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
297
Horizontal section
Section cut through the object horizontally.
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1617
Eluviation, Eluvial horizon
The movement of soil material from one horizon to another within the soil, in solution or in suspension, in locations where there is an excess of rainfall over evaporation; horizons that have lost material through eluviation are referred to as `eluvial horizons`and those that have received material as `illuvial horizons`......
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1618
Illuvial horizon
A soil layer or horizon in which the material carried on an overlying layer (eluvial horizon) has been precipitated from the solution or deposited from suspension. The layer of accumulation......
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1619
Soil horizon
A layer of soil, approximately parallel to the soil surface, with characteristics produced by soil-forming processes.
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1620
Soil horizon symbols
The symbols used to designate soil horizons are marked with the capital letters H, O, A, B, C, E and R.
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1621
Master horizons
Under this title are listed the principal soil horizons and layers in soil profiles: H, O, A, E, and B, and the underlying C and R......
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1622
H horizon
Is an organic horizon formed or forming an accumulation of organic material deposited on the surface, that is saturated with water for prolonged periods, unless artificially drained. H horizons form at the surface of wet soils, either as thick cumulative layers in organic soil or as thin layers of peat or muck over mineral soils. Even when ploughed.....
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1623
O horizon
Is an organic horizon formed or forming from an accumulation of organic material deposited on the surface, that is not saturated with water for more than a few days a year and contains 20% or more organic carbon. O horizons are the organic horizons that develop on top of some mineral soils. For example, the raw humus which covers certain acid soils.....
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1624
A horizon
A mineral horizon formed or forming at or adjacent to the surface that shows: a) an accumulation of organic matter intimately associated with the mineral fraction, or b) a morphology acquired by soil formation but lacking the properties of E and B horizons......
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1625
E Horizon
Is a mineral horizon showing a concentration of sand and silt fractions high in resistant minerals, resulting from a loss of silicate clay, iron or aluminum or some combination of them. E horizons are usually eluvial horizons which underlie on H, O, or A horizons. Their colour is generally lighter than that of the surface soil......
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1626
B horizon
Is a mineral horizon in which rock structure is obliterated or is but faintly evident, characterized by one or more of the following features: a) an illuvial cementation of silicate clay, iron, alumininum, or organic matter, above or in combination; b) a residual concentration of sesquioxides relative to source materials; c) an alteration of materi.....
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1627
C horizon
Is a mineral horizon (or layer) of unconsolidated material from which the solum is presumed to be formed, and which does not show properties diagnostic of any other master horizons......
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1628
R horizon
A layer of continuous indurated rock, sufficiently cohesive when moistened as to make hand digging with a spade impracticable......
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2102
Recurrence horizon
Thin layer between the older and the younger horizons of raised bogs.
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2161
Soil horizon of carbonate accumulation
A developed soil horizon, beneath the surface, containing more calcium (or magnesium and calcium) carbonate than the soil above it or the soil material below it......
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2511
Horizontal joint, or Construction lift
A joint introduced between the lifts to provide sufficient cooling between pours.
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2545
Horizontal drainage blanket, Pervious blanket, or Drainage filter
A blanket of pervious material provided at the foundation level, commencing from the impervious zone to the downstream of an earthdam or the landside of a levee to allow the seepage water to travel and minimize the possibility of failure by piping or a blow out or sub-surface erosion......
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2584
Horizontal creep
1 - The creep in the horizontal direction. 2 - The distance measured along the horizontal creep. 3 - According to `Lane`, the creep along a slope flatter than 45o is also treated as a horizontal creep......
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2871
Hydraulic rollers, Circular roller, Elliptical roller, Vertical roller, Horizontal roller, Inclined roller, Submerged roller, or Surface roller
Flow of water adopting circular or elliptical motion round a vertical, horizontal or inclined axis lending the appearance of a roller within or at the surface of the stream.  They are named circular or elliptical rollers according to the shape adopted while the direction of axis lends the designation of vertical, horizontal or inclined rollers.  Ac.....
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3392
Splay, Taper, Angle of splay, Splay angle, Angle of contraction, Contraction angle, Convergence angle, Angle of divergence, Divergence angle, Angle of horizontal flare, Angle of expansion
The inclination in plan of the transition curve from the centre line of the channel in case of open conduits or from the horizontal axis in case of closed conduits. Expressed either as an angle or tangent of that angle. The splay of the contracting side is known as `angle of contraction` or `convergence angle` the splay of the diverging sides is kn.....
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3393
Flare, Angle of flare, Flare angle, Flaring angle, Horizontal flare, Angle of horizontal flare, Vertical flare, or Angle of vertical flare
1 - In contraction transitions, it is the inclination in elevation of the contracting sides expressed as an angle or tangent of that angle. 2 - In expansion transitions, it is the inclination in both plan and elevation of the diverging sides expressed as angles or tangents of these angles. The inclination in plan is specified as `angle of horizonta.....
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3508
Horizontal grill type sand trap
A type of sand trap in which the water is let into a sediment basin immediately above the weir. The water then passes through horizontal grills fixed into the sediment basin and drops its coarse sediment into it which is sluiced away. De-sedimented water passes over the weir (illustrated)......
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3675
Horizontal orifice
An orifice lying in a horizontal plane.
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4147
Horizontal well
A well drilled horizontally into a mountain or hillside to tap a trapped water supply.
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4515
Horizontal pump
1 - A reciprocating pump in which the piston or plunger moves in a horizontal direction. 2 - A centrifugal pump in which the pump shaft is in a horizontal position......
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