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
1049
Alluvial-slope spring, Boundary spring, or Border spring
A spring that occurs on the lower slope of an alluvial cone at the point where the water table slope and the surface gradient are equal. This point is often located at the point of gradation from pervious sand with a flat water table slope to less pervious alluvial material which calls for a steep slope to carry the water supplied from above......
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1158
Water surface slope
The inclination of the water surface expressed as change of elevation per unit of length. The tangent of the angle that the surface makes with the horizontal. .....
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1159
Slope
The inclination of a line, channel bed, water surface, pipeline or other structure, expressed as the difference in elevation of two points divided by their horizontal distance......
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1237
Submerged weir, or Drowned weir
A weir  for which the water level on the downstream side at an elevation equal to, or higher than, the weir crest; the rate of discharge is affected by the tail water......
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1540
Slope protection
Riprap, paving, pitching, revetment, brush or other material laid or placed for protection on the sloping part of an embankment or levee or sea shore, to prevent erosion, slipping or caving, or to withstand external hydraulic pressure......
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2245
Weir
1 - A low dam or wall across a stream to raise the upstream level (illustrated). Termed `fixed-crest weir` or `ungated weir` when uncontrolled. 2 - A structure built across a stream or channel for the purpose of measuring flow. Sometimes described as `measuring weir` or `gauging weir`. Types of measuring weir include `broad crested`, `sharp crested.....
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2247
Diversion weir
A low dam or wall across a stream for the purpose of diverting part or all the water from a stream into a canal.
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2248
Closed weir, Overflow diversion dam, Fixed crest weir, Blind weir, or Ungated weir
A low dam built as a complete obstruction across the river so that the entire stream flow can pass over it. It may or may not be fitted with crest gates; when not fitted with crest gates, it is also called `fixed crest weir`, or `blind weir`, or `ungated weir`......
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2249
Open weir, or Open diversion dam
A diversion weir across a river to produce least obstruction to the flow. It comprises undersluices and several other bays having falling shutters fitted on a permanent structure......
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2251
Pick-up weir, Regulating weir, or Regulating pondage weir
A diversion weir built downstream of and as an adjunct to a dam especially built when the areas to use the diverted water lie farther from the dam......
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2252
Subsidiary weir
A structure constructed downstream of the main weir or on the apron to increase the tail water level to ensure formation of a hydraulic jump whenever the tail water level is lower than required for hydraulic jump formation......
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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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2255
Fixed buttress weir, Ambursen dam or Ambursen weir
A fixed dam consisting of water-supporting upstream face supported by buttresses which are equally spaced walls or struts proportioned to transmit the water load and the weight of the structure, to the foundations. Note - It is classified as open or closed Ambursen weir according to the absence or provision of downstream face slab.(originated by Sw.....
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2256
Impermeable weir
A weir made up of impermeable material, such as rock, stone, brick masonry, concrete, steel, or timber. It can be of a fixed or movable type......
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2257
Impermeable fixed weir, or Solid fixed weir
A fixed weir whose water bearing surfaces are of watertight construction. It may be built with timber, masonry, concrete (plain or reinforced), steel, or combinations thereof......
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2258
Timber weir
A fixed weir where timber baulks, timber piling or timber surfaces primarily make the body of the weir watertight.
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2259
Piles weir
A semi-permeable weir when the desired water level raising is effected by driving piles.
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2260
Gravity weir, or Masonry weir
A watertight weir made of stone or brick masonry or of concrete, depending solely on its weight for stability. It may be of overall or slope-weir type......
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2261
Slope weir
A weir with sloping surfaces extending from the crest, so that the water remains in contact with the weir surface all the way down and is guided by it as per design......
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2263
Solid slope masonry weir
An impermeable-slope weir made up of rock, stone, brick masonry or concrete. It may or may not have falling shutters for headwater control......
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2264
Permeable weir
A weir made of loose and permeable construction, such as loose rock, stones, timber, brushwood, or crib.
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2265
Rockfill weir
A permeable weir, whose body is formed by loose stones or boulders laid between intervening masonry walls or piles upto the top surface of the weir. It can be constructed without any wall of concrete or masonry......
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2266
Crib weir
A permeable weir formed by timber cribs. Cribs are constructed of round timbers in a block-house like fashion, sometimes with transverse walls. The timbers are joined together at their intersection with clamps, nails, or bolts. The cribs are filled with gravel and stones......
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2267
Brushwood weir
A permeable weir whose body is formed by brushwood, round timber and gravel.
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2268
Falling crest weir, or Falling shutter weir
A weir having falling shutters fitted along its crest that may be put down to pass floods. Falling crest arrangement is installed in both permeable and impermeable weirs......
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