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<br />"08.99 <br /> <br />. <br /> <br />. <br /> <br />excess of crop needs results in deep percolation beyond the plants <br /> <br />root zone, greater evaporation and increased surface runoff. By <br /> <br />far the most important on-farm loss is crop transpiration -- water <br /> <br />consumed by the plants. The vast majority of on-farm conveyance <br />systems have an average efficiency of less than 65% (the percentage <br />of water delivered to the farm which is used by the crop), nearly <br />half are below 45%. California and significant parts of Texas <br />and Washington are an exception with on-farm average efficiencies <br />/ <br />over 65%. - <br /> <br />It would appear that significant quantities of water could <br />be conserved through improved efficiency of farm delivery systems. <br /> <br />However, these efficiency figures do not mean that water now <br /> <br />diverted for irrigation can be saved and made available for other <br /> <br />uses. The effectiveness of any particular conservation measure <br /> <br />is difficult to quantify because conserving water either off-farm <br /> <br />or on-farm may only appear to reduce waste. Again, there is no <br /> <br />change in the amount of water circulating in the hydrologic cycle, <br /> <br />and there may be little or no net savings in the amount available <br /> <br />for human use. Most of the water lost by any given irrigation <br /> <br />system is recoverable for reuse. Only incidental irrecoverable <br /> <br />losses can be "saved." Therefore, water use efficiency in the <br /> <br />basin will be much greater than either on-farm or off-farm efficiency. <br /> <br />There are many ways of improving off-farm and on-farm irrigation <br /> <br />system efficiencies. Some of the more effective measures include: <br /> <br />/I <br />