International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage

Multilingual Technical Dictionary (MTD)
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Term No.Term Name/Term DescriptionAction
1766
Exchange complex, or Absorbing complex
The surface-active constituents of soil (both inorganic and organic) that are capable of cation exchange.
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1768
Exchangeable
Describes ions capable of replacement in the exchange (absorbing complex).
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1769
Ion exchange, Cation exchange, or Anion exchange
The replacement in a colloidal system of an ion by another with a charge of the same sign. Cation exchange refers to the interchange of positively charged ions (cations) and anion exchange to the replacement of negatively charged ions (anions) by other anions......
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1770
Exchange capacity, Cation exchange capacity, Base exchange capacity, or Saturation capacity
The total cation exchange, usually expressed as milliequivalents per 100 grams. Measured value of cation exchange capacity depends somewhat on the method used for the determination......
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1786
Exchangeable-sodium percentage (ESP)
The degree of saturation of the soil exchange complex with sodium. It may be calculated by the formula :
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1788
Exchange acidity
Acidity produced by treating soil with a solution of a neutral salt.
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1789
Exchangeable acidity or Potential acidity
H+ ions held in reserve
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3068
Eddy viscosity, Mechanical velocity, Exchange coefficient, or Eddy conductivity
Analogous to the dynamic viscosity, but depends upon the Reynolds number and other parameters. Referred to by various writers as the `mechanical velocity`, `exchange coefficient` and `eddy conductivity`......
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4051
Change of slope (of a canal)
Altering the functioning levels of a canal or canal reach so as to either improve its functioning by gravity or preventing silting or scour......
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5032
Change in salinity
This change is indicated by the average rate of change in the electric conductivity (EC) of the saturated soil water extract defined by the following ratio : .....
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5100
Exchangeable sodium percentage (ESP)
The degree of saturation of the soil exchange complex with sodium. It may be calculated by the formula:
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5624
Volume change (of concrete)
The expansion and contraction of hardened concrete resulting from wetting and drying or temperature variations. May produce various types of undesirable conditions in concrete......
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6361
Environmental protection
In the context of irrigation projects, judicious use of agricultural inputs; fertilizers, herbicides and pesticides; and control of water application with the purpose of reducing waste and controlling leaching, with the objective of preventing degradation of soil, surface water bodies, drainage network, streams, rivers, groundwater and the atmosphe.....
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6584
Environmental quality
The properties and characteristics of the environment, either generalized or local,  as they impinge on human beings and other organisms......
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6591
Environmental agents
Physical, biological, man-made and natural chemical substances found in the environment.
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6592
Environmental stress
Perturbations likely to cause observable changes in ecosystems.
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6593
Environmental geology
The application of geologic data and principles to the solution of problems likely to be created by human occupancy and use of the physical environment......
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6594
Environmental region
A  region of the earth’s surface that has a unique set of physical environmental factors and supports a distinct ecosystem......
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6600
Environmental change
A natural or man‑induced alteration in the environment.
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6603
Environmentally sensitive area
An area having beneficial qualities or natural assets; such as  wetlands, floodplains, critical habitats of endangered species, or recharge zones of sole source aquifers; that might be easily and adversely affected by human activities or natural phenomena......
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6604
Environmental parameters
Physical, chemical, or biological attributes of the environment that can be stated in quantitative terms.
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6653
Environmental tracer
A tracer that is found naturally in the environment.
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6784
Environmental resources
Those elements, features, conditions and areas valued by man, that can be characterized as physiographic, biological, cultural, and aesthetic......
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7098
Environmental pollution
The contamination of air, land, or water;  or making the same injurious to public health, harmful for commercial or residential use, or deleterious to animal or plant life.  .....
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7155
Environmental fate
The destiny of a chemical after release to the environment.  Involves considerations such as transport through air, soil and water, bioconcentration, degradation, etc.  .....
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