C

General Head Boundary (Mahomet Bedrock Valley)

General Head Boundary^ (Illinois Basin)

and modern state K values

Constant Head

Boundary (Mississippi R.)

Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Layer 7 Layer 8 Layer 9 Layer 10

and modern state K values

Figure 11.2 (a) Generalized model geometry and boundary conditions along flowline A-A' (see Fig. 11.1). Horizontal length is 1040 km. Vertical exaggeration is 100X. Illustrated stratigraphy shows ten modelled hydrostratigraphic units (not to scale) (see Table 11.1 for a description of hydrostratigraphic units). (b) Groundwater flow vectors under simulated modern conditions. (c) Groundwater flow vectors based on modern K values, with Lake Michigan Lobe present and a 7-mm-thick film at the ice-bed interface. The vector scale varies between illustrations.

Figure 11.2 (a) Generalized model geometry and boundary conditions along flowline A-A' (see Fig. 11.1). Horizontal length is 1040 km. Vertical exaggeration is 100X. Illustrated stratigraphy shows ten modelled hydrostratigraphic units (not to scale) (see Table 11.1 for a description of hydrostratigraphic units). (b) Groundwater flow vectors under simulated modern conditions. (c) Groundwater flow vectors based on modern K values, with Lake Michigan Lobe present and a 7-mm-thick film at the ice-bed interface. The vector scale varies between illustrations.

Table 11.1 Model hydrostratigraphy and hydraulic conductivity values in Illinois

Model

Hydrostratigraphic description

K (m s-1) assigned Geometric

-1?

+1?

Total

layer

to the validation mean simulation*

(ms-1)

(ms-1)

observations

1 Quaternary Drift 1

2 Quaternary Drift 2

3 Pennsylvanian through to

Middle Devonian rocks

4 Silurian-Devonian carbonates

5 'Maquoketa Shale, Galena, Dolomite, and the Decorah, Platteville, and Glenwood Formations'

1 Quaternary Drift 1

2 Quaternary Drift 2

3 Pennsylvanian through to

Middle Devonian rocks

4 Silurian-Devonian carbonates

5 'Maquoketa Shale, Galena, Dolomite, and the Decorah, Platteville, and Glenwood Formations'

1816

Table 11.1 Continued

Model

Hydrostratigraphic description

K (m s-1) assigned Geometric

-1?

+1?

Total

layer

to the validation mean simulation*

(ms-1)

(ms-1)

observations

'St Peter Sandstone, Prairie du Chien Group and the Jordan Sandstone' 'St Peter Sandstone, Prairie du Chien Group, and the Jordan Sandstone (southern third of the flow line)' St Lawrence and Franconia Formations St Lawrence and Franconia Formations (southern third of the flow line) Ironton-Galesville Sandstones Ironton and Galesville Sandstones (southern quarter of the flow line) Eau Claire Formation

Eau Claire Formation (southern third of the flow line) Mount Simon Sandstone and Elmhurst Sandstone

1.6 x 10-6 6.4 x 10-5 539 1.6 x 10-6 6.4 x 10-5 539

58 58

*All K values except those of Quaternary drift are based on the best estimates of the Northern Midwest Regional Aquifer System Assessment (Mandle & Kontis, 1992). Standard deviation data are available only for the bedrock aquifer units. K values assigned to the confining units are close to the values estimated by Walton (1960) and Young (1976). Quaternary drift K is one order of magnitude less than Walton's (1965) estimate for diverse drift deposits in Illinois.

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