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The article presents the authors' reply to S. Neuman's comments which advocates the need for an adequate hydrogeological characterization of aquifers. It provides a brief summary of their work that was overlooked by Neuman's comment which include a critical reexamination of the field data collected by L.W. Gelhar et al especially those referred to as of medium or low reliability and the addition of new data what were again screened for reliability.

Though the essence of the scientific literature is to be a repository of unaffiliated truths, scientific advancement fundamentally stems from the insights and efforts of individuals. This dichotomy can hide exemplars for young scholars of how to contribute to scientific understanding. This section of Water Resources Research addresses eminently successful strategies for advancement of the science of hydrology by exploring the ramifications of the work from Drs. Wilfried Brutsaert and Jean-Yves Parlange, colleagues who made many of the most significant contributions to the understanding of hydrologic processes of the last 50 years. The generous scope of the special section follows the key areas of their contributions, but the content looks forward from their work. Important and novel results span solute transport, infiltration, streamflow generation, and evaporation. [ABSTRACT FROM AUTHOR]

Detailed numerical analyses of flow and transport were used to investigate the effect of spatially connected features on transport in three-dimensional (3-D), spatially heterogeneous, combined vadose zone-groundwater flow systems. Formations with spatially connected fine-textured and coarse-textured features (F-formation and C-formation, respectively), representing the10th and the 90th percentiles of the distributions of the formation's hydraulic parameters, respectively, were considered here. Results of the analyses suggest that in steady state flow, when the unsaturated zone of the combined flow domains is relatively wet, as compared with a Multivariate-Gaussian (MG) formation, spatially connected features may reduce the solute first arrival time, particularly in the C-formation, and may enhance the spreading of the solute breakthrough, particularly in the F-formation. The effect of the spatially connected features on the hydrological response, however, decreases as the unsaturated zone becomes drier. The latter result stems from the decrease in the fraction of the water-filled, pore-space occupied by the connected structures, with decreasing water content. The latter finding also explains the result that the response of more realistic, combined flow systems, whose unsaturated zone is associated with relatively low, intermittent water contents, is essentially independent of the spatially connected features of the formations, regardless of their soil texture. [ABSTRACT FROM AUTHOR]