Scientific Investigations Report 2006–5316
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5316
DOE/ID-22201
Geostatistical Modeling of Sediment Abundance in a Heterogeneous Basalt Aquifer
at the Idaho National Laboratory, Idaho
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
Table of Contents
Conversion Factors, Datums, Abbreviations,
and Acronyms
Abstract
Introduction
Geohydrologic Setting
Geostatistical Methods
Geostatistical Analysis and Modeling
Summary and Conclusions
Acknowledgments
References Cited
Figures
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.
Tables
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.
U.S.
Department of the Interior | U.S. Geological
Survey
