Mapping Hydraulic Conductivity: Sequential Conditioning with Measurements of Solute Arrival Time, Hydraulic Head, and Local Conductivity

Abstract

We present a method for estimating the spatial pattern of aquifer hydraulic conductivity from three types of measurements: solute arrival time quantiles, hydraulic heads, and direct local measurements. Results indicate that arrival times and heads provide different, but complementary, information about the large features of the conductivity field which serve as flow paths and barriers. We compare the information provided by head and arrival time measurements by plotting the correlation between measurement and conductivity over the entire domain. We also compare the value of head and arrival time data by estimating the conductivity with only one type of data, and by incorporating the different data types into the estimation procedure in different sequences. Using quantiles of arrival time, rather than concentrations, has three advantages: (1) Arrival times are independent of the amount of dilute solute introduced into the aquifer. (2) Under some conditions, by measuring the median arrival time, the accuracy of the conductivity field estimate is not degraded by poor knowledge of the local dispersivity. (3) The estimation procedure is greatly simplified by relying on a single quantile to represent the critical information contained in a breakthrough curve that is constructed from many concentration measurements. For the case examined here, incorporating arrival time quantiles that describe the tails of the breakthrough curves did not significantly improve our estimate of the conductivity field.