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
55
Partial duration series above a given base
A list of all events, such as, floods, occurring above a selected base, without regard to the number within a given period. In the case of floods, the selected base is usually equal to the lowest annual flood, in order to include at least one flood, each year......
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342
Base units
The seven fundamental units of measurement upon which the International System of Units is based viz. Length (metre), weight mass (kilogram), time (second), electric current (ampere), thermodynamic temperature (kelvin), amount of substance (mole) and luminous intensity (candela)......
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376
Heat capacity, Entropy
img:equations//374_380_e.jpg
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377
Specific heat capacity
img:equations//374_380_e.jpg
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874
Infiltration capacity
The maximum rate at which a given soil in a given condition can absorb rain as it falls, or irrigation water as it is applied......
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890
Evaporativity, Evaporative capacity, Evaporation power, Potential rate of evaporation, or Evaporation potential
Rate of evaporation under existing atmospheric conditions from a free surface of water that is chemically pure and has the temperature of the surrounding atmosphere......
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917
Base flow, Basic flow, or Permanent flow
1 - The sustained or dry weather flow of streams resulting from the outflow of permanent or perched groundwater, and from the drainage of large lakes and swamps. Also water from glaciers, snow and all other possible sources not resulting from direct runoff. 2 – The discharge of a surface channel when the soil in its catchment area is in a conditi.....
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954
Channel capacity
The maximum flow which a given channel is capable of carrying without overtopping its banks.
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1044
Artesian capacity
The rate at which a well will yield water at the ground surface as the result of artesian pressure.
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1097
Field capacity, Normal field capacity, Normal moisture capacity, Maximum field carrying capacity, Field capillary (moisture) capacity, Effective water-holding capacity, Specific retention
1 - The amount of water held in the soil after the excess gravitational water has drained away and after the rate of downward movement of water has materially decreased. Essentially the same as `specific retention`, a more general term used in studies of groundwater, except that specific retention is generally given as a percentage by volume wherea.....
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1572
Transportation capacity
Value of maximum sediment discharge through a homogenous portion of a canal that can be evaluated with the help of formulae on sediment discharge......
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1721
Air capacity of soil
The quantity of air in the soil when the soil is at field moisture capacity.
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1762
Base
1 - A compound capable of reacting with acids to form salts, either with or without the elimination of water. With reference to exchangeable or absorbed bases, the elements sodium, potassium, calcium and magnesium are considered bases rather than the oxides or hydroxides of these elements. 2 - See 4892 and 5766......
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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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1772
Base saturation
Exchange capacity saturated with metallic cations of pH 7 or over.
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1775
Depletion of bases
Removal of exchangeable cations after displacement by H+.
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1781
Buffering capacity
The amount of alkali or acid required to produce a given change in pH.
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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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1815
Moisture-holding capacity, Saturation capacity or Maximum water capacity
The amount of water required to fill all the pore spaces between the soil particles, i.e. the upper limit of the possible moisture content. It is often expressed as the percentage of the dry weight or as equivalent inches of water per foot of soil depth......
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1816
Field capacity
1 - The amount of water expressed as a percentage of the oven-dry soil, held in a soil after the excess of gravitational water has drained away, and after the rate of downward movement of water has materially decreased.  2 ‑The water content of a soil after excess water has just finished draining by gravity. 3 ‑ See 1097 and 5249......
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