Identifying Temporal Change in the Spatial Correlation of Regional Groundwater Contamination

by John M. Shafer, Illinois State Water Survey, United States,
Mark D. Varljen, Illinois State Water Survey, United States,
H. Allen Wehrmann, Illinois State Water Survey, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


An approach for estimating the semivariogram based on the jackknife method can be used in connection with standard confidence procedures to set closely approximate confidence limits on the semivariogram. Confidence limits allow for meaningful comparison of semivariograms estimated from data for different time periods, thus facilitating the identification of a significant temporal change in spatial correlation. Temporal changes in the spatial correlation of target contaminants should be considered when geostatistical techniques are used to design optimized groundwater quality monitoring networks. The jackknife approach was demonstrated using nitrate-nitrogen concentrations in samples of shallow groundwater collected over two different short time intervals from an approximately 12 mi.2 area of northern Illinois.

Subject Headings: Groundwater pollution | Correlation | Confidence intervals | Groundwater quality | Spatial data | Comparative studies | Hydraulic design | Groundwater | Illinois | United States

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