F. X. Browne, Inc. Glossary - B

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B-HORIZON—The lower soil zone which is enriched by the deposition or precipitation of material from the overlying zone, or A-Horizon. Along with the A-horizon, constitutes part of the Zone of Eluviation.

BABBLE—to make a continuous low, murmuring sound, as flowing water.

BAC—see Biological Activated Carbon (BAC) Process.

BACKBAR CHANNEL—A channel formed behind a bar connected to the main channel but usually at a higher bed elevation than the man channel. Backbar channels may or may not contain flowing or standing water.

BACKFILL, or Backfilling—process of filling the notches carved in the earth from strip mining in order to restore the original slope. This is intended to reduce soil erosion and allow for the reestablishment of vegetation.

BACKFLOW—the backing up of water through a conduit or channel in the direction opposite to normal flow. A reverse flow condition created by a difference in water pressures that causes water to flow back into the distribution pipes of a drinking water supply from any source other than the intended one. Also referred to as Back Siphonage.

BACKGROUND—Value for a parameter that represents the conditions in a system prior to a given influence in space or time.

BACK PRESSURE—a pressure that can cause water to Backflow into the water supply when a user's waste water system is at a higher pressure than the public system.

BACKRUSH—the seaward return of water after the landward motion of a wave. Also referred to as Backwash.

BACKSET—An eddy or countercurrent in water.

BACKSHORE—The part of a shore between the Foreshore and the landward edge that is above high water except in the most severe storms.

BACK SIPHONAGE—A reverse flow condition created by a difference in water pressures that causes water to flow back into the distribution pipes of a drinking water supply from any source other than the intended one. Also referred to as Backflow.

BACK SWAMP—Marshy area of a flood plain at some distance from and lower than the banks of a river confined by natural levees.

BACKWASH—A backward flow or water, also referred to as Backrush. (Water Quality) The reversal of flow through a rapid sand filter to wash clogging material out of the filtering medium and reduce conditions causing loss of head (pressure).

BACKWASHING—In a wastewater or water treatment facility, the flow of clean water in a direction opposite (upward) to the normal flow of raw water through rapid sand filters in order to clean them.

BACKWATER—(1) A small, generally shallow body of water attached to the main channel, with little or no current of its own. (2) Water backed up or retarded in its course as compared with its normal or natural condition of flow. In Stream Gauging, a rise in Stage produced by a temporary obstruction such as ice or weeds, or by the flooding of the stream below. The difference between the observed stage and that indicated by the Stage-Discharge Relation, is reported as backwater.

BACKWATER CURVE—The longitudinal profile of the water surface in an open channel where the water surface is raised above its normal level by a natural or artificial obstruction. The term is sometimes used in a generic sense to denote all water surface profiles, or profiles where the water is flowing at depths greater than critical.

BACKWATER EFFECT—The rise in surface elevation of flowing water upstream from and as a result of an obstruction to flow. In stream gaging, a rise in stage produced by a temporary obstruction such as ice or weeds, or by the flooding of the stream below. The difference between the observed stage and that indicated by the stage-discharge relation is reported as backwater.

BACKWATER FLOODING—Flooding caused by a restriction or blocking of flow downstream. Examples include a narrowing of the channel, logjam, ice jam, high flow in a downstream confluence stream, or high tide blocking high river flows from entering estuaries.

BACKWATER POOLS—A pool type formed by an eddy along channel margins downstream from obstructions such as bars, rootwads, or boulders, or resulting from backflooding upstream from an obstructional blockage. Backwater pools are sometimes separated from the channel by sand or gravel bars.

BACTERIA (Singular: Bacterium)—Microscopic unicellular organisms, typically spherical, rod-like, or spiral and threadlike in shape, often clumped into colonies. Some bacteria cause disease, while others perform an essential role in nature in the recycling of materials, for example, decomposing organic matter into a form available for reuse by plants. Some forms of bacteria are used to stabilize organic wastes in wastewater treatment plants, oil spills, or other pollutants. Disease-causing forms of bacteria are termed "pathogenic." Some forms of bacteria harmful to man include:

[1] Total Coliform Bacteria—A particular group of bacteria that are used as indicators of possible sewage pollution. They are characterized as aerobic or facultative anaerobic, gram-negative, nonspore-forming, rod-shaped bacteria which ferment lactose with gas formation within 48 hours at 3C. In the laboratory these bacteria are defined as all the organisms that produce colonies with a golden-green metallic sheen within 24 hours when incubated at 35C plus or minus 1.0C on M-Endo medium (nutrient medium for bacterial growth). Their concentrations are expressed as numbers of colonies per 100 milliliter (ml)l of sample.
[2] Fecal Coliform Bacteria—Bacteria that are present in the intestine or feces of warm-blooded animals. They are often used as indicators of the sanitary quality of the water. In the laboratory they are defined as all the organisms that produce blue colonies within 24 hours when incubated at 44.5C plus or minus 0.2C on M-FC medium (nutrient medium for bacterial growth). Their concentrations are expressed as numbers of colonies per 100 ml of sample.
[3] Fecal Streptococcal Bacteria—Bacteria found also in the intestine of warm-blooded animals. Their presence in water is considered to verify fecal pollution. They are characterized as gram-positive, cocci bacteria which are capable of growth in brain-heart infusion broth. In the laboratory they are defined as all the organisms that produce colonies which produce red or pink colonies within 24 hours at 35C plus or minus 1.0C on KF-streptococcus medium (nutrient medium for bacterial growth). Their concentrations are expressed as numbers of colonies per 100 ml of sample.

BACTERIAL PLATE COUNT—A system used to quantify the number of bacteria in a sample of solid or liquid material by measuring the growth of bacterium into full colonies.

BACTERICIDAL—Able to kill bacteria.

BACTERIOSTATIC—A substance that inhibits bacterial growth but is not necessarily lethal.

BADLANDS—Barren land characterized by roughly eroded ridges, peaks, and mesas.

BADT—Best Available Demonstrated Technology.

BAFFLE—A flat board or plate, deflector, guide, or similar device constructed or placed in flowing water or slurry systems to cause more uniform flow velocities to absorb energy and to divert, guide, or agitate liquids.

BAG OF WATERS—The double-walled fluid-filled sac that encloses and protects the fetus in the womb and that breaks releasing its fluid during the birth process

BAIL—To remove water, as from the bottom of a boat or other vessel.

BAILER—An instrument such as a long pipe with a valve at the lower end used to extract a water sample from a groundwater well. Also used to remove slurry from the bottom or side of a well as it is being drilled.

BAJADA—A long outwash detrital (sedimentary) slope at the base of a mountain range.

BALANCED OPERATION—Operation of a canal system where the water supply exactly matches the total flow demand.

BALANCED GROUNDWATER SCENARIO (BGS)—A term referring to the development of a scenario exploring changes in cropping patterns such that long-term ground water withdrawals do not exceed long-term groundwater recharge rates. Also see Agricultural Restructuring Scenario (ARS), Ground Water Overdraft, and Ground Water Mining.

BALLAST—Heavy material, often seawater, placed in the hold of a ship to gain stability. Periodic discharges of this ballast water from oil tankers constitute a significant portion of the oil introduced into the oceans of the world each year.

BALL COCK—A self-regulating device controlling the supply of water in a tank, cistern, or toilet by means of a float connected to a valve that opens or closes with a change in water level.

BALL VALVE—A valve regulated by the position of a free-floating ball that moves in response to fluid or mechanical pressure.

BANK, and BANKS—The slope of land adjoining a body of water, especially adjoining a river, lake, or a channel. With respect to flowing waters, banks are either right or left as viewed facing in the direction of the flow. As Banks, a large elevated area of a sea floor.

BANK AND CHANNEL STABILIZATION—Implementation of structural features along a streambank to prevent or reduce bank erosion and channel degradation.

BANKFULL STAGE—The stage at which a stream first begins overflows its natural banks. More precisely, an established river stage at a given location along a river which is intended to represent the maximum safe water level that will not overflow the river banks or cause any significant damage within the river reach. Bankfull stage is a hydraulic term, whereas Flood Stage implies resultant damage.

BANKING (WATER)—See Water Banking.

BANK STORAGE—The water absorbed into the banks of a stream, lake, or reservoir, when the stage rises above the water table in the bank formations, then returns to the channel as effluent seepage when the stage falls below the water table. Bank storage may be returned in whole or in part as seepage back to the water body when the level of the surface water returns to a lower level.

BAPTISM—(1) A Christian sacrament marked by ritual use of water and admitting the recipient to the Christian community; (2) A non-Christian rite using water for ritual purification.

BAR—(1) An elongated landform generated by waves and currents, usually running parallel to the shore, composed predominantly of unconsolidated sand, gravel, stones, cobbles, or rubble and with water on two sides. (2) A unit of pressure equal to 106 dynes per cm2, 100 kilopascals, or 29.53 inches of mercury.

BAROTHERMOGRAPH—An instrument which records simultaneous barometric pressure and temperature on the same chart.

BAR RACKS—(Water Quality) The closely spaced rods, often in the form of a screen, that remove large solids from the wastewater entering a sewage treatment plant.

BARRAGE—An artificial obstruction, such as a dam or an irrigation channel, built in a watercourse to increase its depth or to divert its flow either for navigation or irrigation. Sometimes the purpose is to control peak flow for later release.

BARREL—(1) A measure of liquid volume (conventionally) equal to 42 U.S. gallons (34.9723 Imperial gallons), or 158.9873 liters. (2) Any of various units of volume or capacity. In the U.S. Customary System, it varies, as a liquid measure, from 31 to 42 U.S. gallons (approximately 120 to 159 liters) as established by law or usage.

BAR SCREEN—(Water Quality) In wastewater treatment, a device used to remove large solid materials.

BASALT—(Geology) A dark volcanic rock composed of microscopic grains of augite, feldspar, and olivine. Some basalts have many holes that give the rock a swiss-cheese-like appearance. As the lava cools, gases escape, leaving holes of different sizes.

BASALT AQUIFERS—Aquifers found in basalt rock in areas of past volcanic activity, particularly in the Pacific Northwest region of the United States and in Hawaii.

BASE—(1) Any of various typically water-soluble and bitter tasting compounds that in solution have a pH greater than 7, are capable of reacting with an acid to form a salt, and are molecules or ions able to take up a proton from an acid or able to give up an unshared pair of electrons to an acid. (2) Chemicals that release hydroxide ions (OH-) in solution. Such solutions have a soapy feel, neutralize acids, and conduct electricity.

BASE FLOOD (100-YEAR FLOOD)—The flood having a 1 percent average probability of being equaled or exceeded in a given year at a designated location. It may occur in any year or even in successive years if the hydrologic conditions are conducive for flooding. Also see Hundred-Year Flood, X-Year Flood, and X-Year Flood, Y-Duration Rain.

BASE FLOOD ELEVATION—The height in relation to mean sea level (MSL) expected to be reached by the waters of the base flood at pertinent points in the floodplain of Riverine areas.

BASE FLOODPLAIN—The floodplain that would be inundated by a one percent chance flood (100-Year Flood).

BASE FLOW—The fair-weather or sustained flow of streams; that part of stream discharge not attributable to direct runoff from precipitation, snowmelt, or a spring. Discharge entering streams channels as effluent from the groundwater reservoir. Also referred to as Groundwater Flow.

BASE LEVEL—The lowest level to which a land surface can be reduced by the action of running water.

BASELINE—The condition that would prevail if no action were taken.

BASELINE (DATA)—A quantitative level or value from which other data and observations of a comparable nature are referenced. Information accumulated concerning the state of a system, process, or activity before the initiation of actions that may result in changes.

BASE PERIOD—A period of time specified for the selection of data for analysis. The base period should be sufficiently long to contain data representative of the averages and deviations from the averages that must be expected in other periods of similar and greater length. For example, the U.S. Weather Bureau computes values of average, heavy, and light monthly precipitation from data observed during the base period of 1931-1960. For ground-water studies, the base period should both begin and end at the conclusion of a dry trend so that the difference between the amount of water in transit in the soil at the ends of the base period is minimal.

BASE RUNOFF—Sustained or fair weather runoff. In most streams, base runoff is composed largely of ground-water effluent. The term base flow is often used in the same sense as base runoff. However, the distinction is the same as that between streamflow and runoff. When the concept in the terms base flow and base runoff is that of the natural flow in a stream, base runoff is the more appropriate term.

BASE WIDTH—(1) The time interval between the beginning and end of the direct runoff produced by a storm. (2) The time period covered by a Unit Hydrograph.

BASIC—Describing a solution, sediment, or other material that has a pH greater than 7.0. see Alkaline

BASIC HYDROLOGIC DATA—Includes inventories of features of land and water that vary only from place to place (e.g., topographic and geologic maps), and records of processes that vary with both place and time (e.g., records of precipitation, streamflow, ground-water, and quality-of-water analyses). Basic Hydrologic Information is a broader term that includes surveys of the water resources of particular areas and a study of their physical and related economic processes, interrelations and mechanisms.

BASIN—(1) A geographic area drained by a single major stream; consists of a drainage system comprised of streams and often natural or man-made lakes. Also referred to as Drainage Basin, Watershed, or Hydrographic Region. (2) A naturally or artificially enclosed harbor for small craft, such as a yacht basin.

BASIN AND RANGE [Nevada]—A region of north-trending mountains ranges and valleys encompassing western Utah and essentially all of Nevada. This geologic territory includes virtually all of the Great Basin and extends south and east through Arizona, New Mexico, and Texas all the way into Mexico. The Basin and Range can be differentiated from its surrounding geologic regions by its uplifted and tilted ranges separated by broad elongated basins. The Great Basin forms a unique part of this geologic region in as much as this hydrologic area has no drainage to the ocean.

BASIN FILL—Unconsolidated material such as sand, gravel, and silt eroded from surrounding mountains and deposited in a valley.

BASIN LAG—(1) The time from the centroid (centermost point in time based on total period rainfall) of rainfall to the hydrograph peak. (2) The time from the centroid of rainfall to the centroid of the Unit Hydrograph.

BASIN MANAGEMENT (of Water)—Also referred to as Water or Watershed Management, it is the analysis, protection, development, operation, or maintenance of the land, vegetation, and water resources of a drainage basin for the conservation of all its resources for the benefit of man. Basin management for water production is concerned with the quality, quantity, and timing of the water which is produced.

BASIN YIELDS—The amount of water which will flow from a drainage or catchment area in a given storm.

BASINS [Nevada]—The U.S. Geological Survey (USGS) and the Nevada Division of Water Resources, Department of Conservation and Natural Resources, have divided the state into discrete hydrologic units for water planning and management purposes. These have been identified as 232 Hydrographic Areas (256 areas and sub-areas, combined) within 14 major Hydrographic Regions or Basins. These 14 Nevada Hydrographic Regions (Basins), along with the approximate surface areas, counties of coverage, and number of hydrographic areas and sub-areas are:

[1] Northwest Region—Covers 3,052 square miles (1,953,280 acres) of northern Washoe and Humboldt counties and encompasses 16 hydrographic areas;
[2] Black Rock Desert Region—Covers 8,632 square miles (5,524,480 acres) of parts of Washoe, Humboldt, and Pershing counties and includes 17 valleys (hydrographic areas), two of which are divided into two sub-areas each;
[3] Snake River Basin—Covers 5,230 square miles (3,347,200 acres) in parts of Elko and Humboldt counties to include eight hydrographic areas;
[4] Humboldt River Basin—Covers over 16,843 square miles (10,779,520 acres) in parts of eight counties—Elko, White Pine, Eureka, Humboldt, Lander, Nye, Pershing, and Churchill—and the largest stream (Humboldt River) wholly within Nevada. This basin contains 34 hydrographic areas and one sub-area;
[5] West Central Region—Covers 1,656 square miles (1,059,840 acres) and includes parts of Pershing, Lyon, and Churchill counties and comprises five hydrographic areas;
[6] Truckee River Basin—Encompasses 2,300 square miles (1,472,000 acres) containing parts of Washoe, Pershing, Douglas, Carson City, and Storey counties comprising 12 hydrographic areas;
[7] Western Region—Covers 602 square miles (385,280 acres) and is wholly contained in Washoe County and contains nine valleys (hydrographic areas) one of which is divided into two sub-areas and another divided into one sub-area;
[8] Carson River Basin—Covers 3,634 square miles (2,325,760 acres) and includes parts of six counties—Douglas, Carson City, Lyon, Storey, Churchill, and Pershing—containing five hydrographic areas and one sub-area along the Carson River and its tributaries;
[9] Walker River Basin—Covers 2,931 square miles (1,875,840 acres) of Mineral, Lyon, and Douglas counties (and a very small portion of Churchill County) including five hydrographic areas, one of which has been divided into three sub-areas;
[10] Central Region—By far the largest hydrographic region in Nevada covering 46,783 square miles (29,941,120 acres) in 13 counties—Nye, Elko, White Pine, Lincoln, Clark, Humboldt, Pershing, Churchill, Lander, Eureka, Lyon, Mineral, and Esmeralda. This region includes 78 valleys (hydrographic areas), 10 of which are divided into two sub-areas and one into three sub-areas;
[11] Great Salt Lake Basin—Covers 3,807 square miles (2,436,480 acres) of the easternmost portions of Elko, White Pine, and Lincoln counties. It consists of eight hydrographic areas, one of which is divided into four sub-areas;
[12] Escalante Desert Basin—This basin covers a large area in Utah but only a very small part of it is in Lincoln County—106 square miles (67,480 acres)—and is made up of only one hydrographic area;
[13] Colorado River Basin—Covers 12,376 square miles (7,920,640 acres) including parts of Clark, Lincoln, Nye, and White Pine counties and is divided into 27 hydrographic areas;
[14] Death Valley Basin—Covers 2,593 square miles (1,659,520 acres) of Nye and Esmeralda counties including eight hydrographic areas, one of which has been divided into two sub-areas.

[A listing of Nevada's Hydrographic Areas and Sub-Areas is presented in Appendix A-1 (listed sequentially by Hydrographic Area number and Hydrographic Region/Basin), Appendix A-2 (listed alphabetically by Hydrographic Area and Sub-Area name), and Appendix A-3 (listed alphabetically by principal Nevada county(ies) in which located).]

BASS—Any of a number of North American fish found in streams and lakes. Bass are used for food.

BAT—Best Available Technology [Economically Achievable]

BATH—The act of soaking or cleansing a body, as in water or steam. Also, the water used for such cleansing.

BATHE—(1) To take a bath or go into the water for swimming or other recreation. (2) To become immersed in or as if in liquid; to seem to wash or pour over; suffuse.

BATHING WATER—Water in swimming pools or natural fresh or marine waters used for swimming.

BATHOLITH—A mass of Igneous rock that forms intrusively and can rise to the surface.

BATHOMETER—An instrument used to measure the depth of water.

BATHTUB—A large tub to bathe in.

BATHTUB EFFECT—The accumulation of Leachate in a landfill containing a good liner, but not equipped with a leachate collection and removal system.

BATHYAL ZONE—The ocean stratum beneath the Euphotic Zone and above the Abyssal Zone, or to the bottom of the Continental Shelf. The density of life in this zone depends on organic material settling from the euphotic zone and is generally inversely proportional to the depth.

BATHYMETRIC MAP—A map showing the depth (bottom contours) of water in lakes, streams, or oceans. Can be used to calculate lake volume.

BATHYMETRY—(1) The measurement of the depth of large bodies of water (oceans, seas, ponds and lakes). (2) The measurement of water depth at various places in a body of water. Also the information derived from such measurements.

BATHYSCAPHE—A free-diving, self-contained deep-sea research vessel consisting essentially of a large flotation hull with a crewed observation capsule fixed to its underside, capable of reaching depths of 10 kilometers (6.2 miles) or more.

BATHYSPHERE—A reinforced spherical deep-diving chamber in which persons are lowered by a cable to study the oceans. The bathysphere, limited to depths of about 900 meters (3,000 feet), has been supplanted by the safer and more navigable Bathyscaphe.
BATHYTHERMOGRAPH—An instrument designed to record water temperature as a function of depth.

BAUMÉ—Being, calibrated in accordance with, or according to either of two arbitrary hydrometer scales for liquids lighter than water or for liquids heavier than water that indicate specific gravity in degrees.

BAY—A part of a sea, reservoir, or lake, indenting the shoreline; a wide inlet not so large as a Gulf.

BAY-DELTA [California]—Refers to the region encompassing the Sacramento-San Joaquin river delta system forming a basically delta or triangular structure extending from south Sacramento in the north to below Stockton in the south to the San Francisco Bay in the west. The Bay-Delta is the largest remaining Estuarine system on the West Coast of the United States. The Bay-Delta contains approximately 738,000 total acres (1,153 square miles) interlaced with hundreds of miles of water waterways. Of this total area, 520,000 acres are in agriculture, 35,000 acres are contained in cities and towns, 50,000 acres are covered with water, and 133,000 acres remain undeveloped. The gross value of the Bay-Delta's agricultural production totals over $500 million per year. Deep water ship channels run through the Bay-Delta and connect both Sacramento and Stockton to the San Francisco Bay and the Pacific Ocean. As much of the Bay-Delta's land area is up to 21 feet below the water level, waters flowing throughout this system are controlled by over 1,100 miles of levees. Rivers flowing into the Bay-Delta include the Sacramento, San Joaquin, Mokelumne, Cosumnes, and Calaveras, which, along with their tributaries, carry 47 percent of California's total surface runoff. The Bay-Delta serves as the major collection point for the water that serves over two-thirds of California's total population. Along with associated pumping facilities, the Bay-Delta provides the source waters for a number of major water development projects to include the California Aqueduct, the Central Valley Project's Delta-Mendota Canal, the Contra Costa Canal, and the North and South Bay Aqueducts. Within the Bay-Delta system may be found extensive populations of fauna and flora to include 230 species of birds, 45 species of mammals, 52 species of fish, 25 species of reptiles and amphibians, and 150 species of flowering plants. Major Anadromous fish using the Bay-Delta include Salmon, Striped Bass, Steelhead Trout, American Shad, and Sturgeon. Also referred to as the Sacramento-San Joaquin Delta. Also see Central Valley Project (CVP) [California] and State Water Project (SWP) [California].

BAYESIAN INFERENCE—(Statistics) Bayes' theorem recognizes that a decision maker usually has some expectation (an a priori model) of what will occur even before acquiring information, and provides a procedure for using new evidence to produce a revised a posteriori estimate of probability. Also see Statistical Inference and Classical Inference.

BAYOU—In general, a creek, secondary watercourse, or minor river, tributary to another river or other body of water. A term regularly used in the lower Mississippi River basin and in the Gulf-coast region of the United States to denote a large stream or creek, or small river, characterized by a slow or imperceptible current through alluvial lowlands or swamps. May also refer to an estuarial creek or inlet on the Gulf coast; a small bay, open cove, or harbor; also, a lagoon, lake or bay, as in a sea marsh or among salt-marsh islands.

BCF—Bioconcentration Factor.

BCP—Bioconcentration Potential.

BCT—Best [conventional] Control Technology.

BEACH—A sloping landform on the shore of larger water bodies, generated by waves and currents and extending from the water to a distinct break in landform or substrate type (e.g., a foredune, cliff, or bank.)

BEACH EROSION—The carrying away of beach materials by wave action, tidal currents, or littoral currents, or by wind.

BEAD—A small, round object, especially a drop of moisture, as beads of sweat.

BEAUFORT'S SCALE—(Meteorology) A scale devised by Sir F. Beaufort, Royal Navy, in 1805, in which the strength of the wind is indicated by numbers from 0 to 12. The corresponding terms are: calm [0], light air [1], light breeze [2], gentle breeze [3], moderate breeze [4], fresh breeze [5], strong breeze [6], moderate gale [7], fresh gale [8], strong gale [9], whole gale [10], storm [11], hurricane [12]. Also see Wind Scale.

BED—(1) An underwater or intertidal area in which a particular organism is established in large numbers. (2) The bottom of a body of water, such as a stream. (Geology) A rock mass of large horizontal extent bounded, especially above, by physically different material (as in Bedrock).

BEDEW—To wet with or as if with Dew.

BED LOAD—Material in movement along a stream bottom, or, if wind is the moving agent, along the surface. Contrast with material carried in suspension or solution.

BED MATERIAL—The sediment mixture of which a streambed, lake, pond, reservoir, or estuary bottom is composed.

BEDROCK—(Geology) The solid rock beneath the soil (Zone of Aeration or Zone of Saturation) and superficial rock. A general term for solid rock that lies beneath soil, loose sediments, or other unconsolidated material.

BEHEADED STREAM—The lower section of a stream that has lost its upper portion through diversion or Stream Piracy.

BELL—A hollow, usually inverted vessel, such as one used for diving deep below the surface of a body of water.

BELT OF SOIL MOISTURE—Subdivision of the Zone of Aeration. Belt from which water may be used by plants or withdrawn by soil evaporation. Some of the water passes down into the intermediate belt, where it may be held by molecular attraction against the influence of gravity.

BENCH FLUME—A flume built on constructed benches or terraces along hillsides or around mountain slopes when the ground is too rough or too steep to permit the use of an excavated canal.

BENCH LAND (Soils)—A general term describing porous and coarse-textured (sandy-gravelly) well-drained soils, overlying a deep water table (if occurring), that exhibits relatively low water holding capacity and rapid infiltration of irrigation water.

BENCH LANDS [Nevada]—The U.S. Department of the Interior, Bureau of Reclamation criteria (revised 1992) has defined Bottom Land for Nevada's Newlands Irrigation Project, located in Churchill County, Nevada, as "those lands with a five-foot soil profile having a holding capacity equal to or exceeding 8 inches and/or a water table within 6 feet of the surface for a period equal to or exceeding 150 days. If neither of these factors apply, the land is designated as Bench Land." Lands classified as bench (or bottom) according to Bureau of Reclamation criteria, above, will be limited to maximum water deliveries (duty) in accordance to the provision of the Orr Ditch Decree and the Alpine Decree, which are identical in establishing water duties and establish the following limits: (1) Eligible lands designated as Bench Lands may receive a maximum of 4.5 acre-feet per acre per year (AF/acre/year); (2) eligible lands designated as Bottom Lands may receive a maximum of 3.5 acre-feet per acre per year (AF/acre/year).

BENCHMARK—Data used as a base for comparative purposes with comparable data.

BEND—The stream bends to the left just beyond that boat.

BENEFICIAL USE (of Water)—(1) The amount of water necessary when reasonable intelligence and diligence are used for a stated purpose. Most states recognize the following uses as beneficial:

[1] domestic and municipal uses;
[2] industrial uses;
[3] irrigation;
[4] mining;
[5] hydroelectric power;
[6] navigation;
[7] recreation;
[8] stock raising;
[9] public parks;
[10] wildlife and game preserves.

(2) The cardinal principle of the (Prior) Appropriation Doctrine. A use of water that is, in general, productive of public benefit, and which promotes the peace, health, safety and welfare of the people of the State. A certificated water right is obtained by putting water to a beneficial use. The right may be lost if beneficial use is discontinued. A beneficial use of water is a use which is of benefit to the appropriator and to society as well. The term encompasses considerations of social and economic value and efficiency of use. In the past, most reasonably efficient uses of water for economic purposes have been considered beneficial. Usually, challenges have only been raised to wasteful use or use for some non-economic purpose, such as preserving in-stream values. Recent statutes in some states have expressly made the use of water for recreation, fish and wildlife purposes, or preservation of the environment a beneficial use. Also see Appropriative Water Rights.

BENEFIT-COST RATIO—The relationship of the economic benefits of an action to its total costs.

BENTHIC DEPOSITS—Bottom accumulations which may contain bottom-dwelling organisms and/or contaminants in a lake, harbor, or stream bed.

BENTHIC INVERTEBRATES—Aquatic animals without backbones that dwell on or in the bottom sediments of fresh or salt water. Examples are clams, crayfish, and a wide variety of worms.

BENTHIC ORGANISMS—Those organisms living at or near the bottom of a body of water.

BENTHIC REGION—The bottom of a body of water, supporting the Benthos.

BENTHIC ZONE—The bottom zone of a lake.

BENTHOS—All the plant and animals living on or closely associated with the bottom of a body of water (within or attached to the sediment of lakes, streams, and oceans). The phytobenthos includes the aquatic macrophytes and bottom-dwelling algae. The zoobenthos (benthic fauna) includes a variety of invertebrate animals, particularly larval forms and mollusks.

BENTONITE—A clay material that swells as it dries, filling gaps and sealing itself against a well casing. It is commonly used to seal abandoned dewatering wells at mines. Concrete, by contrast, shrinks as it cures, and can therefore leave gaps around a wellhead casing that can allow contaminated water from the surface to penetrated into the well.

BERG—A mass of floating or stationary ice; and Iceberg.

BERNOULLI EFFECT—The phenomenon of internal pressure reduction with increased stream velocity in a fluid. Named after Daniel Bernoulli.

BERNOULLI'S EQUATION—Under conditions of steady flow of water, the sum of the velocity head, the pressure head, and the head due to elevation at any given point is equal to the sum of these heads at any other point plus or minus the head losses between the points due to friction or other causes.

BERM—(1) A narrow ledge or path as at the top or bottom of a slope, stream bank, or along a beach. (2) (Dam) A horizontal step or bench in the upstream or downstream face of an Embankment Dam.

BEST AVAILABLE DEMONSTRATED TECHNOLOGY (BADT)—The level of effluent limitation technology required by the 1972 Clean Water Act (CWA) to be used in setting new source performance standards for new industrial direct dischargers of water pollutants.

BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE (BAT)—A national goal under the Water Pollution Control Act of 1972 (Public Law 92-500, commonly referred to as the Clean Water Act) which provides that industry shall use the best treatment technically and economically achievable for a category or class of point sources. Under this concept, pollution control will consider such factors as the age of the facilities and equipment involved, processes employed, engineering aspects of the control techniques, process changes, cost of the reductions, and environmental impacts other than water quality, including energy requirements.

BEST CONVENTIONAL CONTROL TECHNOLOGY (BCT) —The level of water pollution control technology required of existing dischargers for the treatment of conventional pollutants by the 1977 Clean Water Act (CWA).

BEST MANAGEMENT PRACTICES (BMP) —(1) Accepted methods for controlling Non-Point Source (NPS) Pollution as defined by the 1977 Clean Water Act (CWA); may include one or more conservation practices. Also refers to water conservation techniques of proven value. (2) State-of-the-art techniques and procedures used in an operation such as farming or waste disposal in order to minimize pollution or waste. See, for example, Best Management Practices (BMP)—Urban Water Use.

BEST MANAGEMENT PRACTICES (BMP)—URBAN WATER USE—Water conservation measures that generally meet one of two criteria: (1) Constitutes an established and generally accepted practice among water purveyors that provides for the more efficient use of existing water supplies or contributes towards the conservation of water; or (2) Practices which provide sufficient data to clearly indicate their value, are technically and economically reasonable, are environmentally and socially acceptable, are reasonably capable of being implemented by water purveyors and users, and for which significant conservation or conservation-related benefits can be achieved. See Appendix B-1, Best Management Practices—Urban Water Use, for a more complete itemization of BMPs and Potential BMPs.

BEST PRACTICABLE CONTROL TECHNOLOGY (BPT) —A national goal under the Water Pollution Control Act of 1972 (Public Law 92-500, or the Clean Water Act) which provides that industry shall use the best treatment practices practical, with due consideration to cost, age of the plant and equipment, and other factors.

BGS—Balanced Groundwater Scenario.

BIA—Bureau of Indian Affairs (USDI).

BIAS—An error in data gathering or analysis caused by faulty program design, mistakes on the part of personnel, or limitations imposed by available instrumentation or data sources.

BICARBONATE—(Water Quality) A compound containing the HCO3- group, for example, sodium bicarbonate (NaHCO3), which ionizes in solution (water) to produce HCO3-. Also see Carbonate and Carbonate Buffer System.

BIENNIAL PLANT—A plant that lives for two years, producing vegetative growth the first year, usually blooming and fruiting in the second year, and then dying.

BIFURCATE—Dividing structure which splits the flow of water.

BILGE WATER—Water that collects and stagnates in the bilge or bottom-most areas of a ship.

BILLABONG—(Australian) (1) A dead-end channel extending from the main stream of a river. (2) A streambed filled with water only in the rainy season. (3) A stagnant pool or backwater.

BILLION—One thousand times one million, 1,000,000,000

BILLOW—A large wave or swell of water.

BIMODAL DISTRIBUTION—(Statistics) A collection of observations with a large number of values centered (as in a Normal Distribution) around each of two points. For example, in a sampling of the heights of a population, the sample results would tend to be concentrated around an average heights for males and a second average height for females.

BIOACCUMULANTS—Substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. Also see Biological Magnification.

BIOACCUMULATION—(1) The increase in concentration of a chemical in organisms that reside in environments contaminated with low concentrations of various organic compounds. Also used to describe the progressive increase in the amount of a chemical in an organism resulting from rates of absorption of a substance in excess of its metabolism and excretion. (2) Food chain is the sequence of algae being eaten by small aquatic animals (zooplankton) which in turn are eaten by small fish which are then eaten by larger fish and eventually by people or predators. Certain chemicals, such as PCBs mercury, and some pesticides, can be concentrated from very low levels in the water to toxic levels in animals through this process.

BIOASSAY—A method for quantitatively determining the concentration of a substance by its effects on the growth of a suitable animal, plant, or microorganism under controlled conditions.

BIOCHEMICAL OXIDATION—The process by which bacteria and other microorganisms feed on complex organic materials and decompose them. Self-purification of waterways and activated sludge and trickling filter wastewater treatment processes depend on this principle.

BIOCHEMICAL OXYGEN DEMAND (BOD)—(1) A measure of the amount of oxygen removed from aquatic environments by aerobic micro-organisms for their metabolic requirements. Measurement of BOD is used to determine the level of organic pollution of a stream or lake. The greater the BOD, the greater the degree of water pollution. (2) The amount of dissolved oxygen needed to break down organic materials to carbon dioxide, water, and minerals in a given volume of water at a certain temperature over a specified time period. Also, referred to as Biological Oxygen Demand (BOD).

BIOCHEMICAL OXYGEN DEMAND (BOD) LOADING —(Water Quality) The BOD content, commonly expressed in pounds/day, of wastewater passing into a waste treatment system or a body of water. The greater the BOD content, the greater the degree of pollution.

BIOCIDE—A chemical substance that kills living organisms. Typically used to include materials that can kill desirable as well as undesirable organisms.

BIOCLIMATIC ZONES—Also referred to as Biomes, these constitute the earth's ten zones differentiated by climate, soil, water, and plant and animal life. See Biome.

BIOCOENOSIS—A community of animal and plant life.

BIOCONCENTRATION—The increase in concentration of a chemical in an organism resulting from absorption levels exceeding the rate of metabolism and excretion.

BIOCONCENTRATION FACTOR (BCF)—Used to describe the accumulation of chemicals in aquatic organisms that live in contaminated environments. Also see Bioconcentration.

BIOCONCENTRATION POTENTIAL (BCP)—The maximum concentration of a chemical in an organism resulting from the rate of absorption equaling the rate of metabolism and excretion.

BIOCONVERSION—The conversion of organic materials, such as plant or animal waste, into usable products or energy sources by biological processes or agents, such as certain microorganisms.

BIODEGRADABLE—Capable of being decomposed by biological agents, especially bacteria. The property of a substance that permits it to be broken down by micro-organisms into simple, stable compounds such as carbon dioxide and water.

BIODEGRADATION—The metabolic breakdown of materials into simpler components by living organisms. A more specific form of Biotransformation.

BIODENITRIFICATION—The controlled use of microbes, usually bacteria, to reduce level of nitrates (NO3-) and thereby reclaim contaminated water or wastewater. The process consists of several stages to decompose the nitrates first into nitrites and then into nitrogen gas, N2. Upon entering the treatment process, sodium sulfite (Na2SO3) is added as a reducing agent to the wastewater to remove the oxygen from the water. To break down the nitrates, the bacteria must have a carbon food source and typically ethanol is added for the bacteria to feed on. In order to survive, however, the bacteria need oxygen which they obtain by breaking down the nitrate ions, first to nitrite and then to harmless nitrogen gas. Also referred to as Endogenous Respiration.

BIODISC—(Water Quality) A large rotating cylinder possessing surface features that allow for the growth of attached microorganisms. The cylinder revolves and contacts the wastewater along one side while the other side is exposed to air, thereby maximizing the oxygenation of the water and stimulating decomposition of dissolved or suspended organic material.

BIODIVERSITY—Refers to the variety and variability of life, including the complex relationships among microorganisms, insects, animals, and plants that decompose waste, cycle nutrients, and create the air that we breathe. Diversity can be defined as the number of different items and their relative frequencies. For biological diversity, these items are organized at many levels, ranging from complete Ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, and genes. It is generally accepted that human survival is dependent upon the conservation and preservation of this diversity of life forms. Typically five levels of biodiversity are recognized:

[1] Genes—Genetic diversity encompasses the variety of genetically coded characteristics of plant and animal populations;
[2] Populations—Groups of individuals of a species that interbreed or interact socially in an area;
[3] Species—The level at which most organisms are recognizable as distinct from all others;
[4] Natural Communities—Groups of species that typically occur in recognizable units, such as redwood forests, coastal sage scrub, or oak woodlands. A natural community includes all the vegetation and animal life, and their interactions within that community; and
[5] Ecosystems—A collection of natural communities. An ecosystem can be as small as a rotting log or a puddle of water, but current management efforts typically focus on larger landscape units, such as a mountain range, a river basin, or a watershed.

BIOFOULING—The gradual accumulation of waterborne organisms (as bacteria and protozoa) on the surfaces of engineering structures in water that contributes to corrosion of the structures and to a decrease in the efficiency of moving parts.

BIOGAS—Methane gas produced during the Anaerobic decomposition of the remains of plants or animal wastes by bacteria.

BIOGENIC—Used to describe changes in the environment resulting from the activities of living organisms.

BIOGEOCHEMICAL CYCLING—The flow of chemical substances to and from the major environmental reservoirs: Atmosphere, Hydrosphere, Lithosphere, and Biosphere. As chemicals move in the cycle, they often change chemical form, usually existing in a characteristic form in each reservoir. As an example, carbon (in the lithosphere) exists mainly as carbon dioxide in the atmosphere, carbonic acid, bicarbonate, or the carbonate ion when dissolved in water (hydrosphere), and as more complex organic compounds in animals and plants (biosphere).

BIOGEOCHEMISTRY—The study of the transformation and movement of chemical materials to and from the Lithosphere, the Atmosphere, the Hydrosphere, and the bodies of living organisms (the Biosphere).

BIOGEOGRAPHY—The study of the geographic distribution of organisms.

BIOINDICATOR—A living organism that denotes the presence of a specific environmental condition. For example, the presence of coliform bacteria identifies water that is contaminated with human fecal material.

BIOLOGICAL ACTIVATED CARBON (BAC) PROCESS—The combination of Ozonation and Granular Activated Carbon (GAC) for the removal of dissolved organics, particularly Dissolved Organic Carbon (DOC) from drinking water. This water treatment method has seen more widespread use in Europe primarily due to: (1) the generally poorer quality of surface waters there; (2) the greater concern and more stringent standards for chlorination byproducts; and (3) the strict aesthetic demand of European consumers. Also referred to as the Biologically Enhanced Activated Carbon Process.

BIOLOGICAL ADDITIVES—Cultures of bacteria, enzymes, or nutrients that are introduced into an oil discharge or other wastes to promote decomposition.

BIOLOGICAL COMMUNITY—All of the living things in a given environment.

BIOLOGICAL CONTROL—The direct human introduction of living organisms—predators, parasites, or pathogens—to eliminate or control undesirable species. The practice is usually considered an ecologically sound alternative to the application of chemical pesticides.

BIOLOGICAL DIVERSITY—The number and kinds of organisms per unit area of volume; the composition of species in a given area at a given time.

BIOLOGICAL MAGNIFICATION—Refers to the process whereby certain substances such as pesticides or heavy metals move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which in turn are eaten by large birds, animals or humans. The substances become concentrated in tissues or internal organs as they move up the chain. Also see Bioaccumulants and Bioaccumulation.

BIOLOGICAL OPINION—A document which states the opinion of the U.S. Fish and Wildlife Service (USFWS) as to whether a federal action is likely to jeopardize the continued existence of a threatened or endangered species or result in the destruction or adverse modification of critical habitat.

BIOLOGICAL OXIDATION—Decomposition of complex organic materials by microorganisms. Occurs in the self-purification of water bodies and in activated sludge wastewater treatment processes.

BIOLOGICAL OXYGEN DEMAND (BOD)—(Water Quality) An indirect measure of the concentration of biologically degradable material present in organic wastes. It usually reflects the amount of oxygen consumed in five days by biological processes breaking down organic waste. Also see BOD5. Also referred to as Biochemical Oxygen Demand (BOD).

BIOLOGICAL PROCESSES—Processes characteristic of, ore resulting from, the activities of living organisms.

BIOLOGICAL TREATMENT—A treatment technology that uses bacteria to consume organic wastes.

BIOLOGICAL WASTEWATER TREATMENT—The use of bacteria to degrade and decompose organic materials in wastewater.

BIOLOGIST—Person who specialized or works in biology.

BIOLOGY—(1) The science of life and of living organisms, including their structure, function, growth, origin, evolution, and distribution. It includes Botany and Zoology and all their subdivisions. (2) The life processes or characteristic phenomena of a group or category of living organisms. (3) The plant and animal life of a specific area or region.

BIOMASS—(1) The total mass of living matter within a given unit of environmental area. (2) Plant material, vegetation, or agricultural waste used as a fuel or energy source. (3) The total quantity of plants and animals in a lake. Measured as organisms or dry matter per cubic meter, biomass indicates the degree of a lake system's eutrophication or productivity. Some methods of determining biomass in a sample include:

[1] Ash Mass—The mass or amount of residue present after the residue from the dry mass determination has been ashed in a muffle furnace at a temperature of 500C for 1 hour. The ash mass values of zooplankton and phytoplankton are expressed in grams per cubic meter (g/m3), and periphyton and benthic organisms in grams per square mile (g/mi2).
[2] Dry Mass—The mass of residue present after drying in an oven at 105C for zooplankton and periphyton, until the mass remains unchanged. This mass represents the total organic matter, ash and sediment, in the sample. Dry-mass values are expressed in the same units as ash mass.
[3] Organic Mass or Volatile Mass—Refers to the mass of a living substance as the difference between the dry mass and ash mass and represents the actual mass of the living matter. The organic mass is expressed in the same units as for the ash mass and dry mass.
[4] Wet Mass—The mass of living matter plus contained water.

BIOMAT—(1) (Hydraulics) A term used in subsoil hydraulics to describe a clogging layer of typically densely packed decaying organic matter which impedes the downward flow of water. (2) (Water Quality) A restrictive layer that develops beneath the distribution lines of the Soil Absorption System (SAS) of Septic Tanks at the gravel-soil or bed-soil interface. As the Septic Tank Effluent (STE) is not suitable for direct discharge into surface waters or onto land surfaces because of the presence of biodegradable organics and high bacterial content that may include Pathogens, the effluent typically undergoes further purification by three processes: absorption, filtration, and microbiological decomposition. The biomat constitutes a clogging mat, Anaerobic in nature, characterized as a black slimy layer, and composed of accumulated suspended solids, minerals, bacterial cells, microorganism fragments, polysaccharides, and polyuronides. The biomat is extremely active biologically and helps ensure the conditions for optimal treatment of the effluent by restricting the infiltration rate into the soil, inducing unsaturated soil conditions and reducing the chances of high dispersion below the system. Biomats are also highly effective in removing bacterial and pathogens from the STE and can also detain viruses that can be present in the effluent. Also referred to as Biocrust, Clogging Mat, and Clogging Zone.

BIOME—A major regional or global Biotic community of plants and animals whose composition is determined by soil and the prevailing climate. The earth is characterized by ten Bioclimatic Zones or Biomes which consist of:

[1] Tundra—treeless areas between the icecap and the tree line of Arctic regions, having a permanently frozen subsoil and supporting low-growing vegetation such as lichens, mosses, and stunted shrubs.
[2] Taiga—the Subarctic, evergreen coniferous forests of northern Eurasia located just south of the tundra and dominated by firs and spruces.
[3] Temperate Forest—forested areas characterized by deciduous plants and moderate temperatures, weather, or climate.
[4] Grassland—areas, such as a prairie or meadow, of grass or grass-like vegetation.
[5] Savanna—flat grasslands of tropical or subtropical regions.
[6] Desert—barren or desolate areas, especially dry, often sandy regions of little rainfall, extreme temperatures, and sparse vegetation.
[7] Montane—cool, moist zones usually located near the timberline and usually dominated by evergreen trees.
[8] Tropical Rain Forest —dense evergreen forests occupying a tropical region typically with an annual rainfall of at least 2.5 meters (100 inches).
[9] Tropical Dry Forest —tropical or subtropical forests similar to tropical rain forests excepting that many of the plant species are deciduous and there exists a well-defined dry season.
[10]Islands—land masses, especially ones smaller than a continent, entirely surrounded by water.

BIOMONITORING—The use of living organisms to test the suitability of an effluent for discharge into receiving waters or to test the quality of such receiving waters downstream from the discharge. Also see Bioassay.

BIOREMEDIATION—Simply, the use of biological techniques to clean up pollution. More specifically, the use of specialized, naturally-occurring micro-organisms with unique biological characteristics, appetites, and metabolisms as a form of waste cleanup. A critical underpinning of this process is the ability to economically generate a sufficient biomass of the appropriate microbes to accomplish in weeks or months what would normally take nature years to do. Typically, this is done either by applying a sufficient concentration of such microbes directly to the polluted area or by applying various concentrations of chemicals which, in turn, stimulate and foster the rapid growth of appropriate micro-organisms.

BIOSOLIDS—A nutrient-rich organic material resulting from the treatment of wastewater. Biosolids contain nitrogen and phosphorus along with other supplementary nutrients in smaller doses, such as potassium, sulfur, magnesium, calcium, copper and zinc. Soil that is lacking in these substances can be reclaimed with biosolids use. The application of biosolids to land improves soil properties and plant productivity, and reduces dependence on inorganic fertilizers. The terms biosolids, Sludge, and Sewage Sludge can be used interchangeably.

BIOSPHERE—In its broadest sense, the entire planetary ecosystem including all living organisms and those parts of the earth and its atmosphere in which living organisms exist or that are capable of supporting life, to include, in addition to the plant and animal species:

[1] Atmosphere—the gaseous layer covering the earth;
[2] Lithosphere—the solid portion of the earth's crust and mantle;
[3] Hydrosphere—that portion of the earth composed of liquid water; and

Also referred to as the Ecosphere. In a more restrictive sense, may also refer to only the living organisms on earth and not to their physical and chemical environments.

BIOTA—The plant (flora) and animal life (fauna) of a region or ecosystem, as in a stream or other body of water.

BIOTECHNOLOGY—The use of microorganisms, such as bacteria or yeasts, or biological substances, such as Enzymes, to perform specific industrial or manufacturing processes. Applications include the production of certain drugs, synthetic hormones, and bulk foodstuffs as well as the Bioconversion of organic waste and the use of genetically altered bacteria in the cleanup of oil spills and other hazardous materials.

BIOTIC—Pertaining (1) to life or living things, or caused by living organisms. (2) or to biological factors or influences, concerning biological activity.

BIOTIC COMMUNITY—A naturally occurring assemblage of plants and animals that live in the same environment and are mutually sustaining and interdependent. Also see Biome.

BIOTOWER—(Water Quality) A means of wastewater treatment in which the waste is allowed to fall through a tower packed with synthetic media, on which there is biological growth. Similar to a trickling filter in concept.

BIOTRANSFORMATION—Conversion of a substance into other compounds by organisms. A more general form of Biodegradation.

BITTERN—The bitter water solution of bromides, magnesium, and calcium salts remaining after sodium chloride is crystallized out of seawater.

BLACK ICE—A thin, nearly invisible coating of ice, as on the surface of a road or sidewalk, that is usually caused by freezing mist and is extremely hazardous.

BLACK SMOKER—A vent in a geologically active region of the sea floor from which issues superheated water laden with minerals (as sulfide precipitates).

BLACKWATER—Water that contains animal, human, or food wastes; wastewater from toilet, latrine, and agua privy flushing and sinks used for food preparation or disposal of chemical or chemical-biological ingredients. Compare to Greywater.

BLANCH—To scald or parboil in water or steam in order to remove the skin from, whiten, or stop enzymatic action in (as food for freezing).

BLANKET (of a Dam)—A portion of the physical structure of a dam designed to affect the dams hydrologic characteristics, particularly its seepage and strength characteristics. Types of dam blankets include:

[1] Drainage Blanket—A drainage layer placed directly over the dam's foundation material;
[2] Grout Blanket—The injection of grout to consolidate a layer of the foundation, resulting in greater impermeability and/or strength; and
[3] Upstream Blanket—An impervious layer placed on the reservoir floor upstream of a dam; in the case of an Embankment Dam, the blanket may be connected to the impermeable element in the dam itself.


BLEAR—To dim with water or tears.

BLENDING—The mixing or combination of one water source with another, typically a finished source of water with raw water to reuse water while still satisfying water quality standards, for example, mixing of product water from a desalting plant with conventional water to obtain a desired dissolved solids content, or mixing brine effluents with sewage treatment plant effluents in order to reduce evaporation pond size.

BLINDS—Water samples containing a chemical of known concentration given a fictitious company name and slipped into the sample flow of the lab to test the impartiality of the lab staff.

BLM—Bureau of Land Management (USDI)

BLOOM—(1) In aquatic ecosystems, the rapid growth or proliferation of algae, usually visible to the naked eye, commonly referred to as Algal Bloom or Algae Bloom; often related to pollution, especially when pollutants accelerate growth. (2) Also a visible, colored area on the surface of bodies of water caused by excessive planktonic growth.

BLOWDOWN—The water drawn from boiler systems and cold water basins of cooling towers to prevent the buildup of solids.

BLOWHOLE—A hole in ice to which aquatic mammals, such as dolphins and seals, come to breathe.

BLOWOUT—A sudden escape of a confined gas or liquid, as from a well.

BLUE-GREEN ALGAE—A group of phytoplankton which often cause nuisance conditions in water, so called because they contain a blue pigment in addition to chlorophyll. Blue-green algae are often associated with problem blooms in lakes. Some produce chemicals toxic to other organisms, including humans. They often form floating scum as they die. Many can fix nitrogen (N2) from the air to provide their own nutrient.

BLUE WATER—The open sea.

BMP—See Best Management Practices (BMP) and Best Management Practices (BMP)—Urban Water Use.

BOAT—A small vessel used to travel on water.

BOATHOUSE—A building for storing boats.

BOB—To move up and down briefly or repeatedly, as in water.

BOD—See Biochemical Oxygen Demand (Biological Oxygen Demand).

BOD5—The amount of dissolved oxygen consumed in five days by biological processes breaking down organic matter. Also see Biological Oxygen Demand (BOD).

BODY FLUID—the total body water, contained principally in blood plasma and in intracellular and interstitial fluids. Also see Body Water Content.

BODY WATER CONTENT—That portion of the human body composed of water; expressed as a percentage of total body volume. Specifically, the human body is comprised of approximately 65-70 percent water: 67 percent of the water in the body is located within cells; 25 percent between cells; and the rest, about 8 percent, is located in the blood. If more than 8 percent of the body's water is lost, death will result.

BOG—A term frequently associated with Wetlands. A quagmire filled with decayed moss and other plant and vegetable matter; wet spongy ground, where a heavy body is apt to sink; a small, soggy marsh; a morass. (Ecology) A wet, overwhelmingly vegetative substratum which lacks drainage and where humic and other acids give rise to modifications of plant structure and function. Bogs depend primarily on precipitation for their water source, and are usually acidic and rich in plant residue with a conspicuous mat of living green moss. Only a restricted group of plants, mostly mycorrhizal (fungi, heaths, orchids, and saprophytes), can tolerate bog conditions. Also referred to as Peat Bog. Also see Peatland.

BOG HOLE—A hole containing soft mud or quicksand.

BOIL—To change from a liquid to a vapor by the application of heat till bubbles form and steam is given off. Also see Boiling Point.

BOILING POINT—The temperature at which the vapor pressure of a liquid is equal to the pressure exerted on the liquid. (Water) When the atmospheric pressure is 86 centimeters of mercury (sea level), the boiling point of water is, by definition, 100C (Celsius) or 212F (Fahrenheit). The boiling point decreases with elevation.

BOILING WATER REACTOR (BWR)—A nuclear reactor in which water, used as both coolant and moderator, is allowed to boil in the core. The resulting steam can be used directly to drive a turbine generating electric power.

BOILOFF—The vaporization of liquid.

BOLSON—An alluvium-floored basin, depression, or wide valley, mostly surrounded by mountains and drained by a system that has no surface outlet; an undrained basin. Bolson fill is the alluvial Detritus that fills a bolson; also commonly called bolson deposits.

BONG—A water pipe that consists of a bottle or a vertical tube partially filled with liquid and a smaller tube ending in a bowl, used often in smoking narcotic substances.

BOOM—A floating device used to contain oil on a body of water.

BORAX—A white crystalline compound that consists of a hydrated sodium borate Na2B4O710H2O, that occurs as a mineral or is prepared from other minerals, and that is used especially as a flux, cleansing agent, and water softener, as a preservative, and as a fireproofing agent.

BORDER DITCH—A ditch used as a border of an irrigated strip or plot, water being spread from one or both sides of the ditch along its entire length.

BORDER IRRIGATION—A surface method of irrigation by flooding between two confining border levees or dikes. Typically, these borders vary from 100 to 200 feet wide by 1,000 to 3,960 feet long.

BORE—A high, often dangerous wave caused by the surge of a flood tide upstream in a narrowing Estuary or by colliding tidal currents. Also referred to as an Eagre.

BOREAL FOREST—A northern forest, as in the boreal forest Biome, characterized by evergreen conifers and long winters. The boreal forest, also referred to as a Taiga, is found in the northern parts of North America, Europe, and Asia.

BOREHOLE—A hole bored or drilled in the earth, as an exploratory well; a small-diameter well drilled especially to obtain water.

BOTANY—The branch of Biology that studies plants, including their structure, function, growth, origin, evolution, and distribution.

BOTTLED WATER [General]—Water sold commercially generally for its health, therapeutic, or purity values. In the United States, bottled water is considered a food product and as such is regulated by the Food and Drug Administration (FDA). Beginning in May 1996, the FDA required all bottled waters to carry accurate labels: "spring water" must come from a spring; "mineral water" must carry a certain mineral content; "sterile" water must be processed to meet FDA standards for commercial sterility; and if water comes from municipal supplies, it must be labeled as such. See Bottled Water [Food and Drug Administration] and Bottled Water [Nevada].

BOTTLED WATER [Food and Drug Administration]—As defined by the FDA [Department of Health and Human Services, Federal Register, Part III, 21 CFR Part 165, Subpart B—Requirements for Specific Standardized Beverages, effective May 13, 1996] bottled water is water that is intended for human consumption and that is sealed in bottles or other containers with no added ingredients except that it may optionally contain safe and suitable anti-microbial agents. Fluoride may be optionally added within certain specified limitations. Bottled water may be named bottled water, drinking water, or alternatively one of the following terms may be used as appropriate:

[1] Artesian Water or Artesian Well Water—Water from a well tapping a confined aquifer in which the water level stands at some height above the tope of the aquifer.
[2] Ground Water—Water from a subsurface saturated zone that is under a pressure equal to or greater than atmospheric pressure; ground water must not be under the direct influence of surface water.
[3] Mineral Water—Water containing not less than 250 parts per million (ppm) total dissolved solids (TDS), coming from a source tapped at one or more bore holes or springs, originating from a geologically and physically protected underground water source; mineral water shall be distinguished from other types of water by its constant level and relative proportions of minerals and trace elements at the point of emergence from the source; no minerals may be added to this water.
[4] Purified Water—Water that has been produced by distillation, deionization, reverse osmosis, or other suitable processes and that meets the definition of "purified water" in the United States Pharmacopeia. May also be called demineralized water, purified drinking water, or alternatively, based on the process used, deionized (drinking) water, distilled (drinking) water, reverse osmosis (drinking) water, etc.
[5] Sparkling Bottled Water—Water that, after treatment and possible replacement of carbon dioxide, contains the same amount of carbon dioxide from the source that it had at emergence from the source.
[6] Spring Water—Water derived from an underground formation from which water flows naturally to the surface of the earth; shall be collected only at the spring or through a bore hole tapping the underground formation feeding the spring.
[7] Sterile or Sterilized Water—Water that meets the requirements under "Sterility Tests" in the United States Pharmacopeia.
[8] Well Water—Water from a hole bored, drilled, or otherwise constructed in the ground which taps the water of an aquifer.

Other label statements for bottled water include "low mineral content" for TDS levels below 500 ppm, "high mineral content" for TDS levels above 1,500 ppm, or when the water comes from a community water system, it must be labeled "from a community water system," or, alternatively, "from a municipal source."

BOTTLED WATER [Nevada]—According to Nevada Administrative Code (NAC) Chapter 445A, "Bottled Water," effective November 1994, bottled water may be labeled and sold as:

[1] Distilled Water—Water that is demineralized by distillation and complies with the requirements for purified water set forth in the United States Pharmacopeia.
[2] Drinking Water—Water that is filtered and disinfected by a process approved by the health authority.
[3] Mineral Water—Water that is clearly distinguishable from other types of water by its specific content of minerals and trace elements which remain constant at the water's point of emergence; boreholes or springs from which mineral water is produced must originate from an underground source which is geologically and physically protected from contamination.
[4] Natural Water—Water that is produced from a well (Natural Well Water) or an artesian well (Natural Artesian Water) and no minerals have been added or removed from the water; may be filtered and must be disinfected by a process approved by the health authority.
[5] Purified Water—Water that is demineralized by distillation, deionization, or reverse osmosis and complies with the requirements for purified water set forth in the United States Pharmacopeia.
[6] Spring Water—Water that is produced from a point at the surface where the water flows naturally from an underground formation or through a borehole adjacent to that point n a manner approved by the health authority.
[7] Municipal Water—Water that is produced from a public water system; may be sold and labeled as distilled water, drinking water, purified water if it complies with specific filtration and disinfection requirements.

BOTTOM—(1) The deepest or lowest part, as the bottom of a well. (2) The solid surface under a body of water. (3) Often Bottoms: Low-lying alluvial land adjacent to a river, also referred to as bottomland. (4) (Nautical) The part of a ship's hull below the water line.

BOTTOMLAND, also Bottom Land (Soils)—A general term describing generally rich, loamy or fine-textured and poorly drained soils, overlying a shallow water table or possibly adjacent to a stream, lake or other body of water, that exhibits relatively good water holding capacity and slow to moderate infiltration of irrigation water; often associated with a river's floodplain.

BOTTOM LAND HARDWOODS—Forested freshwater Wetlands adjacent to rivers in the southeastern United States, especially valuable for wildlife breeding, nesting, and habitat.

BOTTOM LANDS [Nevada]—The U.S. Department of the Interior, Bureau of Reclamation (USBR) criteria (revised 1992) has defined Bottom Land for Nevada's Newlands Irrigation Project, located in Churchill County, Nevada, as "those lands with a five-foot soil profile having a holding capacity equal to or exceeding 8 inches and/or a water table within 6 feet of the surface for a period equal to or exceeding 150 days. If neither of these factors apply, the land is designated as Bench Land." Lands classified as bottom (or bench) according to USBR criteria, above, will be limited to maximum water deliveries (duty) in accordance to the provision of the Orr Ditch Decree and the Alpine Decree, which are identical in establishing water duties and establish the following limits: (1) Eligible lands designated as Bench Lands may receive a maximum of 4.5 acre-feet per acre per year (AF/acre/year); (2) eligible lands designated as Bottom Lands may receive a maximum of 3.5 acre-feet per acre per year (AF/acre/year).


BOTTOM OUTLET—An opening at a low level from a reservoir generally used for emptying or for scouring sediment and sometimes for irrigation releases. Also referred to as Low-Level Outlet or Sluiceway.

BOULDER—Rock fragments larger than 60.4 cm (24 inches) in diameter.

BOUNDARY CONDITIONS—Flow conditions imposed at the ends of a pipeline or canal reach by various physical structures, which must be described mathematically to solve the general equation of flow for hydraulic transient computer models.

BOUNDARY LAYER—The layer of reduced velocity in fluids, such as air and water, that is immediately adjacent to the surface of a solid past which the fluid is flowing.

BOUND WATER—Water molecules that are held tightly to soil or other solids. This water is not easily removed by normal drying and is not available for other purposes such as plant growth.

BOURN, also Bourne—A stream, brook, or rivulet; in southern England, a winter stream of the chalk downs.

BP—Barometric Pressure.

BPI PAN—A circular evaporation pan, 6 feet in diameter and 2 feet deep, made of unpainted galvanized iron. The pan is buried in the ground so that about 4 inches of the rim extend above the surrounding ground and the water surface is maintained at about ground level. (BPI stands for Bureau of Plant Industry, USDA, which introduced this instrument.)

BPT—Best Practicable Control Technology.

BRACKISH—Having a somewhat salty taste, especially from containing a mixture of seawater and fresh water. Also see Brackish Water.

BRACKISH WATER—Generally, water containing dissolved minerals in amounts that exceed normally acceptable standards for municipal, domestic, and irrigation uses. Considerably less saline than sea water. Also, Marine and Estuarine waters with Mixohaline salinity (0.5 to 30 due to ocean salts). Water containing between 1,000-4,000 parts per million (PPM) Total Dissolved Solids (TDS). The term brackish water is frequently interchangeable with Saline Water. The term should not be applied to inland waters.

BRAIDED STREAM—A complex tangle of converging and diverging stream channels (Anabranches) separated by sand bars or islands. Characteristic of flood plains where the amount of debris is large in relation to the discharge.

BRAIDING (of River Channels)—Successive division and rejoining of riverflow with accompanying islands.

BRANCH—(1) A tributary of a river or other body of water. (2) A divergent section of a river, especially near the mouth.

BRANCH WATER—(Chiefly Southern United States) Plain water from a stream, especially when mixed with a liquor such as whiskey.

BRASH—A mass or pile of rubble, refuse, or fragments, as of stone, brush, or ice.

BRAWL—To flow noisily, as turbulent water.

BREACH—(1) A gap or rift, especially in or as if in a solid structure such as a dike or dam. (1) The breaking of waves or surf.

BREAK—(1) To emerge above the surface of the water. (2) (Geology) A marked change in topography such as a fault or deep valley.

BREAKER—(1) A small water cask. (2) A large foaming wave that breaks on rocky or sandy shores.

BREAKPOINT CHLORINATION—The addition of chlorine to water or wastewater until the chlorine demand has been satisfied and further additions result in a residual that is directly proportional to the amount added beyond the breakpoint.

BREAKTHROUGH—A crack or break in a filter bed that allows the passage of Floc or particulate matter through a filter. As a result, it will cause an increase in filter effluent Turbidity.

BREAKTHROUGH CURVE—A plot of relative concentration versus time, where relative concentration is defined as C/C0; the concentration at a point in the ground-water flow domain divided by the source concentration.

BREAKUP—The cracking and shifting of ice in rivers or harbors during the spring.

BREAKWATER—A barrier that protects a harbor or shore from the full impact of waves.

BREW—To prepare (as tea) by infusion in hot water.

BRIDGE—An over the lake, stream or river structure built so that people can get from one side to the other.

BRIM—The upper surface of a body of water.

BRINE—(1) Water saturated with or containing large amounts of a salt, especially of sodium chloride. According to U.S. Geologic Survey (USGS) classification, water classified as brine contains more than 35,000 ppm (parts per million) total dissolved solids (TDS) of salt; (2a) The water of a sea or an ocean; (2b) A large body of salt water. (3) The wastewater resulting from desalting. It is higher in dissolved solid content than feedwater or product water. Also see Saline Water.

BRINE DISPOSAL—Removing water that contains high concentrations of salt.

BRINE MUD—Waste material, often associated with well-drilling or mining, composed of mineral salts or other inorganic compounds.

BRINK—(1) The upper edge of a steep or vertical slope. (2) The margin of land bordering a body of water.

BRITISH THERMAL UNIT (BTU)—A unit of heat energy equal to the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit. More precisely, the quantity of heat required to raise the temperature of one pound of water from 60F to 61F at a constant pressure of one atmosphere. Also, the quantity of heat equal to 1/180 of the heat required to raise the temperature of one pound of water from 32F (its freezing point) to 212F (its boiling point) at a constant pressure of one atmosphere. The British Thermal Unit is used when the measurement is in degrees Fahrenheit (F) on the Fahrenheit Scale and the Calorie is used when temperature is measured in degrees Celsius (C) on the Centigrade Scale.

BROAD-LEAVED DECIDUOUS—Woody Angiosperms (trees or shrubs) with relatively wide, flat leaves that are shed during the cold or dry season; e.g., black ash (Fraxinus nigra).

BROAD-LEAVED EVERGREEN—Woody Angiosperms (trees or shrubs) with relatively wide, flat leaves that generally remain green and are usually persistent for a year or more; e.g., red mangrove (Rhizophora mangle).

BROMIDE—A salt which naturally occurs in small quantities in sea water; a compound of bromine.

BROOK—A natural stream of water, smaller than a river or creek; especially a small stream or rivulet which breaks directly out of the ground, as from a spring or seep; also, a stream or torrent of similar size, produced by copious rainfall, melting snow and ice, etc.; a primary stream not formed by tributaries, though often fed below its source, as by rills or runlets; one of the smallest branches or ultimate ramifications of a drainage system.

BROWNIAN MOVEMENT—The constant, random, zigzag movement of small particles dispersed in a fluid medium, caused by collision with molecules of the fluid. Named after Robert Brown (1773-1858), the British botanist who first described it. Also referred to as Brownian Motion.

BSC—Biological Sciences Center. (DRI)

BTU—British Thermal Unit.

BUBBLE—(1) A thin, usually spherical or hemispherical film of liquid filled with air or gas, as a soap bubble. (2) A globular body of air or gas formed within a liquid, as air bubbles rising to the surface of a body of water.

BUBBLER—A drinking fountain from which a stream of water bubbles upward.

BUCKET—(1) A cylindrical vessel used for holding or carrying water or other liquids; a pail. (2) A receptacle on various machines, such as the compartments on a water wheel, used to gather and convey water.

BUDDLE—An inclined trough in which crushed ore is washed with running water to flush away impurities.

BUFFER—A solution which is resistant to pH changes, or a solution or liquid whose chemical makeup tends to neutralize acids or bases without a great change in pH. Surface waters and soils with chemical buffers are not as susceptible to acid deposition as those with poor buffering capacity.

BUFFER STRIPS—Strips of grass or other erosion-resisting vegetation between or below cultivated strips or fields. Also referred to as Buffer Zones.

BUFFER ZONE—A protective, neutral area between distinct environments.

BULK SEDIMENT ANALYSIS—Analysis of soil material or surface sediment deposits to determine the size and relative amounts of particles composing the material.

BULKHEAD—A low wall of stones, concrete, or piling built to protect a shore, or fills, from wave erosion.

BULKING SLUDGE—(Water Quality) Sludge that does not settle to the bottom of a clarifier, causing a rise in the level of suspended solids and biochemical oxygen demand in water leaving a wastewater treatment facility.

BUND—An embankment used especially in India to control the flow of water.

BUOY—(Nautical) A float, often having a bell or light, moored in water as a warning of danger or as a marker for a channel. Also, to keep afloat or aloft.

BUOYANCY—The tendency of a body to float or rise when submerged in a fluid.

BURAN—A violent windstorm of the Eurasian steppes, accompanied in summer by dust and in winter by snow.

BURBLE—(1) A gurgling or bubbling sound, as of running water. (2) A separation in the Boundary Layer of a fluid about a moving streamlined body, such as the wing of an airplane through air or the keel of a sailboat through water, causing a breakdown in the smooth flow of fluid and resulting in turbulence.

(UNITED STATES) BUREAU OF INDIAN AFFAIRS (BIA)—An agency of the U.S. Department of the Interior which has the primary responsibility for exercising the federal government's trust relationship with Indian tribes. The BIA was first established in 1824 in the War Department, then transferred to the Department of the Interior in 1849. The BIA has prime responsibility to provide services to Indian tribes and plays a central role in the settlement process of Indian water rights disputes. The BIA exercises prime trust responsibility in providing federal government protection for Indian resources and federal assistance in resource development and management. Quite often this responsibility complicates the Department of the Interior's other broad responsibilities to manage the use of lands and natural resources on public lands through its Bureau of Land Management (BLM) land use programs, its Bureau of Reclamation (USBR) water-related projects, and its U.S. Fish and Wildlife Service (USFWS) wildlife and habitat restoration programs, which may frequently come in conflict with the Bureau of Indian Affairs Indian water rights issues. [For example, in Nevada v. United States (463 U.S. 129{1983}), the United States Supreme Court held that the United States [Department of the Interior] could adequately represent more than one interest simultaneously, and so it is not subject to the same standards as a private trustee. In this case, the Court found that claims made by the United States on behalf of the Pyramid Lake Paiute Indian Tribe to protect fisheries should have been asserted in prior litigation. Nevertheless, the Court found the failure to do so was not a breach of its trust obligations to the tribe, even though the United States also had protected the competing interests of non-Indian irrigators.] Also see Negotiated Settlement and Truckee River Operating Agreement (TROA).

(UNITED STATES) BUREAU OF LAND MANAGEMENT (BLM)—An agency of the U.S. Department of the Interior responsible for the stewardship of the nation's public lands. The Bureau of Land Management is committed to the sustained management, protection, and improvement of these lands in a manner consistent with the needs of the American people. The BLM's management philosophy is based on the principles of multiple use and sustained yield of our nation's resources within a framework of environmental responsibility and scientific technology. The resources under the BLM's oversight include recreation, rangelands, timber, minerals, watersheds, fish and wildlife, wilderness, air, and scenic, scientific and cultural values. The BLM oversees the largest natural resource base in the federal government. This base includes 270 million acres of public lands ranging from old growth forests in the Pacific Northwest to sun drenched desert ecosystems in the Southwest to Arctic tundra in Alaska. The BLM also supervises mineral leasing and operations on an additional 300 million acres of federal mineral estate that underlie other surface ownerships. BLM managed public lands provide habitat for thousands of wildlife and plant species, including some 220 federally-listed threatened and endangered species and 1,200 species considered candidates for listing. The BLM manages over 169,000 miles of fish bearing streams and more than 50 million acres of forested lands. In addition, the BLM is caretaker of an estimated 4 million cultural properties, including 400 listed in the National Register of Historic Places. The BLM also manages more than 1.6 million acres of designated wilderness and 22.8 million acres of wilderness study areas. More than 46,500 wild horses and burros roam BLM land in the West. The BLM permits and manages various uses of the public lands, including grazing, mining, recreation, and timber operations. These activities traditionally have been managed on an individual basis. However, more recently the BLM's management efforts have shifted to a more comprehensive ecosystem basis of managing such lands to insure sustained benefits for future generations of Americans. The Bureau of Land Management has its headquarters office in Washington, D.C. There are an additional eleven state offices for managing resources in the western states of Alaska, Arizona, California, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, and Wyoming. BLM resources for the Eastern United States are managed out of Springfield, Virginia. The BLM also supports a National Interagency Fire Center (NIFC) in Boise, Idaho as well as a public information service center (SC) in Denver, Colorado and a centralized employee training center in Phoenix, Arizona. In Nevada alone, the BLM manages some 48 million acres of public lands or approximately 67 percent of all lands in Nevada.

(UNITED STATES) BUREAU OF RECLAMATION (USBR)—An agency of the U.S. Department of the Interior responsible for many of the dam, reservoir, and irrigation projects in the Western United States. The USBR reclamation program was authorized by the Reclamation Act of 1902 which was initially intended to reclaim the arid and semiarid lands of the Western United States by conserving and supplying irrigation water to make them productive. Since that beginning, the USBR's mission has expanded considerably to include multipurpose water development by providing water for irrigation, hydroelectric power, water for homes, businesses and factories, outdoor recreation, flood control, fish and wildlife enhancement, improved water quality, river regulation and control, and other related uses of water. Currently the USBR administers some 322 storage dams, 14,490 miles of canals, 174 pumping plants, and 50 hydroelectric plants. USBR water irrigates 146,000 farms in the West, provides part or all the water needs on nearly 10 million acres, yielding enough food for 33 million people, and also provides 620 billion gallons of water a year of municipal and industrial use in western towns and cities. In terms of its original intent and broad governing guidelines, the U.S. Bureau of Reclamation is primarily responsible for water projects with respect to developing water sources for agriculture and commerce, while the U.S. Army Corps of Engineers (COE) has had primary responsibility for water projects which protect property from potential flood damage. In reality, however, quite often these federal agencies' project goals overlap with USBR's dams and reservoirs providing important flood protection and the COE's water projects—dams, locks, and canals—providing important water transportation linkages and benefits to commerce.

BURIED DRAIN—A covered drain usually made of clay, concrete, or plastic pipe installed beneath the ground surface at a planned grade and depth for conveyance of excess groundwater.

BURN—(Chiefly Scottish) (1) A brook; a rivulet. (2) Water, especially that used in brewing.

BUSHEL—(1) A unit of volume or capacity in the U.S. Customary System, used in dry measure and equal to 4 pecks, 2,150.42 cubic inches, or 35.24 liters. (2) A unit of volume or capacity in the British Imperial System, used in dry and liquid measure and equal to 2,219.36 cubic inches or 36.37 liters.

BUTT—A large cask especially for wine, beer, or water.

BUTTRESS DAM—A dam consisting of a watertight upstream face supported at intervals on the downstream side by a series of buttresses. Also see Dam.

BWR—Boiling Water Reactor.

BYPASS, also By-Pass—A pipe or channel used to conduct a liquid around another pipe or a fixture.

BYPASS SYSTEM—A structure in a dam that provides a route for fish to move through or around the dam without going through the turbines.