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
994
Artesian well
A well that penetrates an aquifer in which the piezometric head is higher than the confined water surface.
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1190
Gauge well, Stilling well, Float well, or Recorder well
1 – A chamber or a compartment with closed sides and bottom, provided with an inlet or inlets communicating with the river or canal. Its purpose is to dampen waves or surges in the parent stream while permitting the water level in the well to rise and fall with the fluctuations of the level in the river or canal. 2 – See 2479......
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1364
Well graded soil
A continuous distribution of grain sizes from the coarsest to the finest components in a proportions that the successively smaller size grains just fill the spaces between the larger grains......
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2253
Siphon weir
A weir operating on the siphon principle. The siphonic arrangement is usually fitted in gravity weirs.
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2479
Stilling well shaft, or Gauge well
1 - A special shaft sometimes included in the design of a dam opening in the reservoir below the minimum reservoir level and containing a floating mechanism to record fluctuations of water level in the reservoir. 2 - See 1190......
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2502
Drainage wells
Openings between the watertight arches and the supporting mass in a dam with Levy-type facing.
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2505
Joint drain, Vertical drain, or Vertical well
Vertical drain provided at construction joints as a precaution against development of excessive pressure in the joints during the construction period and against seepage of water through the joints during the operating period......
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2526
Gate chamber of sluice well
A structure located within the abutment main body of the dam or the dam embankment where the regulating gates or emergency gates are installed. The lower portion of the chamber provides an anchorage for the gates and liner while the upper portion furnishes a working space for the removal of the gate leaf and other parts for repair or for installati.....
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2559
Drain well, Relief well, or Pressure relief well
A deep cylindrical drain located in the foundations of a dam or on its downstream to relieve the seepage pressures in pervious strata deep enough to be reached by trench drains and to drain localized concentrations of seepage, where a continuous trench of pervious blanket is not warranted; they are also employed to correct bed seepage conditions......
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2706
Siphon-pit setting
A type of turbine setting used when the head is insufficient to provide a permanent water seal to the turbine. The water passes through the turbine under siphonic action (illustrated)......
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2769
Siphon spillway
A spillway operating on the siphon principle.
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2770
Siphon, or Syphon
1 - A tube, pipe or a hose through which liquid can be moved from a higher to a lower level over an intervening (higher) barrier.  The movement is caused by atmospheric pressure forcing the liquid through the upstream portion of the siphon while the weight of the liquid in the downstream leg causes continuous downward flow. Because the upper part r.....
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2771
High head siphon
A siphon acting under a difference in water level of more than the barometric height of the water column, i.e. 10.33 metres......
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2772
Low head siphon
A siphon acting under a difference in water level of less than the barometric height of the water column, i.e. less than 10.33 metres......
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2773
Saddle siphon, or Hood siphon
A siphon having its duct formed of a U-shaped hood. The inlet lip of the hood is submerged below the full reservoir level and that of the outlet lip terminates in a water seal formed by various devices. The siphons are sometimes named according to the water seal provided (illustrated)......
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2774
Siphon duct, or Siphon barrel
The annular space between the dam (body wall) and the hood (illustrated).
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2787
Baby siphon type water seal, or Maramsilli baby siphon type water seal
A water seal provided by a baby siphon which by virtue of being at a lower level gets primed earlier and its issuing jet itself seals the downstream end of the siphon duct. A siphon employing this device is also called a `Maramsilli baby siphon` (illustrated)......
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2788
Baby siphon, or Maramsilli baby siphon
A smaller siphon operating at a lower level than the main siphon in the Maramsilli baby siphon. Sometimes, the baby siphon is also referred to as `Maramsilli baby siphon` (illustrated)......
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2789
Auxiliary siphon type water seal
A water seal created by providing a baby siphon placed either in front or by the side of the main siphon. The two siphons are connected through a pipe conduit......
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2795
Battery of siphons
A number of siphons installed close to each other.
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2796
Volute siphon
A siphon consisting of a bent pipe (barrel), the vertical portion is usually funnel-shaped at the top. Volutes are placed on the funnel or outside the vertical pipe near its top and due it is to this that it owes its name. The funnel is covered by a dome placed at some distance. The dome is supported by a cylindrical drum resting on pillars leaving.....
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2802
Priming siphon
A siphon device usually of smaller capacity installed with a main siphon or battery of siphons to reduce priming depth in the latter......
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2986
Howell-bunger valve
A valve having two telescopic cylinders with a streamline dispersing cone secured to the inner cylinder by radial webs. The apex and axis of this cone are coincidental with the centre line of the conduit and valve body and its apex faces upstream. The outer cylinder closes the sideway opening between the cone and the inner cylinder when it is slide.....
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3155
Well siphon
A siphon in which wells are provided at each end of the siphon.
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3364
Standing swell
A swell in the form of a single undular surface rise that will not be followed by further undulations.
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