| Evapotranspiration is an important component of the water budget in riparian environments. Atmospheric measurements of riparian evapotranspiration (RET) are difficult to accomplish because of the limited aerial extents of riparian zones. Several approaches have been proposed for estimating RET using subsurface water balance; however, some of these approaches become inaccurate when there is a nearby surface water body, such as a stream. Since quantitative observations of the impact of RET on low-flow streamflow patterns is limited, numerical modeling has been used to simulate the influence of RET on conditions in a coupled subsurface-surface water domain. Two modeling approaches have been utilized: first, a two-dimensional cross-sectional model has been created using the VS2D software package to estimate daily evapotranspiration fluxes using a water balance approach, and second, a one-dimensional model using a Dupuit approximation for subsurface flow has been coupled with a pond water balance to address how surface water---groundwater interactions affect estimates of RET. The effect of soil composition, seasonality, initial simulation conditions, and flow system geometry on subsurface behavior and ET estimates has been analyzed and discussed for both models, and recent modeling techniques, such as plant functional grouping and depth-dependant ET flux, have been explored. A simple method for estimating daily ET fluxes from correlated stream and water table fluctuations has also been presented. |
