Scientific Investigations Report 2006–5316
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5316
Prepared in cooperation with the U.S. Department of Energy
By John A. Welhan, Idaho Geological Survey, Renee L. Farabaugh, Department of Geosciences, Idaho State University, Melissa J. Merrick, Department of Geosciences, Idaho State University, and Steven R. Anderson, formerly with U.S. Geological Survey
Conversion Factors, Datums, Abbreviations, and Acronyms
Geostatistical Analysis and Modeling
Summary and Conclusions
Figure 1. Study area, major topographic features, ground-water flow model extent, and locations of borehole data used for this analysis in and near the Idaho National Laboratory, Idaho.
Figure 2. Principal volcanic, structural, and geologic features in the study area, showing the inferred location of the Big Lost Trough in relation to major volcanic constructional zones.
Figure 3. Cross section A-A’ showing composite stratigraphic units 1 through 14, ground-water model layers A through F, and the relation between model layers and actual stratigraphy.
Figure 4. Geographic distribution of sediment-rich and sediment-poor boreholes that fully penetrate composite stratigraphic units 1 through 7 and 8 through 14, as defined by Anderson and Liszewski (1997).
Figure 5. Comparative distributions of sediment abundances showing the effect of spatial clustering on summary statistics.
Figure 6. Distribution of thickness of total accumulated sediment in boreholes that fully penetrate individual composite units 1 through 7 and in boreholes that penetrate the oldest units 8 to 14 combined.
Figure 7. Sediment abundance in each of composite units 1 through 7 and in combined unit 8 to 14, as a percentage of composite unit thickness.
Figure 8. Distributions of sediment percentage in various groupings of composite units showing evidence of statistical similarity among the youngest (other than composite unit 1) and the oldest.
Figure 9. Distributions of total sediment thickness among various groupings of composite units.
Figure 10. Availability of boreholes that fully penetrate each model layer and that were used to model the two-dimensional spatial abundance of sediment in each model layer.
Figure 11. Distributions of sediment percentages in boreholes that fully penetrate layers A, B, and C, showing similar distributions, and in the unsaturated zone (layer U), which has a substantially different distribution because of the influence of composite unit 1.
Figure 12. Distributions of sediment percentage from fully penetrating wells in model layers A, B, and C in different areas north and south of the stratigraphic discontinuity and among clustered and nonclustered areas shown in figure 10.
Figure 13. Relative variograms of sediment thickness within composite units 1 through 6, based on the inverted correlogram statistic.
Figure 14. Cumulative frequency distributions (CFDs) of sediment percentage in boreholes that fully penetrate layers A, B, and C showing CFD probabilities calculated from equation 1.
Figure 15. Examples of multiple indicator semivariograms at selected thresholds for layer A, showing the nature of the autocorrelation structure and the progressive change in nuggets, sills, and ranges as thresholds increase.
Figure 16. Results of multiple indicator variogram analysis for layer A, showing the progressive change in autocorrelation structure across a range of indicator thresholds.
Figure 17. Median percentage of sediment derived from multiple indicator kriging of layers A, B, and C.
Figure 18. Ordinary kriging variance () in layers A, B, and C, reflecting the relative uncertainty of kriging estimates based on the availability and arrangement of borehole data.
Figure 19. Distribution of sediment-rich and sediment-poor areas in the model domain.
Figure 20. Comparison of local cumulative frequency distributions (CFDs) derived from multiple indicator kriging (mIK) at two locations in Layer A, representing locations with low (location 1) and high (location 2) estimation variance.
Figure 21. Zones of hydraulic conductivity estimated from the kriged sediment content in layer A.
Figure 22. Layer A’s bulk hydraulic conductivity (Kbulk) classified according to the relative confidence in the kriged estimates as defined by the ordinary kriging variance.
Table 1. Summary of composite stratigraphic units, thicknesses, and time spans as defined by Anderson and Liszewski (1997) and used in this study.
Table 2. Results of nonparametric tests of similarity of median sediment content between various groupings of younger and older composite units, where sediment content is expressed in percent.
Table 3. Results of nonparametric tests of similarity of median sediment content between groups of younger and older composite units, where sediment content is expressed as sediment thickness.
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Send questions or comments about this report to the author, John A. Welhan, 208-282-3235.