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
597
Head of water in metres
img:equations//596_630_e.jpg
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598
Head of water in metres
img:equations//596_630_e.jpg
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729
Headwater, or Headwaters
The upper reaches of a stream near its source.
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873
Infiltration head
The depth of water on the surface porous media which causes infiltration.
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913
Hydraulic head
1  The energy at a given point in a liquid, expressed as the equivalent height of a column of the liquid above a given datum. 2   See 1830, 5258 and 6491......
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961
Headwater storage
Works designed to store or otherwise retain  runoff, where it originates or as near thereto as practicable, to  reduce the crest downstream......
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1039
Artesian head
Pressure head of artesian water.
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1078
Highest stage of the water table, or Phreatic height
At a given place and for a given cycle of fluctuation, it is the highest elevation reached by the water table.
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1150
Head loss (in an aquifer)
The difference in height of the groundwater table in different parts of the same aquifer resulting from resistance to flow through the aquifer......
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1233
Velocity-head rod, Velocity-head stick, Run-up
A device for measuring velocity through culverts, or over weirs, dams, etc., by placing the rod vertically in the flow and observing the `run-up` (the difference in water levels obtained at upstream and downstream of the rod); the rod is, generally, calibrated to read velocity, or discharge......
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1337
Beheaded stream
A stream with original headwater drainage area, separated from it by another stream which is more active and has greater erosive power, now drains into the other stream......
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1378
Headward erosion
1 - The erosion of a stream bed by the action of scour at the bottom of a vertical cliff or waterfall where the flow of the stream plunges, causing undermining of the cliff and its movement upstream, so that the deepened section extends upstream. It differs from cataract action in as much as only a small flow may be necessary to keep it going, or a.....
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1480
High water training, or Training for discharge
The provision of efficient cross-sectional area for the expeditious passage of the maximum flood in a river.
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1484
Groyne, Groin, Bankhead, Spur, Spur dike, Transverse dike, Jetty
1 - A structure built from the bank of a river in a direction transverse to the current. The groynes may be permeable, semi-permeable or impermeable. 2 - See 3479 and 8028......
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1491
Denehy`s `T` headed spur
A spur having its nose in `T` shape. In such type of spurs both the noses of `T` are protected against scouring. (Illustrated).....
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1499
Strong head
The head or outer end of a groyne specially armoured or protected with stone mesh, pitching, etc., to resist erosion.
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1500
Fending groyne, or Bankhead
Groyne which fends the current of flow of water and prevents erosion. Denehy`s groyne is an example of this type (illustrated)......
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1829
Tension head
The pressure in the liquid phase of an unsaturated soil, relative to atmospheric pressure, expressed in units of length of water column. In an unsaturated soil, the tension head will be sub-atmospheric, or negative, and can be thought of as the vertical distance from a saturated porous cup in contact with the soil down to the free water surface in .....
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1830
Hydraulic head
1 - The height with respect to a standard datum at which water stands in a riser (or piezometer or manometer) that connects to the point in question. Porous cups make it possible to measure the hydraulic head, which will be negative, i.e. less than atmospheric, in unsaturated soil. 2 – See 913, 5258, and 6491.......
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1838
Capillary head
The difference between ultimate capillary lift and the actual position to which the water has been raised at any particular time......
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1839
Minimum capillary head
The distance from the free water surface to the highest elevation at which the maximum degree of saturation exists.
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1840
Maximum capillary head
The highest elevation to which any continuous channel of water exists above the free water surface.
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1841
Saturation capillary head
The distance from the free water surface to the highest elevation at which complete saturation exists.
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1994
Drainage head
The difference between the water level in a normal working drain and the lowest level of the surroundings near ground.
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2007
Tide head
The head of the stretch of land up to which the influence of the tide is felt or the utmost limit of the land coming within the zone of influence of the tide......
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