NPDP Dam Dictionary

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Term AKA Definition
Rapid A 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 flow Also refered to as supercritical flow, rapid flow is distinguished from tranquil flow by a dimensionless number called the Froude number. If the Froude number is less than one, the flow is tranquil. If the Froude number is greater than one, the flow is rapid. If the Froude number is equal to one, the flow is critical. Surface waves can propagate only in the downstream direction. Control of rapid flow depth is always at the upstream end of the rapid flow region
Raptors Birds of prey.
Rated head Water depth for which a hydroelectric generator and turbines were designed.
Reach Any specified length of stream or conveyance. A portion of a stream or a river. The area of a canal or lateral between check structures.
Reattachment deposit Sand deposit located where downstream flow meets the channel bank at the downstream end of a recirculating zone.
Recirculation zone Area of flow composed of one or more eddies immediately below a constriction in the channel.
Recreational benefit Value of recreational activity to the recreationist usually measured in dollars above the cost of participating in the recreational activity (travel, entrance fees, etc). Used for valuing recreational resources produced through Federal projects, synonymous with the consumer surplus associated with the recreational activity.
Rectangular weir A contracted or suppressed weir with a horizontal crest, rectangular in shape, having vertical sides.
Redd The nest that a spawning female salmon digs in gravel to deposit her eggs.
Refill Material which had previously been excavated as a result of construction activities and again placed to the lines as shown on the drawings.
Refuge compatibility requirements Requirements under the Refuge Administration Act that all uses of a national wildlife refuge must be compatible with the purpose for which the refuge was established.
Regulating dam A dam impounding a reservoir from which water is released to regulate the flow in a river.
Regulating gate (operating) A gate used to regulate the rate of flow through an outlet works.
Rehabilitation The process of renovating a facility or system whose performance is failing to meet the original criteria and needs of the project.
Reimbursable Costs of constructing, operating, or maintaining a Reclamation project that are repaid to the Federal Government by some other individual, entity, or organization.
Relative density Used in construction control for cohesionless soils where the in- place density is compared to the minimum and maximum density of the soil from laboratory tests.
Reliability Probability that a device will function without failure over a specified time period or amount of usage.
Relict A species, population, etc., which is a survivor of a nearly extinct group. Any species surviving in a small local area and widely separated from closely related species.
Relief Term designating the path of least resistance through which energy from explosions can be released. This path is usually taken to a free face or surface where rock can displace and energy can be released.
Relief well See drainage well.
Remote operation Operation of mechanical features from an on-site location other than at the feature.
Remote sensing Method for determining characteristics of an object, organism or community from afar.
Reregulation dam See afterbay dam.
Reserve generating capacity Extra generating capacity available to meet unanticipated capacity demand for power in the event of generation loss due to scheduled or unscheduled outages of regularly used generating capacity.
Reserved works Facilities operated and maintained by Reclamation.
Reservoir Artificially impounded body of water. Dam design and reservoir operation utilize reservoir capacity and water surface elevation data. To ensure uniformity in the establishment, use, and publication of these data, the following standard definitions of water surface elevations shall be used. See maximum controllable water surface, maximum water surface, normal water surface, top of active conservation capacity, top of dead capacity, top of exclusive flood control capacity, top of inactive capacity, and top of joint use capacity.
Reservoir Storage The capacity of the reservoir, usually in acre-feet. Dam design and reservoir operation utilize reservoir capacity and water surface elevation data. To ensure uniformity in the establishment, use, and publication of these data, the following standard definitions of reservoir capacities shall be used. Reservoir capacity as used here is exclusive of bank storage capacity. See active capacity, active conservation capacity, dead capacity, exclusive flood control capacity, flood control capacity, inactive capacity, joint use capacity, live capacity, and total capacity.
Resilience Ability of any system to resist or to recover from stress or hardship.
Response spectrum A 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 frequencies, when the oxcillators are subjected to a vibratory ground motion.