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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2154
Degree of salinity
Percentage of soluble salts in the root zones.
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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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6569
Water salinity
The presence of dissolved ions in water. May refer to ground water, soil water or to water supplies for domestic, industrial or agricultural uses. Generally water can be used without restriction for any such purpose if salinity is below some threshold value, but as salinity increases above the threshold, its use is restricted as it begins to cause .....
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6600
Environmental change
A natural or man‑induced alteration in the environment.
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7667
Cation exchange capacity
See 1770.
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7670
Base exchange capacity
A measure of the absorptive capacity of a soil for bases or exchangeable ions (OH).
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7845
Climate change
1 - A statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period of time (typically decades or longer).  2- See 9296......
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8777
Salinity wedge
A wedge-like formation when saline water intrudes into fresh water at the bottom and when the buoyancy effects predominate over turbulent mixing. Salinity wedge results in distinct stratification in velocity fields over the vertical......
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8815
Salinity control
Abatement or prevention of salt water contamination of agricultural, industrial and municipal water supplies, or reducing alkaline salts and preventing deterioration of cultivable lands......
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8961
Change Management
The process of identifying, documenting, approving and implementing changes within a project.
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9170
Salinity control benefits
Benefits based on value of damage prevented, reduction in costs, and increased use, similar to flood control.
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9296
Climate Change
1 - Climate change refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differs from that in the United Nations Framework Convention on Climate Change (UNFCCC), which defines “climate change” as: “a change of climate which is attributed directly or indirectly to human activ.....
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9367
United Nations Framework Convention on Climate Change (UNFCCC)
1 - The Convention was adopted on 9 May 1992, in New York, and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Community. Its ultimate objective is the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate sys.....
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