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<br />WATER BUDGET ANALYSIS <br /> <br />Water is diverted from the river at several points, transported through <br />a network of canals and laterals and finally delivered to the farms for <br />irrigation. Off-farm transmission losses occurring through seepage, <br />evaporation and transpiration, and spillage have been evaluated by <br />others and will not be addressed in this report. Analysis indicates <br />that of the water diverted for irrigation about 374,000 acre feet <br />ultimately is delivered to the farms and present on-farm irrigation <br />efficiency is 25 percent. This water, classified by components related <br />to the irrigation process, is defined as follows: <br /> <br />(1) Seepage - Water losses from the on-farm supply and field head <br />ditches and tailwater pickup ditches. <br /> <br />(2) Deep Percolation - The irrigation water which moves below the <br />root zone and is not available for plant growth. <br /> <br />(3) Runoff - The irrigation water that leaves the field as surface <br />flow and is discharged into a drainage channel. Some runoff <br />seeps from tailwater pickup ditches or may be intercepted and <br />reused. <br /> <br />(4) Crop Use - The water consumptively used by crop evapotrans- <br />piration. It is the water supplied by irrigation. exclusive <br />of precipitation, that is stored in the root zone for use by <br />the plants and must be replenished periodically to sustain <br />plant growth. <br /> <br />(S) On-farm Irrigation Efficiency - Efficiency is the crop use, <br />less effective precipitation divided by farm delivery multi- <br />p 1 i ed by 100. <br /> <br />Results of the Water Budget Analysis, shown in Table 18, compare the <br />present conditions with results expected from each of four alternative <br />programs for improvement. <br /> <br />\6'5'1 <br /> <br />47 <br />