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Glossary for the Surface Water Quality Viewer

Definitions of terms used within the Surface Water Quality Viewer.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Surface Water Quality Viewer

7Q2Seven-day, two-year low-flow.

acute toxicityToxicity that exerts a stimulus severe enough to rapidly induce an effect. The duration of exposure applicable to acute toxicity is typically 96 hours or less. Tests of total toxicity normally use lethality as the measure of acute impacts. (Direct thermal impacts are excluded from definitions of toxicity.)

algae—Plants that lack true roots, stems, and leaves. For the physical assessment described herein, algae consist of nonvascular plants that attach to rocks and debris or float freely in the water. Such plants may be green, blue-green, or olive-green and slimy to the touch; they usually have a coarse filamentous structure.

ambient—Refers to the existing water quality in a particular water body.

ammonia-nitrogen (NH3-N)—Ammonia, naturally occurring in surface and wastewaters, is produced by the breakdown of compounds containing organic nitrogen.

AP—aquifer protection.

aquatic macrophyte—A vascular plant of a kind that usually are arranged in zones corresponding closely to successively greater depths in shallow water. The characteristic plant forms that dominate these gradients (in order of decreasing depth) are: (1) submersed rooted aquatics, (2) floating-leaved rooted aquatics, (3) emergent rooted aquatics, and (4) marginal mats. Some vascular plants (like duckweed) may live unattached in the water and may occur anywhere on the water surface.

AS—Agricultural water supply.

attainable use—A use that can be reasonably achieved by a water body in accordance with its physical, biological, and chemical characteristics whether it is currently meeting that use or not. Guidelines for the determination and review of attainable uses are provided in the standards implementation procedures. The designated use, existing use, or presumed use of a water body may not necessarily be the attainable use.

benthos—Aquatic bottom-dwelling organisms including worms, leeches, snails, flatworms, burrowing mayflies, and clams.

best management practices—Schedules of activities, maintenance procedures, and other management practices to prevent or reduce the pollution of water in the state from point and nonpoint sources, to the maximum extent practicable. Best management practices also include treatment requirements, operating procedures, and practices to control plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.

bioaccumulation—An increase in the concentration of a chemical in an organism over time, compared to the chemical’s concentration in the environment. Usually the result of the organism preying upon others that are contaminated with the chemical.

biological integrity—The species composition, diversity, and functional organization of a community of organisms in an environment relatively unaffected by pollution.

bloom—The accelerated growth of algae, higher aquatic plants, or both in a body of water. Bloom is often related to pollutants that increase the rate of growth.

BMP—best management practices.

channelization—Straightening and deepening streams so water will move faster, a method of flood control that disturbs fish and wildlife habitats and can interfere with a water body’s ability to assimilate waste.

chloride (Cl-1)—One of the major inorganic ions in water and wastewater. Concentrations can be increased by industrial processes. High chloride concentrations can affect metallic objects and growing plants.

chlorophyll a—A photosynthetic pigment found in all green plants. The concentration of chlorophyll a is used to estimate phytoplankton biomass (all of the phytoplankton in a given area) in surface water.

chronic toxicity—Toxicity that continues for a long period after exposure to toxic substances. Chronic exposure produces sub-lethal effects, such as growth impairment and reduced reproductive success, but it may also kill. The duration of exposure applicable to the most common chronic-toxicity test is seven days or more.

classified—Refers to a water body that is listed and described in Appendix A or Appendix C in the Texas Surface Water Quality Standards. Site-specific uses and criteria for classified water bodies are listed in Appendix A.

conductivity—A measure of the carrying capacity for electrical current, in mhos/cm, of 1 cm3 of water at 25°C. Dissolved substances in water dissociate into ions with the ability to conduct electrical current. Conductivity is a measure of how salty the water is; salty water has high conductivity.

contact recreation (CR)—Recreational activities involving a significant risk of ingestion of water, including wading by children, swimming, water skiing, diving, and surfing. See also noncontact recreation.

CR—contact recreation.

criteria—Water-quality conditions that are to be met in order to support and protect desired uses.

designated use—A use that is assigned to specific water bodies in Appendix A or in Appendix D in the Texas Surface Water Quality Standards. Typical uses that may be designated for specific water bodies include domestic water supply, categories of aquatic-life use, kinds of recreation, and aquifer protection.

dissolved oxygen (DO)—The oxygen freely available in water. Dissolved oxygen is vital to fish and other aquatic life and for the prevention of odors. Traditionally, the level of dissolved oxygen has been accepted as the single most important indicator of a water body’s ability to support desirable aquatic life.

DO—dissolved oxygen.

E—exceptional aquatic-life use.

ecological impact—The effect that a man-made or natural activity has on living organisms and their abiotic (non-living) environment.

E. coliEscherichia coli, a member of the total coliform group of bacteria found in feces. It indicates fecal contamination and possible presence of enteric pathogens (viral, protozoan, and bacterial pathogens of the gastrointestinal route).

effluent—Wastewater (treated or untreated) that flows out of a treatment plant or industrial outfall (point source), prior to entering a water body.

enterococci—A subgroup of fecal streptococcal bacteria (mainly Streptococcus faecalis and Streptococcus faecium) found in the intestinal tracts and feces of warm-blooded animals. It is used as an indicator of the potential presence of pathogens.

estuary—Regions of interaction between rivers and nearshore ocean waters, where tidal action and river flow create a mixing of fresh and salt water.

euphotic zone—The zone of water from the surface to depth of light penetration. Photosynthesis respiration in this zone.

eutrophic—Refers to shallow, murky bodies of water that have excessive concentrations of plant nutrients resulting in increased algal production.

eutrophication—The slow aging process during which a lake, estuary, or bay evolves into a bog or marsh and eventually disappears.

fecal coliform—A subset of the coliform bacteria group that is found in the intestinal tracts and feces of warm-blooded animals; heat-tolerant bacteria from other sources can sometimes be included. It is used as an indicator of the potential presence of pathogens.

H—high aquatic life use.

habitat—The area in which an organism lives.

I—intermediate aquatic life use.

impoundment—A body of water confined by a dam, dike, floodgate or other barrier.

indicator organism—An organism, species, or community that indicates the presence of a certain environmental condition or conditions.

inorganic—Refers to any compound lacking carbon.

intermittent stream—A stream that has a period of zero flow for at least one week during most years. Where flow records are available, a stream with a 7Q2 flow of less than 0.1 ft3/s is considered intermittent.

intermittent stream with perennial pools—An intermittent stream that maintains persistent pools even when flow in the stream is less than 0.1 ft3/s.

IS—industrial water supply.

L—limited aquatic life use.

macrophyte—Any large vascular plant that can be seen without the aid of a microscope or magnifying device (cattail, rush, arrowhead, water lily, etc.).

MCL—Maximum contaminant level (for public drinking-water supplies).


natural vegetative buffer—An area of either natural or native vegetation that buffers a water body from terrestrial runoff and the activities of humans. In natural areas, it may be much greater than the riparian zone width. In human-altered settings, the natural vegetative buffer limit would be at the point of human influence in the riparian zone such as a road, parking lot, pasture, or field of crops. It is the width of this buffer that we are most interested in measuring for purposes of quantifying potential stream impairments.

NCRNoncontact recreation.

nekton—Free-swimming organisms (e.g., fish, insects).

nitrate-nitrogen (NO3-N)—A compound containing nitrogen that can exist as a dissolved solid in water. Excessive amounts can have harmful effects on humans and animals (>10 mg/L).

nitrite-nitrogen (NO2-N)—An intermediate oxidation state in the nitrification process (ammonia, nitrite, nitrate).

non-point source—A pollution source that is diffuse and does not have a single point of origin or is not introduced into a receiving stream from a specific outfall. The pollutants are generally carried off the land by stormwater runoff. The commonly used categories for non-point sources are: agriculture, forestry, urban, mining, construction, dams and channels, land disposal, and saltwater intrusion.

noncontact recreation—Aquatic recreational pursuits not involving a significant risk of water ingestion and limited body contact incidental to shoreline activity, including fishing, commercial and recreational boating. See also contact recreation.

nutrient—Any substance used by living things to promote growth. The term is generally applied to nitrogen and phosphorus in water and wastewater, but is also applied to other essential and trace elements.

OOyster waters.


orthophosphate (O-P)—Nearly all phosphorus exists in water in the phosphate form. The most important form of inorganic phosphorous is orthophosphate, making up 90% of the total. Orthophosphate, the only form of soluble inorganic phosphorus that can be directly used, is the least abundant of any nutrient and is commonly the limiting factor.

outfall—A designated point of effluent discharge.

oyster waters—Waters producing edible species of clams, oysters, or mussels.

pH—The hydrogen-ion activity of water caused by the breakdown of water molecules and presence of dissolved acids and bases.

phosphorus—A nutrient essential to the growth of organisms; it can be the nutrient that limits the primary productivity of water. In excessive amounts—from wastewater, agricultural drainage and certain industrial wastes—it also contributes to the eutrophication of lakes and other water bodies.

photosynthesis—The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll using sunlight as an energy source.

phytoplankton—See plankton.

plankton—Organisms (plants and animals) that live in open water, either suspended or floating. Phytoplankton (plant): (1) Microscopic; (2) movement dependent on currents; (3) primary producers (solar radiation and nutrients used for growth) that affect water quality. Zooplankton (animal): (1) microscopic, but some can be seen by the naked eye; (2) capable of movement; (3) secondary producers [they feed on phytoplankton, bacteria and detritus (dead organic matter)].

point source—Any discernible, confined and discrete conveyance—including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, item of rolling stock—concentrated animal-feeding operation, or vessel or other floating craft, from which pollutants or wastes are, or may be, discharged into or adjacent to any water in the state.

pollution—The alteration of the physical, thermal, chemical, or biological quality of, or the contamination of, any water in the state that renders the water harmful, detrimental, or injurious to humans, animal life, vegetation, or property or to the public health, safety, or welfare, or impairs the usefulness or the public enjoyment of the water for any lawful or reasonable purpose.

pool—A portion of a stream where water velocity is slow and the depth is greater than the riffle, run, or glide. Pools often contain large eddies with widely varying directions of flow compared to riffles and runs where flow is nearly exclusively downstream. The water surface gradient of pools is very close to zero and their channel profile is usually concave.

PS—public water supply.

public drinking water supply—A water body designated to provide water to a public water system as defined in Chapter 290 of this title (relating to Public Drinking Water).

receiving water—A river, stream, lake or other body of surface water into which wastewater or treated effluent is discharged.

reservoir—Any natural or artificial holding area used to store, regulate or control water.

riparian zone—Generally includes the area of the stream bank and out onto the flood plain that is periodically inundated by the flood waters from the stream. The limit of the zone depends on many factors including native plant community make up, soil moisture levels, and distance from the stream (or the limit of interaction between land and stream processes). It is periodically inundated by the flood waters from the stream. Interaction between this terrestrial zone and the stream is vital for the health of the stream.

river basin—The land area drained by a river and its tributaries.

runoff—The part of precipitation or irrigation water that runs off land into streams and other surface water.

sediment—Particles and/or clumps of particle of sand, clay, silt, and plant or animal matter carried in water and are deposited in reservoirs and slow-moving areas of streams and rivers.

segment—A water body or portion of a water body that is individually defined and classified in the Texas Surface Water Quality Standards. A segment is intended to have relatively homogeneous chemical, physical, and hydrological characteristics. A segment provides a basic unit for assigning site-specific standards and for applying water quality management programs of the agency. Classified segments may include streams, rivers, bays, estuaries, wetlands, lakes, or reservoirs.

seven-day, two-year low-flow (7Q2)—The lowest average stream flow for seven consecutive days with a recurrence interval of two years, as statistically determined from historical data. Some quality standards do not apply at stream flows that are less than the 7Q2 flow.

significant aquatic life use—A broad characterization of aquatic life that indicates that a subcategory of aquatic-life use (limited, intermediate, high, or exceptional) is applicable.

standards—The designation of water bodies for desirable uses and the narrative and numerical criteria deemed necessary to protect those uses.

storm water—Rainfall runoff, snow-melt runoff, surface runoff, and drainage.

stream order—A classification of stream size, where the smallest, unbranched tributaries of a drainage basin are designated first-order streams. Where two first-order streams join, a second-order stream is formed; where two second-order streams join, a third-order stream is formed, etc. For the application of water-quality standards, stream order is determined from USGS topographic maps with a scale of 1:24,000.

submerged vegetation—Rooted plants with almost all leaves below the water surface (e.g. alligator weed, hydrilla or elodea).

sulfate (SO4-2)—An ion derived from rocks and soils containing gypsum, iron sulfides, and other sulfur compounds. Sulfates are widely distributed in nature.

surface water quality standards—The designation of water bodies for desirable uses and the narrative and numerical criteria deemed necessary to protect those uses.

sustainable fisheries—Describes water bodies that potentially have sufficient fish production or fishing activity to allow significant long-term human consumption of fish. Sustainable fisheries include perennial streams and rivers with a stream order of three or greater; lakes and reservoirs with an area greater than or equal to 150 acre-feet or 50 surface acres; and all bays, estuaries, and tidal rivers.

TDS—total dissolved solids.

tidal—Descriptive of coastal waters that are subject to the ebb and flow of tides. For purposes of standards applicability, tidal waters are considered to be saltwater. Classified tidal waters include all bays and estuaries with a segment number that begins with 24xx, all streams with the word tidal in the segment name, and the Gulf of Mexico.

TMDLtotal maximum daily load.

tributary—A stream or river that flows into a larger one.

Total Maximum Daily Load (TMDL)—The total amount of a substance that a water body can assimilate and still meet the Texas Surface Water Quality Standards.

total dissolved solids—The amount of material (inorganic salts and small amounts of organic material) dissolved in water and commonly expressed as a concentration in terms of milligrams per liter. The term is equivalent to filterable residue as used in the publication Standard Methods for the Examination of Water and Wastewater.

toxicity—The occurrence of adverse effects to living organisms due to exposure to toxic materials.

water quality limited—a designation for water-body segments in which (1) surface water quality monitoring data has shown significant violations of the Texas Surface Water Quality Standards; (2) advanced waste treatment for point source wastewater discharges is required to meet water quality standards;(3) existing conditions of exceptional water quality are to be protected; or (4) the segment is a domestic water-supply reservoir.

water quality standards—Established limits of certain chemical, physical, and biological parameters in a water body; established for the different designated uses of a water body (e.g., aquatic-life use, contact recreation, public water supply).

watershed—The area of land from which precipitation drains to a single point. Watersheds are sometimes referred to as drainage basins or drainage areas.

WF—waterfowl habitat.

zooplanktonSee plankton.