Plants that lack true roots, stems and leaves. For the physical assessment described in this document, 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.

The existing water quality in a particular water body.

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

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.

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 to the maximum extent practicable. Best management practices 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.

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 on 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.

Biological Monitoring
Field monitoring that includes collecting data about habitat (both on shore and instream), macrobenthic communities, and fish communities.

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

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.

Refers to a water body that is listed and described in Appendix A or Appendix C of the Texas Surface Water Quality Standards.

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

Conventional Parameters
A list of basic parameters that require laboratory analyses. The parameters frequently include, but are not limited to, solids (TSS, TDS, VSS), nutrients (nitrogen and phosphorus compounds), chlorides, sulfates, hardness, and TOC.

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 of 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.

A family of polychlorinated chemicals found in waste from the paper bleaching processes and the combustion of chlorinated compounds. It is considered carcinogenic and can disrupt the reproductive and immune systems in humans.

Dissolved Oxygen
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.

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

Escherichia coli (E. coli)
E. coli is 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).

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

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.

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

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.

Field Parameters
A list of basic tests generally collected in the field using equipment and meters. The list also includes visual observations.

The area in which an organism lives.

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.

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.

Macrobenthic Invertebrate
Aquatic bottom-dwelling fauna. Common types are flat worms, leeches, snails, and various insect species.

A toxic metal that is released into the aquatic environment from natural and human processes. The compound methylmercury is highly toxic to aquatic life and humans.

Natural Vegetative Buffer
An area of natural or native vegetation that buffers a water body from terrestrial runoff and human activity. 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. The width of this buffer is important to measure for purposes of quantifying potential stream impairments.

Free-swimming organisms (for example, 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, and nitrate).

Nonpoint 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 nonpoint 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, and commercial and recreational boating. See also contact recreation.

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.

Nearly all phosphorus exists in water in the phosphate form. The most important form of inorganic phosphorous is orthophosphate, making up 90 percent 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.

A designated point of effluent discharge.

Oyster Waters
Waters producing edible species of clams, oysters, or mussels.

Polychlorinated Biphenyls
A class of organic compounds used in dielectric fluids in transformers, capacitors, and coolants. PCBs are highly toxic and are associated with endocrine disruption and neural toxicity in humans.

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

A nutrient that is 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 waste it also contributes to the eutrophication (the natural aging progression) of lakes and other water bodies.

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

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, or 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, vessel or other floating craft from which pollutants or wastes are, or may be, discharged into or adjacent to any water.

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

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, as 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.

Public Drinking Water Supply
A water body designated to provide water to a public water system.

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

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

Riparian Zone
Generally includes the area of a stream bank and 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 makeup, soil moisture levels, distance from the stream, or the limit of interaction between land and stream processes. 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.

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

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

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. Classified segments may include streams, rivers, bays, estuaries, wetlands, lakes, and reservoirs.

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

Rainfall runoff, snow-melt runoff, surface runoff, and drainage.

Submerged Vegetation
Rooted plants with almost all leaves below the water surface (for example, 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.

Descriptive of coastal waters 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.

A stream or river that flows into a larger one.

Total Maximum Daily Load
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.

Total Suspended Solids
The amount of organic and inorganic suspended particles in water.

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

Volatile Suspended Solids
The amount of inorganic suspended particles in water that are derived from a TSS measurement.

Water Quality Limited
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
Limits of certain chemical, physical, and biological parameters in a water body established for different designated uses (for example, aquatic-life use, contact recreation, public water supply).

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