NPDP Dam Dictionary

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Term AKA Definition
Pressure relief pipes Pipes used to relieve uplift or pore- water pressure in a dam foundation or in the dam structure.
Prestressed dam A dam, the stability of which depends in part on the tension in steel wires, cables, or rods that pass through the dam and are anchored into the foundation rock. See Stewart Mountain Dam.
Probable maximum flood PMF The largest flood that may be expected at a point on a stream from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible on a particular watershed. This term, as used in official documents of the Corps of Engineers, identifies estimates of hypothetical flood characteristics (peak discharge, volume, and hydrograph shape) that are considered to be the most severe reasonably possible" at a particular location based on relatively comprehensive hydrometeorological analyses of critical runoff-producing precipitation (and snowmelt if pertinent) and hydrologic factors favorable for maximum flood runoff. "
Probable maximum precipitation PMP Theoretically, the greatest depth of precipitation for a given duration that is physically possible over a given size storm area at a particular geographic location at a certain time of the year.
Production Act or process of producing electrical energy from other forms of energy; also, amount of electrical energy produced expressed in kilowatt-hours (kWh).
Profundal Deepest part of the ocean or lake where light does not penetrate. This layer usually has fewer nutrients, more silt, and fewer organisms than the surface.
Psychological value See Social value.
Public involvement Process of obtaining citizen input into each stage of development of planning documents. Required as a major input into any EIS.
Publics Any interested group or individual, including Federal, State and local agencies, interest groups, ad hoc groups, and the general public.
Puddling A method of compacting soil with the soil deposited into a pool of water and then stirred or rodded.
Pumped-storage plant Powerplant designed to generate electric energy for peakload use by releasing water previously pumped into an elevated storage reservoir, usually during off-peak periods.
Pumping energy Energy required to pump water from the lower reservoir to the upper reservoir of a pumped-storage plant.
Pumplift The vertical distance that a pump will raise waters.
Purpose The purpose(s) of the reservoir could be one or more of the following: 1. Irrigation 2. Hydroelectric 3. Flood Control and Storm Water Management 4. Navigation 5. Water Supply 6. Recreation 7. Fir Protection, Stock, Or Small Farm Pond 8. Fish and Wildlife Pond 9. Debris Control 10. Tailings 11. Other