Figure 5-1. Measured data for water-level examples--A, original data; B, original data without dropped sites; C, original data with added sites (added sites indicated with +) (cont)

ETL 1110-1-175
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ETL 1110-1-175

30 Jun 97

Figure 5-1. (Sheet 2 of 3)

circumstances there is usually a fairly uniform and

shape and a linear drift was identified. Once the

general groundwater movement that is generally

drift was identified and characterized, universal

expressed in terms of direction. This uniform and

kriging procedures were used.

general nature introduces a nonstationary element

d. A Gaussian model is usually appropriate

to the data that, in geostatistics, is referred to as

drift. As indicated in Chapter 4, the presence of

for variograms with highly continuous variables

drift is indicated by a parabolic variogram shape.

such as groundwater-elevation data, and it is par-

In this example, the initial variogram in the raw

ticularly appropriate in this example. The vario-

variogram analysis had a characteristic parabolic

gram (Figure 5-2a) at small lags beyond the nugget

5-3