Experiences in implementing the White Method : estimating evapotranspiration using fluctuations of water table elevation Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/5x21tm02s

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  • Evapotranspiration (ET) is the process by which water is transferred from land to the atmosphere. ET is the second most important component of a hydrologic budget and remains difficult to estimate. The primary objective of this project was to determine the limitations of estimating ET from water table elevation fluctuations analyzed using the White Method (White, 1932). Secondary objectives include: determining if specific yield is a function of water table depth, investigating the effect of hysteresis on water table fluctuation shape, estimating groundwater recharge rate, and using vegetation data to gain clues regarding spatiotemporal water availability. They are 5 major results from this investigation. Nachabe's modified soil moisture balance (Nachabe et al. 2005) outperformed the classical White Method (White, 1932) in ability to estimate a daily rate of evapotranspiration. Specific yield is not a constant and changes with water table depth below ground surface level. Hysteresis can explain the break in slope in water table rise observed during the night of many records of water table fluctuations. The White Method is more suitable to estimate groundwater upwelling rather than evapotranspiration. Finally, vegetation sampling can provide clues to intra-seasonal and inter-seasonal water availability across a site.
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