Conditional expectation for evaluation of risk groundwater flow and solute transport: One-dimensional analysis

Tai Sheng Liou, Hund-Der Yeh*

*Corresponding author for this work

Research output: Contribution to journalArticle

28 Scopus citations


A one-dimensional groundwater transport equation with two uncertain parameters, groundwater velocity and longitudinal dispersivity, is investigated in this paper. The analytical uncertainty of the predicted contaminant concentration is derived by the first-order mean-centered uncertainty analysis. The risk of the contaminant transport is defined as the probability that the concentration exceeds a maximum acceptable upper limit. Five probability density functions including the normal, lognormal, gamma, Gumbel, and Weibull distributions are chosen as the models for predicting the concentration distribution. The risk for each distribution is derived analytically based on the conditional probability. The mean risk and confidence interval are then computed by Monte Carlo simulation where the groundwater velocity and longitudinal dispersivity are assumed to be lognormally and normally distributed, respectively. Results from the conditional expectation of an assumed damage function show that the unconditional expectation generally underestimates the damage for low risk events. It is found from the sensitivity analysis that the mean longitudinal dispersivity is the most sensitive parameter and the variance of longitudinal dispersivity is the least sensitive one among those distribution models except the gamma and Weibull distributions.

Original languageEnglish
Pages (from-to)378-402
Number of pages25
JournalJournal of Hydrology
Issue number3-4
StatePublished - 10 Dec 1997


  • Ground water
  • Monte Carlo analysis
  • Risk assessment
  • Sensitivity analysis
  • Solute transport

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