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<br />1) The sOil-slope group adapted to sprinklers. <br />2) The peak consumptive use rates for various crops. <br />3) Maximum allowable sprinkler application rate. <br />4) Available water holding capacities of soils. <br />5) The estimated application efficiencies. <br /> <br />The time of application depends upon the rate at which the water is <br />applied, and must be computed individually. <br /> <br />Canal and Ditch Lining Systems <br /> <br />A fixed lining of impervious material installed in existing or newly <br />constructed irrigation field ditches, irrigation canals or laterals will <br />prevent water-logging of land, maintain water quality, prevent erosion, <br />and reduce water loss. <br /> <br />The choice of a suitable material for ditch lining, non-reinforced <br />concrete, or a flexible membrane depends on the existing conditions and <br />the results required. <br /> <br />Non-reinforced concrete lining should be installed only in well- <br />drained soils or on sites where subgrade drainage facilities are instal- <br />led with or below the lining. They should not be installed on sites <br />subject to severe frost heave or on sites where the sulphate salt concen- <br />tration in the soil causes rapid concrete deterioration. <br /> <br />Flexible membrane linings such as plastic, rubber or asphalt, should <br />be used on side slopes which will be statically stable. They should be <br />protected by an earth and/or gravel covering and the material itself <br />should meet individual required thickness standards. Quality of the <br />lining is important, and care in installation is necessary to maintain <br />that quality. The membrane must be sufficiently anchored to prevent <br />movement. <br /> <br />Water Control Structures <br /> <br />Water control structures are used to regulate and maintain water <br />levels to control water table, fish and wildlife management, and for <br />flooding land surfaces. The control is accomplished by use of gates or <br />stoplogs that can be fitted into several types of structures. Water <br />control structures can be used to control drainage, flooding, and for <br />water level regulation. Diversions, headgates, etc. are typical water <br />control structures used for irrigation. <br /> <br />Pipeline Distribution Systems <br /> <br />Irrigation pipelines can be used for the same purposes or in place <br />of open channels. Water distribution efficiency is high as they almost <br />eliminate losses from evaporation and seepage. They are particularly <br />adapted to areas where seepage losses from ditches are high. Buried <br />pipelines have many advantages over open ditches. Pipelines require care- <br />ful planning for the correct location, capacity requirements, selection <br />of materials and construction methodS. <br /> <br />B-3 <br /> <br />'.'; I r"", ~~!J <br />UJl.uu.t <br />