Gedeon Dagan is Professor Emeritus at the Faculty of Engineering,Tel Aviv University, Israel. He made significant theoretical contributions to Naval Hydrodynamics and Groundwater Hydrology in his early career. Subsequently, he became one of the leading hydrologists in the world, having initiated a new field within hydrogeology, namely Stochastic Subsurface Hydrology, by coupling physical and biogeochemical processes along subsurface water pathways. His theoretical results were the first to provide a rational basis for assessing the limitations of predictive modeling and quantifying prediction uncertainty related to subsurface pollution and restoration. Gedeon Dagan has contributed fundamental advances to stochastic modeling of a broad range of natural phenomena related to subsurface hydrology. These include major contributions to the following issues: (i) Statistical characterization of aquifers and soil properties, (ii) Prediction of spreading of solutes in natural aquifers, (iii) Effective properties of subsurface systems, (iv) Travel time analysis of transport, (v) The general idea of effective spreading, where the interplay between the pollutant and the heterogeneity lengthscales play a crucial role in the transport dynamics, (vi) Nonuniform flow towards well in heterogeneous formations, (vii) Analysis of solute dilution, as opposed to spreading, as a local measure of concentration decay, (viii) Water and contaminant dynamics in highly heterogeneous porous formations.