File:Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products (1913) (14804277513).jpg

Identifier: cu31924073873089 (find matches)
Title: Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products
Year: 1913 (1910s)
Authors: Newell, Frederick Haynes, 1862-1932 Murphy, Daniel William
Subjects: Irrigation Agricultural engineering
Publisher: New York : McGraw-Hill Book Company
Contributing Library: Cornell University Library
Digitizing Sponsor: MSN

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large amount of resistance to the flowof the water and prevents it acquiring a high velocity in its descent.These channels are sometimes constructed of rough stones so placedas to offer the maximum resistance to flow. In addition to the roughwalls and bottom, rock barriers projecting above the water surfaceare placed at frequent intervals in the channel. Another and veryeffective method of reducing velocity in an inclined drop is to con-struct it in the form of a series of vertical drops with a water cushionat the foot of each. By such a device the velocity is killed at eachwater cushion and the maximum velocity which will be acquired willdepend upon the height of the secondary drops. In the design and construction of drops for a canal over countrywhere the slope is considerable, it is necessary to do a large amount ofpreliminary work in order to reach the most economical solution.The principal points to be considered in this connection are the 76 PRINCIPLES OF IRRIGATION ENGINEERING
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1 i-m / I-KI \ -/--1—V \ -77S.S—^ *-!f—> «-,7«,S HIs I CANAL STRUCTURES 77 relative costs of a canal with fewer drops of greater height, comparedto one with more drops of lesser height. In the former case it mustbe taken into account also that more excavation will be required onaccount of the increased depth of the canal below the high drops.In some cases where the slope of the country is very great it is moreeconomical to line a canal with masonry so that it will stand highvelocities, than to construct the necessary drops to reduce its veloc-ity to a maximum for an earth canal. The latter method is inefifect the construction of a long inclined drop. No general state-ments can be made relative to the most economic method of handlingspecial cases, each must be considered in the light of all factors whichaffect its efficiency and cost in order to reach a satisfactory solution.(See Plate VI, Fig. C.) Checks and drops are frequently combined in one structure,which is, in fact,

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