Debates—Stochastic subsurface hydrology from theory to practice: Does stochastic subsurface hydrology help solving practical problems of contaminant hydrogeology?

While stochastic subsurface hydrology has been tremendously successful in understanding how the spatial variability of hydraulic conductivity affects conservative solute transport in idealized settings, it has gained little impact in practice. This is the case because typical assumptions needed for the derivation of analytical expressions are too restrictive for practical applications and often geologically implausible, small-scale variation of hydraulic conductivity is by far not the only cause of uncertainty when considering the fate and remediation of pollutants, and the research community has not developed enough methods that can directly be used by practitioners. To overcome these shortcomings, we propose putting more emphasis on providing easy-to-use tools to generate realistic realizations of subsurface properties that are conditioned on all data measured at a site, extending the focus from hydraulic conductivity only to all parameters and processes relevant for reactive transport, making use of self-organizing principles of reactive transport to conceptually simplify the problem, and addressing conceptual uncertainty by stochastic methods.