HR: 0830h
AN: H31D-0498    [PDF]
TI: Application of Analytical Models of Pumping Induced Stream Depletion to Real Stream-Aquifer Systems: a Practical Approach?
AU: * Kollet, S J
EM: skollet@unlserve.unl.edu
AF: Department of Geosciences, University of Nebraska-Lincoln, 214 Bessey Hall, Lincoln, NE 68588 United States
AU: Zlotnik, V A
EM: vzlotnik1@unlnotes.unl.edu
AF: Department of Geosciences, University of Nebraska-Lincoln, 214 Bessey Hall, Lincoln, NE 68588 United States
AB: Two-dimensional analytical models of stream-aquifer interactions are commonly used to predict pumping induced stream depletion (SD) rates from drawdown data. In the case of most natural streams, however, predicted SD rates are virtually impossible to verify with direct measurements obtained via stream gauging due to relatively large measurement errors in the field. Thus, other ways must be found to test the applicability of these models to real stream-aquifer systems. This study utilizes three-dimensional numerical flow models to test the applicability of analytical models based on the assumption that more flexible numerical models can represent real stream-aquifer systems more realistically. The stream-aquifer system considered in this study consists of an aquifer associated with the braided-river depositional environment that is hydraulically connected with a naturally meandering stream at the top. Drawdown data from two pumping tests performed in presence and absence of streamflow were collected in a dense monitoring network on both stream banks (point bar and cut bank). The drawdown data were analyzed using simple analytical models and more realistic numerical models that incorporate aquifer heterogeneity, the plane stream geometry, an approximation of the stream-aquifer interface, and aquifer return flow. The numerical models consistently explained the measured system's responses under the distinct hydrologic conditions. Comparison of SD rates obtained with the analytical and numerical models suggests that analytical models can provide a good proxy of SD. In the analytical models, however, the streambed conductance concept of a semi-pervious streambed has only little resemblance in the field as follows from direct observations. This concept is better interpreted as an operational theory in our case. Techniques applied in this study are useful for SD rate estimation, delineation of aquifer heterogeneity, and streambed characterization.
DE: 1803 Anthropogenic effects
DE: 1829 Groundwater hydrology
DE: 1836 Hydrologic budget (1655)
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2003 Fall Meeting