NPDP Dam Dictionary

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Term AKA Definition
Nameplate Power generation capacity of a generator that can be guaranteed under continuous operation.
NATDAM ID Identification number assigned to a dam in the U.S. National Inventory of Dams.
National Weather Service Please visit the website:
Natural frequency The natural frequencies of a structure are the frequencies of free vibration. Free vibration is vibration that occurs in the absence of forced vibration. In a structure undergoing vibration, a mode of vibration is a characteristic pattern (shape) assumed by the structure in which the motion of every particle is simple harmonic motion with the same frequency. The fundamental mode of vibration of a structure is the mode having the lowest natural frequency
Natural period of vibration T The period of vibration of a a structure is the time required for one cycle of the simple harmonic motion in one of these characteristic patterns (shapes). T = 1/f.
Naturalness Area which generally appears to have been affected primarily by the forces of nature, with the imprint of man's work substantially unnoticeable.
Neatlines (of structure) A line which defines the limits of work, such as an excavation, cut stone, etc. Also, the true face line of a building regardless of the projections of the stones; a line back of, or inside of, incidental projections. Any material removed beyond the neat line is overbreak.
Neotropic migrant A bird that migrates to tropical regions during the winter.
Net economic benefits Economic benefits less economic costs.
NID Core Type The watertight or impermeable part of a dam. Types include: Bituminous Concrete, Concrete, Earth, Metal, Plastic, Unlisted/unknown. Core positions include: Upstream Facing, Homogenous Dam, Core, Unlisted/unknown. Core certainty is listed as Known or Estimated.
Non-reimbursable Cost of constructing, operating, or maintaining a Reclamation project that is borne by the Federal taxpayer and is not reimbursed by any other individual, entity, or organization.
Non-uniform flow The velocity varies with position.
Non-utility generators NUG's Facilities for generating electricity that are not owned exclusively by an electric utility and which operate connected to an electric utility system.
Nonconsumptive water uses Water uses that do not substantially deplete water supplies, including swimming, boating, waterskiing, fishing, maintenance of stream related fish and wildlife habitat, and hydropower generation.
Nonfirm power Power that is not available continuously and may be interruptible. This power may be marketed on a short-term basis.
Nonpoint source A contributing factor to water pollution that cannot be traced to a specific spot. Man-made or man-induced alteration of the chemical, physical, biological, or radiological integrity of water, originating from any source other than a point source.
Normal depth The depth of flow that would exist for a steady-uniform flow condition.
Normal Storage The normal storage in acre-feet. It is defined as the total storage space in a reservoir below the normal retention level, including dead and inactive storage and excluding and flood control or surcharge storage.
Normal water surface The highest elevation that water is normally stored, or that elevation which the reservoir should be operated for conservation purposes. Usually the elevation at the top of the active conservation capacity. The maximum elevation to which the reservoir may rise under normal operating conditions exclusive of flood control capacity.
NPDP Dams Directory The NPDP Dams Directory is a comprehensive database of dams in the U.S. It is being developed to include: 1. All dams in the U.S. regulated by state regulatory agencies. 2. Dams in the U.S. that state dam safety programs maintain a record of (whether regulated or not). 3. All dams in the current U.S. National Inventory of Dams (NID). 4. Dams the NPDP has information on that pre-date the National Inventory of Dams or state dam safety programs (i.e., Teton Dam failed in 1976 and pre-dates the NID). Unlike the NID, which maintains data on dams currently in operation, the NPDP Dams Directory retains all dams?historic, currently operating, and recently removed or retired. Features of the Dams Directory are: 1. All dams remain in the database, including those that have been removed, failed and not re-built or repaired, etc. 2. The capability to maintain a history of changes to a dam (e.g., changes to the spillway capacity, raising of the dam crest, removal of dam gates, etc.) 3. Data on structures, systems and components at a dam can be included in the database (as such information becomes available). 4. Dams no longer in service are retained. 5. The Dams Directory is linked to the NPDP dam incident database, consequence, database, etc.
NPDP ID Unique identification number assigned to each dam in the NPDP Dams Directory. The NPDP ID is equivalent to the U.S. National Inventory of Dams ID (NATDAM ID) for dams that have been assigned a NATDAM ID. For dams that pre-date the National Inventory of Dams (i.e., failed or were retired prior to the creation of the national inventory) or are not included in the current inventory (i.e., do not satisfy the NID size criteria), the NPDP staff assigns an identificaiton number. Format: AAnnnnn, where AA is the abbreviation for the state or territory where the dam is located, and nnnnn is a sequentially assigned index number. For NPDP assigned IDs, the format is AASnnnnn.
NPDP Remarks (Non-Public) Use this field to provide notes about the consequences, things that should be verified, etc.
Nutrients Animal, vegetable, or mineral substance which sustains individual organisms and ecosystems.