Evacuation warningA public warning message that local officials would issue following declaration of Response Level III by personnel of the dam operating organization.
EvaporationThe conversion of a liquid to a vapor (gas), usually by means of heat.
Evaporation PanA pan used to hold water during observations for the determination of the quantity of evaporation at a given location.
Evaporation RateIn hydrologic terms, the quantity of water, expressed in terms of depth of liquid water, which is evaporated from a given surface per unit of time.
EvaporimeterAn instrument which measures the evaporation rate of water into the atmosphere.
EvapotranspirationThe net water loss (in vapour form) per unit area of land, both directly from the land surface, and indirectly through transpiring leaves.
Examination reportA written report that documents the condition of the facility during the examination, operation and maintenance activities accomplished since the last…
ExcavationThe action or process of excavating (to dig or remove earth). See common excavation, rock excavation, and unclassified excavation.
Excess capacityPower generation capacity available on a short-term basis that exceeds the firm energy on a long-term contract offered to an electricity customer.
Excess landIrrigable land, other than exempt land, owned by any landowner in excess of the maximum ownership entitlement under applicable provision of Reclamation…
Excess RainEffective rainfall in excess of infiltration capacity.
Exchange capacityThe capacity to exchange ions as measured by the quantity of exchangeable ions in a soil or rock.
Exclusive Economic Zone (EEZ)The assertion of jurisdiction under the EEZ (3 nautical miles/3.45 statute miles to 200 nautical miles/230.
Exclusive flood control capacityThe reservoir capacity assigned to the sole purpose of regulating flood inflows to reduce flood damage downstream.
Executive OrdersNumbered consecutively, Executive Orders (EOs) are legally binding orders given by the President, acting as the head of the Executive Branch, to Federal…
Exempt landIrrigation land in a district to which the acreage limitation and pricing provisions of Reclamation law do not apply.
Existence valueValue people place on simply knowing an area or feature continues to exist in a particular condition.
Existing groundThe earth's surface as it is prior to any work. See original ground surface.
Exit conferenceA discussion following a facility review examination involving examination team members and interested representatives of the water uses, project, and…
Exotic speciesA non-native species that is introduced into an area.
Expansion jointA separation between adjoining parts of a concrete structure which is provided to allow small relative movements, such as those caused by temperature…
ExploitExcavate in such a manner as to utilize material in a particular vein or layer, and waste or avoid surrounding material.
ExtradosThe curved upstream surface of horizontal arch elements in an arch dam. See intrados.
ExtrapolationEstimation of unknown values by extending or projecting from known values.
FaceExposed surface of dam materials (earth, rockfill, or concrete), upstream and downstream. The external surface which limits the structure, see neatlines.
FacilitiesStructures associated with Reclamation irrigation projects, municipal and industrial water systems, power generation facilities, including all storage…
FacingWith reference to a wall or concrete dam, a coating of a different material, masonry or brick, for architectural or protection purposes, e.g.
Factor of safetyThe ratio of the ultimate strength of the material to the allowable or working stress.
Fahrenheit (F)Unit of temperature. Degrees Fahrenheit equals (9/5)x(degrees Celsius)+(32).
FailureAn incident resulting in the uncontrolled release of water from a dam. Destroyed and made useless, ceases to function as a dam.
Failure potential assessmentA judgment of the potential for failure of an essential element within the expected life of the project.
FallThe amount of slope given to horizontal runs of pipe.
Farm loss (water)Water delivered to a farm which is not made available to the crop to be irrigated.
Fatal flawAny problem, lack, or conflict (real or perceived) that will destroy a solution or process.
Fatality rateA multiplication factor based on the estimated severity of the flood, potential warning times, and the judgement related to the understanding of the flood…
Fault"Fault" means adultery, alcohol abuse, drug abuse, physical abuse, domestic violence, abandonment or reckless spending.
Fault-block (horst)Uplifted section of rock bounded on both sides by faults. See graben.
FaultingThe movement which produces relative displacement along a fracture in rock.
FaunaThe community of animals in a specific region or habitat.
FeasibilityA determination that something can be done. A feasibility report is required in some planning processes to examine the situation and determine if a…
Feasibility estimateAn estimate used for determining the economic feasibility of a project, the probable sequence and cost for construction of a project, and as a guide in…
FeatherIn a wind energy conversion system, to pitch the turbine blades so as to reduce their lift capacity as a method of shutting down the turbine during high…
Federal Advisory Committee ActAuthorizes the establishment of a system governing the creation and operation of advisory committees in the executive branch of the federal government.
Federal Energy Regulatory Commission (FERC)(FERC)This is an independent regulatory agency within the U.S. DOE that has jurisdiction over interstate electricity sales, wholesale electric rates, natural…
Federal organizationsAgencies, departments, or their components of the Federal Government that have a role in dam safety emergency planning and preparedness (i.e.
Federal Power ActEnacted in 1920, and amended in 1935, the Act consists of three parts. The first part incorporated the Federal Water Power Act administered by the former…
Federal Power Commission (FPC)The predecessor agency of the Federal Energy Regulatory Commission (FERC). The Federal Power Commission was created by an Act of Congress under the…
Federal Snow SamplerA snow sampler consisting of five or more sections of sampling tubes, one which has a steel cutter on the end.
FeldsparGroup of light-colored minerals often found as crystals in intrusive igneous rocks. The most common rock-forming mineral.
Field capacity (field moisture capacity)Depth of water retained in the soil after ample irrigation or heavy rain when the rate of downward movement has substantially decreased, usually one to…
Field Moisture DeficiencyThe quantity of water, which would be required to restore the soil moisture to field moisture capacity.
Field tileShort lengths of clay pipe that are installed as subsurface drains.
File Transfer Protocol (FTP)(FTP)A method of data transfer that can take place between Frame Relay Networks, and Workstations.
FillMan-made deposits of soil and rock and/or waste material.
Fill DamAny dam constructed of excavated natural materials or of industrial wastes.
Filter (Filter Zone)One or more layers of granular material which is incorporated in an embankment dam and is graded (either naturally or by selection) to allow seepage…
FinesPortion of a soil finer that a No. 200 U.S. Standard sieve. Clay or silt particles in soil.
Finger drainsA series of parallel drains of narrow width (instead of a continuous drainage blanket) draining to the downstream toe of the embankment dam.
Finished gradeThe elevation or surface of the earth after all earthwork has been completed (also finish grade). The final grade required by specifications.
Firm energy (power)Non-interruptible energy and power guaranteed by the supplier to be available at all times, except for uncontrollable circumstances.
Firm yieldThe maximum quantity of water that can be guaranteed with some specified degree of confidence during a specific critical period.
Firn (Snow)Old snow on top of glaciers, granular and compact and not yet converted into ice. It is a transitional stage between snow and ice. Also called Neve.
Firn LineThe highest level to which the fresh snow on a glacier's surface retreats during the melting season.
Fischer & Porter Punched Tape Recorder GageA precipitation gage which converts weight into a code disk position. The code disk position is then punched on paper tape in a binary decimal format…
Fish & Wildlife Service (FWS)The U.S. Fish and Wildlife Service is the principal Federal agency responsible for conserving, protecting and enhancing fish, wildlife and plants and…
Fish ladder (fishway)An inclined trough which carries water from above to below a dam so that fish can easily swim upstream.
FisheryA term used for a lake, river or stream where people can catch fish, or even a particular kind of fish, such as a bass or trout fishery.
Fishery Closure AreaA fishery closed or restricted by a government entity. Such closure prohibits fishing for commercial, recreational, or subsistence purposes.
Fishery Management CouncilsRegional councils which were established under the Magnuson-Stevens Fishery Conservation and Management Act.
Fishery Management ZoneAreas where fishing for some or all species is prohibited to protect critical habitats, rebuild fish stocks, ensure against overfishing, or enhance…
FishingThe operation of recovering an object left or dropped in a drill hole.
Fixed amount-frequency schedulingMethod of irrigation scheduling that involves water delivery at a fixed rate or a fixed volume and at constant intervals.
FlailA hammer hinged to an axle so that is can be used to break or crush material.
FlangeA ridge that prevents a sliding motion. A rib or rim for strength or for attachments. A rim or collar attached to one end of a pipe to give support.
Flap GateA gate hinged along one edge, usually either the top or bottom edge. Examples of bottom-hinged flap gates are tilting gates and fish belly gates - so…
Flash FloodA sudden flood event through a valley, canyon, or wash, following a short duration, high-intensity rainfall.
Flash Flood Guidance (FFG)(FFG)An internal product produced by the RFCs containing rainfall threshold values which must be exceeded in order to produce a flash flood.