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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281
Replication
The execution of an experiment or survey or observation more than once so as to increase the precision and to obtain a closer estimation of sampling errors......
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334
Classification chart
Chart showing the subdivision of a whole and the interrelation of its parts to each other.
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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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734
Desiccation
In climatology, a prolonged decrease or disappearance of  water, due to decrease of rainfall, failure to maintain irrigation or deforestation or overcropping, or to changes in other climatic controls. Desiccation is manifested by the drying up of streams and lakes, the destruction of vegetation, or the loss of surface soil......
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735
Exsiccation
In climatology, the drying up of an area due to some change which decreases the amount of moisture by draining or evaporation without reducing the rainfall. This should be carefully distinguished from desiccation......
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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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981
Zone of saturation
That part of the earth crust where the functional interstices of permeable rock or earth are completely filled with water under positive hydrostatic pressure, that is, pressure in excess of atmospheric pressure. It is that portion of the earth crust that supplies water to springs and wells and which contains the groundwater. Strictly speaking, part.....
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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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1144
Intermittent saturation zone
The zone between the highest and lowest levels of the groundwater table as it responds to seasonal and short term weather changes......
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1148
Zone of permanent non saturation
The strata above the highest water level reached in an aquifer when the groundwater table moves up and down in response to seasonal and shorter term weather changes; marks the lower limit of the permanent non saturation zone.  .....
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1149
Zone of permanent saturation
The saturated portion of an aquifer that lies below the lowest water level reached when the  groundwater table moves up and down in response to seasonal and shorter term weather changes......
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1451
Bifurcation
A forking, or a division into two branches.
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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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1678
Soil classification
Broad systematic groupings are made on the basis of general characteristics and subdivisions on the basis of more detailed differences in specific properties or soil horizons. A classifiation system has been used in the U.S. since 1938, with several revisions and with an additional great soil group in 1949 and another in 1960 by the Soil Survey Sta.....
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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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1760
Cation
An ion carrying a positive charge of electricity.
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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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