Operator and integro-differential representations of conditional and unconditional stochastic subsurface flow

S. Orr, S. P. Neuman

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Operator representations of stochastic subsurface flow equations allow writing their solutions implicitly or explicitly in terms of integro-differential expressions. Most of these representations involve Neumann series that must be truncated or otherwise approximated to become operational. It is often claimed that truncated Neumann series allow solving groundwater flow problems in the presence of arbitrarily large heterogeneities. Such claims have so far not been backed by convincing computational examples, and we present an analysis which suggests that they may not be justified on theoretical grounds. We describe an alternative operator representation due to Neuman and Orr (1993) which avoids the use of Neumann series yet accomplishes a similar purpose. It leads to a compact integro-differential form which provides considerable new insight into the nature of the solution. When written in terms of conditional moments, our new representation contains local and nonlocal effective parameters that depend on scale and information. As such, these parameters are not unique material properties but may change as more is learned about the flow system.

Original languageEnglish (US)
Pages (from-to)157-172
Number of pages16
JournalStochastic Hydrology and Hydraulics
Issue number2
StatePublished - Jun 1994

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Modeling and Simulation
  • Water Science and Technology
  • Safety, Risk, Reliability and Quality
  • Ocean Engineering
  • Environmental Science(all)
  • Mechanical Engineering


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