, and North and South Bay Aqueducts. Principle facilities of the federal CVP include Shasta, Trinity, Folsom, Friant, Clair Engle, Whiskeytown, and New Melones dams, Delta facilities, and the Delta Mendota Canal. Joint CVP/SWP facilities include San Luis Reservoir and Canal and various Delta facilities. Also see Bay-Delta [California].

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 sludge through use of centrifugal forces.

CEQA—See California Environmental Quality Act (CEQA).

CERCLA—See Comprehensive Environmental Response, Compensation, and Liability Act.

CERES—California Environmental Resources Evaluation System

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.

CF—Cubic Feet (or Foot).


CFR—Code of Federal Regulations.

CFS (Cubic Foot per Second)—A unit of discharge for measurement of flowing liquid (usually water in a stream) 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.

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.

CHAIN OF LAKES—A number of lakes tied together by live connecting streams or natural channels.

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 (LAKE)—In instances sub-lacustrine channels appear where a lake has been formed by the submergence of a valley, or the drowning of a river; the channels formed under subaerial conditions by stream cutting may remain unfilled by sediments, on the lake bottom.  Channel is applied to a surface water way, either natural or artificial, which connects two lakes and provides for boat travel; to river distributaries and connecting water in a delta; and to trench-like excavations extended inland from a lake shoreline to provide water frontages and boat access for back lots.

CHANNEL (LAKE BASIN)—The deeper, narrow elogated or more sharply trenched part of a lake bottom.

CHANNEL (WATERCOURSE)—A natural stream that conveys 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.

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.

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 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.

CHANNELED—Having one or more longitudinal grooves.

CHANNELIZATION—The artificial enlargement or realignment of a stream channel.

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 experiments describing convection and mixing in fluids, in wave motion, in oscillating chemical reactions, and in electrical currents in semiconductors. It is also found in the dynamics of animal populations and attempts are being made to apply chaotic dynamics in the social sciences, such as the study of business cycles. A chaotic system is defined as one that shows "sensitivity to initial conditions." That is, any uncertainty in the initial state of the given system, no matter how small, will lead to rapidly growing errors in any effort to predict its future behavior. This "sensitivity to initial conditions" will make any long-term prediction of such phenomenon virtually impossible in reality. In other words, the system is chaotic and as such its behavior can be predicted only if the initial conditions are known to an infinite degree of accuracy, which is impossible. The possibility of chaos in a natural, or deterministic, system was first envisaged by the French mathematician Henri Poincare in the late 19th century. More recently, predictions have been made that the transition to chaotic turbulence in a moving fluid would take place at a well-defined critical value of the fluid's velocity (or some other important factor controlling the fluid's behavior). The term chaotic dynamics refers only to the evolution of a system in time. Chaotic systems, however, also often display spatial disorder—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.

CHARA—Muskgrasses or stoneworts - An unusual type of algae that has a grown form resembling a higher plant, but a close look reveals each joint of the stem is a single cell with no connective tissue.

CHAROPHYTES—A group of green algae, visible to the naked eye, with a characteristic structure in which the 'stems' are very large single cells, from which whorls of similarly constructed branches emerge. Charophytes are anchored in sediments by branching cellular systems, not roots. They often deposit marl (calcium carbonate) giving them a rough texture and the common name of 'stoneworts', though not all do this. They also have a characteristic smell, which some people describe as 'garlicky'.

CHASM—Sometimes water filled, deep crack or opening in the earth's surface.

CHATTER MARK, also Chattermark —(Geology) One of a series of short scars made by glacial drift on a surface of bedrock.

CHECK DAM—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.

CHEMICAL—A substance made by chemistry. Oxidation is a chemical process in which iron combines with oxygen, commonly called rusting.

CHEMICAL EFFLUENTS—Non-natural liquids or emulsions discharged to a stream or lake.

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) 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 Biochemical Oxygen Demand (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 PARAMETERS—The constituent chemicals found in a sample of a media, such as water.

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.

CHEMIST—A person who specializes or works in chemistry.

CHEMISTRY—The science of substances. It describes their characteristics, catalogs them and determines what happens when they are combine together and react.

CHEMOAUTOTROPH—An organism that utilizes oxidation of inorganic chemicals for its energy and carbon dioxide for cell growth. Also called a Chemosynthetic Autroph.

CHEMOCLINE—(1) The transition zone between layers in a Meromictic Lake. Here the density is usually controlled more with what is dissolved in the water than the temperature of a fluid. (2) The boundary between mixolimnion and monolimnion. The density gradient of a 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.

CHILILE—Inshore lake bottom.

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—(1) 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. (2) Major light gathering pigment of all photosynthetic organisms and is essential for the process of photosynthesis. The amount present in lake water depends on the amount of algae and is therefore used as an common indicator of water quality.

CHLOROPHYLL MAPPING—Showing the variation of chlorophyll over the surface of a water body on a map.

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.

CHOLOPHYTE—Green algae, algae of the division Chlorophyta.

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.

CHRYSOPHYTE—Golden or yellow-green algae, algae of the division Chrysophyta.

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.

CIR—Consumptive Irrigation Requirement/Crop Irrigation Requirement.

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.

CIRQUE LAKE—A lake occupying a rock basin usually at the head of a valley in high mountain ranges.

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.

CLADOCERA—Water fleas. A group of crustaceans up to a few millimeters long, which either filter particles from water for food or grasp larger particles such as smaller animals. The best known genus is Daphnia.

CLAM—A mollusk with a hinged shell in two parts(bi-valve) and a soft body. An filter feeder in flowing fresh and salt waters.

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.

CLARITY—The transparency of a water column. Measured with a Secchi disc.

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. (Lakes) Grouping by similar water quality. For a description of soil classifications, see Land Capability Classes.

CLASTIC—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.

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.

CLAYBALLS—Both small and fairly large chunks of clay rounded by wave action. These are occasionally observed on Michigan beaches, especially a narrow strand bordered by steep clay banks of hard glacial till. Also known as mud balls, armored mud balls, pudding balls. Balls of a different origin, aggregates from clay in suspension or in a viscous state, are also sometimes formed in the beds of lakes and rivers.

CLAYBANKS (LAKESHORE)—Term applied to lake bluffs, or cliffs, composed almost entirely of till clay or glacial lacustrine clay.

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.

CLEAN (Water)—Water that is free from foreign matter or pollution; not infected; unadulterated.

CLEAN LAKES PROGRAM—Federal program evolved from Section 314 of the Clean Water Act.

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.

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.

CLIFF—Steep, vertical or overhanging rock faces. Provide physical protection for wildlife and concentrate a variety of reptiles, birds and mammals into relatively small but stable environments.

CLIFF (LAKESHORE)—Often used interchangeably with bank and bluff, in technical descriptions cliff is preferred for the wave-cut nearly vertical acclivity or abrupt slope which borders the waterline, or marks the position of the present or former shore lines of lakes.

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 science and study dealing with climate and climatic phenomena as exhibited by temperature, winds, and precipitation.

CLIMAX—The final stage of vegetation succession; a climax community reproduces itself and is in equilibrium with the existing environment.

CLOD—A compact, coherent mass of soil ranging in size from 5 to 10 millimeters (0.20 to 0.39 inch) to as much as 200 to 250 millimeters (7.87 to 9.84 inches) produced artificially, usually by the activity of man by plowing, digging, etc., especially when these operations are performed on soils that are either too wet or too dry for normal tillage operations.

CLOSED BASIN—A basin is considered closed with respect to surface flow if its topography prevents the occurrence of visible surface outflow. It is closed hydrologically if neither surface nor underground outflow can occur.

CLOSED-BASIN LAKE—A lake which has no outlet, from which water escapes only by evaporation.

CLOSED CANOPY—Forest trees dense enough that tree crowns fill or nearly fill the canopy layer.

CLOSED CONDUIT SYSTEM—A conveyance system where the flow of water is confined on all boundaries (i.e., pipe systems).

CLOSED-CYCLE COOLING—A process in which cooling water used in industrial processes or in the generation of electrical energy is not discharged into receiving streams, where direct discharge can have adverse effects, but is circulated through cooling towers, evaporators, ponds, or canals to allow the dissipation of the heat, and the water to be reused.

CLOSED DRAIN—Subsurface drain, tile, or perforated pipe that receives surface water through surface inlets.

CLOSED LAKES—Those that do not have an effluent in contrast to drainage lakes or open lakes which do have outlet streams. Closed lakes are common in arid and semi-arid regions where they usually contain saline or brackish water.

CLOSED-LOOP RECYCLING—Recycling or reusing wastewater for non-potable purposes in an enclosed process.

CLOSED WATER LOOP—A process in which decontaminated wastewater is not discharged into a receiving stream but is reused. Any water lost during the process through evaporation or binding with some material is replaced by makeup water. Contrast with Open Water Loop.

CLOSET—A water closet; a toilet.

CLOUD—A cloud is any concentration of gas, liquid droplets, or solid particles suspended as a distinct body in a gas or liquid. Generally, however, the term cloud is used to refer to the suspension of small ice or water particles in the Atmosphere. Cloud Formation—Clouds in the atmosphere form whenever the relative Humidity of an air mass, or parcel, reaches slightly more than 100 percent. This can occur for a number of reasons: the upward motion of air, which causes expansion and cooling; input of water from outside the parcel; or loss of heat by radiation. Among the major producers of the upward motion that results in clouds are the Low-Pressure systems with their cold, warm, and occluded Fronts; tropical disturbances such as Hurricanes, Cyclones, or Typhoons; and the lifting of air as it flows over hilly and mountainous terrain. The size of cloud droplets and ice crystals ranges from about 1 to 100 micrometers (4/100,000 to 4/1,000 in). Particles this small fall to the ground so slowly that they appear suspended in air, tending to move with the wind. The fall of larger particles, at much greater speeds, is called Precipitation. About 1 million cloud droplets, with an average radius of 10 micrometers (4/10,000 inch), are required to make a typical raindrop of 1 mm (4/100 inch). Cloud droplets can exist at temperatures below 0C (32F) and are then referred to as supercooled. When supercooled water and ice crystals occur at the same location, the ice grows at the expense of the water, and an ice cloud forms. This occurs because at a given temperature ice has a greater affinity than liquid water for water vapor. Cloud droplets and ice crystals first form on certain types of small particles of dust or other airborne materials. They are called condensation nuclei when water droplets are formed and ice nuclei when ice crystals result. The nuclei generally range in size from as small as 0.01 micrometer to about 1 micrometer (4/10,000,000 to 4/100,000 inch). The number of nuclei vary widely, depending on the source of the air mass in which the parcel is imbedded. The atmosphere over the ocean generally has the lowest number of nuclei, whereas polluted air has the highest. The more nuclei, and therefore the more water droplets or ice crystals, the slower the process of formation of precipitation-sized particles, because the competition for the available water is greater. Thus, although Rain often falls shortly after a cloud forms over the ocean, a much longer time is required over continental areas. Cloud Classification—Clouds are classed as warm if their temperature throughout is above 0C (32F) and cold if they extend to heights where temperatures are less than 0 C. Cold clouds containing both supercooled water and ice are defined as mixed clouds; clouds composed entirely of ice are said to be glaciated. Some cold clouds contain only supercooled water. These clouds are hazardous to aviation because the water, freezing on impact with an airplane, can cause ice to build up on the fuselage and wings. Clouds, defined in terms of their gross physical characteristics, can be classified as Stratiform or Cumuliform. Stratiform, or layered, clouds form when the upward motion is relatively uniform over an area, and cumuliform, or cottony, billowing clouds develop when upward and downward air currents are separated by fairly short distances. When clouds form at ground surface they are called Fog. Clouds that form in the middle Troposphere are called Altostratus and Altocumulus, and those in the upper troposphere are referred to as Cirrocumulus, Cirrostratus, or Cirrus. For those with bases in the lower troposphere, the terms Stratus and Cumulus are used. When precipitation is falling from these clouds, they are referred to with such terms as Nimbostratus or Cumulonimbus. Nimbostratus are the gray, leaden-sky clouds often produced by large-scale winter Cyclones in which precipitation is fairly steady and long-lasting. Cumulonimbus clouds, on the other hand, are associated with typical summertime Thunderstorms, in which rainfall is generally brief but heavy. A system of classifying clouds according to their physical characteristics has been devised by the World Meteorological Organization. Some of the more common cloud types are listed below:

[1] Cirrus—A high-altitude cloud composed of narrow bands or patches of thin, generally white, fleecy parts, typically at an average height of 7 miles (11.3 kilometers);
[2] Cirrocumulus—A high-altitude cloud composed of a series of small, regularly arranged cloudlets in the form of ripples or grains, typically at an average height of 5 miles (8 kilometers);
[3] Cirrostratus—A high-altitude, thin hazy cloud, usually covering the sky and often producing a halo effect, typically at an average height of 6 miles (9.7 kilometers);
[4] Altostratus—A somewhat high level, blue to grayish blue cloud that forms a sheet or layer, typically at an average height of 3.5 miles (5.6 kilometers);
[5] Altocumulus—A fleecy cloud, usually a rounded mass, but which can change radically and unexpectedly, producing intermediate forms, typically at an average height of 2.5 miles (4 kilometers);
[6] Cumulonimbus—An extremely dense, vertically developed cumulus with a relatively hazy outline and a glaciated top extending to great heights, usually producing heavy rains, thunderstorms, or hailstorms, typically at an average height of 4 miles (6.4 kilometers);
[7] Cumulus—A dense, white, fluffy, flat-based cloud with a multiple rounded top and a well-defined outline, usually formed by the ascent of thermally unstable air masses, typically at an average height of 2 miles (3.2 kilometers);
[8] Nimbus/Nimbostratus—A rain cloud, especially a low dark layer of clouds precipitating continuous rain or snow, typically at an average height of .25 mile (.4 kilometer);
[9] Stratus—A low-altitude cloud formation consisting of a horizontal layer of gray clouds, typically at an average height of .25 mile (.4 kilometer);
[10] Stratocumulus—A low-lying cloud formation occurring in extensive horizontal layers with rounded summits, typically at an average height of 1 mile (1.6 kilometers).

CLOUDBURST—A sudden and extremely heavy downpour of rain that is small in areal extent, of short duration, and may be accompanied by lightening, thunder, and strong gusts of winds. Also, a torrential (hard) downpour of rain, which by its spottiness and relatively high intensity suggests the bursting and discharge of water from a cloud all at once.

CLOUD CHAMBER—A vessel containing air saturated with water vapor whose sudden expansion reveals the passage of an ionizing particle by a trail of visible droplets.

CLOUD MODIFICATION—Any process by which the natural course of development of a cloud is altered by artificial means. Also referred to as Weather Modification.

CLOUD SEEDING—A Weather Modification technique involving the injection of a substance into a cloud for the purpose of influencing the cloud's subsequent development. Ordinarily, this refers to the injection of a nucleating agent, which creates a nucleus around which precipitation will form. In common practice, cloud seeding involves the aerial release of silver iodide particles into convective clouds to create thunderstorms.

CLOUDY—(1) When the sky is covered with clouds. A cloudy sky makes for a dark and gray day. (2) Water is cloudy and not clear so we couldn't see the stream bottom.

CLR—Classical Linear Regression Model.

CLUSTER DEVELOPMENT—Placement of housing and other buildings of a development in groups to provide larger areas of open space between groups.

CNE—Curve Number Equation.

COAGULANT—(1) An agent that causes a liquid or sol to coagulate. (2) (Wastewater Treatment) A chemical compound, such as Alum (aluminum sulfate), used to produce coagulation.

COAGULANT AID—(Wastewater Treatment) Fine particles with high surface area and high specific gravity providing for increased particle collisions during the neutralization process in wastewater treatment plants. They also improve settling and strengthen flocs in the coagulation process. They are generally used in much smaller doses than the coagulant itself. For example, Sodium Bicarbonate increases the efficiency of coagulation and extends the pH range to a level at which Alum (aluminum sulfate), is effective.

COAGULATE—To cause the transformation of a liquid or sol, for example, into or as if into a soft, semisolid, or solid mass.

COAGULATION—The clumping of particles which results in the settling of impurities. It may be induced by coagulants such as lime, alum, and iron salts.

COAL SLURRY PIPELINE—A pipeline which transports pulverized coal suspended in liquid, usually water.

COAST—According to prevailing usage, the term is applied to land bordering seas.  The shorelands of the Great Lakes are also called coasts.

COASTAL ZONE—Coastal waters and adjacent lands that exert a measurable influence on the uses of the seas and their resources and biota.

COASTAL ZONE MANAGEMENT ACT (CZMA)—A 1972 federal law, amended in 1980, that provides guidance and financial assistance to voluntary state and local coastal management programs. Goals of the program include the protection of natural resources and the management of land development in coastal areas, along shorelines, and on shorelands (extending inland as far as a strong influence on the shore is expected). The state programs established under the CZMA vary widely in their approach and application.

COASTLINE—The shape or outline of a coast.

COBBLE—Rock fragments 7.6 cm (3 inches) to 25.4 cm (10 inches) in diameter.


COD—See Chemical Oxygen Demand.

COD—See Cone of Depression.

CODE OF FEDERAL REGULATIONS (CFR)—The annual compilation of all current regulations that have been issued in final form by any federal regulatory agency. The publication is organized by subject titles. Environmental regulations are covered under Title 40, Protection of the Environment.

CO-DOMINANT—Two or more plant species providing about equal areal cover which in combination control the environment.

COE—Corps of Engineers

COEFFICIENT TERM—(Statistics) The weight applied to one of the Independent (or Exogenous) Variables in the best prediction of the Dependent (or Endogenous) Variable. It is interpreted as the slope of the relation between the independent variable and the dependent variable, or the change in the dependent variable for a unit change in the independent variable.

COEFFICIENT OF DETERMINATION (R2)—(Statistics) A common measure of the "Goodness of Fit" in Regression Analysis used to assess the degree of causation between two variables or between one or more independent variables and a single dependent variable. The coefficient of determination is equivalent to the square of the Correlation Coefficient and reflects the percent of variation in the dependent (explained) variable that is explained by the variations in the independent (explanatory) variable(s). The value of the coefficient of determination various between 0 (0 percent) and 1 (100 percent) with higher numbers representing better explanatory powers of a model in explaining the trends in historical data.

COEFFICIENT OF DISCHARGE—The ratio of the observed to theoretical discharge.

COEFFICIENT OF LINEAR EXTENSIBILITY—The ratio of the difference between the moist and dry lengths of a Clod to its dry length. The measurement correlates with the volume change of a soil upon wetting and drying.

COEFFICIENT OF MECHANICAL DIFFUSION—The rate at which solutes are mechanically mixed during Advective Transport, caused by the velocity variations at the microscopic level.

COEFFICIENT OF MOLECULAR DIFFUSION—(1) The rate at which solutes are transported at the microscopic level due to variations in the solute concentrations within the fluid phases. (2) The rate of dispersion of a chemical caused by the kinetic activity of the ionic or molecular constituents. Also referred to as the Diffusion Coefficient. See Molecular Diffusion.

COEFFICIENT OF ROUGHNESS—Factor in fluid flow determination expressing the character of a surface and its fractional resistance to flow. Also referred to as Roughness Coefficient.

COEFFICIENT OF RUNOFF—Factor in the rational runoff formula expressing the ratio of peak runoff rate to rainfall intensity.

COEFFICIENT OF STORAGE—The volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head.

COEFFICIENT OF TRANSMISSIVITY (t)—The rate at which water of the prevailing kinematic viscosity is transmitted through a unit width of the aquifer under a unit Hydraulic Gradient. It is equal to an integration of the hydraulic conductivities across the saturated part of the aquifer perpendicular to the flow paths. Also, the rate at which water is transmitted through a unit width of an aquifer under a unit hydraulic gradient. Transmissivity values are given in gallons per minute through a vertical section of an aquifer 1 foot wide and extending the full saturated height of an aquifer under a hydraulic gradient of one in the English Engineering System; in the Standard International System, transmissivity is given in cubic meters per day through a vertical section of an aquifer 1 meter wide and extending the full saturated height of an aquifer under hydraulic gradient of one. It is a function of properties of the liquid, the porous media, and the thickness of the porous media. Also see Transmissivity.

COEFFICIENT OF VARIATION, or VARIABILITY—The Standard Deviation of a statistic expressed as a fraction of the mean or a percentage.

COEFFICIENT OF VISCOSITY—The degree to which a fluid resists flow under an applied force, measured by the tangential friction force per unit area divided by the velocity gradient under conditions of streamline flow.

COFFERDAM—A temporary watertight enclosure that is pumped dry to expose the bottom of a body of water so that construction, as of piers, a dam, and bridge footings, may be undertaken. Also, a watertight chamber attached to the side of a ship to facilitate repairs below the water line. A Diversion Cofferdam prevents all downstream flow by diverting the flow of a river into a pipe, channel, or tunnel. Also see Dam, Caisson and Camel.

COHESION—A molecular attraction by which the particles of a body are united throughout the mass whether like of unlike. Compare to Adhesion.

COI—Cone of Influence.

COLD VAPOR—A method to test water for the presence of mercury.

COLD-WATER—Lacking modern plumbing or heating facilities, as a cold-water residence.

COLDWATER FISH—A fish that requires relatively cool water for survival. While the optimum temperature varies by species, most are found in water where temperatures are 20C (68F) or less.

COLIFORM (BACTERIA)—A group of organisms (Colon bacilli) usually found in the colons of all warm blooded animals and humans; non-pathogenic microorganisms used in testing water to indicate the presence of pathogenic bacteria. The presence of coliform bacteria in water is an indicator of possible pollution by fecal material. Generally reported as colonies per 100 milliliters (ml) of sample.

COLIFORM INDEX—An index of the bacteriological quality of water, based on a count of the numbers of coliform bacteria.

COLLECTION SITE—A stream, lake, reservoir, or other body of water fed by water drained from a watershed.

COLLECTOR SEWERS—Pipes used to collect and carry wastewater from individual sources to an interceptor sewer that will carry it to a treatment facility.

COLLECTOR SYSTEM—Conveys water from several individual sources such as groundwater wells and drains and surface inlet drains for rainstorm and snowmelt runoff to a single point of diversion. The collector system is associated with projects that increase water supply and decrease flood damage.

COLLECTOR WELL—A well located near a surface water supply used to lower the water table and thereby induce infiltration of surface water through the bed of the water body to the well.

COLLOIDAL SUSPENSION—Suspension in water of particles so finely divided that they will not settle under the action of gravity, but will diffuse, even in quiet water, under the random impulses of Brownian Movement. Particles typically range in size from about one micron (0.000001 millimeter) to about one millimicron; however, there is no distinct differentiation by particle size between true Suspension and colloidal suspension or between colloidal suspension and Solution.

COLLOIDS—Quantities of extremely small particles, typically 0.0001 to 1 micron in size, and small enough to remain suspended in a fluid medium without settling to the bottom. Substances that, when apparently dissolved in water or other liquid, diffuse not at all or very slowly through a membrane and show other special properties, as lack of pronounced effect on the freezing point or vapor pressure of the solvent. Colloids represent intermediate substances between a true dissolved particle and a suspended solid, which will settle out of solution.

COLLUVIAL MATERIAL—(Geology) Material consisting of Alluvium in part and also containing angular fragments of the original rocks. Typically found at the bottom or on the lower slopes of a hill.

COLLUVIUM—A general term used to describe loose and incoherent deposits of rock moved downslope by gravitational force in the form of soil Creep, slides, and local wash. Also see Colluvial Material.

COLON BACILLUS—(Microbiology) A rod-shaped bacterium, especially Escherichia coli (E. coli), a normal, generally nonpathogenic commensal found in all vertebrate intestinal tracts, but which can be virulent, causing diarrhea and other dysenteric symptoms. Its presence in water is an indicator of fecal contamination.

COLONIZATION—(Biology) As applied to vegetation, the invasion of a disturbed area; annual plants are often colonizing species.

COLOR—(1) Measured in units that relate to a standard. A yellow-brown natural color is associated with lakes or rivers receiving wetland drainage. The average color value for Wisconsin lakes is 39 units, with the color of state lakes ranging from zero to 320 units. Color also affects light penetration and therefore the depth at which plants can grow. (2) One control of light transmission through water. High color values in many lakes result from the decomposition of vegetation, which gives the water a brown, tea-like color. Determined by a comparison with standardized colored-glass discs and reported in platinum-cobalt (Pt-Co) units.

COLOR (OF LAKE WATERS)—An effect of light penetration, radiation absorption and reflection.  Related to: transparency and depth of water;type of lake bottom and matter held in solution; suspension or floating. Blues and greens are commonly observed in clear water lakes with clean bottoms of sand, rock or marl. Often, the blue tints are in deeper water and greens in shallower sections. Greens are often due to large populations of blue green and green algae in suspension or on the lake bottom. Yellows may be due to certain species of algae and to diatoms in large populations, and in certain types of lakes yellows have been attributed to sulfur bacteria. Pale yellows, yellow brown and coffee color or "black," can be produced by large quantities of dissolved humic substances and by particulate organic matter in suspension. Reds may be a reflection of the pigment color of certain algae; and may be caused by the presence of certain micro-crustaceans and other zooplankton; the "blood lakes" of central Europe are attributed to the presence of the microorganism Euglena sanguinea. Lake waters may be variously colored by suspended particulate inorganic matter especially that which is clayey or colloidal in nature. Some glacial lakes may be milky because of "glacial flour" in suspension, and the shallow water of marl lakes is often milky. Some colors are reflections of yellow sands on shallow bottoms, or from the black of organic sediments; or the blue of the sky. Colors vary with the weather, the time of day and the season. The words white and black have been used to describe lake waters. White has been applied where the water is merely colorless, and sometimes where it is milky from grey or white particulate matter in suspension. Black may be due to: large amounts of humic matter in solution, such as that in water flowing from some kinds of bogs; reflection of black bottoms; the dull appearance of some waters when the sky is heavily overcast. Unusual colors may be produced by pollution from industrial wastes.

COLORADO RIVER COMMISSION [Nevada]—An agency of the State of Nevada consisting of seven members, to include four members appointed by the Governor and three members from the Southern Nevada Water Authority Board of Directors. The Colorado River Commission has broad statutory authority to establish policies for the management of Nevada's allocation of power and water resources from the Colorado River and for the development of designated land in Southern Nevada.

COLORADO RIVER COMPACT—An agreement entered into on November 24, 1922 and ratified by the legislatures of the seven states within the Colorado River Basin—Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming—agreeing to the general allocation of the waters of the Colorado River. The compact divided the Colorado River Basin into an Upper Basin and a Lower Basin, with the division point established at Lees Ferry, a point in the mainstream of the Colorado River approximately 30 river miles south of the Utah-Arizona boundary. The Upper Basin was defined to include those parts of the states of Arizona, Colorado, New Mexico, Utah, and Wyoming within and from which waters naturally drain into the Colorado River system above Lees Ferry, and all parts of these states that are not part of the river's drainage system but may benefit from water diverted from the system above Lees Ferry. The Lower Basin was defined to include those parts of the states of Arizona, California, Nevada, New Mexico, and Utah within and from which waters naturally drain into the Colorado River system below Lees Ferry, and all parts of these states that are not part of the river's drainage system but may benefit from water diverted from the system below Lees Ferry. The compact did not apportion water to any state; however, it did apportion to each upper and lower basin the exclusive, beneficial consumptive use of 7,500,000 acre-feet of water per year from the Colorado River system in perpetuity. Further, the compact gave to the Lower Basin the right to increase its annual beneficial consumptive use of such water by 1,000,000 acre-feet. This compact cleared the way for federal legislation for the construction of Hoover Dam. Subsequently, the Upper Basin states entered into the Upper Colorado River Basin Compact on October 11, 1948 which provided Arizona to use 50,000 acre-feet of water per year from the upper Colorado River system and apportioned the remaining water to the Upper Basin states according to the following percentages: Colorado, 51.75 percent; New Mexico, 11.25 percent; Utah, 23 percent; and Wyoming, 14 percent. The Lower Basin states could not come to an agreement on apportionment on their own, and in October 1962, the U.S. Supreme Court ruled that of the first 7,500,000 acre-feet of mainstream water in the Lower Basin, California is entitled to 4,400,000 acre-feet (58.67 percent), Arizona to 2,800,000 acre-feet (37.33 percent), and Nevada to 300,000 acre-feet (4.00 percent).

COLVIN ALGORITHM—A canal flow control structure technique that operates the gates based on the rate of deviation of the water surface level from the setpoint.

COMBINED AVAILABLE CHLORINE—Concentration of chlorine which is combined with ammonia as chloramine or as other chloro-derivatives yet is still available to oxidize organic matter.

COMBINED RESIDUAL CHLORINATION—(Water Quality) The drinking water treatment method that involves the addition of chlorine to water at levels sufficient to produce, in combination with ammonia and/or organic amines, a Combine Available Chlorine residual. This chlorine residual maintains the treatment's disinfecting power throughout the water distribution system. Another approach to water chlorination is Breakpoint Chlorination.

COMBINED SEWER OVERFLOW (CSO)—(Water Quality) The condition that occurs when a Combined Sewer System (CSS) that is already loaded with wastewater experiences an influx of stormwater runoff from a heavy rain or melting snows. This causes the sewers to overload and excess stormwater and wastewater to discharge directly into receiving streams through overflow ports without treatment.

COMBINED SEWER SYSTEM (CSS)—A sewage system that carries both sanitary sewage and storm water runoff. During dry weather, combined sewers carry all wastewater for treatment. During storm events, part of the load may be intercepted to prevent overloading of the processing facility. In this case, the untreated portion is frequently allowed to enter the receiving stream. Also see Combined Sewer Overflow.

COMET—A celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated, curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist primarily of ammonia, methane, carbon dioxide, and water.

COMMERCIAL FRONTAGE (LAKE)—Riparian lands zoned for commercial use.

COMMERCIAL WATER USE—Water for motels, hotels, restaurants, office buildings, and other commercial facilities and institutions, both civilian and military. The water may be obtained from a public supply or may be self supplied. Also see Public Water Supply System and Self-Supplied Water.

COMMISSION—A group of persons choosen to do or oversee certain work.

COMMITTEE—A group of persons chosen to complete certain work.

COMMUNITY—(1) A naturally occurring, distinctive group of different organisms which inhabit a common environment, interact with each other, and are relatively independent of other groups. (2) A group of people who participate in a social and economic network of statistically significant frequency and within the cultural and geographic boundaries of the network.

COMMUNITY BEACH—Beach dedicated for the semi-exclusive use of a definite subdivision. Property owners in the subdivision may use the beach, but others are excluded. This riparian right should be properly defined on the deed of each lot. The actual ownership of the community beach may be vested in an association or each separate lot owner may be vested with a riparian interest.

COMMUNITY WATER SYSTEM—A public water system with 15 or more connections and serving 25 or more year-round residents and thus is subject to the U.S. Environmental Protection Agency (EPA) regulations enforcing the Safe Drinking Water Act (SDWA).

COMPACT, WATER—An agreement between states, ratified by Congress, providing for the division and apportionment of waters of an interstate river or other body of water.

COMPACTION—A physical change in soil properties that result in an increase in soli bulk density and a decrease in Porosity. The packing together of soil particles by forces exerted at the soil surface, resulting in increased soil density.

COMPENSATION LEVEL—The level in a body of water, usually occurring at the depth of 1 percent light penetration, which forms the lower boundary of the Zone of Net Metabolic Production. Also see Metabolism.

COMPENSATION POINT—The point under water at which plant photosynthesis just equals plant respiration. The water depth defines the lower boundary, where photosynthesis takes place, of the Euphotic Zone. Also referred to as the Compensation Level.

COMPLETE TREATMENT—A method of treating water that consists of the addition of coagulant chemicals, flash mixing, coagulation-flocculation, sedimentation, and filtration. Also referred to as Conventional Filtration.

COMPLETED TEST—(Water Quality) The third, and last, part of the examination of water for the presence of bacteria of fecal origin. Cultures that are scored as positive in the earlier steps of the analysis (Presumptive Test and Confirmed Test) are subjected to a verification by inoculating appropriate media (eosin methylene blue agar plates) and performing a gram-positive/gram-negative stain on isolated colonies.

COMPLETION—Sealing off access of undesirable water to the well bore by proper casing and/or cementing procedures.

COMPLIANCE CYCLE—(Water Quality) The 9-year calendar year cycle, beginning January 1, 1993, during which public water systems must monitor. Each cycle consists of three 3-year compliance periods.

COMPLIANCE MONITORING—(Water Quality) Collection and evaluation of data, including self-monitoring reports, and verification to show whether pollutant concentrations and loads contained in permitted discharges are in compliance with the limits and conditions specified in the permit.

COMPLIANCE SCHEDULE—(Water Quality) A negotiated agreement between a pollution source and a government agency that specifies dates and procedures by which a source will reduce emissions and, thereby, comply with a regulation.

COMPLY (EPA)—A term used to indicate compliance or adherence with Clean Water Standards, specifically with respect to a schedule or plan ordered or approved by a court of competent jurisdiction, the U.S. Environmental Protection Agency (EPA), or a water pollution control agency in accordance with the requirements of the Federal Water Pollution Control Act (Clean Water Act) [Public Law 92-500] and regulations issued pursuant thereto.

COMPOSITE SAMPLE—(Water Quality) A representative water or wastewater sample made up of individual smaller samples taken at periodic intervals and composited into one representative sample for analysis.

COMPOST—A mixture that consists largely of decayed organic matter, used for fertilizing and conditioning land.

COMPOUND—A substance composed of separate elements, ingredients, or parts. Water is a compound consisting of hydrogen and oxygen, chemical symbol H2O.

COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION, AND LIABILITY ACT (CERCLA)—Also referred to as the Superfund Law, this statute, originally enacted in 1980 and substantially modified in 1986, establishes the U.S. Environmental Protection Agency's (EPA) authority for emergency response and cleanup of hazardous substances that have been spilled, improperly disposed of, or released into the environment. The primary responsibility for response and cleanup is on the generators or disposers of the hazardous substances, with a backup federal response using a trust fund provision.

COMPREHENSIVE PLAN—(Natural Resource) A plan for water and related land resources development, that does consider all economic and social factors and provides the greatest overall benefits to the region as a whole.

COMPUTER APPLICATIONS—Computer programs written to perform certain tasks, such as word processing, mapping, etc.

COMPUTER MODELLING—Representing a system using mathematical equations and measured values.

COMPUTER PROGRAMS—Code used by the computer to accomplish a task.

CONCENTRATE—To make a solution or mixture less dilute, as by removing water from a solution.

CONCENTRATION—The amount of Solute present in proportion to the total Solution. More specifically, a measure of the average density of pollutants or other constituents, usually specified in terms of mass per unit volume of water or other Solvent (e.g., milligrams per liter) or in terms of relative volume of solute per unit volume of water (e.g., parts per million).

CONCENTRATION TIME—The period of time required for storm runoff to flow from the most remote point of a catchment or drainage area to the outlet or point under consideration. Concentration time varies with depth of flow and channel condition.

CONCENTRATION UNITS—Express the amount of a chemical dissolved in water. The most common ways chemical data is expressed is in milligrams per liter (mg/l) and micrograms per liter (ug/l). One milligram per liter is equal to one part per million (ppm). To convert micrograms per liter (ug/l) to milligrams per liter (mg/l), divide by 1000 (e.g. 30 ug/l = 0.03 ug/l). To convert milligrams per liter (mg/l) to micrograms per liter (ug/l), multiply by 1000 (e.g. 0.5 mg/l=500 ug/l). Microequivalents per liter (ueq/l) is also sometimes used, especially for alkalinity; it is calculated by dividing the weight of the compound by 1000 and then dividing that number into the milligrams per liter.

CONCORDANT FLOWS—Flows at different points in a river system that have the same Recurrence Interval, or the same frequency of occurrence. It is most often applied to flood-flows.

CONCRETE—A mixture of water, cement, sand, and pebbles. The hydration of cement and drying of concrete causes it to become very hard.

CONCRETE-GRAVITY STRUCTURE—A type of concrete structure in which resistance to overturning is provided only by its own weight.

CONDEMNATION—Taking private property for public use, with compensation to the owner, under the right of Eminent Domain.

CONDENSATE—A product of Condensation.

CONDENSATION—(1) (Physics) The process by which a gas or vapor changes to a liquid or solid; also the liquid or solid so formed. (2) (Chemistry) A chemical reaction in which water or another simple substance is released by the combination of two or more molecules. The opposite of Evaporation. In meteorological usage, this term is applied only to the transformation from vapor to liquid.

CONDENSE—(1) To cause a gas or vapor to change to a liquid. (2) To remove water from a substance, as from milk, for example.

CONDITIONAL WATER PERMIT—An authorization for the permittee to construct any facilities (such as a well and irrigation system) and to begin utilization of the water. A water right and a water permit are not the same thing. Also see Water Right.

CONDUCTANCE—A rapid method of estimating the dissolved solids content of a water supply by determining the capacity of a water sample to carry an electrical current.

CONDUCTIVITY—(1)A measure of the ability of a solution to carry an electrical current. (2)Measures water's ability to conduct an electric current or the total ionic concentration of water. Conductivity is reported in micromhos per centimeter (umhos/cm) and is directly related to the total dissolved inorganic chemicals in the water. Values are commonly two times the water hardness unless the water is receiving high concentrations of contaminants introduced by humans. A conductivity meter tests the flow of electrons through the water which is heightened in the presence of electrolytes (total dissolved solids). see Specific Conductance.

CONDUCTOR CASING—The temporary or permanent steel casing used in the upper portion of the borehole to prevent collapse of the formation during the construction of the well or to conduct the gravel pack to the perforated or screened areas of the casing.

CONDUIT—(1) A natural or artificial channel through which fluids may be conveyed. (2) (Dam) A closed channel for conveying discharge through, under, or around a dam.

CONE OF DEPRESSION (COD)/CONE OF INFLUENCE (COI)—A cone-like depression of the water table or other piezometric surface that has the shape of an inverted cone and is formed in the vicinity of a well by withdrawal of water. The surface area included in the cone is known as the area of influence of the well. Also referred to as the Pumping Cone and the Cone of Drawdown.

CONFIDENCE LIMITS—(Statistics) Bounds of statistical probability, e.g., 95 percent, 98 percent, 99 percent, etc., established as part of the testing criteria. The confidence limits express the statistical probability associated with the acceptance of an econometric model's results.

CONFINED AQUIFER—An aquifer which is bounded above and below by formations of impermeable or relatively impermeable material. An aquifer in which ground water is under pressure significantly greater than atmospheric and its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than that of the aquifer itself. See Artesian Aquifer.

CONFINED GROUND WATER—A body of ground water covered by material so impervious as to sever the hydraulic connection with overlying ground water except at the intake or recharge area. Confined water moves in pressure conduits due to the difference in head between intake and discharge areas of the confined water body.

CONFINED WATER (ARTESIAN)—Water under artesian pressure. Water that is not confined is said to be under water table conditions.

CONFINING BED—A body of "impermeable" material stratigraphically adjacent to one or more aquifers. It may lie above or below the aquifer. In nature its hydraulic conductivity may actually range from nearly zero to some value distinctly lower than that of the aquifer. In some literature, the term confining bed has now supplanted the terms Aquiclude, Aquitard, and Aquifuge. Also referred to as Confining Layer.

CONFINING UNIT—A hydrogeologic unit of relatively impermeable material, bounding one or more aquifers. This is a general term that has replaced Aquitard, Aquifuge, and Aquiclude and is synonymous with Confining Bed.

CONFIRMED TEST—(Water Quality) The second stage in the examination of water for the presence of bacteria of fecal origin. Cultures that are positive on the first portion of the testing procedure (the Presumptive Test) are inoculated into tubes of brilliant green lactose bile broth and examined for fermentation when incubated at 35C (95F) for 48 hours. If fermentation is present, a third stage, the Completed Test, is performed.

CONFLICTING USES (OF LAKE)—Uses that act to the detriment of other users. Technically, conflicts of use may exist only between riparians because all acts of others would be in the realm of trespass.

CONFLUENCE—(1) The act of flowing together; the meeting or junction of two or more streams or rivers; also, the place where these streams meet. (2) The stream or body of water formed by the junction of two or more streams or rivers; a combined flood.

CONFLUENT GROWTH—(Water Quality) A continuous bacterial growth covering all or part of the filtration area of a membrane filter in which the bacteria colonies are not discrete. In coliform testing, abundant or overflowing bacterial growth which makes accurate measurement difficult or impossible.

CONFOUNDING VARIABLE—(Statistics) A variable which is associated with two or more observed variables and which directly affects the relationship between the observed variables. Often causal relationships are attributed to the observed variables when, in fact, it is the confounding variable that is the true causal factor. By holding the behavior of the confounding variable constant, the relationship between the two observed variables is no longer evident. Also see Secondary (Indirect) Association.

CONIFER—A tree belonging to the order Coniferae with cones and leaves of needle shape or "scalelike."

CONIFEROUS—Pertaining to Conifers, which bear woody cones containing naked seeds.

CONJUNCTIVE MANAGEMENT—The integrated management and use of two or more water resources, such as a (ground water) aquifer and a surface water body.

CONJUNCTIVE OPERATION—The operation of a ground water basin in combination with a surface water storage and conveyance system. Water is stored in the ground water basin for later use by intentionally recharging the basin during years of above-normal water supply.

CONJUNCTIVE (WATER) USE—The combined use of surface and ground water systems and sources to optimize resource use and prevent or minimize adverse effects of using a single source.

CONNATE WATER—Water that was trapped in the interstices of a sedimentary or extrusive igneous rock at the time of its deposition. It is usually highly mineralized and frequently saline.

CONNECTING STREAM—A stream connecting a lake with another lake or stream.

CONNECTOR SYSTEM—Conveys water from a single source to a different location typically without intermediate collection of diversions. The connector system is associated with regulation reservoirs and intakes to pumping plants or powerplants.

CONSENT DECREE—(Environmental) A legal document approved by a judge, that formalizes an agreement reached between the U.S. Environmental Protection Agency (EPA) and a Potentially Responsible Party (PRP) or parties through which the PRP will conduct all or part of a cleanup action at a Superfund Site, cease or correct actions or processes that are polluting the environment, or otherwise comply with EPA initiated regulatory enforcement actions to resolve the contamination at the Superfund site involved. The consent decree describes the actions the PRP will take and may be subject to a public comment period.

CONSEQUENT ISLAND—An original island. An elevation in the lake basin which remained above the water surface at the time of the formation of the lake. Also called a residual island.

CONSEQUENT LAKE—Lake existing in a depression representing the original inequality in a new land surface. The ponds and lakes in depressions on the recently uplifted plains of sedimentation bordering the Atlantic Coast and forming a part of the Coastal Plain of the Southeastern US are consequent. Also called newland lakes. Lakes in a plain of glacial deposition may also be consequent.

CONSEQUENT STREAM—A stream following a course that is a direct consequence of the original slope of the surface on which it developed.

CONSERVATION—(1) Increasing the efficiency of energy use, water use, production, or distribution. (2) The careful and organized management and use of natural resource, for example, the controlled use and systematic protection of natural resources, such as forests, soil, and water systems in accordance with principles that assure their optimum long-term economic and social benefits. Also, preservation of such resources from loss, damage, or neglect.

CONSERVATION DISTRICT—A public organization crated under state-enabling law as a special purpose district to develop and carry out a program of soil, water, and related resource conservation, use, and development within its boundaries. In the United States, such districts are usually a subdivision of state government with a local governing body and are frequently called a soil conservation district or a soil and water conservation district.

CONSERVATION EASEMENT—An agreement negotiated on privately owned lands to preserve open space or protect certain natural resources.

CONSERVATION EDUCATION—A comprehensive concept that spans curricula from kindergarten through adult, post-graduate programs and links the subject to natural resource conservation, stressing the characteristics and interrelationships in management and use of our natural resources that will result in knowledgeable citizenry with attitudes of responsibility toward the conservation of those natural resources.

CONSERVATION PLAN—A collection of material containing land user information requested for making decisions regarding the conservation of soil, water, and related plant and animal resources, along with necessary habitat, for all or part of an operating unit.

CONSERVATION PRACTICE—A technique or measure used to meet a specific need in planning and carrying out soil and water conservation programs for which standards and specifications have been developed.

CONSERVATION STANDARDS—Standards for various types of soils and land uses, including criteria, techniques, and methods for the control of erosion and sediment and impacts on plant and animal species and necessary habitat resulting from land disturbing activities.

CONSERVATION STORAGE—The portion of water stored in a reservoir that can be later released for useful purposes such as municipal water supply, power, or irrigation. Conservation storage is the volume of water stored between dead reservoir storage and flood control storage.

CONSERVATION TILLAGE—A level of reduced tillage combined with one or more soil and water conservation practices designed to reduce loss of soil or water relative to conventional tillage. Such activities often take the form of non-inversion tillage that retains productive amounts of residue mulch on the surface.

CONSERVATIVE SUBSTANCES—Non- interacting substances, undergoing no kinetic reactions; chloride and sodium are approximate examples.

CONSOLIDATED AQUIFER—An aquifer made up of consolidated rock that has undergone solidification or lithification.

CONSOLIDATED FORMATION—Geological formations which occur naturally and have been turned to stone. The term is sometimes used interchangeably with the word Bedrock. It includes rock such as basalt, rhyolite, sandstone, limestone and shale. Typically, these formations will stand at the edges of a bore hole without caving.

CONSOLIDATION—(Soil Mechanics) Adjustment of a soil in response to increased load; involves squeezing of water from the pores and a decrease in void ratio (pore space). Frequently the geologic term Compaction is used instead.

CONSOLIDATION GROUTING (of a Dam)—The injection of grout to consolidate a layer of the foundation, resulting in greater impermeability and/or strength. Also referred to as Blanket Grouting. Also see Blanket (of a Dam).

CONSOLUTE—Of or relating to liquid substances that are capable of being mixed in all proportions.

CONSTANT HEAD ORIFICE TURNOUT (Canal)—A calibrated structure containing an adjustable orifice gate and a gate downstream to control a constant head differential across the orifice gate to divert and measure water from a main irrigation canal to a distributing canal.

CONSTANT VOLUME OPERATION METHOD (Canal)—A canal operation that maintains a relatively constant water volume in each canal pool.

CONSTITUENTS—Any of the chemical substances found in water. Typically, measurements of such constituents in sampled drinking water may consist of Total Dissolved Solids (TDS), Hardness (concentrations of Calcium and Magnesium, specifically), Sodium, Potassium, Sulfate, Chloride, Nitrate, Alkalinity, Bicarbonate, Carbonate, Fluoride, Arsenic, Iron, Manganese, Copper, Zinc, Barium, Boron, Silica, as well as other physical characteristics and properties such as water color, turbidity, pH, and electro-conductivity (EC). [As an example of constituents and their acceptable levels for drinking water, see Appendix D-5, Nevada Drinking Water Standards.]

CONSTRUCTED WETLANDS—(1) Wetlands constructed by man either as part of a Wetland Banking, Wetland Clumping (Aggregation), or Wetland Mitigation program, or to achieve some other environmental preservation or restoration program. (2) (Water Quality) Wetlands constructed specifically for the purpose of treating waste water effluent before re-entering a stream or other body of water or being allowed to percolate into the groundwater. Also see Lagoon.

CONSTRUCTION—The process of building.

CONSTRUCTION JOINT (of a Dam)—The interface between two successive placings or pours of concrete in a dam's structure where a bond, and not a permanent separation, is intended.

CONSUMABLE WATER SUPPLY—That amount of river water available for consumption at a given point on the river after existing prior water rights have been met.

CONSUMERS—Organisms that obtain their energy by eating other organisms; generally divided into primary consumers (herbivores), secondary consumers (carnivores), and microconsumers (decomposers).

CONSUMPTION, DOMESTIC—The quantity or quantity per capita (person) of water consumed in a municipality or district for domestic uses during a given period, usually one day. Domestic consumption is generally considered to include all uses included in "municipal use of water," in addition to the quantity of water wasted, lost, or otherwise unaccounted for. Also see Consumption, Municipal; Municipal Use of Water.

CONSUMPTION, INDUSTRIAL—The quantity of water consumed in a municipality or district for mechanical, trade, and manufacturing uses during a given period, usually one day.

CONSUMPTION, MUNICIPAL—The quantity of water consumed through use in developed urban areas. Also see Consumption, Domestic; Consumptive Use.

CONSUMPTIVE IRRIGATION REQUIREMENT (CIR)—The quantity of irrigation water, exclusive of precipitation, stored soil moisture, or ground water, that is required consumptively for crop production.

CONSUMPTIVE USE (LAKE WATERS)—Implies withdrawal of water for such purposes as irrigation, power generation and industrial, municipal and domestic water supplies. Destructive use, such as for waste disposal or as a carrier for sewage, is considered consumptive. Nonconsumptive uses (those that do not reduce the supply) are: recreational, bathing, fishing, boating and hunting, navigable waterways and for aquaculture.

CONSUMPTIVE WASTE—Water that returns to the atmosphere without providing benefit to humans.

CONSUMPTIVE WATER USE—(1) A use which lessens the amount of water available for another use (e.g., water that is used for development and growth of plant tissue or consumed by humans or animals). (2) The portion of water withdrawn from a surface or groundwater source that is consumed for a particular use (e.g., irrigation, domestic needs, and industry), and does not return to its original source or another body of water. The terms Consumptive Use and Nonconsumptive Use are traditionally associated with water rights and water use studies, but they are not completely definitive. No typical consumptive use is 100 percent efficient; there is always some return flow associated with such use either in the form of a return to surface flows or as a ground water recharge. Nor are typically nonconsumptive uses of water entirely nonconsumptive. There are evaporation losses, for instance, associated with maintaining a reservoir at a specified elevation to support fish, recreation, or hydropower, and there are conveyance losses associated with maintaining a minimum streamflow in a river, diversion canal, or irrigation ditch.

CONSUMPTIVE WATER USE, IRRIGATION—The quantity of water that is absorbed by the crop and transpired or used directly in the building of plant tissue, together with that evaporated from the cropped area. Does not include runoff or deep percolation in support of the Crop Leaching Requirement.

CONSUMPTIVE WATER USE, NET—The consumptive use decreased by the estimated contribution by rainfall toward the production of irrigated crops. Net consumptive use is sometimes referred to as the Crop Irrigation Requirement.

CONSUMPTIVE WATER USE REQUIREMENT (CROP)—The annual irrigation consumptive use expressed in feet or acre-feet per acre.

CONTACT RECREATION (Water)—Recreational activities involving a significant risk of ingestion of water, including wading by children, swimming, water skiing, diving and surfing.

CONTACT STABILIZATION—A modification of the Activated Sludge Process wherein a contact basin provides for the rapid adsorption of the waste. A separate tank is provided for stabilization of the solids before they are reintroduced into the raw wastewater flow.

CONTAMINANT—(Water Quality) In a broad sense any physical, chemical, biological, or radiological substance or matter in water. In more restricted usage, a substance in water of public health or welfare concern. Also, an undesirable substance not normally present, or an usually high concentration of a naturally-occurring substance, in water, soil, or other environmental medium.

CONTAMINATE—To make impure or unclean by contact or mixture.

CONTAMINATION (WATER)—Impairment of the quality of water sources by sewage, industrial waste, or other matters to a degree which creates a hazard to public health. Also, the degradation of the natural quality of water as a result of man's activities. There is no implication of any specific limits, since the degree of permissible contamination depends upon the intended end use, or uses, of the water. See Pollution.

CONTENTS (STORAGE)—The volume of water in a reservoir. Unless otherwise indicated, reservoir content is computed on the basis of a level pool and does not include bank storage.

CONTINENTAL DIVIDE—A drainage divide separating the rivers which flow toward opposite sides of a continent.

CONTINENTAL DIVIDE [United States]—A ridge of the Rocky Mountains forming the North American watershed that separates rivers flowing in an easterly direction from those flowing in a westerly direction.

CONTINENTAL DRIFT—The theory that continents slowly shift their positions as a result of currents in the molten rocks of the earth's mantle.

CONTINENTAL SHELF—The submerged shelf of land that slopes gradually from the exposed edge of a continent for a variable distance to the point where the steeper descent (the Continental Slope) to the ocean bottom begins, commonly at a depth of about 600 feet (183 meters).

CONTINUITY EQUATION—The relation, based on the conservation of mass, that equates the Volumetric Flow Rate, Q, of an incompressible fluid in a duct or pipe to the product of the fluid velocity, V, and the cross-sectional area, A, of the duct or pipe, by

Q = VA

If the area, A, increases, then the velocity, V, must decrease, and conversely. The equation is also applied to liquid flow through a system, stating that the flow in, Qin, flow out, Qout, and the change in the storage volume for a given time must be in balance, or

QinQout = Change in Storage Volume

CONTINUOUS DELIVERY—A method of delivering water to the farm headgate from an irrigation conveyance system on a continuous basis, as opposed to a demand delivery where flows are delivered on a rotational time schedule and/or upon demand.

CONTINUOUS DISCHARGE—A routine release to the environment that occurs without interruption, except for infrequent shutdowns for maintenance, process changes, etc.

CONTINUOUS RECORDER (GAGE)—A device which measures stream flow levels on a continual basis.

CONTINUOUS SAMPLE—A flow of water from a particular place in a plant to the location where samples are collected for testing. May be used to obtain Grab Samples or Composite Samples.

CONTOUR—A line on a map that indicates a line of equal elevation on the land or water in feet over mean sea level. A line of equal thickness of water depth, soil or sediment thickness, or geologic structure thickness.

CONTOUR DITCH—An irrigation ditch laid out approximately on the contour, or elevation of the land.

CONTOUR FLOODING—Irrigation method resulting in flooding fields from Contour Ditches.

CONTOUR-FURROW IRRIGATION—The application of irrigation water in furrows that run across the slope with a forward grade in the furrows.

CONTOUR FURROWS—Furrows plowed approximately on the contour on pasture and rangeland to prevent runoff and increase infiltration; also, furrows laid out approximately on the contour for irrigation purposes.

CONTOUR PLOWING—A soil tilling technique that follows the shape of the land to minimize erosion.

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 crops.

CONTOUR TRENCHING—Development of water storage Detention or Retention Facilities along the contour by excavation and placement of soils as an embankment along the downstream side. Intervals vary with precipitation, slope, and soil.

CONTRACT (USBR)—Any repayment or water service contract between the United States and a district providing for the payment of construction charges to the federal government, including normal operation, maintenance, and replacement costs pursuant to federal reclamation law. All water service and repayment contracts are considered contracts even if the contract does not specifically identify that portion of the payment which is to be attributed to operation and maintenance and that which is to be attributed to construction.

CONTRACT RATE (USBR)— The repayment or water service rate set forth in a contract to be paid by a district to the federal government.

CONTRAIL—A visible trail of streaks of condensed water vapor or ice crystals sometimes forming in the wake of an aircraft. Also referred to as Vapor Trail.

CONTRIBUTING AREA—That portion of a watershed which contributes to measured runoff under normal conditions.

CONTROL—A natural constriction of the channel, a long reach of the channel, a stretch of rapids, or an artificial structure downstream from a Gaging Station that determines the Stage-Discharge Relation at the gage. A control may be complete or partial. A complete control exists where the stage-discharge relation at a gaging station is entirely independent of fluctuations in stage downstream from the control. A partial control exists where downstream fluctuations have some effect upon the stage-discharge relation at a gaging station. A control, either partial or complete, may also be shifting. Most natural controls are shifting to a degree, but a shifting control exists where the stage-discharge relation experiences frequent changes owing to impermanent bed or banks.

CONTROL DAM—A dam or structure with gates to control the discharge from the upstream reservoir or lake.

CONTROL POINTS (Horizontal and Vertical)—Small monuments that are securely embedded in the surface of a dam and used to detect any movement with respect to Permanent Monuments placed away from the dam itself.

CONTROL SCHEME (Canal)—The collection of methods and algorithms brought together to accomplish control of a canal system.

CONTROL STRUCTURE (LAKE LEVEL)—Dam, dike, pump or any structure built for the purpose of controlling the water level of a lake or pond.

CONTROL SYSTEM (Canal)—An arrangement of electronic, electrical, and mechanical components that commands or directs the regulation of a canal system.

CONTROLLED DRAINAGE—(Irrigation) Regulation of the water table to maintain the water level at a depth favorable for optimum crop growth.

CONTROLLED VOLUME OPERATION METHOD (Canal)—An operation in which the volume of water within a canal reach between two check structures is controlled in a rescribed manner for time variable inflows and outflows such as off-peak pumping or canal-side deliveries.

CONVECTION—(1) (Physics) Heat transfer in a gas or liquid by the circulation of currents from one region to another; also fluid motion caused by an external force such as gravity. (2) (Meteorology) The phenomenon occurring where large masses of warm air, heated by contact with a warm land surface and usually containing appreciable amounts of moisture, rise upward from the surface of the earth.

CONVECTIVE CLOUDS—Clouds generated by the rising of air over a relatively warm land mass.

CONVECTIVE PRECIPITATION—Precipitation resulting from vertical movement of moisture-laden air, which upon rising, cools and precipitates its moisture.

CONVECTIVE TRANSPORT—The component of movement of heat or mass induced by thermal gradients in ground water. Also see Advection.

CONVENTIONAL ACTIVATED SLUDGE—A process in which influent and recycled sludge enter at the head of the aeration tank.

CONVENTIONAL METHOD (Canal)—Where operations personnel (ditchrider and watermaster) control the canal system onsite. Labor-saving devices and machinery may be used to assist in the control of the canal facilities.

CONVENTIONAL SYSTEMS—(Water Quality) Systems that have been traditionally used to collect municipal wastewater in gravity sewers and convey it to a central primary or secondary treatment plant prior to discharge to surface waters.

CONVENTIONAL TILLING—Tillage operations considered standard for a specific location and crop and that tend to bury the crop residues; usually considered as a base for determining the cost effectiveness of control practices.

CONVENTIONAL WATER—A natural freshwater supply as opposed to desalted or brackish water.

CONVEYANCE LOSS—Water that is lost in transit from a pipe, canal, conduit, or ditch by leakage, seepage, evaporation, or evapotranspiration. Generally, these conveyance losses are not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a ground-water source and be available for further use.

COOLANT—An agent, such as water, that produces cooling as by drawing off heat by circulating through an engine or by bathing a mechanical part.

COOLING POND—Usually a man-made water body used by power plants or large industrial plants that enables the facility to recirculate once-through cooling water. The water levels in the pond are usually maintained by rainfall or augmented by pumping (withdrawal) water from another source. Also see Cooling Water and Once-Through Cooling Water.

COOLING TOWER—A large tower or stack that is used for heat exchange of once-through cooling water generated by steam condensers. Hot water from the plant is sprayed in the tower and exchanges heat with the passing air. The water is then collected at the bottom of the tower and used again. A small amount of water is lost (consumed) through evaporation in this process. Also see Cooling Water and Once-Through Cooling Water.

COOLING WATER—Water used for cooling purposes by electric generators, steam condensers, large machinery or products at industrial plants, and nuclear reactors. Water used for cooling purposes can be either fresh or saline and may be used only once or recirculated multiple times. Also see Cooling Pond and Once-Through Cooling Water.

COOLING WATER CONSUMPTION (POWER)—The cooling water which is lost to the atmosphere, caused primarily by evaporation due to the temperature rise in the cooling water as it passes through the condenser. The amount of consumption (loss) is dependent on the type of cooling employed—Once-Through Cooling Water, Cooling Pond, or Cooling Tower.

COOLING WATER LOAD—The waste heat energy dissipated in the cooling water.

COOLING WATER REQUIRED (POWER)—The amount of water needed to pass through the condensing unit in order to condense the steam to water.

COORDINATED RESOURCE MANAGEMENT AND PLANNING—A planning process used by the U.S. Department of the Interior, Bureau of Land Management (BLM) that includes public users, interest groups, agencies and affected individuals in the decision-making process before on-the-ground implementation of an activity plan.

COORDINATED RESOURCE PLAN—A conservation plan including privately-owned land and public land.

COPEPODITES—The penultimate five, out of a total of twelve, life history stages of copepods.

COPEPODS—Group of crustaceans more diverse in the sea than freshwaters. Some species filter particles for food, others grasp larger particles such as smaller animals. The life history comprises six successively larger naupliar and then five copepodite stages before the sexually reproducing adults are formed as the twelfth stage.

CO-PERMITTEE—A permittee to a NPDES permit that is only responsible for permit conditions relating to the discharge for which it is operator.

CORE—(Geology) The central portion of the earth below the Mantle, beginning at a depth of about 2,900 kilometers (1,800 miles) and probably consisting of iron and nickel. It is made up of a liquid outer core and a solid inner core.

CORE WALL (of a Dam)—A wall built of impervious material, usually concrete or asphaltic concrete, in the body of an Embankment Dam to prevent leakage.

CORIOLIS EFFECT—(Climatology and Oceanography) The Coriolis effect, named for French physicist Gaspard Coriolis (1792-1843), is an imaginary force that appears to be exerted on an object moving within a rotation system. The apparent force is simply the acceleration of the object caused by the rotation. This effect may seen on a large scale in the movement of winds and ocean currents on the rotating earth. It dominates weather patterns, producing the counterclockwise flow observed around low-pressure zones in the Northern Hemisphere and the clockwise flow around such zones in the Southern Hemisphere. This effect is also responsible for the rotation of water funnels in the drains of tubs and water basins; the funnels will rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Along the equator, there will be no such rotation.

CORMIX—Cornell Mixing Zone Expert System.

CORN SNOW—Snow that has melted and refrozen into a rough, granular surface.

CORONA—(Astronomy) A faintly colored luminous ring appearing to surround a celestial body visible through a haze or thin cloud of water vapor, especially such a ring around the moon or sun, caused by the diffraction of light from suspended matter in the intervening medium. Also referred to as Aureole.

(U.S. ARMY) CORPS OF ENGINEERS (COE)—See (United States) Army Corps of Engineers (COE). [See Appendix C-2 for the U.S. Army Corps of Engineers' organizational structure and primary missions and objectives.]

CORRASION—The wearing away of earth materials through the cutting, scraping, scratching, and scouring effects of solid material carried by water or air.

CORRELATION—(Statistics) A statistical means to measure the degree of "coincidence of change" between two variables, producing a value of variance termed the Correlation Coefficient. In strict correlation analysis, no inference of causation, i.e., one variable being "explained" by the variations of another, is made. Therefore, high correlations do not provide for an inference of causality; one must use previous information that the two sampled variables are indeed related to one another. The concept of the Coefficient of Determination, on the other hand, used as a common measure of "Goodness of Fit" in Regression Analysis, is used to assess the degree of causation between two variables or between one or more independent variables and a single dependent variable. The coefficient of determination is equivalent to the square of the correlation coefficient and reflects the percent of change in the dependent (explained) variable that is explained by the variations in the independent (explanatory) variable.

CORRELATION COEFFICIENT (R)—(Statistics) A measure of the coincidence of change between two variables. The use of the correlation coefficient makes no inference as to causation, i.e., one variable causing changes to occur in another; it only represents a measure of the simultaneous behavior between two variables which either are related or are being affected similarly by a third variable. The value of the correlation coefficient will vary between -1.00 (-100 percent) and +1.00 (+100 percent) with higher numbers representing stronger levels of coincidence of changes. Positive correlation coefficients denote that the two series evidence changes in the same direction while negative correlation coefficients reflect an inverse relationship between changes in one series and another.

CORRELATIVE ESTIMATE—A discharge or stream flow estimate determined by Correlation, or comparisons to other, possibly influencing factors, e.g., rainfall, snowpack, levels of upstream lakes and reservoirs, etc. A correlative estimate represents a likely value of the discharge or flow for any particular period—commonly a month—according to a specified method of analysis and the explanatory variables chosen.

CORRELATIVE (WATER) RIGHTS—Certain rights of land owners over a common ground water basin are coequal, or correlative, so that any one owner cannot take more than his share even if the rights of others are impaired. Where a source of water does not provide enough for all users, the water is reapportioned on the basis of prior water rights held by each user.

CORROSIVE—A substance that deteriorates material, such as pipe, through electrochemical processes.

CORRUGATION IRRIGATION—Spreading water by directing it into small channels across the field. Also referred to as Furrow Irrigation.

COSMETIC SOLUTION—Acting upon symptoms or given conditions without correcting the actual cause of the symptoms or conditions.

COST-BENEFIT ANALYSIS (CBA)—Analysis technique which compares the cost of a project with the benefits derived from it. Expressed as a ratio of benefits to costs. Ratios greater than 1.0 are deemed to be cost-effective. The determination of costs and benefits to be included in the analysis can be a contentious issue, particularly for public goods and the monetization of natural resources.

COTTAGE-WATER RATIO—The ratio between the number of shoreland cottages or lake homes (whose owners or occupants have access to the water) and the area (expressed in acres) of the lake surface.

COULEE—(1) (Western U.S.) A deep gulch or ravine with sloping sides, often dry in summer. (2) (Louisiana and Southern Mississippi) A streambed, often dry according to the season; a small stream, bayou, or canal. (3) (Upper Midwest) A valley with hills or either side. (4) (Geology) A stream of molten lava; a sheet of solidified lava.

COULOIR—A deep mountain gorge or gully.

COUPON TEST—A method of determining the rate of corrosion or scale formation by placing metal strips (or coupons) of a known weight in the pipe.

COURSE (WATER)—The route or path taken by flowing water, such as a stream or river.

COVARIANCE—(Statistics) A measure of the linear association between two variables. If both variables are always above and below their means at the same time, the covariance is said to be positive. If one variable is above its mean when the other variable is below its mean and vice versa, the covariance is said to be negative. The value of the covariance is dependent upon the units in which each variable is measured whereas the Correlation Coefficient is a measure of this association which has been normalized and is therefore "unit free."

COVE—A small sheltered inlet, creek, or bay; a recess in the shore.

COVER—(1) Vegetation or other material providing protection to a surface. (2) The area covered by live above-ground parts of plants.

COVER CROP—A close-growing crop grown primarily for the purpose of protecting and improving soil between periods of regular crop production or between trees and vines in orchards and vineyards.

CP—Cultural Practices.

CPI—Consumer Price Index.

CRADLE—A supporting structure shaped to fit the conduit it supports.

CRANBERRY—A sour, red berry grown on low bushes in bogs and swamps. Used to make jelly, juice and sauce.

CRANBERRY BOG—A bog dominated by this mat-forming evergreen shrub; common in eastern North America. Most commercial operations require planting and some form of water level control for frost protection and to facilitate harvesting.

CRATER LAKE—A lake formed in a crater. Caldera are basins formed by the collapse of magma in the vents of volcanoes. Maars are volcanic basins formed by single explosive eruptions. Depressions in the earth's surface made by impact of falling meteors are also called craters, although the existence of only a few crater lakes of this origin has been clearly established.

CRAYFISH—Freshwater crustacean smaller than a lobster. Also called crawfish.

CREAMS—Chemicals, Runoff and Erosion from Agricultural Management Systems.

CREEK—A small stream of water which serves as the natural drainage course for a drainage basin; a flowing rivulet or stream of water normally smaller than a river and larger than a brook. The term is often relative according to size and locality. Some creeks in a humid region would be called rivers if they occurred in an arid area.

CREEP—Slow mass movement of soil and soil material down relatively steep slopes, primarily under the influence of gravity but facilitated by saturation with water and by alternate freezing and thawing.

CREEPER—A grappling device for dragging bodies of water, such as lakes or rivers.

CREOSOTE—Chemical used in wood preserving operations and produced by distillation of tar, including Polycyclic Aromatic Hydrocarbons and Polynuclear Aromatic Hydrocarbons (PAHs and PNAs). Contaminating sediments, soils, and surface water, creosotes may cause skin ulcerations and cancer with prolonged exposure.

CREST—(1) The top of a dam, dike, or spillway, which water must reach before passing over the structure; in international usage it refers to the crown of an overflow section of a dam. (2) The summit or highest point of a wave. (3) The highest elevation reached by flood waters flowing in a channel as in Crest Stage or Flood Stage.

CREST GAGE—An instrument used to obtain a record of flood crests at sites where recording gages are not installed.

CREST GATE—A temporary or movable gate installed on top of a spillway crest to provide additional storage or prevent flow over the crest.

CREST LENGTH—The length of the top or crest of a dam, including the length of the spillway, powerhouse, navigation lock, fish pass, etc., where these structures form part of the length of a dam. If detached from a dam, these structures would not be included in the crest length.

CREST STAGE—The highest value of river Stage (or streamflow) attained in a flood.

CREST WIDTH (or Top Thickness)—The thickness or width of a dam at the level of the top (crest) of the dam. In general, the term "thickness" is used for Gravity and Arch Dams and the term "width" is used for other dams.

CREVASSE—(1) A deep crack or fissure, especially in a glacier. (2) A break in the levee of a river, dike, or similar structure. Also see Levee.

CRIB DAM—A barrier or form of Gravity Dam constructed of timber forming bays, boxes, cribs, crossed timbers, gabions or cells that are filled with earth, stone or heavy material. Also see Dam.

CRICK—(Inland Northern U.S. and Western U.S.) Variant of Creek.

CRITERIA—Water quality conditions which are to be met in order to support and protect desired uses.

CRITERIA, TESTING (R2, t-Statistic, and F-Statistic)—(Statistics) In criteria testing of the appropriateness of a econometric forecast model's structure (Specification), certain testing criteria are used most frequently. Specifically, the Coefficient of Determination, R2, is used as an overall measure of the "goodness of fit," the t-Statistic, is used as a measure of the appropriateness of individual explanatory variables, and the F-Statistic, is used as a measure of the appropriateness of the inclusion or exclusion of a set of explanatory variables simultaneously. Also see Model and Regression Analysis.

CRITERIA, WHPA—Conceptual standards that form the basis for Wellhead Protection Area (WHPA) delineation. WHPA criteria can include distance, drawdown, time of travel, assimilative capacity, and flow boundaries. See Wellhead Protection Area (WHPA) and Wellhead Protection (Program).

CRITICAL—(Chemistry and Physics) Of or relating to the value of a measurement, such as temperature, at which an abrupt change in a quality, property, or state occurs. For example, a critical temperature of water is 100C (212F), its boiling point at standard atmospheric pressure.

CRITICAL AQUIFER PROTECTION AREA (CAPA)—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 Amendments of 1986, and for which an areawide ground-water protection plan has been approved under Section 208 of the Clean Water Act (CWA) prior to such enactment.

CRITICAL AREA—An area that, because of its size, location, condition, or importance, must be treated with special consideration because of inherent site factors and difficulty of management. Also, a severely eroded, sediment-producing area that requires special management to establish and maintain vegetation to stabilize the soil.

CRITICAL (GROUND WATER) AREA—An area that has certain ground water problems, such as declining water levels due, for example, to the use of underground water that approaches or exceeds the current recharge rate. These designated areas are usually limited in their development and use.

CRITICAL DEPTH—The depth of water flowing in an open channel or conduit under conditions of critical flow at which specific energy is a minimum for a given discharge.

CRITICAL DRY PERIOD—As a general definition, describes a series of water-deficient years, usually a historical period, in which a full reservoir storage system at the beginning is drawn down to minimum storage at the end without any spill.

CRITICAL DRY YEAR—A dry year in which the full commitments for a dependable water supply cannot be met and deficiencies are imposed on water deliveries.

CRITICAL FLOW—(1) The flow conditions at which the discharge is a maximum for a given specific energy, or at which the specific energy is a minimum for a given discharge. (2) In reference to Reynolds' critical velocities, the point at which the flow changes from streamline or non-turbulent to turbulent.

CRITICAL HABITAT—The area of land, water, and airspace required for normal needs and survival (e.g., forage, reproduction, or cover) of a plant or animal species.

CRITICAL LOW-FLOW—Low flow conditions below which some standards (Criteria) do not apply. The impacts of permitted discharges are typically analyzed at critical low-flow.

CRITICAL POINT—(1) (Physics) The temperature and pressure at which the liquid and gaseous phases of a pure stable substance become identical. Also referred to as the Critical State. (2) (Water Quality) The location downstream from a waste discharge at which the dissolved oxygen of the water is at its lowest. Also referred to as the Critical Reach.

CRITICAL REACH—The point in the receiving stream below a discharge point at which the lowest dissolved oxygen level is reached and recovery begins. Also referred to as the Critical Point.

CRITICAL SLOPE—That slope that will sustain a given discharge at uniform, Critical Depth in a given channel.

CRITICAL VELOCITY—Velocity at which a given discharge changes from tranquil to rapid flow; that velocity in open channels for which the specific energy (the sum of the depth and velocity head) is a minimum for a given discharge.

CRITICAL WILDLIFE HABITAT—Habitat that is vital to the health and maintenance of one or a variety of species based on habitat features such as nesting sites, denning sites, food sources, breeding grounds, etc.

CROP—(1) Plants, seeds, flowers and root tubers that are grown to be used as food or to be sold for profit. (2)Total amount of plants of one type harvested.

CROP COEFFICIENT—The ratio of evapotranspiration occurring with a specific crop at a specific stage of growth to potential evapotranspiration at that time.

CROP CONSUMPTIVE USE (Crop Requirement)—Often called Evapotranspiration. The amount of water used by vegetative growth of a given area by transpiration and that evaporated from adjacent soil or intercepted precipitation on the plant foliage in any specified time (acre-feet/acre).

CROP IRRIGATION REQUIREMENT— The amount of irrigation water in acre-feet per acre required by the crop; it is the difference between Crop Consumptive Use, or Crop Requirement, and the effective precipitation for plant growth. To this amount the following items, as applicable, are added: (1) irrigation applied prior to crop growth; (2) water required for leaching; (3) miscellaneous requirements of germination, frost protection, plant cooling, etc.; and (4) the decrease in soil moisture should be subtracted.

CROPLAND—Land currently tilled, including cropland harvested, land on which crops have failed, summer fallowed land, idle cropland, cropland planted in cover crops or soil improvement crops not harvested or pastured, rotation pasture, and cropland being prepared for crops, or newly seeded cropland. Cropland also includes land planted in vegetables and fruits, including those grown on farms for home use. All cultivated (tame) hay is included as cropland. Wild hay is excluded from cropland and included in pasture and range.

CROP REQUIREMENT— See Crop Consumptive Use.

CROP ROTATION—A pattern of changing the crops grown in a specific field from year to year in order to control pests and maintain soil fertility.

CROP SUBSIDY—A price support paid to farmers by the government.

CROSS CONNECTION—A physical connection through which a supply of potable water could become contaminated. May include any actual or potential connection between a drinking water system and an unapproved water supply or other source of contamination.

CROSS-SECTIONAL ANALYSIS—(Statistics) Observations or characteristics of a variable analyzed without respect to variations due to time. Cross-sectional econometric models provide information on the behavior of a variable due to external factors. Contrast with Time-Series Analysis.

CRP—Conservation Reserve Program. US Department of Agriculture program that provides incentives and assistance to farmers and ranchers for establishing conservation practices. It encourages farmers to plant permanent covers of grass and trees on land that is subject to erosion, where vegetation can improve water quality or provide food and habitat for wildlife.

CRUD—(Sports) Heavy, sticky snow that is unsuitable for skiing.

CRUSTACEA—One of several jointed-legged groups of animals that comprise the Arthopoda. Crustaceans have no particular set body pattern, as do the insects and spiders, often form a shell or carapace rich in calcium and are predominantly aquatic. They include the water fleas, copepods and mysids.

CRUSTACEAN—A fresh and salt water animal that has a hard shell. Such as a skud, shrimp, or lobster.

CRYOLOGY—The science of the physical aspects of snow, ice, hail, sleet, and other forms of water produced by temperatures below 0C (32F).

CRYOSCOPE—An instrument used to measure the freezing point of a liquid.

CRYPTO OOCYST—The hard shell in which the parasite, Cryptosporidium parvum, resides. This hard shell protects the parasite in the environment and remains viable for up to six months. This shell also protects the protozoa from chlorine disinfection treatment.

CRYPTODEPRESSION (LAKE)—Lake basin whose deep parts are below sea level.

CRYPTOMONADS—A group of brown colored flagellate algae, very common in the phytoplankton.

CRYPTOPHYTE—Algae of variable pigment concentrations, with various other unusual features. Algae of the division Cryptophyta.

CRYPTOSPORIDIOSIS—A disease of the intestinal tract caused by the parasite Cryptosporidium parvum. Common symptoms include stomach cramps and diarrhea.

CRYPTOSPORIDIUM PARVUM—A parasite often found in the intestines of livestock which contaminates water when the animal feces interact with a water source. Literally, cryptosporidium means "mystery spore," and the parasite was not recognized as a human pathogen until 1976. In healthy individuals, infection may result in an acute diarrheal illness lasting for 2-3 weeks. In immuno-suppressed individuals (e.g., AIDs patients, children, elderly), Cryptosporidiosis, the disease from infection by the parasite, may be life-threatening. While much needs to be learned about the infectious level of crypto, studies have indicated that it takes five to ten cysts to make someone sick. Of particular concern to health officials and public drinking water supplies is that the most widely used agent to disinfect tap water—chlorine—does not kill the parasite. Also, the laboratory tests used to detect crypto are time-consuming, laborious, and expensive. As an additional complication in the detection process, there are several varieties of crypto, but only one—Cryptosporidium parvum—is infectious to humans. Also, laboratory tests cannot determine whether a Crypto Oocyst, the hard shell that protects the protozoa, is alive or dead. Currently, the only effective treatment for water supplies is through filtration (crypto oocysts are only 3 to 7 microns in size) and the use of ozone gas rather than chlorine. As of January 1997, the U.S. Environmental Protection Agency (EPA), through the Information Collection Rule (ICR), has required that all public water supply systems serving more than 100,000 connections to monitor for cryptosporidium.

CSO—See Combined Sewer Overflow.

CSS—Combined Sewer System.

CSTR—Continuously Stirred Tank Reactor.

CU—Catalog Unit.

CUBIC FEET PER SECOND (CFS)—A unit expressing rate of discharge, typically used in measuring streamflow. One cubic foot per second is equal to the discharge of a stream having a cross section of 1 square foot and flowing at an average velocity of 1 foot per second. It also equals a rate of approximately 7.48 gallons per second, 448.83 gallons per minute. 1.9835 acre-feet per day, or 723.97 acre-feet per year.

CUBIC FEET PER SECOND DAY (CFS-DAY)—The volume of water represented by a flow of one cubic foot per second for 24 hours. It equals 86,400 cubic feet, 1.983471 acre-feet, or 646,317 gallons.

CUCKING STOOL—A chair formerly used for punishing offenders (as dishonest tradesmen) by public exposure or ducking in water.

CULTIVAR—Plant form originating from under cultivation.

CULTURAL EUTROPHICATION—Accelerated eutrophication (generally enrichment by nutrients) that occurs as a result of human activities in the watershed that increase nutrient loads in runoff water that drains into lakes.

CULTURAL LANDSCAPE—Man-made features of a region reflecting land-use patterns, population distribution, and other activities of man that have altered the natural landscape.

CULVERT—A transverse drain or waterway under a road, railroad, canal, or other obstruction.

CULVERT DAM—When culverts are constructed under roads that cross over the effluent (outlet) stream of a lake, they may be laid at a higher level than the original stream bed. When installed in this fashion, they act as low head dams and may raise the level of the entire lake. The culvert acts as an outlet when the water rises to its level.

CUMULATIVE IMPACT—The environmental impacts of a proposed action in combination with the impacts of other past, existing and proposed actions. Each increment from each action may not be noticeable but cumulative impacts may be noticeable when all increments are considered together.

CUMULATIVE INFILTRATION—The summation of the depth of water absorbed by a soil in a specified elapsed time in reference to the time of initial water application.

CUMULONIMBUS CLOUDS—A principal cloud type; the ultimate stage of development of Cumulus clouds. Cumulonimbus clouds are very dense and very tall, commonly 5 to 10 miles in diameter, and sometimes reaching heights of 12 miles or more. The upper portion is at least partly composed of ice crystals, and it often takes the form of an anvil or vast plume. The base of the cloud is invariably dark and is often accompanied by low, ragged clouds. Also commonly called Thundercloud, Thunderhead, Thunderstorm. Also see Cloud.

CUMULUS CLOUDS—A principal cloud type characterized by vertical development; usually isolated with a dark, nearly horizontal base and upper parts resembling domes or towers and usually formed by the ascent of thermally unstable air masses. Also see Cloud.

CUNETTE—A longitudinal channel constructed along the center and lowest part of a channel or through a detention or retention facility and intended to carry low flows. Also referred to as a Trickle Channel.

CURB STOP—A water service shutoff valve located in a water service pipe near the curb and between the water main and the building.

CURL—A hollow arch of water formed when the crest of a breaking wave spills forward.

CURRENT—(1) The portion of a stream or body of water which is moving with a velocity much greater than the average of the rest of the water. The progress of the water is principally concentrated in the current. (2) The swiftest part of a stream; (3) A tidal or nontidal movement of lake or ocean water; (4) Flow marked by force or strength; (5) Currents of various types and names have been recognized: littoral, longshore, undertow, rip, density, convection, turbidity, eddies, stream.

CURRENT CANAL—The current caused by an influent (inlet) or effluent (outlet) stream may effectively limit the growth of aquatic plants and create canal-like openings through weed beds.

CURRENT METER—An instrument for measuring the velocity of water flowing in a stream, open channel, or conduit by ascertaining the speed at which elements of the flowing water rotate a vane or series of cups.

CUSP, BEACH—Triangular deposit of sand, or other current drift, spaced along a shore. Size and configuration is apparently controlled by the magnitude and direction of wave action or current forces. Cusps are transient under some conditions, formed by storm waves and erased by a succeeding storm, but under other conditions are fairly long and relatively permanent features.

CUSPATE FORELAND—Formation consisting of a V-bar and a foreland created from the joining of two spits in a lake. The space between the enclosing sides may be water; or the foreland may be a complex of beach deposits which are cuspate in form.

CUT AND BUILT TERRACE—See Wave Built Terrace or Littoral Shelf.

CUTBACK IRRIGATION—Water applied at a faster rate at the beginning of the irrigation period and then reduced or cutback to a lesser rate, usually one-half the initial rate or that amount to balance with the intake rate.

CUTICLE—Waxy protective layer on the surface of a leaf or stem.

CUTOFF, also Cut-Off—(1) (Hydraulics) The new and shorter channel formed either naturally or artificially when a stream cuts through the neck of a bank or oxbow. (2) (Dam) An impervious construction or material which reduces seepage or prevents it from passing through the foundation material of a dam structure.

CUTOFF TRENCH (of a Dam)—An excavation later to be filled with impervious material to form a Cutoff. Sometimes used incorrectly to describe the cutoff itself.

CUTOFF WALL (of a Dam)—A wall of impervious material (e.g., concrete, asphaltic concrete, steel sheet piling) built into the foundation of a dam to reduce or prevent seepage under the dam.

CUTWATER—(1) (Nautical) The forward part of a ship's prow. (2) The wedge-shaped end of a bridge pier, designed to divide the current and break up ice floes.

CVP—Central Valley Project (State of California).

CWA—Clean Water Act (EPA).

CYANAZINE—A herbicide listed by the U.S. Environmental Protection Agency (EPA) as a "possible human carcinogen" and found frequently in streams and rivers, particularly following floods and periods of heavy rain and runoff from agricultural lands. Cyanazine is used extensively for weed control for corn, sorghum, and sugarcane. Along with another common farm herbicide, Atrazine, Cyanazine concentrations can soar to levels much higher than federal standards during the peak growing season.

CYANOBACTERIA—See Blue-green Algae.

CYANOPHYTE—Blue green algae, algae of the division Cyanophyta actually a set of pigmented bacteria.

CYCLE—(Statistics) A periodic, repetitive fluctuation in time series data from either a constant mean or trend line. Typically, the oscillations of a cycle will be greater than one year in length. Cycles within a year are termed Seasonality.

CYCLE OF EROSION—A qualitative description of river valleys and regions passing through the stages of youth, maturity, and old age with respect to the amount of erosion that has been effected.

CYCLONE—(Meteorology) An atmospheric system characterized by the rapid, inward circulation of air masses about a low-pressure center, usually accompanied by stormy, often destructive, weather. Cyclones circulate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also see Typhoon and Coriolis Effect.

CYCLONIC PRECIPITATION—Precipitation which results from the lifting of air converging into a low-pressure area, or Cyclone.

CYPRESS KNEES—Part of a cypress tree's root system that juts out of the ground, extending above the high water mark.

CYPRESS PONDS—Ponds or lakes characterized by growths of cypress (Taxodium spp.).

CYPRESS SWAMP—A wetland environment common throughout the southeastern United States in which cypress trees are a dominant species.

CYPRIERE—In Louisiana, a cypress swamp. Cypress swamps generally are permanently water covered areas.

CZMA—Coastal Zone Management Act (EPA).