. Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products. main canal, usually possess points of supe-riority either in soil, exposure or drainage. It frequently happensthat excess-water accumulates on the low lands, reducing the valueof these. It is sometimes possible, under such conditions, to utilizecheap power transmitted by electrical devices in draining these lands,this waste water being used for the reclamation of additional drainage waters are used for irrigation, attention must begiven to their quality, as they
. Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products. main canal, usually possess points of supe-riority either in soil, exposure or drainage. It frequently happensthat excess-water accumulates on the low lands, reducing the valueof these. It is sometimes possible, under such conditions, to utilizecheap power transmitted by electrical devices in draining these lands,this waste water being used for the reclamation of additional drainage waters are used for irrigation, attention must begiven to their quality, as they frequently contain large quantities ofharmful alkali salts in solution. In considering hydroelectric developments of this character,the units commonly employed are the cubic foot per second for rateof flow and the horse-power or kilowatt (i. = kw. or i kw. = ). Assuming the weight of water as lb. per cubic foot,this amount falling i ft. per second develops = it another way, i cu. ft. per second falling ft. generates 130 PRINCIPLES OF IRRIGATION ENGINEERING. o J3 J4 § 3 •a B O o 1^ IRRIGATION BY PUMPING 131 one theoretical horse-power, or i kw. per hour equals i acre-footraised i ft. high. If for convenience in preliminary calculations amotor eflSciency of 80 per cent, is assumed, i second-foot fallingII ft. will generate i or kw. (or i kw. = ).If the power is used for pumping water and the plant efficiency istaken at 50 per cent, for motor, pump, etc., then i acre-foot raisedI ft. high will require at least 2 By this simple rule thetotal power required to irrigate an acre may be apprehended byeasy mental effort. In estimating the energy created by falling water, it is convenientto make certain assumptions, as to the efficiency of the variousforms of apparatus. The turbine water-wheel is assumed to havean efficiency under good conditions of 80 per cent, or over, somehave reached in pra
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectirrigat, bookyear1913
