OBSERVATIONS OF MEASURED HYDRAULIC CONDUCTIVITY IN 2 ARTIFICIAL, CONFINED AQUIFERS WITH BOUNDARIES

Recent theoretical efforts have provided story evidence that the effec tive conductivity varies with distance between monitoring wells and a point source. In the present study, two artificial confined aquifers w ere subjected to steady state pumping tests, Analysis of these experim ental results indicates dependence of the estimated hydraulic conducti vity on distance from the pumping well and the form of the physical he terogeneity present. As the precision of the measured hydraulic heads within the experimental apparatus was limited to similar to 0.5 mm, th e experimental results were reproduced numerically. Although some mino r discrepancies were noted between the numerical and experimental resu lts, the primary observations were consistent. In all cases the Thiem equation was used in combination with image well theory (to account fo r the boundary conditions) to analyze the response at 25 observation p oints (87 observation points used in the numerical experiments), provi ding a number of estimates of the hydraulic conductivity. Within each experiment it was observed that the variance of the conductivity estim ate decreased with the distance between the two observation wells used in the calculation. Further, the mean conductivity varied with distan ce from the pumping well. In an experiment in which the medium was con structed to mimic a second-order stationary random field the mean cond uctivity approached, at large distance from the pumping well, the cond uctivity for a random, anisotropic medium under mean uniform flow. In an experiment in which the medium was constructed to mimic a structure d (scaled) medium the mean conductivity decreased, at large distance f rom the pumping well, below the geometric mean and approached a value between the geometric and the harmonic means of the conductivity field . While the boundary conditions make it difficult to fully analyze the large-dimension behavior of these two media, it is clear from the res ults that the structured medium performs quite differently than the ra ndom field at large-measurement scale.