HR: 0800h
AN: H11C-0636    [Abstracts]
TI: Mathematical Model for Solute Transport in a Single Borehole Dipole Flow Tracer Test
AU: * Chen, J
EM: jschen@app.geo.ncu.edu.tw
AF: Graduate Institute of Applied Geology, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County, 32001, Taiwan
AU: Chan, Y
EM: 946204004@cc.ncu.edu.tw
AF: Graduate Institute of Applied Geology, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County, 32001, Taiwan
AU: Liang, C
EM: sc048@mail.fy.edu.tw
AF: Department of Environmental Engineering and Science, Fooyin University, 151, Chinhsueh Rd., Ta-liao, Kaohsiung, 831, Taiwan
AB: The basic design of a single-borehole dipole-flow tracer test involves a well with an injection and an extraction chamber separated by some vertical distance and isolated from one another both using an inflatable packer. The test utilizes a small pump to create a vertical dipole-flow field. After the flow field is stabilized and the pumping rate and drawdowns in these chambers are recorded, a tracer mass is introduced instantaneously into injection chamber and the concentration breakthrough curve is monitored in the extraction chamber. The horizontal hydraulic conductivity, the vertical hydraulic conductivity and longitudinal dispersivity can be determined by using an appropriate mathematical model to analyze the breakthrough curves and drawdowns in these chambers. Existing mathematical models based on streamtube approach are only effective for interpreting tracer tests under advective-dominated condition. Furthermore, these solutions are appropriate for generation of breakthrough curve in the extraction chamber only because the transverse dispersion term is neglected. This study presents a novel mathematical model for describing solute transport in a single-borehole dipole-flow tracer test. In developing the mathematical model, a steady-state analytical solution for drawdown distribution is first obtained and the radial and vertical components of pore velocity are determined. Subsequently, the two-dimensional advection-dispersion equation in cylindrical coordinates for describing tracer transport in a dipole-flow field is derived based on the second order dispersion tensor theory. The Laplace transformed finite difference technique is applied to solve the two-dimensional advection-dispersion equation in cylindrical coordinates with variable- dependent coefficients. The developed model has an advantage over the existing models because it can be valid under a wide range of longitudianl dispersivity. The novel mathematical model is applied to simulate the concentration contour in the aquifer and the breakthrough curves in the chambers. Moreover, a curve-fitting method is proposed to determine the longitudinal dispersivity.
DE: 1800 HYDROLOGY
DE: 1832 Groundwater transport
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting