HR: 1340h
AN: H43F-0550    [Abstracts]
TI: Laboratory Investigation of Submarine Groundwater Flow and Recirculation Patterns in Coastal Aquifers
AU: * Clement, P
EM: clement@auburn.edu
AF: Auburn University, Department of Civil Engineering, 212 Harbert Engineering Center, Auburn University, Auburn, AL 36849 United States
AU: Goswami, R R
EM: goswarr@auburn.edu
AF: Auburn University, Department of Civil Engineering, 212 Harbert Engineering Center, Auburn University, Auburn, AL 36849 United States
AU: Hogan, M B
EM: hoganmb@auburn.edu
AF: Auburn University, Department of Civil Engineering, 212 Harbert Engineering Center, Auburn University, Auburn, AL 36849 United States
AB: Submarine groundwater discharge (SGWD) is an important discharge process occurring in the vicinity of the saltwater-freshwater boundary in coastal unconfined aquifers. It is now well established that the SGWD has a regional freshwater flow component and a re-circulated saltwater flow component. In an unconfined aquifer, the freshwater and saltwater regions are separated by a distinct interface and freshwater flow occurs above the interface and saltwater flow occurs beneath the interface. Under natural conditions, the interface is at a dynamic equilibrium established by the movement of fresh and saltwater flows. Currently, there is a considerable controversy in the estimated values of these fresh and saltwater flow rates. For example, in a classic field study, Moore (Nature, v.380, p.612-614, 1996) discovered very high rates (much higher than estimated regional freshwater flux) of SGWD into a coastal aquifer. Younger (Nature, v.382, p.121-122, 1996) argued that only four percent of the SGWD estimated by Moore is from the land (fresh groundwater) and the rest of SGWD is of marine origin. The objective of this work is develop a physical model for a coastal unconfined aquifer and perform careful studies to visualize the freshwater and saltwater flow patterns near a coastal interface. We conducted laboratory studies of the saltwater intrusion phenomenon in two flow tanks filled with a homogeneous porous medium. Our small tank has dimensions of 53 cm x 32 cm x 2.7 cm, and our large tank has dimensions of 110 cm x 65 cm x 5 cm. By completing experiments in two difference scales we hope to address the scaling issues related to this complex flow problem. Our experimental setup allowed us to quantify both freshwater and seawater fluxes; further, the circulation patterns of seawater and the discharge patterns of freshwater were also observed. Tracer studies were conducted to quantify the residence times. In this presentation, we will present the data collected from our experiments and correlate the observed fluxes and circulation patterns with certain dimensional parameters. SGWD can be an important phenomenon that controls the overall nutrient budgets of coastal water. Our study would aid in developing a better understanding of seawater circulation and its relationship to SGWD.
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: Fall Meeting 2005