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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />For an eight year period from 1987 to 1994, the average annual tailwater flow within the District <br />was calculated to be approximately 408,395 acre-feet. (On-Farm Irrigation Efficiency, Boyle <br />Engineering, 1993 and 1995) Without additional improvements in on-farm management <br />practices these reservoirs are estimated to reduce tail water flows by 15 percent, resulting in an <br />annual water conservation potential of about 25,800 acre-feet [(Approximate acres of coverage <br />/projected total farmed acres) x total tailwater x percent reduction in tailwater; (180,000/427,600) <br />x 408,395 x 0.15)]. The water conserved by this project depends entirely upon how well a water <br />user manages the on-farm reservoir. Thus, a combination of studies to determine management <br />practices and water user incentives to manage the on-farm reservoir to save more water may <br />result in as much as 77,400 additional acre-feet of savings. <br /> <br />To fully implement this project, it is expected that a reservoir should be built for every active <br />delivery gate that serves 160 acres or more. Total water conservation potentials are based upon <br />the possible implementation of 1,000 on-farm reservoirs. Based on the time required to build a <br />tailwater return system, a minimum of 20 to 22 years would be required to install these <br />reservoirs, assuming a construction rate of about 50 reservoirs each year. While water <br />conservation is the goal of this project, a burden is also placed on the water users. Land will <br />need to be taken out of production to construct the reservoirs, on-farm management of the <br />reservoirs becomes necessary, and in the summer, higher water temperatures in the reservoirs <br />may pose problems. This project, however, would not require District rules and operations to be <br />modified. These systems will utilize gravity flow inlets and four cubic feet per second (cfs) <br />pump outlets. <br /> <br />Improved irrigation management includes irrigation scheduling to determine how much water to <br />apply and when, irrigation event evaluations and increased management effort to use water more <br />efficiently. Irrigation scheduling methods include soil-water balance models, infrared <br />thermometers, experience and combinations of these methods. Every grower's irrigation water <br />management is unique and depends on the set of constraints and incentives which exist for an <br />individual operation. <br /> <br />Draft: Subject To Revision 12/21/95 <br /> <br />35 <br />