Characterization of the heterogeneity of a fractured aquifer based on hydraulic travel time inversion

Abstract

The spatial distribution of aquifer hydraulic parameters is an important and basic factor to study groundwater seepage, groundwater pollutant transport processes and many other groundwater related problems.However, due to the limitation of conventional exploration technology, the spatial heterogeneity of aquifer hydraulic parameters cannot be described accurately and intuitively.Especially for fractured aquifers, the heterogeneity of hydraulic parameters is much stronger.In order to solve this problem, this study attempts to characterize the hydraulic properties of a fractured aquifer by using travel time based hydraulic tomography.Firstly, the head data at 8 different depths (receivers) in the observation well are recorded through 64 multi-level short-term pumping tests at 8 pumping intervals (sources) in the pumping well with help of double packers performed in Goettingen Germany.All these 64 head response data are used to calculate the hydraulic parameters (K and Ss) with Jacobian analytical solution.Subsequently, the derived hydraulic travel times between each source and receiver are utilized to obtain the hydraulic diffusivity distribution based on hydraulic travel time inversion.For the validation, the inversion results are finally compared with the results from Jacobian analytical solution and thermal tracer test.It shows that the estimated parameters of analytical solution indicate the vertical heterogeneity, but it cannot describe the spatial distribution of these parameters between wells.Results of thermal tracer test have proven the plausibility of the travel time based hydraulic tomography for the characterization of the fractured aquifer.

Keywords

• hydraulic tomography
• fractured aquifer
• hydraulic travel time inversion
• heterogeneity
• thermal tracer test