Glossary of Water Resource Terms

A

abandoned water right

a water right which was not put to beneficial use for a number of years, generally five to seven years.

abandoned well

a well which is no longer used. In many places, abandoned wells must be filled with cement or concrete grout to prevent pollution of ground water bodies.

absorption

the uptake of water, other fluids, or dissolved chemicals by a cell or an organism (as tree roots absorb dissolved nutrients in soil).

accretion

a gradual increase in land area adjacent to a river.

acid rain

the acidic rainfall which results when rain combines with sulfur oxides emissions from combustion of fossil fuels.

acidic

the condition of water or soil that contains a sufficient amount of acid substances to lower the pH below 7.0.

acre-foot

the amount of water required to cover one acre to a depth of one foot. An acre-foot equals 325,851 gallons, or 43,560 cubic feet. A flow of 1 cubic feet per second produce 1.98 acre-feet per day.

activated carbon adsorption

the process of pollutants moving out of water and attaching on to activated carbon.

adhesion

the molecular attraction asserted between the surfaces of bodies in contact. Compare cohesion.

adjudication

a court proceeding to determine all rights to the use of water on a particular stream system or ground water basin.

administrative order

a legal document signed by U.S. EPA directing an individual, business, or other entity to take corrective action or refrain from an activity. It describes the violations and actions to be taken, and can be enforced in court. Such orders may be issued, for example, as a result of an administrative complaint ordering the respondent to pay a penalty for violations of the Clean Water Act.

administrative order on consent

a legal agreement signed by U.S. EPA and an individual, business, or other entity through which the violator agrees to pay for correction of Clean Water Act violations, take the required corrective or cleanup actions, or refrain from an activity. It describes the actions to be taken, may be subject to a comment period, applies to civil actions, and can be enforced in court.

adsorption

the adhesion of a substance to the surface of a solid or liquid. Adsorption is often used to extract pollutants by causing them to be attached to such adsorbents as activated carbon or silica gel. Hydrophobic, or water-repulsing adsorbents, are used to extract oil from waterways in oil spills.

advanced wastewater treatment

any treatment of sewage that goes beyond the secondary or biological water treatment stage and includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids.

aerated lagoon

a holding and/or treatment pond that speeds up the natural process of biological decomposition of organic waste by stimulating the growth and activity of bacteria that degrade organic waste.

aeration

the mixing or turbulent exposure of water to air and oxygen to dissipate volatile contaminants and other pollutants into the air.

aeration tank

a chamber used to inject air into water.

aerobic treatment

process by which microbes decompose complex organic compounds in the presence of oxygen and use the liberated energy for reproduction and growth. Such processes include extended aeration, trickling filtration, and rotating biological contactors.

aerobic

life or processes that require, or are not destroyed by, the presence of oxygen.

aggressive water

water which is soft and acidic and can corrode plumbing, piping, and appliances.

algae

simple rootless plants that grow in sunlit waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.

algal bloom

a phenomenon whereby excessive nutrients within a river, stream or lake cause an explosion of plant life which results in the depletion of the oxygen in the water needed by fish and other aquatic life. Algae bloom is usually the result of urban runoff (of lawn fertilizers, etc.). The potential tragedy is that of a "fish kill," where the stream life dies in one mass extinction.

algicide

substance or chemical used specifically to kill or control algae.

alkaline

the condition of water or soil that contains a sufficient amount of alkali substance to raise the pH above 7.0.

alkalinity

the measurement of constituents in a water supply which determine alkaline conditions. The alkalinity of water is a measure of its capacity to neutralize acids. See pH.

alluvial

relating to, composed of, or found in alluvium.

alluvium

sediments deposited by erosional processes, usually by streams.

alvusion

a sudden or perceptible change in a river's margin, such as a change in course or loss of banks due to flooding.

ambient background concentration

a representative concentration of the water quality in a receiving water body, determined from monitoring. The statistic or data used to determine the value from the range of data is dependent on the purpose of the monitoring and the application of the data.

ambient medium

material surrounding or contacting an organism (e.g., outdoor air, indoor air, water, or soil through which chemicals or pollutants can reach the organism.

amprometric titration

a way of measuring concentrations of certain substances in water using the electric current that flows during a chemical reaction.

anaerobic

a life or process that occurs in, or is not destroyed by, the absence of oxygen.

annular space

the space between two concentric cylindrical objects, one of which surrounds the other, such as the space between the walls of a drilled hole and a casing.

anti-degradation clause

part of federal and water quality requirements prohibiting deterioration where pollution levels are above the legal limit.

appropriative rights

"first in time, first in right” principle of allocating water rights based. Usually involves a user being allowed to take water from a particular source without regard to the contiguity of the land to the source.

aquatic

growing in, living in, or frequenting water.

aquiclude

a formation which, although porous and capable of absorbing water slowly, will not transmit water fast enough to furnish an appreciable supply for a well or a spring.

aqueous

something made up of water.

aqueous solubility

the maximum concentration of a chemical that will dissolve in pure water at a reference temperature.

aquiculture

the raising or fattening of fish in enclosed ponds. Compare mariculture.

aquifer

a geologic formation that will yield water to a well in sufficient quantities to make the production of water from this formation feasible for beneficial use; permeable layers of underground rock or sand that hold or transmit groundwater below the water table.

aquitard

geological formation that may contain groundwater but is not capable of transmitting significant quantities of it under normal hydraulic gradients. May function as confining bed.

artesian aquifer

a geologic formation in which water is under sufficient hydrostatic pressure to be discharged to the surface without pumping.

artesian well

a water well drilled into a confined aquifer where enough hydraulic pressure exists for the water to flow to the surface without pumping.

artesian zone

a zone where water is confined in an aquifer under pressure so that the water will rise in the well casing or drilled hole above the bottom of the confining layer overlying the aquifer.

assay

a test for a specific chemical, microbe, or effect.

assimilation

the ability of a water body to purify itself of pollutants.

assimilative capacity

the capacity of a natural body of water to receive and dilute wastewaters or toxic materials without damage to aquatic life or humans who consume the water.

average annual recharge

amount of water entering the aquifer on an average annual basis. Averages mean very little for the Edwards because the climate of the region and structure of the aquifer produce a situation in which the area is usually water rich or water poor.

B

background level

the concentration of a substance in an environmental media (water or soil) that occurs naturally or is not the result of human activities.

backpressure

a pressure that can cause water to backflow into the water supply when a user's wastewater system is at a higher pressure than the public system.

backsiphonage

reverse seepage of water in a distribution system.

backwashing

reversing the flow of water through a home treatment device filter or membrane to clean and remove deposits.

bank-full capacity

the rate of water flow that completely fills a channel; the flow rate at which the water surface is level with the flood plain.

bar screen

in wastewater treatment, a device used to remove large solids from the incoming wastewater stream.

barrage

any artificial obstruction placed in water to increase water level or divert it. Usually the idea is to control peak flow for later release.

bedload

the particles in a stream channel that mainly move by bouncing, sliding, or rolling on or near the bottom of the stream.

beneficial use

the amount of water necessary when reasonable intelligence and diligence are used for a stated purpose; Texas law recognizes 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, and (10) game preserves.

Best Management Practice (BMP)

methods or measures designed and selected to reduce or eliminate the discharge of pollutants from point and nonpoint source discharges. As used in the stormwater context, BMPs are a schedule of activities, prohibitions of practices, maintains procedures and other management practices to prevent or reduce the pollution of waters of the state. BMPs include treatment requirements, operating procedures and practices to control plant site runoff, spills or leaks, sludge or waste disposal, or drainage from raw material storage.

bioaccumulation

uptake and retention of substances by an organism from its surrounding medium (usually water) and from food.

bioassay

a test to determine the relative strength of a substance by comparing its effect on a test organism with that of a standard preparation.

bioassessment

monitoring the aquatic environment to determine the health of a stream.

biological integrity

the ability to support and maintain balanced, integrated functionality in the natural habitat of a given region. The concept is applied primarily in drinking water management.

biological oxidation

decomposition of complex organic materials by microorganisms. Occurs in self-purification of water bodies and in activated sludge wastewater treatment.

biomonitoring

a test used to evaluate the relative potency of a chemical by comparing its effect on a living organism with the effect of a standard population on the same type of organism.

bioremediation

a process that uses living organisms to remove pollutants.

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.

biosphere

the earth and all its ecosystems

blackwater

wastewater from toilet, latrine, and agua privy flushing and sinks used for food preparation or disposal of chemical or chemical-biological ingredients.

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.

bloom

a proliferation of algae and/or higher aquatic plants in a body of water; often related to pollution or excessive nutrients, especially when they accelerate growth.

blowdown

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

bog

a type of wetland that accumulates appreciable peat deposits. They depend primarily on precipitation for their water source, and are usually acidic and rich in plant matter with a conspicuous mat or living green moss.

boiling point

the temperature at which a liquid boils. It is the temperature at which the vapor pressure of a liquid equals the pressure on its surface. If the pressure of the liquid varies, the actual boiling point varies. For water it is 212 degrees Fahrenheit or 100 degrees Celsius.

BOD

Biochemical Oxygen Demand. A measure of the amount of oxygen required to neutralize organic wastes.  The BOD of a wastewater is a characteristic reflecting treatability or stage of decomposition.  Compare COD and CBOD.

brackish

mixed fresh and salt water.

breakpoint chlorination

addition of chlorine to the point where all organic matter and ammonia compounds have been destroyed and any additional chlorine becomes a free chlorine residual available for disinfection.

brine

highly salty and heavily mineralized water containing heavy metal and organic contaminants.

buoyancy

the tendency of a body to float or rise when immersed in a fluid; the power of a fluid to exert an upward force on a body placed in it.

C

calcium carbonate

CACO3 - a white precipitate that forms in water lines, water heaters and boilers in hard water areas; also known as scale.

calorie

amount of energy required to raise the temperature of 1 gram of water 1 degree Celsius.

capillary action

movement of water through very small spaces due to molecular forces called capillary forces.

capillary forces

forces that cause ground water to rise above the surface of the saturated zone into the spaces between soil particles in the unsaturated zone.

capillary zone

soil area above the water table where water can rise up slightly through the cohesive force of capillary action. See phreatophytes.

carbamates

a class of new-age pesticides that attack the nervous system of organisms.

carbon adsorption

a treatment system that removes contaminants from ground water or surface water by forcing it through tanks containing activated carbon treated to attract the contaminants.

carbonates

the collective term for the natural inorganic chemical compounds related to carbon dioxide that exist in natural waterways.

casing

a tubular structure intended to be watertight installed in the excavated or drilled hole to maintain the well opening and, along with cementing, to confine the ground waters to their zones of origin and prevent the entrance of surface pollutants.

cavern

a large underground opening in rock (usually limestone) which occurred when some of the rock was dissolved by water. In some igneous rocks, caverns can be formed by large gas bubbles.

CBOD

Carbonaceous Biochemical Oxygen Demand.  A BOD test in which a nitrification inhibitor is added, so that only the carbonaceous oxygen demanding compounds are measured. 

cement grout

a mixture of water and cement in the ratio of not more than 5-6 gallons of water to a 94 pound sack of portland cement which is fluid enough to be pumped through a small diameter pipe.

CERCLA

Comprehensive Environment Response, Compensation and Liability Act. Also known as SUPERFUND. The Act gave EPA the authority to clean up abandoned, leaky hazardous waste sites.

certificate of water right

an official document which serves as court evidence of a perfected water right.

CFU

colony forming units.  Concentrations of water quality indicator organisms such as fecal coliform bacteria are measured in CFU/100 mL.

channelization

natural or intentional straightening and/or deepening of streams so water moves faster and causes less flooding.  Channelization can sometimes exacerbate flooding in other downstream areas.

check dam

a small dam constructed in a gully or other small water course to decrease the streamflow velocity, minimize channel erosion, promote deposition of sediment and to divert water from a channel.

chemical weathering

attack and dissolving of parent rock by exposure to rainwater, surface water, oxygen, and other gases in the atmosphere, and compounds secreted by organisms. Contrast physical weathering.

chlorination

the adding of chlorine to water or sewage for the purpose of disinfection or other biological or chemical results.

chlorine contact chamber

the part of a wastewater treatment plant where treated water is disinfected by chlorine.

chlorine demand

the difference between the amount of chlorine added to water, sewage, or industrial wastes and the amount of residual chlorine remaining at the end of a specific contact period. Compare residual chlorine.

chute spillway

the overall structure which allows water to drop rapidly through an open channel without causing erosion. Usually constructed near the edge of dams.

circulate

to move in a circle, circuit or orbit; to flow without obstruction; to follow a course that returns to the starting point.

cistern

a tank used to collect rainwater runoff from the roof of a house or building.

clarification

the clearing action that occurs during wastewater treatment when solids settle out. Clarification is often aided by centrifugal action or chemically induced coagulation.

clarifier

a tank in which solids settle to the bottom and are subsequently removed as sludge.

Clean Water Act

federal legislation enacted in 1972 to restore and maintain the chemical, physical and biological integrity of the surface waters of the United States. The stated goals of the Act are that all waters be fishable and swimmable.

climatic cycle

the periodic changes climate displays, such as a series of dry years following a series of years with heavy rainfall.

climatic year

a period used in meteorological measurements. The climatic year in the U.S. begins on October 1.

climate

generalized weather at a given place on earth over a fairly long period; a long term average of weather. Compare weather.

cloudburst

a torrential downpour of rain, which by it spottiness and relatively high intensity suggests the bursting and discharge of water from a cloud all at once.

coagulation

in water treatment, the use of chemicals to make suspended solids gather or group together into small flocs.

COD

Chemical Oxygen Demand.  A measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidation.  Differs from the BOD test in that COD uses oxygen derived from chemicals, while BOD uses oxygen derived from air dissolved in water. 

cohesion

a molecular attraction by which the particles of a body are united throughout the mass whether like or unlike. Compare adhesion.

cold vapor

method to test water for the presence of mercury.

coliform bacteria

non-pathogenic microorganisms used in testing water to indicate the presence of pathogenic bacteria.

collector well

a well located near a surface water supply used to lower the water table and thereby induce infiltration of surface water through the bed of the water body to the well.

colloids

finely divided solids which will not settle but which may be removed by coagulation or biochemical action.

combined sewer

a sewer system that carries both sanitary sewage and stormwater runoff. When sewers are constructed this way, wastewater treatment plants have to be sized to deal with stormwater flows and oftentimes some of the water receives little or no treatment. Compare separate sewer.

Combined Sewer Overflow (CSO)

the discharge of a mixture of storm water and domestic waste when the flow capacity of a sewer system is exceeded during rainstorms.

community water system

In Texas, a public water system which has a potential to serve at least 15 residential service connections on a year-round basis or serves at least 25 residents on a year-round basis.

completion

sealing off access of undesireable water to the well bore by proper casing and/or cementing procedures.

composite sample, weighted

a sample composed of two or more portions collected at specific times and added together in volumes related to the flow at time of collection. Compare grab sample.

concentration

amount of a chemical or pollutant in a particular volume or weight of air, water, soil, or other medium.

condensation

the change of state from a gas to a liquid. Compare evaporation, sublimation.

conduit

a natural or artificial channel through which fluids may be conveyed.

cone of depression

natural depression in the water table around a well during pumping.

confined aquifer

an aquifer that lies between two relatively impermeable rock layers.

confining bed or unit

a body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers.

confluent growth

in coliform testing, abundant or overflowing bacterial growth which makes accurate measurement difficult or impossible.

conjunctive management

integrated management and use of two or more water resources, such as an aquifer and a surface water body.

connate growth

water trapped in the pore spaces of a sedimentary rock at the time it was deposited. It is usually highly mineralized.

conservation

to protect from loss and waste. Conservation of water may mean to save or store water for later use.

constituent

an informal term used to describe a detectable element or component or attribute of waste or effluent.>

consolidated formation

naturally occurring geologic formations that have been lithified (turned to stone). The term is sometimes used interchangeably with the term "bedrock." Commonly, these formations will stand at the edges of a bore hole without caving.

consumptive use

the quantity of water not available for reuse. Evapotranspiration, evaporation, incorporation into plant tissue, and infiltration into groundwater are some of the reasons water may not be available for reuse. Compare nonconsumptive use.

contact recreation

activities involving a significant risk of ingestion of water, such as wading by children, swimming, water skiing, diving and surfing. Compare noncontact recreation..

contamination

the introduction into water of sewage or other foreign matter that will render the water unfit for its intended use.

conveyance loss

water loss in pipes, channels, conduits, and ditches by leakage or evaporation.

cooling tower

large tower used to transfer the heat in cooling water from a power or industrial plant to the atmosphere either by direct evaporation or by convection and conduction.

correlative rights

rights that are coequal or that relate to one another, so that any one owner cannot take more than his share.

creek

a small stream of water which serves as the natural drainage course for a drainage basin. The term is relative according to size. Some creeks in a humid region would be called rivers if they occurred in an arid area.

crest

the top of a dam, dike, or spillway, which water must reach before passing over the structure; the summit or highest point of a wave; the highest elevation reached by flood waters flowing in a channel.

critical low flow

low flow conditions below which some standards do not apply. The impacts of permitted discharges are analyzed at critical low-flow.

cross-connection

any actual or potential connection between a drinking water system and an unapproved water supply or other source of contamination.

cross-contamination

a condition created when a drill hole, boring, or improperly constructed well forms a pathway for fluid movement between a saturated zone which contains pollutants and a formerly separated saturated zone containing uncontaminated groundwater. Also, where potable water supplies and sanitary services are interconnected.

cubic foot per second (CFS)

the rate of discharge representing a volume of one cubic foot passing a given point during 1 second. This rate is equivalent to approximately 7.48 gallons per second, or 1.98 acre-feet per day.

current

the portion of a stream or body of water which is moving with a velocity much greater than the average of the rest of the water. The progress of the water is principally concentrated in the current. See thalweg.

D

dam

a structure of earth, rock, or concrete designed to form a basin and hold water back to make a pond, lake, or reservoir.

dead end

the end of a water main that is not connected to other parts of the distribution system.

decomposable waste

waste that under suitable natural conditions can be transformed through biological and chemical processes into compounds that do not impair water quality.

deionized water

water free of inorganic chemicals.

delta

an alluvial deposit made of rock particles (sediment, and debris) dropped by a stream as it enters a body of water.

demand

the number of units of something that will be purchased at various prices at a point in time. Compare supply.

dense non-aqueous phase liquid (DNAPL)

non-aqueous phase liquids, such as chlorinated hydrocarbon solvents or petroleum fractions, with a specific gravity greater than 1.0 that sink through the water column until they reach a confining layer. Because they are at the bottom of aquifers instead of floating on the water table, typical monitoring wells do not indicate their presence.

density

a measure of how heavy a specific volume of a solid, liquid, or gas is in comparison to water.

depletion curve

in hydraulics, a graphical representation of water depletion from storage stream channels, surface soil, and groundwater. A depletion curve can be drawn for base flow, direct runoff, or total flow.

deposit

something dropped or left behind by moving water, as sand or mud.

deposition

the laying down of material by erosion or transport by water or air.

detection limit

the lowest level that can be determined by a specific analytical procedure or test method.

detention time

the time required for a volume of water to pass through a tank at a given rate of flow; in storage reservoirs, the length of time water will be held before being used.

detergent

synthetic washing agent that helps remove dirt and oil. Some contain compounds toxic to bacteria that are useful in the wastewater treatment process; other contain nutrients such as phosphorous that may encourage algae growth when they are in wastewater that reaches receiving waters.

dewater

remove or separate a portion of the water in a sludge or slurry to dry the sludge so it can be handled and disposed; remove or drain the water from a tank, trench, or aquifer.

diatomaceous

consisting of or abounding in diatoms, a class of unicellular or colonial algae having a silicified cell wall that persists as a skeleton after death.

digester

in wastewater treatment, a unit in which anaerobic bacterial action is induced and accelerated in order to break down and stabilize organic matter removed from the treatment process.

diluting water

distilled water that has been stabilized, buffered, and aerated. Used in the BOD test.

dilution ratio

the critical low flow of the receiving water at the point of recycled water discharge divided by the flow of the discharge.  Is used in the biomonitoring test to simulate in-stream conditions that organisms will be exposed to during critical low-flow times.

discharge

the volume of water that passes a given point within a given period of time. It is an all-inclusive outflow term, describing a variety of flows such as from a pipe to a stream, or from a stream to a lake or ocean.

discharge permit

a permit issued by a state or the federal government to discharge effluent into waters of the state or the United States. In many states both State and federal permits are required.

discharger

any person who discharges waste that could affect the quality of state waters. The term includes any person who owns, or is responsible for the operation of, a waste management unit such as a wastewater treatment plant.

disinfectant

a chemical or physical process that kills or inactivates pathogenic organisms in water.  Chlorine is the most commonly used disinfectant for recycled water, potable water supplies, wells, and swimming pools.  Other disinfectants include ozone, bromine, iodine, chlorine dioxide, heat, and ultraviolet light.

disinfection

the killing of the larger portion of the harmful and objectionable bacteria in the sewage. Usually accomplished by introduction of chlorine, but more and more facilities are using exposure to ultraviolet radiation, which renders the bacteria sterile.

disinfection byproducts

halogenated organic chemicals formed when water is disinfected.

dispersion

the movement and spreading of contaminants out and down in an aquifer.

displacement

distance by which portions of the same geological layer are offset from each other by a fault.

dissolve

the process by which solid particles mix molecule by molecule with a liquid and appear to become part of the liquid.

dissolved oxygen (DO)

amount of oxygen gas dissolved in a given quantity of water at a given temperature and atmospheric pressure. It is usually expressed as a concentration in parts per million or as a percentage of saturation.

dissolved solids

inorganic material contained in water or wastes. Excessive dissolved solids make water unsuitable for drinking or industrial uses. See TDS.

distillation

water treatment method where water is boiled to steam and condensd in a separate reservoir. Contaminants with higher boiling points than water do not vaporize and remain in the boiling flask.

distilled water

water that has been treated by boiling and condensation to remove solids, inorganics, and some organic chemicals.

diversion

to remove water from a water body. Diversions may be used to protect bottomland from hillside runoff, divert water away from active gullies, or protect buildings from runoff.

downgradient

the direction that groundwater flows; similar to “downstream” for surface water.

draft

the act of drawing or removing water from a tank, reservoir or groundwater supply.

drainage area

of a stream at a specified location is that area, measured in a horizontal plane, enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into the stream above the specified location.

drainage reuse

reuse of agricultural drainage on salt-tolerant crops.

drainage well

a well drilled to carry excess water off agricultural fields. Because they act as a drain from the surface to the groundwater below, drainage wells can contribute to groundwater pollution.

drawdown

the drop in the water table or level of groundwater when water is being pumped from a well; the amount of water used from a tank or reservoir; the drop in the water level of a tank or reservoir.

dredging

removal of mud from the bottom of water bodies. This can disturb the ecosystem and cause silting that kills aquatic life. Dredging of contaminated mud can expose biota (the flora and fauna of a  region) to heavy metals and other toxics. Dredging activities may be subject to regulation under state and federal laws.

driller's well log

a log kept at the time of drilling showing the depth, thickness, character of the different strata penetrated, location of water-bearing strata, depth, size, and character of casing installed.

dripstone

deposits of calcium carbonate that include stalactites, stalagmites, columns, and cave pearls.

drought

although there is no universally accepted definition of drought, it is generally the term applied to periods of less than average precipitation over a certain period of time. In south Texas ranchers say drought begins as soon as it stops raining.

duplicates

two separate samples with separate containers taken at the same time at the same place.

E

ecosphere

total of all the ecosystems on the planet, along with their interactions; the sphere of air, water, and land in which all life is found.

ecosystem

the interacting system of a biological community and its non-living environmental surroundings; a complex system composed of a community of fauna and flora, taking into account the chemical and physical environment with which the system is interrelated.

Edwards Aquifer

an arch-shaped belt of porous, water bearing limestones composed of the Comanche Peak, Edwards, and Georgetown formations trending from west to east to northeast through Kinney, Uvalde, Medina, Bexar, Comal, Hays, Travis, and Williamson counties.

Edwards outcrop

where the Edwards and associated limestone formations are found at the surface. This area is also referred to as the Recharge Zone.

effective porosity

the portion of pore space in saturated permeable material where the movement of water takes place.

effective precipitation

the part of precipitation which produces runoff; a weighted average of current and antecedent precipitation "effective" in correlating with runoff. It is also that part of the precipitation falling on an irrigated area which is effective in meeting the requirements of consumptive use.

effluent

any substance, particularly a liquid, that enters the environment from a point source. Generally refers to wastewater from a sewage treatment or industrial plant.

effluent limitation

restrictions established by a a regulating agency such as a State or the EPA in an NPDES permit on quantities, rates, and concentrations in wastewater discharges.

electrodialysis

a process which uses an electrical current and an arrangement of permeable membranes to separate soluble minerals from water. It is often used to desalinate salt or brackish water.

endangered species

one having so few individual survivors that the species could soon become extinct in all or part of its region.

enrichment

the addition of nutrients such as nitrogen and phosphorous from wastewater effluent or agricultural runoff to surface water. Enrichment greatly increases the growth potential for algae and other aquatic plants.

enteric viruses

a category of viruses related to human excreta found in waterways.

entrain

to trap bubbles in water either mechanically through turbulence or chemically through a reaction.

environment

aggregate of external conditions that influence the life of an individual organism or population.

environmental indicator

a measurement, statistic or value that provides evidence of the effects of environmental management programs or of the state or condition of the environment.

Environmental Impact Statement (EIS)

a document that analyzes the effects of major federal projects on the environment. Required by the National Environmental Policy Act.  It must be filed with the President and the Council on Environmental Quality, and made available to the public.

EPA

Environmental Protection Agency.  The federal regulatory agency responsible for protecting environmental quality throughout the nation. Also acts in an oversight role to state environmental agencies that carry out federal laws.

epilimnion

warm, less dense top layer in a stratified lake. Compare hypolimnion.

erosion

the wearing away of the land surface by wind, water, ice or other geologic agents. Erosion occurs naturally from weather or runoff but is often intensified by human land use practices.

escarpment

the topographic expression of a fault.

estuarine waters

deepwater tidal habitats and tidal wetlands that are usually enclosed by land but have access to the ocean and are at least occasionally diluted by freshwater runoff from the land (such as bays, mouths of rivers, salt marshes, lagoons).

estuarine zone

area near the coastline that consists of estuaries and coastal saltwater wetlands.

estuary

thin zone along a coastline where freshwater system(s) and river(s) meet and mix with a salty ocean (such as a bay, mouth of a river, salt marsh, lagoon).

euphotic zone

surface layer of an ocean, lake, or other body of water through which light can penetrate. Also known as the zone of photosynthesis.

eutrophic

having a large or excessive supply of plant nutrients (nitrates and phosphates). Compare oligotrophic.

eutrophication (natural)

an excess of plant nutrients from natural erosion and runoff from the land in an aquatic ecosystem supporting a large amount of aquatic life that can deplete the oxygen supply.

evaporation

the change by which any substance is converted from a liquid state and carried of in vapor. Compare condensation, sublimation.

evapotranspiration

combination of evaporation and transpiration of water into the atmosphere from living plants and soil. Distinguish transpiration.

external cost

cost of production or consumption that must be borne by society; not by the producer.

extinction

complete disappearance of a species because of failure to adapt to environmental change.

F

facultative bacteria

bacteria that can live under aerobic or anaerobic conditions.

fecal coliform

the portion of the coliform bacteria group which is present in the intestinal tracts and feces of warm-blooded animals. A common pollutant in water.

fen

a type of wetland that accumulates peat deposits, but not as much as a bog. Fens are less acidic than bogs, deriving most of their water from groundwater rich in calcium and magnesium.

fermentation, anaerobic

process in which carbohydrates are converted in the absence of oxygen to hydrocarbons (such as methane).

field capacity

the amount of water held in soil against the pull of gravity.

filter

a device used to remove solids from a mixture or to separate materials. Materials are frequently separated from water using filters.

filtration

the mechanical process which removes particulate matter by separating water from solid material, usually by passing it through sand.

"first in time, first in right"

phrase indicating that older water rights have priority over more recent rights if there is not enough water to satisfy all rights.

fixed ground water

water held in saturated material that it is not available as a source of water for pumping.

flocculation

large scale treatment process involving gentle stirring whereby small particles in flocs are collected into larger particles so their weight causes them to settle to the bottom of the treatment tank.

flood

an overflow or inundation that comes from a river or other body of water and causes or threatens damage. It can be any relatively high streamflow overtopping the natural or artificial banks in any reach of a stream. It is also a relatively high flow as measured by either gage height or discharge quantity.

floodplain

land next to a river that becomes covered by water when the river overflows its banks .

flora

plant population of a region.

flow

the rate of water discharged from a source expressed in volume with respect to time.

flow augmentation

the addition of water to meet flow needs.

flow meter

a gauge indicating the velocity and/or volume of a flowing liquid.

flume

a natural or artificially made channel that diverts water.

flush

to open a cold-water tap to clear out all the water which may have been sitting for a long time in the pipes; to force large amounts of water through a system to clean out piping or tubing and storage or process tanks.

forebay

the water behind a dam.

forfeited water right

a water right canceled because of several consecutive years of nonuse.

freeboard

the vertical distance between the lowest point along the top of a surface impoundment dike, berm, levee, treatment works or other similar feature and the surface of the liquid contained therein.

free ground water

water in interconnected pore spaces in the zone of saturation down to the first impervious barrier, moving under the control of the water table slope.

freezing

the change of a liquid into a solid as temperature decreases. For water, the freezing point is 32 F or 0 C.

fresh water

water containing less than 1,000 parts per million (ppm) of dissolved solids of any type. Compare saline water.

fresh:salt water interface

the region where fresh water and salt water meet. In the Edwards region, it is commonly referred to as the "bad water line", although it is zone and not a line.

frost

a covering of minute ice crystals on a cold surface.

furrow irrigation

irrigation method in which water travels through the field by means of small channels between each group of rows.

G

gaging station

the site on a stream, lake or canal where hydrologic data is collected.

gallon

A unit of volume. A U.S. gallon contains 231 cubic inches, 0.133 cubic feet, or 3.785 liters. One U.S. gallon of water weighs 8.3 lbs.

game fish

a species such as trout, salmon, or bass, caught for sport.

gas chromatograph

an instrument that identifies the molecular composition and concentrations of various chemicals in water and soil samples.

geohydrology

a term which denotes the branch of hydrology relating to subsurface or subterranean waters; that is, to all waters below the surface.

geologic erosion

normal or natural erosion caused by geological processes acting over long geologic periods and resulting in the wearing away of mountains, the building up of floodplains, coastal plains, etc.

geopressured reservoir

a geothermal reservoir consisting of porous sands containing water or brine at high temperature or pressure.

geyser

a periodic thermal spring that results from the expansive force of super heated steam.

giardia lamblia

a protozoa found in the feces of infected humans and animals that can cause severe gastrointestinal ailments. It is a common contaminant of surface waters.

glacier

a huge mass of land ice that consists of recrystallized snow and moves slowly downslope or outward.

grab sample

a sample taken at a given place and time. Compare composite sample.

granular activated carbon

pure carbon heated to promote "active" sites which can adsorb pollutants. Used in some home water treatment systems to remove certain organic chemicals and radon.

grassed waterway

natural or constructed watercourse or outlet that is shaped or graded and planted in suitable vegetation for the disposal of runoff water without erosion.

greywater

wastewater from clothes washing machines, showers, bathtubs, handwashing, lavatories and sinks that are not used for disposal of chemical or chemical-biological ingredients.

groundwater

water within the earth that supplies wells and springs; water in the zone of saturation where all openings in rocks and soil are filled, the upper surface of which forms the water table.

groundwater hydrology

the branch of hydrology that deals with groundwater; its occurrence and movements, its replenishment and depletion, the properties of rocks that control groundwater movement and storage, and the methods of investigation and utilization of ground water.

groundwater law

the common law doctrine of riparian rights and the doctrine of prior appropriation as applied to ground water.

groundwater recharge

the inflow to a ground water reservoir.

groundwater reservoir

an aquifer or aquifer system in which ground water is stored. The water may be placed in the aquifer by artificial or natural means.

groundwater runoff

the portion of runoff which has passed into the ground, has become ground water, and has been discharged into a stream channel as spring or seepage water.

groundwater storage

the storage of water in groundwater reservoirs.

gully

a deeply eroded channel caused by the concentrated flow of water.

gully reclamation

use of small dams of manure and straw; earth, stone,or concrete to collect silt and gradually fill in channels of eroded soil.

H

habitat indicator

a physical attribute of the environment measured to characterize conditions necessary to support an organism, population, or community in the absence of pollutants. For example, salinity of estuarine waters or substrate type in streams or lakes.

hail

a form of precipitation which forms into balls or lumps of ice over 0.2 inch in diameter. Hail is formed by alternate freezing and melting as precipitation is carried up and down in highly turbulent air currents.

hardpan

a shallow layer of earth material which has become relatively hard and impermeable, usually through the deposition of minerals. In the Edwards region hardpans of clay are common.

hard water

water containing a high level of calcium, magnesium, and other minerals. Hard water reduces the cleansing power of soap and produces scale in hot water lines and appliances.

hardness (water)

condition caused by dissolved salts of calcium, magnesium, and iron, such as bicarbonates, carbonates, sulfates, chlorides, and nitrates.

head

the pressure of a fluid owing to its elevation, usually expressed in feet of head or in pounds per square inch, since a measure of fluid pressure is the height of a fluid column above a given or known point.

headgate

the gate that controls water flow into irrigation canals and ditches. A watermaster regulates the headgates during water distribution and posts headgate notices declaring official regulations.

heat of vaporization

the amount of heat necessary to convert a liquid (water) into vapor.

heavy water

water in which all the hydrogen atoms have been replaced by deuterium.

herbicide

a chemical used to kill nuisance plants. Herbicides can contain pollutants found in runoff.

holding pond

a small basin or pond designed to hold sediment laden or contaminated water until it can be treated to meet water quality standards or be used in some other way.

holding time

the maximum amount of time a sample may be stored before analysis.

hydraulic conductivity

the rate at which water can move through a permeable medium.

hydraulic gradient

the direction of groundwater flow due to changes in the depth of the water table.

hydrocarbons

chemical compounds that consist entirely of carbon and hydrogen; also referred to as volatile organic compound.

hydroelectric plant

electric power plant in which the energy of falling water is used to spin a turbine generator to produce electricity.

hydrogeology

the geology of groundwater, with particular emphasis on the chemistry and movement of water.

hydrograph

a chart that measures the amount of water flowing past a point as a function of time.

hydrologic balance

an accounting of all water inflow to, water outflow from, and changes in water storage within a hydrologic unit over a specified period of time.

hydrologic basin

the drainage area upstream from a given point on a stream.

hydrologic cycle

natural pathway water follows as it changes between liquid, solid, and gaseous states; biogeochemical cycle that moves and recycles water in various forms through the ecosphere. Also called the water cycle.

hydrologic unit

is a geographic area representing part or all of a surface drainage basin or distinct hydrologic feature.

hydrology

the science dealing with the properties, distribution, and circulation of water.

hydrolysis

the decomposition of organic compounds by interaction with water.

hydrometer

an instrument used to measure the density of a liquid.

hydropneumatic

a water delivery system, usually small, that maintains water pressure in the distribution system by means of pressure in a compressed air tank.

hydropower

electrical energy produced by falling water.

hygroscopic nuclei

piece of dust or other particle around which water condenses in the atmophere. These tiny droplets then collide and coalesce, with as many as 10,000 nuclei contributing to formation of a raindrop.

hydrosphere

region that includes all the earth's liquid water, frozen water, floating ice, frozen upper layer of soil, and the small amounts of water vapor in the Earth's atmosphere.

hydrostatic head

a measure of pressure at a given point in a liquid in terms of the vertical height of a column of the same liquid which would produce the same pressure.

hydrostatic pressure

pressure exerted by or existing within a liquid at rest with respect to adjacent bodies.

hypolimnion

bottom layer of cold water in a lake. Compare epilimnion.

I

ice

a solid form of water.

imhoff cone

a clear, cone-shaped container used to measure the volume of settleable solids in a specific volume of water.

immiscibility

the inability of two or more substances or liquids to readily dissolve into one another, such as soil and water.

impaired water body

a water body that has been determined under state and federal law as not meeting water quality standards, or having the potential to do so in the future.

impermeable

material that does not permit fluids to pass through.

impervious

the quality or state of being impermeable; resisting penetration by water or plant roots. Impervious ground cover like concrete and asphalt affects quantity and quality of runoff.

impoundment

a body of water such as a pond, confined by a dam, dike, floodgate or other barrier. It is used to collect and store water for future use.

in-line filtration

a pretreatment method in which chemicals are mixed by flowing water; commonly used in pressure filtration installations.

in-situ flushing

introduction of large volumes of water, at times supplemented with cleaning compounds, into soil, waste, or groundwater to flush hazardous contaminants from a site.

in-situ oxidation

technology that oxidizes contaminants dissolved in groundwater, converting them into insoluble compounds.

in-situ stripping

treatment system that removes or strips volatile organic compounds from contaminated groundwater or surface water by forcing an air stream through the water and causing the compounds to evaporate.

in-situ vitrification

technology that treats contaminated soil in place at high temperatures, at 3,000 degrees Fahrenheit or more.

inchoate water right

an unperfected water right.

indicator organisms

microorganisms, such as coliforms, whose presence is indicative of pollution or of more harmful microorganism.

indicator parameters

measurable physical or chemical characteristics or attributes of water or soil-pore moisture used to indicate the possible presence of waste constituents, or the effects of waste constituents on waters.

indicator tests

tests for a specific contaminant, group of contaminants, or constituent which signals the presence of something else (ex., coliforms indicate the presence of pathogenic bacteria).

infiltration

the penetration of water through the ground surface into sub-surface soil or the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls.

infiltration rate

the quantity of water that can enter the soil in a specified time interval.

inflow

entry of rainwater into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains, and street washing.

influent

water, wastewater, or other liquid flowing into a reservoir, basin, or treatment plant.

initial dilution

the process that results in the rapid and irreversible turbulent mixing of effluent and receiving water around the point of discharge.

injection well

as defined by the U.S. EPA, any bored, drilled or driven shaft, dug pit or hole in the ground into which waste or fluid is discharged, and any associated subsurface appurtenances, the depth of which is greater than the largest surface dimension of the shaft, pit or hole.

injection zone

a geological formation receiving fluids through a well.

inland freshwater wetlands

swamps, marshes, and bogs found inland beyond the coastal saltwater wetlands.

instream use

use of water that does not require withdrawal or diversion from its natural watercourse; for example, the use of water for navigation, recreation, and support of fish and wildlife.

interbasin transfer

the physical transfer of water from one watershed to another; regulated by the Texas Water Code.

interceptor sewer

very large sewer lines that collect the flow from main and trunk lines and carry them to treatment plants.

interface

the common boundary between two substances such as water and a solid, water and a gas, or two liquids such as water and oil.

interfacial tension

the strength of the film separating two immiscible fluids (e.g., oil and water) measured in dynes per, or millidynes per, centimeter.

intermittent stream

one that flows periodically. Compare perennial stream.

interstate water

according to law, interstate waters are defined as (1) rivers, lakes and other waters that flow across or form a part of state or international boundaries; (2) waters of the Great Lakes; (3) coastal waters whose scope has been defined to include ocean waters seaward to the territorial limits and waters along the coastline (including inland streams) influenced by the tide.

interstices

the void or empty portion of rock or soil occupied by air or water.

inert waste

waste that does not contain hazardous waste or soluble pollutants at concentrations in excess of applicable water quality objectives, and does not contain significant quantities of decomposable waste.

irrigation efficiency

the percentage of water applied, and which can be accounted for, in the soil moisture increase for consumptive use.

irrigation return flow

water which is not consumptively used by plants and returns to a surface or ground water supply. Under conditions of water right litigation, the definition may be restricted to measurable water returning to the stream from which it was diverted.

irrigation water

water which is applied to assist crops in areas or during times where rainfall is inadequate.

isotherm

line that connects points of equal temperature.

isohyet

line that connects points of equal rainfall.

J

jar test

a laboratory procedure that simulates a water treatment plant's coagulation/flocculation units with differing chemical doses, mix speeds, and settling times to estimate the minimum or ideal coagulant dose required to achieve certain water quality goals.

jet stream

a long narrow meandering current of high-speed winds near the tropopause blowing from a generally westerly direction and often exceeding a speed of 250 miles per hour.

jetteau

a jet of water.

jetter

one (as a geyser) that sends out a jet.

jetty

a structure (as a pier or mole of wood or stone) extending into a sea, lake, or river to influence the current or tide or to protect a harbor.

K

kalema

a violent surf that occurs on the coast of the Guinea region, West Africa.

kame

a short ridge, hill, or mound of stratified drift deposited by glacial meltwater.

kame terrace

a terrace of stratified sand and and gravel deposited by streams between a glacier and an adjacent valley wall.

kelp beds

significant aggregations of a large, fast growing marine algae throughout the water column.

kinetic energy

energy possessed by a moving object or water body.

kilogram

one thousand grams.

L

laboratory water

purified water used in the laboratory as a basis for making up solutions or making dilutions. Water devoid of interfering substances.

lag time

the time from the center of a unit storm to the peak discharge or center of volume of the corresponding unit hydrograph.

lagoon

a shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater. Lagoons are typically used for the storage of wastewaters, sludges, liquid wastes, or spent nuclear fuel.

lake

an inland body of water, usually fresh water, formed by glaciers, river drainage etc. Usually larger than a pool or pond.

land application

discharge of wastewater onto the ground for treatment or reuse.

landscape impoundment

body of reclaimed water which is used for aesthetic enjoyment or which otherwise serves a function not intended to include contact recreation.

Langelier Saturation Index (LSI)

an index reflecting the equilibrium pH of a water with respect to calcium and alkalinity; used in stabilizing water to control both corrosion and scale deposition.

leachate

water containing contaminants which leaks from a disposal site such as a landfill or dump.

leachate collection system

a system that gathers leachate and pumps it to the surface for treatment.

leaching

extraction or flushing out of dissolved or suspended materials from the soil, solid waste, or another medium by water or other liquids as they percolate down through the medium to groundwater.

lentic system

a nonflowing or standing body of fresh water, such as a lake or pond. Compare lotic system.

levee

a natural or man-made earthen obstruction along the edge of a stream, lake, or river. Usually used to restrain the flow of water out of a rive