Quantitative Precipitation Forecast (QPF)(QPF)A spatial and temporal precipitation forecast that will predict the potential amount of future precipitation for a specified region, or area.
Quantitative precipitation forecastsA projection that uses the interpretation of various observational, numerical, and objective aids to estimate the amount, location, and duration of…
QuarryA rock pit. An open cut mine in rock chosen for physical rather than chemical characteristics.
QuartzVery hard, clear or translucent mineral composed of silica.
QuartziteA hard, metamorphic rock that was originally sandstone.
QuaternaryThe present period, forming the latter part of the Cenozoic Era, originating about 1 million years ago and including the Recent and Pleistocene epochs.
QuicksandFine sand or silt that is prevented from settling firmly together by upward movement of ground water.
Radial gateA pivoted crest gate, the face of which is usually a circular arc, with the center of curvature at the pivot about which the gate swings.
Radial Gate (Tainter Gate)A gate with a curved upstream plate and radial arms hinged to piers or other supporting structures on which the gate pivots.
Radioisotope Snow GageA snow water equivalent gage based on the absorption of gamma radiation by snow; this gage can measure up to 55 inches water equivalent with a 2 to 5…
RADIUSHorizontal distance from the center of rotation.
Raffinate pondsLiquid resulting from extractions with a solvent.
Ramp flumeA flume calibrated to measure the flow of liquid in an open channel.
Ramp rateThe rate at power system load or generator output varies, or the limits to such rates due to mechanical or reliability considerations.
Random earthquakeIn addition to earthquakes that occur on mapped faults, hazards are also presented by earthquakes not associated with known geological structures.
RangeGeographic region in which a given plant or animal normally lives or grows.
RapidA section of a river where the current is very fast moving, caused by a steep descent in the riverbed through a constriction of the main channel.
Rapid flowAlso refered to as supercritical flow, rapid flow is distinguished from tranquil flow by a dimensionless number called the Froude number.
Rated capacityThat capacity which a hydrogenerator can deliver without exceeding mechanical safety factors or a nominal temperature rise.
Rated headWater depth for which a hydroelectric generator and turbines were designed.
Rating CurveA graph showing the relationship between the stage, usually plotted vertically (Y-axis) and the discharge, usually plotted horizontally (X-axis).
Rating TableA table of stage values and the corresponding discharge for a river gaging site.
Ratio of reductionThe relationship between the maximum size of the stone which will enter a crusher, and the size of its product.
ReachAny specified length of stream, channel, or other water conveyance. A portion of a stream or a river.
Reactive PowerThe electrical power that oscillates between the magnetic field of an inductor and the electrical field of a capacitor.
Ready reserveGeneration capacity that can be synchronized and ready to serve load in a short time period, usually 10 minutes or less.
Reattachment depositSand deposit located where downstream flow meets the channel bank at the downstream end of a recirculating zone.
Recession ConstantConstant used to reduce the API value daily in the API method of estimating runoff.
RechargeWater that infiltrates into the ground, usually from above, that replenishes groundwater reserves, provides soil moisture, and affords evapotranspiration.
Recharge rateThe quantity of water per unit time that replenishes or refills an aquifer.
Recirculation zoneArea of flow composed of one or more eddies immediately downstream from a constriction in the channel, such as a debris fan or rock outcrop.
Reclamation Reform Act of 1982 (RRA)The Reclamation Reform Act of 1982 limits the amount of owned land that is eligible to receive project (Reclamation) irrigation water and addresses the…
RecreationRecreational opportunities at more than 1,900 federal recreation sites managed by the Bureau of Reclamation and other federal agencies can be found at the…
Recreation AreaAn area that allows for recreational fishing, diving, boating, kayaking, and other recreational activities.
Recreational benefitValue of recreational activity to the recreationist, usually measured in dollars above the cost of participating in the recreational activity (travel…
RecruitmentRecruitment is the process to attract the attention of individual(s) who may apply for employment.
Rectangular weirA contracted or suppressed weir with a horizontal crest, rectangular in shape, having vertical sides. See weir.
Recurrence IntervalThe average period in years between storm events equal to or larger than a given amount.
ReddAn individual nest or depression in the gravel excavated by trout other members of the trout and salmon family for depositing eggs.
Reference MarkA relatively permanent point of known elevation which is tied to a benchmark.
RefillMaterial which had previously been excavated as a result of construction activities and again placed to the lines as shown on the drawings.
ReflectivityThe measure of the efficiency of a radar target in intercepting and returning Electro Magnetic Energy.
Refuge compatibility requirementsRequirements under the Refuge Administration Act that all uses of a national wildlife refuge must be compatible with the purpose for which the refuge was…
Region or RegionalAn area inclusive of and determined by participating national system sites and systems that is based on common management interests, similar or linked…
Regional officeFive Reclamation offices in the 17 Western States that supervise area, field, and project offices in their respective geographic locations.
Regional Operations Manual Letter (ROML)(ROML)These serve as updates to regional policy and procedure for the National Weather Service Operations Manual (WSOM).
Regional Response Team (RRT)Regional planning and coordination of preparedness and response actions are accomplished through the RRT.
Regional Transmission Group (RTG)A voluntary organization of transmission owners, transmission users, and other entities interested in coordinating transmission planning, expansion…
Regulating dam (reregulating dam)A dam impounding a reservoir from which water is released to regulate the flow downstream. See afterbay dam.
Regulating Gate (Regulating Valve)A gate or valve that operates under full pressure and flow conditions to throttle and vary the rate of discharge.
Regulatory FloodwaySome maps show an area where construction regulations require special provisions to account for this extra hazard. This is a regulatory floodway.
ReimbursableCosts of constructing, operating, or maintaining a Reclamation project that are repaid to the Federal Government by some other individual, entity, or…
Relative densityUsed in construction control for cohesionless soils where the in-place density is compared to the minimum and maximum density of the soil from laboratory…
Relative HumidityA measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature.
ReleaseThe amount of water released after use. The difference between delivery and release is usually the same as consumptive use.
ReliabilityThe consistency of a measure or question in obtaining very similar or identical results when used repeatedly; for example, if you repeated a blood test…
RelictA land surface that was once a basin (valley) floor.
ReliefCarved or molded ornament that projects from a flat surface.
Relief valveA valve which will allow air or fluid to escape if its pressure becomes higher than the valve setting.
Remote operationOperation of mechanical features from an on-site location other than at the feature.
remote sensingMethod for determining characteristics of an object, organism or community from afar.
Renewable resourcesRenewable energy resources are naturally replenishable, but flow limited. They are virtually inexhaustible in duration but limited in the amount of energy…
Reportable discharge of oil (40 CFR 110.3)Harmful quantities of oil discharged or released to navigable waters of the United States are any amount that violates State water quality standards…
Reportable quantitiesQuantities of hazardous substances which require notification to the National Response Center and the appropriate state agency.
Reserve generating capacityExtra generating capacity available to meet unanticipated capacity demand for power in the event of generation loss due to scheduled or unscheduled…
ReservedFor purposes of the National System of MPAs, must be established by and currently subject to federal, state, commonwealth, territorial, local, or tribal…
Reserved worksFacilities operated and maintained by Reclamation.
ReservoirA reservoir of an infectious agent, such as a virus, is any animal, person, plant, soil, substance—or combination of any of these — in which the…
Reservoir AreaThe surface area of a reservoir when filled to normal water level.
Reservoir capacityThe capacity of the reservoir, usually in acre-feet. Dam design and reservoir operation utilize reservoir capacity and water surface elevation data.
Reservoir capacity allocations (RCA) sheetA summary of acre-feet allocations of water, to such purposes as surcharge, exclusive flood control capacity, joint use capacity, active conservation…
Reservoir inflowThe amount of water entering a reservoir expressed in acre-feet per day or cubic feet per second.
Reservoir VolumeThe volume of a reservoir when filled to normal pool or water level.
ResilienceAbility of any system to resist or to recover from stress or hardship.
Resource Management PlanA written plan that addresses the existing resources of an area and provides future objectives, goals, and management direction.
Response spectrumA plot of the maximum response of a series of single-degree-of-freedom damped oscillators (elastic systems) as a function of their natural periods, or…
Response TimeThe amount of time in which it will take a watershed to react to a given rainfall event.
Return FlowDrainage water from irrigated farmlands that re-enters the water system to be used further downstream.
Return-flow system (reuse system)A system of pipelines or ditches to collect and convey surface or subsurface runoff from an irrigated field for reuse.
RevetmentAn embankment or wall of sandbags, earth, etc., constructed to restrain material from being transported away. A facing of stone, cement, sandbags, etc.
RewindAct of putting new copper insulated wire in the armature windings of a generator. Replacement of an armature (stator) winding of a synchronous generator.
RhyoliteVolcanic rock (or lava), characteristically light in color and containing 69% silica or more and generally rich in potassium and sodium (felsic…
Richter scaleA scale of numerical values, proposed by C. F. Richter, to describe the magnitude of an earthquake, ranging from 1 to 9, by measurements made in…
RidgeA line or wall of broken ice forced up by pressure. May be fresh or weathered.
Ridge IceIce piled haphazardly one piece over another in the form of ridges or walls.