On the importance of considering specific storage heterogeneity in hydraulic tomography: Laboratory sandbox and synthetic studies.

• THT analysis treating S s to be homogeneous yields less accurate results. • S s heterogeneity should be considered in THT for improved mapping of K and S s fields. • Reliable geological data helps THT to improve not only K , but also S s estimates. Over the last two decades, various studies on Transient Hydraulic Tomography (THT) have shown that it is an effective approach to characterize subsurface heterogeneity. Typically, high-resolution hydraulic conductivity (K) distributions were recovered, while the spatial variability of specific storage (S s) was found to be smooth. In some studies, S s heterogeneity has been intentionally ignored due to the belief that S s is less variable than K. Therefore, one may question the importance of considering S s heterogeneity during THT and its impact on the reliability of estimated hydraulic parameters. To investigate these issues, three modeling approaches (i.e., effective parameters, geological, and geostatistics-based) were used to obtain K and S s estimates of varying spatial resolutions. The reliability of K and S s estimates were evaluated by comparing their drawdown prediction performances. The values of using different prior K and S s information for THT analyses were investigated. Our results revealed that: (1) the K distribution estimated from the geostatistics-based steady-state HT analysis accurately predicted the late time drawdowns, while further improvements in transient drawdowns were obtained only after jointly treating the S s field as heterogeneous; (2) S s heterogeneity should be considered in addition to K for THT inversions, even when the estimated S s field is smooth; and (3) using K and S s estimates from the calibrated geological model as initial mean distributions for the geostatistical inversion approach were helpful in capturing both interlayer and intralayer heterogeneity of K and S s. These findings suggested that S s heterogeneity should be properly considered during the implementation of THT. [ABSTRACT FROM AUTHOR]