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Water: Archives


Acid neutralizing capacity (ANC):
The equivalent capacity of a solution to neutralize strong acids.
Without oxygen; water and sediment environments without oxygen produce, for example, chemical conditions that precipitate and permanently store many metals from water and that release dissolved phosphorus to the water.
Benefit maximization:
The process of increasing benefits to the greatest extent possible within constraints such as limitation on financial resources.
A good, service, or attribute of a good or service that promotes or enhances the well-being of an individual, an organization, or a natural system.
The state of a toxicant such that there is increased physicochemical access to the toxicant by an organism. The less the bioavailability of a toxicant, the less its toxic effect on an organism.
Best management practice (BMP):
A practice used to reduce impacts from a particular land use.
A conduit formed by the flow of water and debris. The time and volume characteristics of water or debris can be altered by man, by climate change, or by alterations in protective vegetal cover on the land of the watershed. The stream channel adjusts to the new set of conditions.
The practice of straightening a waterway to remove meanders and make water flow faster. Sometimes concrete is used to line the sides and bottom of the channel.
Cost minimization:
The process of reducing costs to the lowest possible amount given constraints such as requirements that a specified level of benefits or other resources be attained or provided.
CWA §101:
The objective of the Act is to restore and maintain the chemical, physical, and biological integrity of the Nation's waters.
CWA §303d:
Requires States to identify waters that do not or are not expected to meet applicable water quality standards with technology-based controls alone. Waters impacted by thermal discharges are also to be identified. After the identification and priority ranking of water quality-limited waters are completed, States are to develop TMDLs at a level necessary to achieve the applicable State water quality standards.
CWA §314:
Establishes the Clean Lakes Program, which supports activities from initial identification of potential water quality problems through post-restoration monitoring. Cooperative grants provide funding for these activities.
CWA §319:
Requires States to develop nonpoint source control programs. EPA awards grants to implement approved programs that include, as appropriate, nonregulatory, and regulatory programs for enforcement, technical assistance, financial assistance, education, training, technology transfer, and demonstration projects.
CWA §320:
Establishes that National Estuary Program (NEP), a demonstration program designed to show how estuaries and their living resources can be protected through comprehensive, action-oriented management. Participation in the NEP is limited to estuaries determined by the EPA Administrator to b of "national significant" after nomination by the Governors of the States in which the estuaries are located.
CWA §402:
Establishes the National Pollutant Discharge Elimination System (NPDES), which provides for the issuance of point source permits to discharge any pollutant or combination of pollutants, after opportunity for public hearing.
CWA §404:
The discharges of dredged or fill material into wetlands is regulated under this section of the
Permits may be issued after notice and opportunity for public hearings.
Drop structure:
A natural or man-placed structure that disrupts the continuous surface flow pattern in a river or stream by producing a pooling of water behind the structure and a rapid drop in the surface gradient for water flowing over the structure; used to improve habitat conditions for aquatic life and to increase the air (especially oxygen) content of water.u
Ecological region that has broad similarities with respect to soil, relief, and dominant vegetation.
Energy cycling:
The movement, or flow, and storage of energy among production and use components of ecological and physiological systems.
The combined conversion of water to water vapor and loss resulting from both evaporation and transpiration.
The geologic study of the evolution and configuration of land forms.
Marginal costs:
The incremental cost of increasing output of a good or service by a small amount.
In streams, a relatively deep area with low velocity; in ecological systems, the supply of an element or compound, such as exchangeable or weatherable cations or adsorbed sulfate, in a defined component of the ecosystem.
Pool-riffle ratio:
The ratio of stream surface area covering pools to stream surface area covering riffles in a given segment of stream.
The rate at which oxygen is absorbed back into water. This is dependent, among other things, upon turbulence intensity and the water depth.
The biological oxidation of organic carbon with concomitant reduction of external oxidant and the production of energy. In aerobic respiration, O2 is reduced to CO2. Anaerobic respiration processes utilize NO3- (denitrification), SO42- (sulfate reduction), or CO2 (methanogenesis).
A shallow section in a stream where water is breaking over rocks or other partially submerged organic debris and producing surface agitation.
Site characterization:
A location-specific or area-specific survey conducted to characterize physical, chemical, and/or biological attributes of an area; such surveys may be conducted at different times to provide information on how these attributes may change over time.
The ability of a chemical (e.g., pollutant) to be dissolved into a solvent (e.g., water column).
Stream meander:
The length of a stream channel from an upstream point to a downstream point divided by the straight line distance between the same two points.
Total Maximum Daily Load (TMDL):
An estimate of the pollutant concentrations resulting from the pollutant loadings from all sources to a waterbody. The TMDL is used to determine the allowable loads and provides the basis for establishing or modifying controls on pollutant sources.
TMDL process:
The approach normally used to develop a TMDL for a particular waterbody or watershed. This process consists of five activities, including selection of the pollutant to consider, estimation of the waterbody's assimilative capacity, estimation of the pollution from all sources to the waterbody, predictive analysis of pollution in the waterbody and determination of total allowable pollution load, and allocation of the allowable pollution among the different pollution sources in a manner that water quality standards are achieved.
Trophic state:
The state of nutrition (e.g., amount of nutrients) in a body of water.
A drainage area or basin in which all land and water areas drain or flow toward a central collector such as a stream, river or lake at a lower elevation.
Watershed Protection Approach (WPA):
The U.S. EPA's comprehensive approach to managing water resource areas, such as river basins, watersheds and aquifers. WPA contains four major features — targeting priority problems, stakeholder involvement, integrated solutions, and measuring success.
Width/depth ratio:
The width to depth ratio describes a dimension of bankfull channel width to bankfull mean depth. Bankfull discharge is defined as the momentary maximum peak flow which occurs several days a year and is related to the concept of channel forming flow.
Width/meander length ratio:
The ratio of the average width of a stream or river over a reach divided by the average length over successive cycles of left and right bends of the stream or river.

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