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<br />Water Supply Reserve Account - Grant Application Form <br /> <br />Form Revised October 2006 <br /> <br />4. Please provide a brief narrative of any related or relevant previous studies. Attach additional <br />sheets as needed. <br /> <br />The lysimeter design and construction was based on consultation with USDA-Agricultural Research <br />Service and Texas A&M staff in Bushland, IX. The following literature review was conducted by Tom <br />Ley(2004). Lysimeters for evapotranspiration (ET) research can be classified as weighing or nOll- <br />weighing, as monolithic or reconstructed soil profiles, and as gravity or vacuum drainage (Howell et aI., <br />1 991 ). <br /> <br />Non-weighing lysimeters, also commonly called volumetric lysimeters, are among the simplest, most <br />common, and least expensive type of lysimeters (Aboukhaled et aI., 1982). These lysimeters are <br />characteristically single tanks placed in the soil to define a control volume. Non-weighing drainage <br />lysimeters work on the principle of volume balance in which ET is the difference of measured inigation <br />and precipitation applied to the control volume less the measured drainage water. Non-weighing <br />lysimeters can be set up to maintain a constant water table level in the soil tank. The contribution to ET <br />from the water table is the volume of water made up periodically to maintain the constant water table <br />level. Both types of lysimeters are limited by soil water movement time delays and changes in soil water <br />storage. While daily estimates of ET can be made under these limitations, the determination of ET is often <br />more accurate over longer periods of time from weekly to monthly intervals (Aboukhaled et aI., 1982). <br />Due to this limitation, non-weighing lysimeters are not considered suitable for reference ET equation <br />verification and crop coefficient research. They may, however, be very suitable low cost alternatives for <br />studying the effects of varying water salinity levels and high water table conditions on crop ET up and <br />down the Arkansas River Valley. <br /> <br />See attached sheets for additional information. <br /> <br />5 <br />