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B

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