Modeling shallow water table evaporation in irrigated regions |
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| Authors: | Chuck Young Wesley Wallender Gerrit Schoups Graham Fogg Blaine Hanson Thomas Harter Jan Hopmans Richard Howitt Ted Hsiao Sorab Panday Ken Tanji Susan Ustin Kristen Ward |
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| Institution: | (1) Stockholm Environment Institute, 133 D Street, Suite F, Davis, CA 95618, USA;(2) Department of Land, Air, and Water Resources, U.C. Davis, One Shields Avenue, Davis, CA 95616, USA;(3) Department of Integrated Environmental Studies, Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium;(4) Department of Agricultural and Resource Economics, U.C. Davis, One Shields Avenue, Davis, CA 95616, USA;(5) Hydrogeologic Incorporated, 1155 Herndon Parkway, Suite 900, Herndon, VA 20170, USA |
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| Abstract: | Groundwater discharge through evaporation due to a shallow water table can be an important component of a regional scale water
balance. Modeling this phenomenon in irrigated regions where soil moisture varies on short time scales is most accurately
accomplished using variably saturated modeling codes. However, the computational demands of these models limit their application
to field scale problems. The MODFLOW groundwater modeling code is applicable to regional scale problems and it has an evapotranspiration
package that can be used to estimate this form of discharge, however, the use of time-invariant parameters in this module
result in evaporation rates that are a function of water table depth only. This paper presents a calibration and validation
of the previously developed MOD-HMS model code using lysimeter data. The model is then used to illustrate the dependence of
bare soil evaporation rates on water table depth and soil moisture conditions. Finally, an approach for estimating the time
varying parameters for the MODFLOW evapotranspiration package using a 1-D variably saturated MOD-HMS model is presented. |
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| Keywords: | Evaporation Groundwater model Shallow water table |
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