Coffer DamA temporary structure enclosing all or part of a construction area so the construction can proceed in a dry area.
CofferdamA temporary structure enclosing all or part of the construction area so that construction can proceed in the dry.
CogeneratorA class of energy producer that produces both heat and electricity from a single fuel.
CohesionThe mutual attraction of soil particles due to molecular and capillary forces in the presence of water.
Cohesionless materials (cohesionless soil)Soil materials that when unconfined have little or no strength when air-dried and that have little or no cohesion when submerged.
Cohesive soilPredominantly clay and silt soil, fine-grained particles, that sticks together whether wet or dry.
Cold jointAn unplanned joint resulting when a concrete surface hardens before the next batch is placed against it. Fresh concrete placed on harden concrete.
Cold-water fisheryWater or water system which has an environment suitable for salmonoid fishes.
ColiformOrganisms common to the intestinal tract of humans and animals; the organisms' presence in waste water is an indicator of pollution.
CollaringStarting a drill hole. When the hole is deep enough to hold the bit from slipping out of it, it is said to be collared.
Colloidal particlesSoil particles that are so small that the surface activity has an appreciable influence on the properties of the aggregate. Particles smaller than 0.
Colloidal suspensionA method of sediment transport in which water turbulence (movement) supports the weight of the sediment particles, thereby keeping them from settling out…
ColluviumA general term to include loose rock and soil material that accumulates at the base of a slope as the result of mass wasting processes.
Columnar IceIce consisting of columnar shaped grain. The ordinary black ice is usually columnar-grained.
Combined cycle plantA plant which achieves higher efficiency by employing two cycles in tandem. For example, heat rejected from a gas-fired turbine is used to generate steam…
Commercial operationCommercial operation begins when control of the loading of the generator is turned over to the system dispatcher.
Commercial river tripTrips organized by boating companies that conduct tours for paying passengers or customers.
Commercial user dayAmount of commercial use within a 24-hour period or any portion thereof.
Commercial water useWater for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions.
Common excavationAll materials excavated not considered as rock. Boulders or detached pieces of solid rock less than 1 cubic yard in volume are classified as common…
Common materialAll earth materials which do not fall under the definition of rock.
CommunityA political entity that has the authority to adopt and enforce floodplain ordinances for the area under its jurisdiction.
Community cohesionAbility of a community to have a unified response when facing a problem; e.g., an external threat to their sustainability.
Compacted backfillBackfill which has been reduced to bulk by rolling, tamping, or soaking.
Compacted embankmentEmbankment which has been reduced in bulk by rolling, tapping, or soaking.
CompactionTo make soil dense by mechanical manipulation. Mechanical action which increases the density by reducing the voids in a material.
Compaction testA laboratory compacting procedure whereby a soil at a known moisture content is placed in a specified manner into a mold of given dimensions, subjected to…
Composite HydrographA stream discharge hydrograph which includes base flow, or one which corresponds to a net rain storm of duration longer than one unit period.
Composite power valueThe value of power including both a capacity and energy component, usually expressed in mills per kilowatt-hour.
Comprehensive Facility Review (CFR)A review performed on a high- or significant-hazard dam every 6 years, which includes a field examination and a state-of-the-art review of a structure's…
CompressibilityProperty of a soil describing its susceptibility to decrease in volume when subjected to load.
CompressionCompression algorithms such as Zip and RLE reduce the size of files saving both storage space and reducing bandwidth required for access and transmission.
Compression curveAny function relating volume change to effective stress.
Computer base stationComputer equipment that is designated to receive data from the data collection platforms and translate that data into useable information for the decision…
Concentrated flow pathAn existing hypothetical avenue of concentrated seepage. The descriptor "concentrated" implies sufficient energy to carry/move material and erode.
Concrete damSee arch dam, buttress dam, or gravity dam. See also masonry dam. A concrete dam generally requires a sound rock foundation.
Concrete liftIn concrete work, the vertical distance between successive horizontal construction joints.
ConcussionShock or sharp air waves caused by an explosion or heavy blow.
CondensationThe process by which water in air changes from a vapor to a liquid due to a change in temperature or pressure; occurs when water vapor reaches its dew…
ConductorThe material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.
ConduitA tubular material used to encase and protect one or more electrical conductors.
Cone of DepressionA depression in the water table that develops around a pumped well.
Cone of InfluenceThe depression, roughly conical in shape, produced in a water table, or other piezometric surface, by the extraction of water from a well at a given rate.
Cone of influence (cone of depression)The depression, roughly conical in shape, produced in the water table by the pumping of water from a well. See circle of influence.
Confined Ground WaterGround water held under an aquiclude or an aquifuge called artesian if the pressure is positive.
Confined spaceA space that is large enough to and so configured that a person can bodily enter and perform assigned work.
ConfluenceThe place where two streams meet, or the stream formed from two joining streams.
ConglomerateA conglomerate is a corporation whose multiple business units operate in different, often unrelated, areas.
Congressional Organic Act of 1890The act that assigned the responsibility of river and floor forecasting for the benefit of the general welfare of the Nation's people and economy to the…
ConifersCone-bearing trees or shrubs, mostly evergreens such as pine, cedar, and spruce.
Conjunctive useThe coordinated use of surface water and ground water resources.
connectionThe physical connection (e.g. transmission lines, transformers, switch gear, etc.
ConsequencesPotential loss of life or property damage downstream of a dam caused by flood waters released at the dam or by waters released by partial or complete…
Conservation StorageStorage of water for later release for usual purposes such as municipal water supply, power, or irrigation in contrast with storage capacity used for…
ConsistencyThe relative ease with which a soil can be deformed.
Consolidated Ice CoverIce cover formed by the packing and freezing together of floes, brash ice and other forms of floating ice.
ConsolidationReduction in particle spacing in a soil, and decrease in water content, resulting from an increase in external pressure.
ConsolidometerApparatus used for one-dimensional consolidation/compression testing.
Constant angle arch damAn arch dam in which the angle subtended by any horizontal section is constant throughout the whole height of the dam.
Constant radius arch damAn arch dam in which every horizontal segment or slice of the dam has approximately the same radius of curvature.
Construction JointConstruction joints are purposely placed in concrete to facilitate construction; to reduce initial shrinkage stresses and cracks; to allow time for the…
Consumer surplusThe value of a commodity, good, or opportunity above the cost to the consumer; measured using willingness to pay, as specified in Federal guidelines for…
Consumptive use(1) Any use of water that permanently removes water from the natural stream system.
Consumptive water useTotal amount of water used by vegetation, man's activities, and evaporation of surface water.
Contact groutingFilling, with cement grout, any voids existing at the contact of two zones of different materials, e.g.
Contact loadSediment particles that roll or slide along in almost continuous contact with the streambed.
Contaminant1. An undesired chemical present in a compound or mixture of compounds. 2. Any micro-organism accidentally introduced into a culture or culture medium.
ContentsThe 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…
Contour ditchIrrigation ditch laid out approximately on the contour.
Contour farmingSystem of farming used for erosion control and moisture conservation whereby field operations are performed approximately on the contour.
Contour floodingMethod of irrigation by flooding from contour ditches.
Contour mapTopographic map that portrays relief or elevation differences by the use of lines (contours) indiciating equal elevation.
Contour plowingPlowing done in accordance with the natural outline or shape of the land by keeping the furrows or ditches at the same elevation as much as possible to…
Contour strip farmingA kind of contour farming in which row crops are planted in strips, between alternating strips of close-growing, erosion resistant forage (grass, grain…
Contract rateThe repayment or water service rate set forth in a contract to be paid by a district to the United States.
Contracted weirThe crest and sides of a retangular weir are far enough from the bottom and sides of the channel so that their effect on flow is negligible.
Contraction jointContraction joints are joints placed in concrete to provide for volumetric shrinkage of a monolithic unit or movement between monolithic units.
Control areaAn electric power system or combination of electric power systems to which a common automatic control scheme is applied in order to: Match, at all times…
Control jointControl joints are joints placed in concrete to provide for control of initial shrinkage stresses and cracks of monolithic units.
Control PointsHorizontal and Vertical: Small monuments securely embedded in the surface of the dam. Any movement of the monument indicates a movement in the dam itself.
Control structure (control house)Concrete portion of an outlet works, located at the downstream end of the tunnel or conduit, housing the control (regulation) gates.
Conventional tillageThe traditional method of farming in which soil is prepared for planting by completely inverting it with a moldboard plow.
Conveyance LossThe loss of water from a conduit due to leakage, seepage, evaporation, or evapo-transpiration.
Conveyance loss (distribution loss)Loss of water from a channel or pipe during conveyance, including losses due to seepage, leakage, evaporation and transpiration by plants growing in or…
Conveyance system efficiencyThe ratio of the volume of water delivered to users in proportion to the volume of water introduced into the conveyance system.
ConveyorA mechanical apparatus for carrying bulk material from place to place; for example, an endless moving belt or a chain of receptacles.