Supercomputers and their use in modeling subsurface solute transport

Supercomputers offer a wide range of possibilities for advancing knowledge and solving difficult, real-world problems. Solute transport-related theory and applications have long been an area of specialization within hydrology. In this review, recent applications of supercomputers to solute transport problems are presented. These applications are based mostly on the assumption of a dilute solute, allowing the governing equations to be decoupled. An application of supercomputers is the simulation of solute transport in large heterogeneous spatial domains by both direct solution of the governing equations and by particle- tracking methods. An impetus for this research has been the rapid increase in predictive dispersion models based on analytical stochastic theory. Up until now, relatively few applications have incorporated algorithms designed with a targeted supercomputer in mind, with the result that the machine’s potential cannot be exploited fully. Since many numerical problems are reduced to solutions of algebraic systems when they are implemented on computers, algorithms for linear algebraic systems of equations suitable for vector and parallel machines are discussed in some detail. Data analysis, necessary both for evaluating emerging theories and for more “routine” applications like determining model parameters, is identified as another general area that is ably handled by supercomputers. In particular, supercomputers offer a way to become less dependent on parametric assumptions and constraints, substituting, instead, raw computational power. Visualization techniques and associated facilities have flourished alongside the development of supercomputer centers. These offer the possibility for real-time viewing of solute transport processes, both real and simulated, although little has been produced thus far. It is expected that many more researchers involved with subsurface solute transport will make use of supercomputers in the future.