Application of transition probability geostatistics in a detailed stratigraphic framework

Heterogeneity of hydraulic properties at multiple scales in an alluvial aquifer is largely controlled by the distribution of facies. Therefore, we require quantified stratigraphic and sedimentologic models in order to incorporate this spatial variability of hydraulic properties into groundwater flow and contaminant transport simulations. Our approach uses sequence stratigraphic concepts, developed for the fluvial fan continental setting to (1) delineate large-scale stratigraphic units in the alluvial aquifer, (2) predict overall facies patterns in the aquifer, and (3) guide development of appropriate Markov chain models used in transition probability geostatistics. After geostatistical simulation, our results are used in groundwater models to estimate groundwater age distributions, evaluate remediation strategies, and model aquifer hydraulic tests in a heterogeneous setting. To illustrate and provide a “how-to” guide to this approach, I use examples from the Kings River fluvial fan, located southeast of Fresno, California (Figure 1).