Water — page 9 of 31

Water terms

801. Dam failure hydrograph A flood hydrograph resulting from a dam breach prepared for a specific location downstream from the dam.
802. Dam foundation The excavated surface or undisturbed material upon which a dam is placed.
803. Dam safety deficiency A physical condition capable of causing the sudden uncontrollable release of reservoir water by partial or complete failure of a dam, appurtenant…
804. Dam safety issue Dam safety related issues and concerns are those which, if not adequately addressed could/would: 1 - Lead to a failure or malfunction reulting in an…
805. Dam tender The person responsible for the daily or routine operation and maintenance activities of a dam and its appurtenant structures.
806. Damping Resistance which reduces vibration by energy absorption.
807. Damping ratio The ratio of the actual damping to the critical damping, critical damping being the minimum amount of damping which prevents free oscillatory vibration.
808. Data collection platform Electronic equipment device that gathers digital and analog data from monitoring devices and remotely relays that data to a central computer for…
809. Data Collection Platform (DCP) (DCP) An electronic device that connects to a river or rainfall gage that records data from the gage and at pre-determined times transmits that data through a…
810. DATACOL The Software System that supports RFC gateway functions.
811. DATANET Hydrologic Data Network Analysis Software
812. DataWeb DataWeb is an electronic presentation of the Bureau of Reclamation's Project Data book and contains historical, statistical, and technical information on…
813. datum Any level surface taken as a plane of reference from which to measure elevations.
814. Day-Second Feet Often abbreviated as SDF. See Second-Day Feet.
815. DBE - design basis earthquake.
816. DD Direct Damage. This is a spell that does all of its damage in one hit rather than spreading its damage over time.
817. De Facto MPA Delineated areas of the marine environment where human access is restricted or where specific activities or uses are regulated for reasons other than…
818. Dead capacity (dead storage) The reservoir capacity from which stored water cannot be evacuated by gravity.
819. Dead Storage The volume in a reservoir below the lowest controllable level.
820. Debris fan Sloping mass of boulders, cobbles, gravel, sand, silt and clay formed by debris flows at the mouth of a tributary.
821. Debris flow A mixture of water-saturated rock debris that flows downslope under the force of gravity (also called lahar or mudflow).
822. Decibel A unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average level at…
823. Decision criteria Set of formal criteria that is used to determine if an event is threatening and what action to implement.
824. Decision makers Designated personnel responsible for interpreting data that has been collected and determining if an event is threatening enough to issue an alert or…
825. Decision making The second of five Early Warning System components consisting of the processes and facilities necessary to translate incoming data about the threatening…
826. Decking Separating charges of explosives by inert material which prevents passing of concussion, and placing a primer in each charge.
827. Decomposition The process of breaking down organic material; reduction of the net energy level and change in physical and chemical composition of organic material.
828. Deed covenant A term used in association with the sale of excess lands. In order for an eligible buyer of excess land to receive Reclamation irrigation water on such…
829. Deep percolation The movement of water by gravity downward through the soil profile beyond the root zone; this water is not used by plants.
830. Deep Percolation Loss Water that percolates downward through the soil beyond the reach of plant roots.
831. Deep Seepage Infiltration which reaches the water table.
832. Deep well A well whose pumping head is too great to permit use of a suction pump.
833. Deficiency Verification Analysis (DVA) This analysis verifies the existence or non-existence of Safety of Dams (SOD) deficiencies at the dam.
834. Deflagration To burn with sudden and startling combustion. Describes explosion of black powder, as opposed to the more rapid detonation of dynamite.
835. Deflation A condition of decreasing prices. Deflation is generally measured by the Consumer Price Index.
836. Deflect A decrease in the vertical diameter of a flexible pipe.
837. Deflection Upstream or downstream movement of a dam or dike.
838. Deformation Change in shape or size.
839. Deformed Ice A general term for ice which has been squeezed together and forced upwards and downwards in places.
840. Degradation Process wherein the elevation of streambeds, sandbars, and flood plains is lowered by erosion. The opposite of aggradation.
841. Delay A device used to obtain detonation of charges at separate times. An electric blasting cap which explodes at a set interval after current is passed through…
842. Delay pattern Order of firing charges obtained by arranging delays to fire separate holes or series of holes at different times.
843. Delivery The amount of water delivered to the point of use. The difference between delivery and release is usually the same as consumptive use.
844. Delta The relationship between an option's price and the price of the underlying stock or futures contract is called its delta.
845. Demand Form PCT/IPEA/401, filed with an International Preliminary Examining Authority, demanding that an international application shall be the subject of an…
846. Demand scheduling Method of irrigation scheduling whereby water is delivered to users as needed and which may vary in flow rate, frequency and duration.
847. Demersal Fish eggs or organisms that hatch on the bottom of a lake or stream.
848. Demographics Relating to the statistical study of human populations.
849. Dendrites Thin branch-like growth of ice on the water surface.
850. Dendritic Channel pattern of streams with tributaries that branch to form a tree-like pattern.
851. Density The average number of people, families, or housing units on one unit of land. Density is also expressed as dwelling units per acre.
852. Density Current A flow of water maintained by gravity through a large body of water, such as a reservoir or lake, and retaining its unmixed identity because of a…
853. Density of Snow The ratio, expressed as a percentage, of the volume which a given quantity of snow would occupy if it were reduced to water, to the volume of the snow.
854. Dentate. See baffle block.
855. Dependable Capacity The load-carrying ability of an electric power plant during a specific time interval and period when related to the characteristics of the load to…
856. Depletion Net loss of water through consumption, export, and other uses to a given area, river system, or basin.
857. Depletion Curve That part of the hydrograph extending from the point of termination of the Recession Curve to the subsequent rise or alternation of inflow due to…
858. Deposition An oral statement made before an officer authorized by law to administer oaths.
859. Depression Storage The volume of water contained in natural depressions in the land surface, such as puddles.
860. Depth of cutoff The vertical distance that the cutoff penetrates into the dam foundation.
861. Depth of Runoff The total runoff from a drainage basin, divided by its area. For convenience in comparing runoff with precipitation, the term is usually expressed in…
862. Derrick Usually a non-mobile tower equipped with a hoist, but may be used as a synonym for a crane.
863. Desalinization The removal of dissolved salts from water by natural means (leaching) or by specific water treatment processes.
864. Desertification When soil erosion is so severe that plants and animals can no longer exist.
865. Desiccant Any compound used to remove moisture or water.
866. Desiccate To dry up; remove moisture from a substance.
867. Desiccation The process of removing moisture; involves evaporation.
868. Design basis earthquake (DBE) The earthquake which the structure is required to safely withstand with repairable damage.
869. Design Criteria The hypothetical flood used in the sizing of the dam and the associated structures to prevent dam failure by overtopping, especially for the spillway…
870. Design Flood The largest flood that a given project is designed to safely accommodate. The reservoir inflow hydrograph used to estimate the spillway discharge capacity…
871. Design response spectra Smooth, broad-banded spectra appropriate for specifying the level of seismic design force, or displacement, for earthquake-resistant design purposes.
872. Design summary A document that summarizes the designers' development of the design that results in the specifications.
873. Design water level The maximum water elevation, including the flood surcharge, that a dam is designed to be able to withstand.
874. Design wind The most severe wind that is reasonbly possible at a particular reservoir for generating wind setup and runup.
875. Designated floodway The channel of a water course and those portions of the adjoining flood plain required to provide for the passage of a selected flood with a small…
876. Designated frequency flood Refers to the probability that a flood will occur in a given year. A 100-year flood is often considered in the design of diversion dams and for…
877. Designers' Operating Criteria (DOC) Detailed operating criteria which stress the designer's intended use and operation of equipment and structures in the interest of safe, proper, and…
878. Desorption The release or removal of an adsorbed material from the surface of a solid adsorbent.
879. Destratification The development of vertical mixing within a lake or reservoir to eliminate (either totally or partially) separate layers of temperature, plant, or animal…
880. Detection The first of five Early Warning System components consisting of the processes and equipment necessary to collect information about the threatening event…
881. Detention Basins Detention basins are normally dry, but are designed to detain surface water temporarily during, and immediately after a runoff event.
882. Detention dam A dam built to store streamflow or surface runoff, and to control the release of such stored water.
883. Detention Storage The volume of water, other than depression storage, existing on the land surface as flowing water which has not yet reached the channel.
884. Detonating cord Round, flexible textile, or plastic cord with a center core of high explosive. A common use is to tie in shots using nonelectric delays (MS connectors)…
885. Detonation Practically instantaneous decomposition or combustion of an unstable compound, with tremendous increase in volume.
886. Detonator A device to start an explosion, as a fuse or cap.
887. Detritus Loose natural materials, such as rock fragments or organic particles, that result directly from disintegration of rocks or organisms.
888. Deviator stress The difference between the major and minor principal stresses in a triaxial test.
889. Dew Moisture in the air that condenses on solid surfaces when the air is saturated with water vapor.
890. Dew point The temperature to which air with a given quantity of water vapor must be cooled to cause condensation of the vapor in the air.
891. Dewatering The separation of free water from the solids portion of spent mash, sludge, or whole stillage by screening, centrifuging, filter pressing, or other means.
892. DHRO Diversity and Human Resources Office.
893. DI durability index.
894. Diagnostic tool Any artifact which, because of form, shape, or function, provides chronological or manufacturing information.
895. Diaphragm pump A pump that moves water by reciprocating motion of a diaphragm in a chamber having inlet and outlet check valves.
896. Diaphragm wall A sheet, thin zone, or facing made of a relatively impervious material such as concrete, steel, wood, plastic, etc. Also see core wall.
897. Diaphragm-type earthfill An embankment dam which is constructed mostly of pervious material and having a diaphragm of impermeable material which forms a water barrier.
898. Diaphragm. (DY-uh-fram) The thin muscle below the lungs and heart that separates the chest from the abdomen.
899. Diatom Single-celled or colonial algae whose cell walls are made of silica.
900. Differential head (unbalanced head) The condition in which the water pressure on the upstream and downstream sides of an object differ.