HR: 0800h
AN: H11D-1313    [Abstracts]
TI: Hyporheic Exchange: Analysis of Aquifer Heterogeneity, Channel Morphology and Bedforms- 2D and 3D Simulations Using MODFLOW and MODPATH
AU: * Matos, J R
EM: sg96d729@drexel.edu
AF: Department of Civil, Architectural and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 United States
AU: Welty, C
H11D-1313 AF: Claire Welty, Center for Urban Environmental Research and Education and Department of Civil and Environmental Engineering, University of Maryland, Baltimore County, TRC 102, 1000 Hilltop Circle, Baltimore, MD 21250 United States
AU: Packman, A
H11D-1313 AF: Aaron Packman, A314 Technological Institute, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109 United States
AB: The main purpose of the simulations in this research is the analysis of three-dimensional surface-groundwater interchange in heterogeneous systems. The effects of channel pattern, bed forms and aquifer heterogeneity on flow interactions between stream and groundwater systems are examined in order to contribute for a better understanding of the hyporheic process. A two-dimensional approach was also adopted to allow comparisons with the three-dimensional results. The grid was designed using the correlation scales of the heterogeneous fields and the scale of the stream meanders. MODFLOW and MODPATH were used to evaluate magnitude, direction and spatial distribution of the exchange flow. PMWIN and PMPATH were used as pre and post-processors during the construction of the models and analysis of results. Gaining and losing streams as well as parallel flow and flow across streams were simulated as idealized cases intended to describe how properties of the streambed and aquifer in low-gradient lowland streams contribute to hyporheic exchange. At first a straight river was analyzed then meandering streams were created with a sine curve and variations on wavelength and amplitude. Bed forms were simulated assuming a sinusoidal distribution of pressure head in the bed surface. Aspects of the influence of bedforms on mechanisms such as "pumping" and "turnover" are expected to be addressed with simulations. Flow velocities between 20 and 40 cm/s in the channel were tested with the objective of showing the influence of river morphology and natural bed forms on the flow exchange in the hyporheic zone. Several meander cycles and four levels of hydraulic conductivity variance were analyzed. Results of flow variances along the cross-sections and wetted perimeter show the increasing on hyporheic exchange as the degree of heterogeneity increases. Particle tracking was performed to define hyporheic residence time distributions. When comparing the homogeneous fields with all degrees of heterogeneity it is possible to see a substantial increasing on travel time. The simulations also showed that heterogeneity increases tailing in cumulative distribution functions of hyporheic residence times. The residence time in the hyporheic zone can be connected to measurable parameters of the streams and will make possible the generalization for other streams and stream conditions.
DE: 1830 Groundwater/surface water interaction
SC: Hydrology [H]
MN: Fall Meeting 2005