NPDP Dam Dictionary

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Term AKA Definition
Void Space in a soil or rock mass not occupied by solid mineral matter. This space may be occupied by air, water, or other gaseous or liquid material.
Void ratio The ratio of the volume of void space to the volume of solid particles in a given soil mass.
Volt V The unit of measurement of electromotive force. It is equivalent to the force required to produce a current of 1 ampere through a resistance of 1 ohm. See kilovolt.
Volt-ampere VA A unit of apparent power in an ac circuit containing reactance. It is equal to the potential in volts multiplied by the current in amperes, without taking phase into consideration.
Voltage E Electrical pressure, i.e. the force which causes current to flow through an electrical conductor. The greatest effective difference of potential between any two conductors of a circuit
Volume of Concrete The total space occupied by concrete forming the dam structure computed between abutments and from the top to the bottom of the dam. No deduction is made for small openings such as galleries, adits, tunnels, and operating chambers within the dam structure. The volume includes all mass concrete appurtenances not separated from the dam by construction or contraction joints. Where a powerplant is located at the downstream toe of a concrete dam, the limit of concrete in the dam should be taken as the downstream face projected to the general excavated foundation surface.
Volume of dam The total space occupied by the materials forming the dam structure computed between abutments and from the top to the bottom of the dam. No deduction is made for small openings such as galleries, adits, tunnels, and operating chambers within the dam structure. Portions of powerhouses, locks spillway, etc., may be included only if they are necessary for the structural stability of the dam.
Vortex A revolving mass of water (whirlpool) in which the streamlines are concentric circles and in which the total head is the same. Water rotating about an axis.
Warm-water fishery Generally, water or water system that has an environment suitable for species of fish other than salmonids.
Wastebank A bank made of excess or unstable material excavated from a construction site.
Water content See moisture content.
Water conveyance structure Any structure that conveys water from one location to another.
Water delivery system Reservoirs, canals, ditches, pumps, and other facilities to move water.
Water management plan A plan developed during construction to help assure water quality compliance for both point and nonpoint pollution sources.
Water saturation That point at which a material will no longer absorb water.
Water surface elevation The elevation of a water surface above or below an established reference level, such as sea level. See datum.
Water table The surface of underground, gravity controlled water.
Water user Any individual, district, association, government agency, or other entity that uses water supplied from a Reclamation project.
Water year WY Period of time beginning October 1 of one year and ending September 30 of the following year and designated by the calendar year in which it ends. A calendar year used for water calculations.
Watershed Surface drainage area above a specified point on a stream.
Waterstage recorder A motor-driven (spring wound or electric) instrument for monitoring water surface elevation.
Waterstop A continuous strip of waterproof material placed at concrete joints designed to control cracking and limit moisture penetration (water bar).
Watt Basic unit of electrical power produced at one time. One watt equals one joule per second. See kilowatt, megawatt, and gigawatt.
Wave wall See parapet wall.
Weep hole A drain embedded in a concrete or masonry structure intended to relieve pressure caused by seepage behind the structure.
Weighting of a slope Additional material placed on the slope of an embankment.
Weir An overflow structure built across an open channel to raise the upstream water level and/or to measure the flow of water. A measuring or gaging weir is calibrated for depth of flow over the crest. See cipolletti weir, rectangular weir, and v-notch weir. Other types of weirs include broad-crested weir sharp-crested weir drowned weir" or "submerged weir." "
Well graded A good representation in the material of all particle sizes present from the largest to smallest.
Wellpoint A pipe fitted with a driving point and a fine mesh screen used to remove underground water. A complete set of equipment for drying up ground including wellpoints, connecting pipe and pump.
Wetlands Lands including swamps, marshes, bogs, and similar areas such as wet meadows, river overflows, mud flats, and natural ponds. An area characterized by periodic inundation or saturation, hydric soils, and vegetation adapted for life in saturated soil conditions.