Special 25th Anniversary Issue of Advances in Water Resources ( C.T. Miller, M.B. Parlange, S.M. Hassanizadeh). Characterizing flow and transport in fractured geological media: A review (B. Berkowitz). Asymptotic regimes in unstable miscible displacements in random porous media (Z.M. Yang, Y.C. Yortsos, D. Salin). Variable-density flow and transport in porous media: approaches and challenges (H.-J.G. Diersch, O. Kolditz). Modelling the fate of oxidisable organic contaminants in groundwater (D.A. Barry, H. Prommer et al.). New modeling paradigms for the sorption of hydrophobic organic chemicals to heterogeneous carbonaceous matter in soils, sediments, and rocks (R.M. Allen-King, P. Grathwohl, W.P. Ball). Processes in microbial transport in the natural subsurface (T.R. Ginn, B.D. Wood et al.). A primer on upscaling tools for porous media (J.H. Cushman, L.S. Bennethum, B.X. Hu). Detailed physics, predictive capabilities and macroscopic consequences for pore-network models of multiphase flow (M.J. Blunt, M.D. Jackson et al.). On the definition and derivatives of macroscale energy for the description of multiphase systems (W.G. Gray). Immiscible two-phase fluid flows in deformable porous media (W.-C. Lo, G. Sposito, E. Majer). Explicit infiltration equations and the Lambert W-function (J.-Y. Parlange, D.A. Barry, R. Haverkamp). Numerical methods for incompressible viscous flow (H.P. Langtangen, K.-A. Mardal, R. Winther). Computational engineering and science methodologies for modeling and simulation of subsurface applications (M.F. Wheeler, M. Peszynska). Multi-scale iterative techniques and adaptive mesh refinement for flow in porous media (J.A. Trangenstein). An overview of research on Eulerian Lagrangian localized adjoint methods (ELLAM) (T.F. Russell, M.A. Celia). Optimal design for problems involving flow and transport phenomena in saturated subsurface systems (A.S. Mayer, C.T. Kelley, C.T. Miller). On the assimilation of uncertain physical knowledge bases: Bayesian and non-Bayesian techniques (G. Christakos). An integrated approach to hydrologic data assimilation: interpolation, smoothing, and filtering (D. McLaughlin). Statistics of extremes in hydrology (R.W. Katz, M.B. Parlange, P. Naveau). Investigating soil moisture feedbacks on precipitation with tests of Granger causality (G.D. Salvucci, J.A. Saleem, R. Kaufmann). Advances in the use of observed spatial patterns of catchment hydrological response (R.B. Grayson, G. Bloschl et al.). Ecohydrology of water-controlled ecosystems (A. Porporato, P. D'Odorico et al.). How representative are local measurements of the surface shear stress for regional values? (K. Eng, W. Brutsaert). Quantifying net ecosystem exchange by multilevel ecophysiological and turbulent transport models (M. Siqueira, G. Katul, C.-T. Lai). Remote sensing in hydrology (T.J. Schmugge, W.P. Kustas et al.). Radar hydrology: rainfall estimation (W.F. Krajewski, J.A. Smith). Conference Diary.