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<br />I <br /> <br />1 .. provides the water user 'addi tional flexibility in his efforcs <br /> <br />2 to improve irrigation efficiency. Pipe distribution. systems, <br /> <br />3 resembling municipal water systems, rrore readily provide this <br /> <br />4 <br /> <br />capability than do open canal systems. <br /> <br />. . . When the source <br /> <br />i,. <br />5 of supply for a distribution system is a canal, >i. frequent ad-'- <br /> <br />6 justment of the canal flow and its control struct'ures is re- <br /> <br />7 quired to match the variation in flov' created by automatic <br /> <br />8 operation of the distribution system to. meet the water users' <br /> <br />9 demand. <br /> <br />10 The capital cost for closed-pipe systems exceeds that of open <br /> <br />11 canals, and closed-conduit distribution systems cost more than surface <br /> <br />12 systems. But, we need to bear in mind that even though capi.tal is <br /> <br />13 short in developing countries, it will be easier to supply these one- <br />I <br /> <br />14 time inputs than it will be to provide the highly skilled technicians <br /> <br />15 needed to operate open supply and distribution systems efficiently. <br /> <br />16 Even in the United States with the highly skilled operators and sophis- <br /> <br />17 ticated communication and automated controls available, open canals and <br /> <br />18 i '.3urface distribution systems always end up with water that cannot be <br /> <br />19 used efficiently. If the'continuing cost of drainage and land reclama- <br /> <br />20 <br /> <br />tion required as the result of poor water ~anagement is considered, <br /> <br />21 <br /> <br />these closed systems may be far more competitive. <br /> <br />"" <br /> <br />Closed water conveyance irrigation water distribution systems are <br /> <br />23 <br /> <br />elegant engineering solutions to the water management problem in the <br /> <br />24 sense that control is built into the system. (Anyone can operate a water <br /> <br />25 tap to draw a glass of water.) A one-time investment replaces the con- <br /> <br />26 tinuous investment of energy, labor, and capital required with open <br /> <br />271 con~eyances and surface irrigation systems. The ~ost highly skilled <br /> <br />C.J2986 <br />